Add escape in strings control to ruby parser.

- Moving lines after themselves didnt work.
- moving empty lines deleted them.
- "w" didnt set state to unmodified in generic buffers.
- in "hl" aligned the numbers (by digits)

ARCHITECTURE.md

@@ -0,0 +1,149 @@
+# Base.
+
+### `PCH`
+
+Brings in all the external and standard headers. <br/>
+Apart from c++std stuff we have:
+- `mruby` and almost all it's subheaders.
+- `pcre2` (For regex.)
+- `grapheme.h` - The suckless libgrapheme (to find utf8 boundaries)
+- `unicode_width.h` - To find terminal width of unicode char's.
+
+*Maybe try removing some of them ive probably stopped using.*
+
+### `definitions.h`
+
+- Defines the `bed` namespace
+- Forward declaration of `BEd` type needed by all.
+- `fatal_error` definition, a msg, code (quits application on being thrown)
+- `ed_error`. just a message (stops the current cycle of the ed repl.)
+
+### `bed.h`
+
+**As this is based heavily on the internals, and so ill look into it at the end.**
+
+# `Internal`
+
+## `Vase`
+
+- This module doesn't depend on any other.
+- It's namespace is `bed::internal::vase`
+- Vase is the module to do with the actual storage and handling of a disk backed immutable and reference counted avl piece tree.
+- It is a O(log n) per edit text datatype.
+
+### `constants.h`
+
+Defines `PETAL_SIZE_MAX` as `32 * 1024`.
+- `PETAL_SIZE_MAX` limits teh size of a petal which makes multiple O(n) in petal searches O(1) as it is now bounded.
+
+### `storage/`
+
+A storage is something that stores the actual text, the text is actually stored in storages which are referenced by the trees.
+
+#### `storage.h`
+
+Defines the virtual `Storage` class.
+It has the methods:
+- `const char *read(uint64_t pos)`: reads text from position `pos` and returns a pointer to it.
+- `uint64_t length()`: returns the length of the storage.
+- `void retain() / release()`: Methods to help with refcounted storages.
+
+#### `original.h`
+
+Defines the `Original` type of storage.
+This is a refcounted storage.
+
+It has the fields:
+- `atomic_uint64_t refs{0}`: refcount
+- `const char *buf`: pointer to the actual text.
+- `uint64_t len`
+- `int fd = -1`: the file descriptor of teh undelying disk storage.
+
+It adds the method `initialize` over the base class.
+
+`src/vase/storage/original.cc`.
+
+The constructor uses `mkstemp` to make a temp file, then unlinks it to hide it from the fs but keeps the fd alive.
+
+`initialize` then `mmap`s the fd into a non modifyable pointer managed by the kernel then closes the fd itself.
+- This is what gives us a pointer to the file contents that the kernel can load and evict from memory as needed, and therefore if we have say a 500MB file loaded, but the cursor is arount 200MB and the user is only editing a couple lines around that, the rest of the file will not be using your memory, it might be loaded but if needed the kernel can evict it.
+
+The call site fills the fd before calling initialze, it cannot be modified after that.
+
+#### `append.h`
+
+Defines the `Append` type of storage.
+This is not actually refcounted, it is to be owned by the application just once and reused all throughout.
+It contains the actively typed stuff.
+
+It has the fields:
+- `const char *buf`: pointer to the actual text.
+- `uint64_t allocated_capacity`: the amount of bytees that can be written to it without needing to increase the size.
+- `uint64_t current_size`: Stores the size of actual text stored in it. (the cursor)
+- `int fd = -1`: the file descriptor of the underlying disk storage.
+
+It has the methods `append` (with 2 overloads) and private `grow` over the base class.
+`retain` and `release` do nothing.
+
+`src/vase/storage/append.cc`.
+
+The constructor uses `mkstemp` an `unlink` similar to the original storage.
+It then `ftruncate`s the file to `2^30` bytes or 1GiB this makes writing 1gb to the file possible but does'nt neccasarily use up 1gb on the disk.
+But when `mmap`ing we set `PROT_READ | PROT_WRITE` and `MAP_SHARED` to be able to write edits to disk.
+
+`grow` works by doubling the capacity `ftruncat`ing the fd to the new capacity and then on `linux` it uses `mremap` to remap to the new file size, but otherwise we `munmap` and `mmap` into the new size.
+
+The append methods append text into the buffer (either a single char or char * + len), they may grow the storage size. (the char*+len version uses memcpy).
+
+### `shard.h`
+
+Defines the actual peice tree.
+
+The tree is a polymorhic set of classes.
+
+The base class `Shard` has:
+- `enum Kind : uint8_t kind`: Branch or Petal.
+- `uint16_t height`: the tree height (for avl balancing.)
+- `atomic_uint32_t refs`: the refcount.
+- `uint64_t length`: the length in bytes of this (sub)tree.
+- `uint64_t lines`: the number of `\n` in this subtree.
+- It starts refcount at 1.
+
+The `Branch` class adds:
+- `Shard *left/right` the subtrees.
+- its constructor takes l, r and sets length/lines `(l->length + r->length)`
+- and height `1 + std::max(l->height, r->height)`
+
+The `Petal` (leaf) class adds:
+- `Storage *` a pointer to the storage used.
+- `uint64_t pos` the position in the storage its text starts at.
+- it takes `(uint64_t length, uint64_t lines, Storage *source, uint64_t pos)`
+- it retains `source`. (usefull for refcounted sotrages.)
+
+A `nullptr` `Shard*` is an empty peice of text (i.e. valid).
+
+`src/internal/vase/shard.cc`: defines a set of static function on the Shard class. (All the applications of it.)
+
+the operations methods are:
+- `retain/release` retain/releases them, if freeing a leaf it also releases the storage and for branches it releases both subtrees. nullptr's are ignored.
+- `balance/rotate_(right/left) and height/balance factor` are for doing simple avl balancing operations.
+- `concat` borrows 2 pointers to `Shard` and returns an owned Shard*.
+- `split` borrows a `Shard` and returns a `pair<Shard*, Shard*>` of 2 owned shards.
+- `merge_leaves` works similar to concat but it tries to merge the middle bit if they have their physical representation in order. for example if i have a shard `hell` and i type the letter `o` and because i'd been typing in order the Append storage will have text `hello` we can merge them into a single petal.
+- `append` similar to concat, but uses merge_leaves, useful for small appends like when typing.
+- `build` takes a pointer to an array of `Shard*` and start and end then makes a single avl balanced `Shard*` out of it it is generally faster than calling concat on each peice when we have many.
+
+Then for building a Shard* in the first place we have:
+- `from_command(const char *cmd)` runs the \0 terminated command string and reads its STDOUT and returns an owned Shard*.
+- `from_file(const std::filesystem::path &path)` reads the file at path.
+- `from_string(const char *data, uint64_t len)` loads the string given into a new storage, (normally inserting text can work by inserting into the append storage but this function loads it into a `OriginalStorage` object.).
+These methods all clip the final newline if it exists.
+And they also create a new `OriginalStorage` object.
+
+### `vase.h`
+
+### `iterators/`
+
+#### `line.h`
+
+#### `petal.h`

Makefile

@@ -36,7 +36,7 @@ CFLAGS_RELEASE :=\
 	-fomit-frame-pointer -DNDEBUG -s \
 	-I./include -I./libs/unicode_width
 
-CFLAGS_DEBUG += $(PCRE_CFLAGS) $(LIBGRAPHEME_CFLAGS) $(MRUBY_CFLAGS) $(C_SANITIZER)
+CFLAGS_DEBUG += $(PCRE_CFLAGS) $(LIBGRAPHEME_CFLAGS) $(MRUBY_CFLAGS)
 CFLAGS_RELEASE += $(PCRE_CFLAGS) $(LIBGRAPHEME_CFLAGS) $(MRUBY_CFLAGS)
 
 UNICODE_SRC := $(wildcard libs/unicode_width/*.c)

README.md

@@ -40,21 +40,8 @@ An ed implementation (mostly posix compliant) but with:
 - Internal buffer:
     - Super fast and memory efficient buffer implementation done.
     - Loading from files/subshell commands done.
-- Most of the posix ed commands except regex ones done.
-
-### Modules
-
-#### `Vase`
-
-Vase is a avl piece tree like structure which handles loading, insertion, erasure, regex searching, regex replacing etc.
-<br/>
-done.
-
-#### `hl`
-
-`hl` is a stateful super fast syntax highlighter.
-<br/>
-mostly done.
+- Syntax highlighter and block parser system done.
+- All ed addressing modes and block addressing done (also `%`).
 
 #### `lsp`
 
@@ -69,5 +56,7 @@ It should support:
 - Error handling.
 - And more.
 
-Not done yet.
+### TODO:
 
+- Make "g" command work.
+- properly handle escapes for %q ' etc in ruby parser (rn everything is escapable.)

flake.nix

@@ -70,9 +70,8 @@
 
         buildPhase = ''
           make \
-            MRBC=${mruby}/bin/mrbc \
-            MRUBY_CFLAGS=-I${mruby}/include \
-            MRUBY_LIBS=-L${mruby}/lib -lmruby
+            MRUBY_CFLAGS="-I${mruby}/include" \
+            MRUBY_LIBS="-L${mruby}/lib -lmruby"
         '';
 
         installPhase = ''
@@ -110,7 +109,6 @@
           export CC="ccache $CC"
           export CXX="ccache $CXX"
 
-          export MRBC=${mruby}/bin/mrbc
           export MRUBY_CFLAGS=-I${mruby}/include
           export MRUBY_LIBS="-L${mruby}/lib -lmruby"
         '';

include/bed.h

@@ -2,34 +2,57 @@
 
 #include "definitions.h"
 #include "internal/buffer/buffer.h"
-#include "internal/commands/commands.h"
-#include "internal/commands/suffixes.h"
+#include "internal/functions/functions.h"
+#include "internal/functions/suffixes.h"
+#include "internal/io/io.h"
 #include "internal/marks/marks.h"
+#include "internal/scripting/ruby.h"
 #include "internal/theme/theme.h"
+#include "internal/ui/command.h"
+#include "internal/ui/text_mode.h"
 #include "pch.h"
 
 namespace bed {
 struct BEd {
-  internal::trie::Trie<internal::commands::Command> commands;
-  internal::commands::Command no_op;
-  internal::commands::Command eof_op;
-  std::array<std::optional<internal::commands::Suffix>, 26> suffixes;
+  internal::scripting::RubyState mrb;
+  internal::trie::Trie<internal::functions::Function> functions;
+  internal::functions::Function no_op;
+  internal::functions::Function eof_op;
+  std::array<std::optional<internal::functions::Suffix>, 26> suffixes;
   internal::theme::Theme theme;
-  std::unordered_map<std::string, internal::syntax::Language> languages;
+  std::unordered_map<std::string, internal::syntax::Language *> languages;
+  internal::io::IO io;
+  internal::vase::AppendStorage append{"/tmp"};
+  std::unordered_map<std::string, internal::buffer::Buffer *> buffers;
 
   bool help_mode = false;
-  std::string last_help = "";
   bool prompt_mode = true;
   std::function<std::string(BEd &)> prompt = nullptr;
   bool suppress_mode = false;
+  bool color_mode = false;
+  bool temporary_current = false;
+  std::string last_help = "";
   std::string last_regex = "";
+  std::string last_symbol = "";
+  std::string last_replacement = "";
+  std::string last_shell = "";
 
-  std::unordered_map<std::string, internal::buffer::Buffer *> buffers;
-  internal::buffer::Buffer *active;
+  internal::buffer::Range prev_1;
+  internal::buffer::Range prev_2;
+  internal::marks::MarksEngine marks;
 
   BEd(std::vector<std::string> args);
   ~BEd();
+
+  internal::buffer::Buffer &buffer(const std::string &);
+  internal::buffer::Line &current();
+  internal::buffer::Range &prev();
+  void mark(uint8_t, internal::buffer::Line);
+
+  void print_help();
   void handle(std::string_view cmd, bool eof);
   void run();
+  void suffix_handle(char s);
+  bool escape_command(std::string &cmd, std::string_view filename);
 };
 } // namespace bed

include/definitions.h

@@ -4,6 +4,8 @@
 #include "pch.h"
 
 namespace bed {
+struct BEd;
+
 struct fatal_error : std::runtime_error {
   uint8_t code;
   fatal_error(std::string msg, uint8_t code)
@@ -13,6 +15,4 @@ struct fatal_error : std::runtime_error {
 struct ed_error : std::runtime_error {
   ed_error(std::string msg) : std::runtime_error(msg) {}
 };
-
-struct BEd;
 } // namespace bed

include/internal/address/address.h

@@ -1,115 +0,0 @@
-#pragma once
-
-#include "definitions.h"
-#include "internal/generic.h"
-#include "pch.h"
-
-namespace bed::internal::address {
-struct address_error : ed_error {
-  address_error(const char *msg) : ed_error(msg) {}
-};
-
-struct Address {
-  // % refers to range of whatever was resulted from the previous modification.
-  // it expands in theory to a Num,Num and so can be followed by chaining more adresses the ed way.
-  // this is handled and resolved by the handle function,
-  // the constuctor and resolve etc. are also only called in the handle function,
-  // i.e. handle is the only public facing API from this namespace & class for now.
-  //
-  // in case of any issue an instance of address_error(const char *) is thrown.
-
-  struct Result {
-    std::array<uint64_t, 2> data{};
-    uint8_t size{0};
-    std::span<const uint64_t> span(uint8_t max = UINT8_MAX) const {
-      return {data.data(), std::min(size, max)};
-    }
-  };
-
-  struct None {};
-
-  // Posix ed types of addressing.
-  struct Current {}; // .
-
-  struct Last {}; // $
-
-  struct Number { // n
-    uint64_t i;
-  };
-
-  struct Mark { // 'm
-    char m;
-  };
-
-  struct RegexLine { // /re/ or ?re?
-    internal::Direction dir;
-    std::string re;
-  };
-
-  // BEd Extended types of addressing.
-  struct Regex {             // &/re/ or &?re?
-    internal::Direction dir; // returns next/previous line containing the regex
-    std::string re;          // (not only if it matches full line)
-  };
-
-  struct Diagnostic { // #n# for diagnostic number n. (From lsp.)
-    uint16_t n;
-  };
-
-  struct DiagnosticNext { // ^ or % for previous/next diagnostic
-    internal::Direction dir;
-  };
-
-  struct SymbolDefinition { // <sym> goto symbol definition. (From lsp or using internal language parsers)
-    std::string sym;
-  };
-
-  struct SymbolReference { // <sym:n> goto nth symbol reference
-    uint16_t n;
-    std::string sym;
-  };
-
-  struct SymbolReferenceNext { // >sym> or <sym<
-    internal::Direction dir;   // goto next or previous symbol reference
-    std::string sym;
-  };
-
-  struct Block { // [ or ] goto start/end of containing block.
-    internal::Direction dir;
-  };
-
-  struct Scripted {   // (function_name:arguments)
-    std::string func; // Calls ruby mapping with name giving the argument as string.
-    std::string arg;  // resolves to line number returned by function (or throws error).
-                      // The mruby runtime also has the full context of the file and extentions etc.
-  };
-
-  std::variant<
-    std::monostate,
-    None,
-    Current,
-    Last,
-    Number,
-    Mark,
-    RegexLine,
-    Regex,
-    Diagnostic,
-    DiagnosticNext,
-    SymbolDefinition,
-    SymbolReference,
-    SymbolReferenceNext,
-    Block,
-    Scripted>
-    base{};
-
-  // they can then be followed by any number of +n or -n etc accumulating in.
-  int64_t offset = 0;
-
-  Address(std::string &cmd, uint64_t &i);
-  Address() = default;
-
-  uint64_t resolve(BEd &ctx);
-
-  static Result handle(BEd &ctx, std::string &cmd, uint64_t &i);
-};
-} // namespace bed::internal::address

include/internal/buffer/buffer.h

@@ -1,39 +1,5 @@
 #pragma once
 
-#include "definitions.h"
-#include "internal/marks/marks.h"
-#include "internal/syntax/parser.h"
-#include "internal/syntax/ruby/parser.h"
-#include "internal/theme/theme.h"
-#include "pch.h"
-
-namespace bed::internal::buffer {
-struct Buffer {
-  vase::Vase vase;
-  marks::MarksEngine marks;
-  std::string language;
-  std::optional<syntax::Parser> parser;
-  uint64_t line = 0;
-  bool modified;
-  std::filesystem::path save_path = "";
-  struct {
-    uint64_t start{0};
-    uint64_t end{0};
-  } prev_range;
-
-  Buffer();
-  Buffer(std::string command);
-  Buffer(std::filesystem::path path);
-
-  ~Buffer() = default;
-
-  void load(std::string command);
-  void load(std::filesystem::path path);
-  void jump(uint64_t n_line);
-  void join(uint64_t start_line, uint64_t end_line);
-  void remove(uint64_t start_line, uint64_t end_line);
-  void append(std::string text, uint64_t line);
-  void print(BEd &ctx, uint64_t start_line, uint64_t end_line);
-  std::string list_string(std::string_view s);
-};
-} // namespace bed::internal::buffer
+#include "./types/clip.h"
+#include "./types/generic.h"
+#include "decl.h"

include/internal/buffer/decl.h

@@ -0,0 +1,148 @@
+#pragma once
+
+#include "definitions.h"
+#include "internal/syntax/parser.h"
+#include "internal/syntax/ruby/parser.h"
+#include "internal/theme/theme.h"
+#include "pch.h"
+
+namespace bed::internal::buffer {
+struct Buffer {
+  enum struct Kind : uint8_t {
+    Generic,
+    History,
+    Clip,
+    Cancel,
+    Shell,
+  } kind;
+
+  enum : uint8_t {
+    Special,
+    Unmodified,
+    Modified,
+    Warned
+  } state;
+
+  std::string name;
+
+  explicit Buffer(std::string name, Kind kind)
+      : kind(kind), state(Unmodified), name(std::move(name)) {};
+  virtual ~Buffer() = default;
+
+  virtual bool waste() = 0;
+  virtual uint64_t lines() = 0;
+  virtual uint64_t bytes() = 0;
+  virtual void set_filename(std::filesystem::path path) = 0;
+  virtual std::filesystem::path filename() = 0;
+  virtual void saved_hook() = 0;
+  virtual void load(BEd &ctx, vase::Shard *text) = 0;
+  virtual vase::Shard *copy(uint64_t start_line, uint64_t end_line) = 0;
+  virtual void substitute(
+    BEd &ctx, uint64_t start_line, uint64_t end_line,
+    std::string &regex, std::string &replacement, std::string &options
+  ) = 0;
+  virtual void join(BEd &ctx, uint64_t start_line, uint64_t end_line) = 0;
+  virtual void remove(BEd &ctx, uint64_t start_line, uint64_t end_line) = 0;
+  virtual void append(BEd &ctx, vase::Shard *text, uint64_t line) = 0;
+  virtual void replace(BEd &ctx, vase::Shard *text, uint64_t start_line, uint64_t end_line) = 0;
+  virtual void print(BEd &ctx, uint64_t start_line, uint64_t end_line) = 0;
+  virtual void number_print(BEd &ctx, uint64_t start_line, uint64_t end_line) = 0;
+  virtual void list_print(BEd &ctx, uint64_t start_line, uint64_t end_line) = 0;
+  virtual uint64_t find_next(std::string_view pattern, uint64_t start) = 0;
+  virtual uint64_t find_prev(std::string_view pattern, uint64_t start) = 0;
+  virtual uint64_t next_closing(uint64_t start) = 0;
+  virtual uint64_t prev_closing(uint64_t start) = 0;
+};
+
+struct Line {
+  std::string buffername;
+  uint64_t number;
+};
+
+struct Range {
+  std::string buffername;
+  uint64_t start;
+  uint64_t end;
+
+  explicit Range(const Line &a, const Line &b) {
+    if (a.buffername != b.buffername)
+      throw ed_error("Invalid range.");
+    if (a.number > b.number)
+      throw ed_error("Invalid range.");
+    buffername = a.buffername;
+    start = a.number;
+    end = b.number;
+  };
+
+  explicit Range(std::string buffername, uint64_t start, uint64_t end)
+      : buffername(buffername), start(start), end(end) {
+    if (start > end)
+      throw ed_error("Invalid range.");
+  };
+
+  explicit Range() : buffername("default"), start(0), end(0) {};
+};
+
+using Address = std::variant<
+  std::string,
+  buffer::Range,
+  buffer::Line>;
+
+inline static std::string list_string(std::string_view s) {
+  uint32_t width = 80;
+  winsize ws{};
+  if (ioctl(STDOUT_FILENO, TIOCGWINSZ, &ws) == 0 && ws.ws_col != 0)
+    width = ws.ws_col;
+  std::string out;
+  out.reserve(s.size());
+  const uint32_t max_width = width > 1 ? width - 1 : 1;
+  uint32_t column = 0;
+  auto append = [&](std::string_view text) {
+    if (column + text.size() > max_width) {
+      out += "\\\n";
+      column = 0;
+    }
+    out += text;
+    column += text.size();
+  };
+  for (unsigned char c : s) {
+    switch (c) {
+    case '\\':
+      append("\\\\");
+      break;
+    case '$':
+      append("\\$");
+      break;
+    case '\a':
+      append("\\a");
+      break;
+    case '\b':
+      append("\\b");
+      break;
+    case '\f':
+      append("\\f");
+      break;
+    case '\r':
+      append("\\r");
+      break;
+    case '\t':
+      append("\\t");
+      break;
+    case '\v':
+      append("\\v");
+      break;
+    default:
+      if (!std::isprint(c)) {
+        char buf[5];
+        std::snprintf(buf, sizeof(buf), "\\%03o", c);
+        append(buf);
+      } else {
+        append(std::string_view((const char *)&c, 1));
+      }
+      break;
+    }
+  }
+  out += '$';
+  return out;
+}
+} // namespace bed::internal::buffer

include/internal/buffer/types/clip.h

@@ -0,0 +1,36 @@
+#pragma once
+
+#include "../decl.h"
+
+namespace bed::internal::buffer {
+struct ClipBuffer : Buffer {
+  ClipBuffer(std::string name)
+      : Buffer(name, Kind::Clip) {};
+  ~ClipBuffer();
+
+  void clip_write(vase::Shard *text);
+  bool waste() override;
+  void saved_hook() override;
+  uint64_t lines() override;
+  uint64_t bytes() override;
+  void load(BEd &ctx, vase::Shard *text) override;
+  void set_filename(std::filesystem::path path) override;
+  std::filesystem::path filename() override;
+  vase::Shard *copy(uint64_t start_line, uint64_t end_line) override;
+  void substitute(
+    BEd &ctx, uint64_t start_line, uint64_t end_line,
+    std::string &regex, std::string &replacement, std::string &options
+  ) override;
+  void join(BEd &ctx, uint64_t start_line, uint64_t end_line) override;
+  void remove(BEd &ctx, uint64_t start_line, uint64_t end_line) override;
+  void append(BEd &ctx, vase::Shard *text, uint64_t line) override;
+  void replace(BEd &ctx, vase::Shard *text, uint64_t start_line, uint64_t end_line) override;
+  void print(BEd &ctx, uint64_t start_line, uint64_t end_line) override;
+  void number_print(BEd &ctx, uint64_t start_line, uint64_t end_line) override;
+  void list_print(BEd &ctx, uint64_t start_line, uint64_t end_line) override;
+  uint64_t next_closing(uint64_t start) override;
+  uint64_t prev_closing(uint64_t start) override;
+  uint64_t find_next(std::string_view pattern, uint64_t start) override;
+  uint64_t find_prev(std::string_view pattern, uint64_t start) override;
+};
+} // namespace bed::internal::buffer

include/internal/buffer/types/generic.h

@@ -0,0 +1,48 @@
+#pragma once
+
+#include "../decl.h"
+#include "readonly.h"
+#include "shard.h"
+
+namespace bed::internal::buffer {
+struct HistoryItem {
+  syntax::ParserSnapshot parse_state;
+  vase::Shard *text;
+  std::chrono::system_clock::time_point timestamp;
+  std::string summary;
+};
+
+struct GenericBuffer : ShardBuffer {
+  uint64_t base_version{0};
+  std::chrono::system_clock::time_point timestamp{std::chrono::system_clock::now()};
+  std::string action{"Created buffer."};
+  std::filesystem::path save_path{};
+  std::vector<HistoryItem> undo_stack;
+  std::vector<HistoryItem> redo_stack;
+
+  GenericBuffer(std::string name)
+      : ShardBuffer(name, nullptr, nullptr, Kind::Generic) {}
+  ~GenericBuffer();
+
+  void language(BEd &ctx, std::string name);
+  void list_history(BEd &ctx);
+  ReadonlyBuffer *get_history(uint64_t version);
+  void snapshot(std::string action);
+  bool undo(BEd &ctx);
+  bool redo(BEd &ctx);
+  uint64_t prune(int);
+  void saved_hook() override;
+  bool waste() override;
+  void load(BEd &ctx, vase::Shard *text) override;
+  void set_filename(std::filesystem::path path) override;
+  std::filesystem::path filename() override;
+  void substitute(
+    BEd &ctx, uint64_t start_line, uint64_t end_line,
+    std::string &regex, std::string &replacement, std::string &options
+  ) override;
+  void join(BEd &ctx, uint64_t start_line, uint64_t end_line) override;
+  void remove(BEd &ctx, uint64_t start_line, uint64_t end_line) override;
+  void append(BEd &ctx, vase::Shard *text, uint64_t line) override;
+  void replace(BEd &ctx, vase::Shard *text, uint64_t start_line, uint64_t end_line) override;
+};
+} // namespace bed::internal::buffer

include/internal/buffer/types/readonly.h

@@ -0,0 +1,42 @@
+#pragma once
+
+#include "../decl.h"
+#include "shard.h"
+
+namespace bed::internal::buffer {
+struct ReadonlyBuffer : ShardBuffer {
+  bool useless = true;
+
+  ReadonlyBuffer(
+    std::string name, vase::Shard *root,
+    const syntax::ParserSnapshot &snapshot
+  ) : ShardBuffer(std::move(name), root, snapshot, Kind::History) {}
+
+  void saved_hook() override {}
+  bool waste() override {
+    return useless;
+  }
+  void load(BEd &, vase::Shard *) override {
+    throw ed_error("This buffer is read-only.");
+  }
+  void set_filename(std::filesystem::path) override {}
+  std::filesystem::path filename() override {
+    return {};
+  }
+  void substitute(BEd &, uint64_t, uint64_t, std::string &, std::string &, std::string &) override {
+    throw ed_error("This buffer is read-only.");
+  }
+  void join(BEd &, uint64_t, uint64_t) override {
+    throw ed_error("This buffer is read-only.");
+  }
+  void remove(BEd &, uint64_t, uint64_t) override {
+    throw ed_error("This buffer is read-only.");
+  }
+  void append(BEd &, vase::Shard *, uint64_t) override {
+    throw ed_error("This buffer is read-only.");
+  }
+  void replace(BEd &, vase::Shard *, uint64_t, uint64_t) override {
+    throw ed_error("This buffer is read-only.");
+  }
+};
+} // namespace bed::internal::buffer

include/internal/buffer/types/shard.h

@@ -0,0 +1,42 @@
+#pragma once
+
+#include "../decl.h"
+
+namespace bed::internal::buffer {
+struct ShardBuffer : Buffer {
+  vase::Shard *root;
+  syntax::ParserSnapshot parse{};
+
+  ShardBuffer(std::string name, vase::Shard *root, syntax::Language *language, Kind kind)
+      : Buffer(std::move(name), kind), root(root) {
+    vase::Shard::retain(root);
+    if (language)
+      parse = syntax::make_parser(root, lines(), language);
+  }
+  ShardBuffer(
+    std::string name,
+    vase::Shard *root,
+    const syntax::ParserSnapshot &snapshot,
+    Kind kind
+  ) : Buffer(std::move(name), kind),
+      root(root),
+      parse(syntax::retain(snapshot)) {
+    vase::Shard::retain(root);
+  }
+  ~ShardBuffer() {
+    vase::Shard::release(root);
+    syntax::release(parse);
+  }
+
+  uint64_t lines() override;
+  uint64_t bytes() override;
+  vase::Shard *copy(uint64_t start_line, uint64_t end_line) override;
+  void print(BEd &ctx, uint64_t start_line, uint64_t end_line) override;
+  void number_print(BEd &ctx, uint64_t start_line, uint64_t end_line) override;
+  void list_print(BEd &ctx, uint64_t start_line, uint64_t end_line) override;
+  uint64_t next_closing(uint64_t start) override;
+  uint64_t prev_closing(uint64_t start) override;
+  uint64_t find_next(std::string_view pattern, uint64_t start) override;
+  uint64_t find_prev(std::string_view pattern, uint64_t start) override;
+};
+} // namespace bed::internal::buffer

include/internal/commands/commands.h

@@ -1,30 +0,0 @@
-#pragma once
-
-#include "definitions.h"
-#include "internal/trie/trie.h"
-#include "pch.h"
-
-namespace bed::internal::commands {
-struct Command {
-  enum struct AddressMode : uint8_t {
-    None,
-    Single,
-    Range
-  } address_mode;
-
-  enum struct SuffixKind : uint8_t {
-    None,
-    Suffix,
-    Argument,
-    Continuation
-  } suffix;
-
-  std::string desc;
-
-  bool accept_zero;
-
-  void (*handle)(BEd &, std::span<const uint64_t>, std::string_view);
-
-  static void register_posix(BEd &ctx);
-};
-} // namespace bed::internal::commands

include/internal/commands/suffixes.h

@@ -1,13 +0,0 @@
-#pragma once
-
-#include "definitions.h"
-#include "pch.h"
-
-namespace bed::internal::commands {
-struct Suffix {
-  std::string desc;
-  void (*handle)(BEd &);
-
-  static void register_suffixes(BEd &ctx);
-};
-} // namespace bed::internal::commands

include/internal/functions/functions.h

@@ -0,0 +1,86 @@
+#pragma once
+
+#include "definitions.h"
+#include "internal/buffer/buffer.h"
+#include "internal/trie/trie.h"
+#include "pch.h"
+
+namespace bed::internal::functions {
+struct Function {
+  struct GlobalArg {
+    char delim;
+    std::string str;
+  };
+  struct RegexArg {
+    std::string expression;
+    std::string replacement;
+    std::string options;
+  };
+  struct ShellArg {
+    std::string cmd;
+  };
+  struct RubyArg {
+    std::string cmd;
+  };
+  using Argument = std::variant<
+    std::monostate,
+    GlobalArg,
+    RegexArg,
+    ShellArg,
+    RubyArg,
+    std::string,
+    std::filesystem::path,
+    int64_t,
+    char,
+    buffer::Range,
+    buffer::Line>;
+
+  enum struct AddressKind {
+    None,
+    Line,
+    Range
+  } address_kind;
+
+  enum struct ArgumentKind {
+    None,
+    Regex,
+    Shell,
+    Ruby,
+    Any,
+    File,
+    Number,
+    Mark,
+    Range,
+    Line,
+    Global
+  } argument_kind;
+
+  enum struct InputMode {
+    None,
+    Text,
+    Interactive,
+    CommandList
+  } input_mode;
+
+  std::string desc;
+  std::string default_address;
+  bool accept_zero;
+
+  std::function<
+    std::tuple<vase::Shard *, syntax::Language *, void *>(
+      BEd &ctx, const buffer::Address &addr, const Argument &arg
+    )>
+    pre_text_mode;
+
+  std::function<
+    void(
+      BEd &ctx, const buffer::Address &addr,
+      vase::Shard *text, const Argument &arg,
+      std::vector<buffer::Line> *marked
+    )>
+    handle;
+
+  static void register_posix(BEd &ctx);
+  static void register_extented(BEd &ctx);
+};
+} // namespace bed::internal::functions

include/internal/functions/suffixes.h

@@ -0,0 +1,14 @@
+#pragma once
+
+#include "definitions.h"
+#include "internal/buffer/buffer.h"
+#include "pch.h"
+
+namespace bed::internal::functions {
+struct Suffix {
+  std::string desc;
+  std::function<void(BEd &)> handle;
+
+  static void register_suffixes(BEd &ctx);
+};
+} // namespace bed::internal::functions

include/internal/generic.h

@@ -7,4 +7,20 @@ enum struct Direction : uint8_t {
   Forward,
   Backward
 };
+
+inline static bool write_all(int fd, const void *data, size_t len) {
+  const char *p = (const char *)data;
+  while (len > 0) {
+    ssize_t n = write(fd, p, len);
+    if (n > 0) {
+      p += n;
+      len -= (size_t)n;
+      continue;
+    }
+    if (n == -1 && errno == EINTR)
+      continue;
+    return false;
+  }
+  return true;
 }
+} // namespace bed::internal

include/internal/io/io.h

@@ -0,0 +1,107 @@
+#pragma once
+
+#include "definitions.h"
+#include "pch.h"
+#include "tokens.h"
+
+namespace bed::internal::io {
+struct KeyEvent {
+  enum struct ReadResult {
+    SUCCESS,
+    EOF_,
+    RESIZE
+  };
+  enum struct KeyType {
+    EOF_,
+    CHAR,
+    SPECIAL,
+    MOUSE,
+    PASTE,
+    RESIZE
+  };
+  enum struct SpecialKey {
+    UP,
+    DOWN,
+    LEFT,
+    RIGHT,
+    DELETE,
+    UNKNOWN
+  };
+  enum struct Modifier {
+    NONE,
+    SHIFT,
+    ALT,
+    CTRL,
+    CTRL_ALT
+  };
+  enum struct MouseState {
+    PRESS,
+    RELEASE
+  };
+
+  KeyType type = KeyType::EOF_;
+  std::string text;
+
+  SpecialKey special_key = SpecialKey::UNKNOWN;
+  Modifier modifier = Modifier::NONE;
+
+  MouseState mouse_state = MouseState::PRESS;
+  uint16_t mouse_x = 0;
+  uint16_t mouse_y = 0;
+};
+
+struct IO {
+  static termios orig_termios;
+  static termios raw_termios;
+  static bool cleaned;
+  static void cleanup();
+  static void enable_raw();
+  static volatile std::atomic_bool resized;
+  static void handle_sigwinch(int);
+  BEd &bed;
+
+  static enum struct Mode {
+    PIPE,
+    TERMINAL
+  } mode;
+
+  std::string pipe_input;
+  std::deque<char> input_queue;
+
+  IO(BEd &);
+  ~IO();
+
+  IO(const IO &) = delete;
+  IO &operator=(const IO &) = delete;
+
+  bool interactive() const {
+    return mode == Mode::TERMINAL;
+  }
+  void apply(const io::Token::Kind &t);
+  void reset();
+  void enable_mouse();
+  void disable_mouse();
+
+  std::pair<uint16_t, uint16_t> terminal_size();
+  std::pair<uint16_t, uint16_t> cursor_position();
+  void move_cursor(uint16_t row, uint16_t col);
+
+  std::pair<std::string, bool> read_pipe();
+
+  KeyEvent read_key();
+  void write(const char *, uint64_t);
+  void write(std::string_view);
+  void write_line(std::string_view);
+  void run_pty(const std::string &);
+
+  KeyEvent::ReadResult get_next_byte(char &out);
+  void enqueue_bytes(const std::string &bytes);
+  static int utf8_seq_len(uint8_t byte);
+
+  KeyEvent::ReadResult read_next_unit(std::string &out);
+  KeyEvent::ReadResult read_bracketed_paste(std::string &out);
+
+  KeyEvent parse_mouse(const std::string &buf);
+  KeyEvent parse_escape(const std::string &buf);
+};
+} // namespace bed::internal::io

include/internal/io/tokens.h

@@ -0,0 +1,99 @@
+#pragma once
+
+#include "definitions.h"
+#include "pch.h"
+
+namespace bed::internal::io {
+struct Token {
+  uint64_t start;
+  uint64_t end;
+  enum Kind : uint8_t {
+    TempCurrent,
+    BufferName,
+    AddressSeperator,
+    AddressSymbol,
+    Number,
+    Mark,
+    RubyFunction,
+    RubyArg,
+    Function,
+    Shell,
+    File,
+    Suffix,
+    Color1,
+    Color2,
+    Color3,
+    Color4,
+    Color5,
+    Warning,
+    Data,
+    Shebang,
+    Comment,
+    Error,
+    String,
+    Escape,
+    Interpolation,
+    Regexp,
+    True,
+    False,
+    Char,
+    Keyword,
+    KeywordOperator,
+    Operator,
+    Namespace,
+    Class,
+    Module,
+    Type,
+    Constant,
+    VariableInstance,
+    VariableGlobal,
+    Annotation,
+    Directive,
+    Label,
+    Brace1,
+    Brace2,
+    Brace3,
+    Brace4,
+    Brace5,
+    Heading1,
+    Heading2,
+    Heading3,
+    Heading4,
+    Heading5,
+    Heading6,
+    Blockquote,
+    List,
+    ListItem,
+    Code,
+    LanguageName,
+    LinkLabel,
+    ImageLabel,
+    Link,
+    Table,
+    TableHeader,
+    Italic,
+    Bold,
+    Underline,
+    Strikethrough,
+    HorizontalRule,
+    Tag,
+    Attribute,
+    CheckDone,
+    CheckNotDone,
+    Count
+  } type;
+};
+
+struct Highlight {
+  enum : uint8_t {
+    None = 0,
+    Bold = 1 << 0,
+    Italic = 1 << 1,
+    Strikethrough = 1 << 2,
+    Underline = 1 << 3,
+  };
+  uint32_t fg;
+  uint32_t bg;
+  uint8_t flags;
+};
+} // namespace bed::internal::io

include/internal/marks/marks.h

@@ -1,7 +1,60 @@
 #pragma once
 
+#include "internal/buffer/buffer.h"
 #include "pch.h"
 
 namespace bed::internal::marks {
-struct MarksEngine {};
+struct MarksEngine {
+  buffer::Line marks[256];
+
+  MarksEngine() {
+    for (auto &m : marks)
+      m = {"", UINT64_MAX};
+  }
+
+  buffer::Line &get(uint8_t m) {
+    return marks[m];
+  }
+
+  void insert(std::string bufname, uint64_t start, uint64_t count) {
+    for (uint16_t i = 0; i <= UINT8_MAX; ++i) {
+      if (marks[i].buffername != bufname)
+        continue;
+      if (marks[i].number == UINT64_MAX)
+        continue;
+      if (marks[i].number > start)
+        marks[i].number += count;
+    }
+  }
+
+  void erase(std::string bufname, uint64_t start, uint64_t count) {
+    for (uint16_t i = 0; i <= UINT8_MAX; ++i) {
+      if (marks[i].buffername != bufname)
+        continue;
+      if (marks[i].number == UINT64_MAX)
+        continue;
+      if (marks[i].number >= start) {
+        if (marks[i].number < start + count)
+          marks[i].number = UINT64_MAX;
+        else
+          marks[i].number -= count;
+      }
+    }
+  }
+
+  void collapse(std::string bufname, uint64_t start, uint64_t count) {
+    for (uint16_t i = 0; i <= UINT8_MAX; ++i) {
+      if (marks[i].buffername != bufname)
+        continue;
+      if (marks[i].number == UINT64_MAX)
+        continue;
+      if (marks[i].number > start) {
+        if (marks[i].number <= start + count)
+          marks[i].number = start;
+        else
+          marks[i].number -= count;
+      }
+    }
+  }
+};
 } // namespace bed::internal::marks

include/internal/parser/parser.h

@@ -0,0 +1,117 @@
+#pragma once
+
+#include "internal/functions/functions.h"
+#include "internal/functions/suffixes.h"
+#include "internal/ui/command.h"
+#include "pch.h"
+
+namespace bed::internal::parser {
+struct AddressPromise {
+  struct None {};    //
+  struct Current {}; // .
+  struct Last {};    // $
+  struct Number {    // n
+    uint64_t i;
+  };
+  struct Mark { // 'm
+    char m;
+  };
+  struct Regex { // /re/ or ?re?
+    internal::Direction dir;
+    std::string re;
+  };
+  struct Diagnostic { // ^ or ~ for previous/next diagnostic
+    internal::Direction dir;
+  };
+  struct SymbolDefinition { // <sym> goto symbol definition. (From lsp or using internal language parsers)
+    std::string sym;
+  };
+  struct SymbolReference {   // >sym> or <sym<
+    internal::Direction dir; // goto next or previous symbol reference
+    std::string sym;
+  };
+  struct Block { // [ or ] goto start/end of containing block.
+    internal::Direction dir;
+  };
+  struct Scripted {   // {function_name:arguments}
+    std::string func; // Calls ruby mapping with name giving the argument as string.
+    std::string arg;  // resolves to line number returned by function (or throws error).
+                      // The mruby runtime also has the full context of the file and extentions etc.
+  };
+  struct LastRange {}; // % , refers to last used range
+
+  std::optional<std::string> bufname;
+  std::variant<
+    None,
+    Current,
+    Last,
+    Number,
+    Mark,
+    Regex,
+    Diagnostic,
+    SymbolDefinition,
+    SymbolReference,
+    Block,
+    Scripted,
+    LastRange>
+    base{};
+  int64_t offset = 0;
+  bool jumping{false}; // ; == jumping and , == non jumping
+  buffer::Line resolve(BEd &ctx);
+  static std::optional<buffer::Line> get_line(BEd &ctx, std::vector<AddressPromise> &);
+  static std::optional<buffer::Range> get_range(BEd &ctx, std::vector<AddressPromise> &);
+};
+
+struct Command {
+  bool temp_address{false};
+  std::vector<AddressPromise> addresses{};
+  functions::Function *function{nullptr};
+  functions::Function::Argument argument{std::monostate()};
+  std::vector<AddressPromise> argument_addresses{};
+  functions::Suffix *suffix{nullptr};
+};
+
+struct CompletionContext {
+  enum {
+    Error,
+    Valid,
+    Incomplete
+  } error;
+  // TODO: store a state of typing context to think about possible completions.
+};
+
+struct Parser {
+  BEd &bed;
+  std::string_view cmd;
+  uint16_t i;
+  Command *command;
+  std::vector<io::Token> *tokens;
+  CompletionContext *completion;
+
+  explicit Parser(
+    std::string_view cmd, BEd &bed, Command *command,
+    std::vector<io::Token> *tokens, CompletionContext *completion
+  );
+
+  void token(io::Token::Kind);
+  void end_token();
+
+  char peek(uint16_t = 0); // == \0 if at eof.
+  std::string_view peek_str(uint16_t = UINT16_MAX);
+  void advance(uint16_t = 1);
+
+  void skip_ws();
+
+  void locator(AddressPromise &);
+  int64_t offset();
+  void address(AddressPromise &addr);
+  void addresses(std::vector<AddressPromise> &addresses);
+
+  void operation();
+
+  void parse();
+  static std::vector<io::Token> get_highlight(std::string_view cmd, BEd &bed);
+  static Command get_command(std::string_view, BEd &);
+  static std::vector<AddressPromise> get_addresses(std::string_view cmd, BEd &bed);
+};
+} // namespace bed::internal::parser

include/internal/scripting/ruby.h

@@ -0,0 +1,124 @@
+#pragma once
+
+#include "definitions.h"
+#include "pch.h"
+
+namespace bed::internal::scripting {
+struct RubyState {
+  mrb_state *state = nullptr;
+  int arena = 0;
+
+  explicit RubyState(BEd *ctx) : state(mrb_open()) {
+    if (!state)
+      throw fatal_error("Failed to initialize mruby.", 1);
+    state->ud = ctx;
+    arena = mrb_gc_arena_save(state);
+  }
+
+  ~RubyState() {
+    state->ud = nullptr;
+    if (state) {
+      mrb_gc_arena_restore(state, arena);
+      mrb_full_gc(state);
+      mrb_close(state);
+    }
+  }
+
+  RubyState(const RubyState &) = delete;
+  RubyState &operator=(const RubyState &) = delete;
+};
+
+struct Block {
+  mrb_state *mrb = nullptr;
+  mrb_value proc = mrb_nil_value();
+
+  Block(mrb_state *mrb, mrb_value proc) noexcept
+      : mrb(mrb), proc(proc) {
+    mrb_gc_register(mrb, proc);
+  }
+
+  Block() noexcept = default;
+
+  ~Block() noexcept {
+    if (!mrb_nil_p(proc) && mrb)
+      mrb_gc_unregister(mrb, proc);
+  }
+
+  Block(const Block &other) noexcept
+      : mrb(other.mrb), proc(other.proc) {
+    if (mrb && !mrb_nil_p(proc))
+      mrb_gc_register(mrb, proc);
+  }
+
+  Block &operator=(const Block &other) noexcept {
+    if (this != &other) {
+      if (mrb && !mrb_nil_p(proc))
+        mrb_gc_unregister(mrb, proc);
+      mrb = other.mrb;
+      proc = other.proc;
+      if (mrb && !mrb_nil_p(proc))
+        mrb_gc_register(mrb, proc);
+    }
+    return *this;
+  }
+
+  Block(Block &&other) noexcept
+      : mrb(other.mrb), proc(other.proc) {
+    other.mrb = nullptr;
+    other.proc = mrb_nil_value();
+  }
+
+  Block &operator=(Block &&other) noexcept {
+    if (this != &other) {
+      if (mrb && !mrb_nil_p(proc))
+        mrb_gc_unregister(mrb, proc);
+      mrb = other.mrb;
+      proc = other.proc;
+      other.mrb = nullptr;
+      other.proc = mrb_nil_value();
+    }
+    return *this;
+  }
+
+  void set_proc(mrb_state *mrb_, mrb_value new_proc) {
+    if (!mrb_nil_p(proc) && mrb)
+      mrb_gc_unregister(mrb, proc);
+    mrb = mrb_;
+    proc = new_proc;
+    mrb_gc_register(mrb, proc);
+  }
+
+  mrb_value call(int argc = 0, mrb_value *argv = nullptr) const {
+    if (mrb_nil_p(proc))
+      return mrb_nil_value();
+    mrb_value result = mrb_funcall_argv(mrb, proc, mrb_intern_cstr(mrb, "call"), argc, argv);
+    if (!mrb->exc)
+      return result;
+    mrb_value exc = mrb_obj_value(mrb->exc);
+    mrb_value msg = mrb_funcall(mrb, exc, "message", 0);
+    std::string error;
+    if (mrb_string_p(msg))
+      error.assign(RSTRING_PTR(msg), RSTRING_LEN(msg));
+    auto *fatal_class = mrb_class_get(mrb, "FatalError");
+    if (mrb_obj_is_kind_of(mrb, exc, fatal_class)) {
+      mrb_value code =
+        mrb_iv_get(mrb, exc, mrb_intern_lit(mrb, "@code"));
+      mrb->exc = nullptr;
+      int c = 1;
+      if (mrb_fixnum_p(code))
+        c = mrb_fixnum(code);
+      throw fatal_error(error, c);
+    }
+    auto *ed_class = mrb_class_get(mrb, "EdError");
+    if (mrb_obj_is_kind_of(mrb, exc, ed_class)) {
+      mrb->exc = nullptr;
+      throw ed_error(error);
+    }
+    mrb->exc = nullptr;
+    throw ed_error("Ruby Exception: " + error);
+  }
+};
+
+void register_basic(BEd &ctx);
+std::string run(BEd &ctx, const std::string &str);
+}; // namespace bed::internal::scripting

include/internal/syntax/decl.h

@@ -1,138 +1,162 @@
 #pragma once
 
+#include "internal/io/tokens.h"
 #include "internal/trie/trie.h"
+#include "internal/vase/vase.h"
 #include "pch.h"
 
 namespace bed::internal::syntax {
-struct Token {
-  uint32_t start;
-  uint32_t end;
-  enum Kind : uint8_t {
-    Data,
-    Shebang,
-    Comment,
-    Error,
-    String,
-    Escape,
-    Interpolation,
-    Regexp,
-    Number,
-    True,
-    False,
-    Char,
-    Keyword,
-    KeywordOperator,
-    Operator,
-    Function,
-    Namespace,
-    Class,
-    Module,
-    Type,
-    Constant,
-    VariableInstance,
-    VariableGlobal,
-    Annotation,
-    Directive,
-    Label,
-    Brace1,
-    Brace2,
-    Brace3,
-    Brace4,
-    Brace5,
-    Heading1,
-    Heading2,
-    Heading3,
-    Heading4,
-    Heading5,
-    Heading6,
-    Blockquote,
-    List,
-    ListItem,
-    Code,
-    LanguageName,
-    LinkLabel,
-    ImageLabel,
-    Link,
-    Table,
-    TableHeader,
-    Italic,
-    Bold,
-    Underline,
-    Strikethrough,
-    HorizontalRule,
-    Tag,
-    Attribute,
-    CheckDone,
-    CheckNotDone,
-    Count
-  } type;
-};
-
 struct ParseEvent {
-  std::string_view name;
-  enum T : uint8_t {
-    Opening,
-    Closing,
-    SymbolDef,
-    Symbol
-  } ev_type;
-  uint8_t type; // type.
-
-  ParseEvent(T t) : ev_type(t) {}
-  ParseEvent(T e_t, std::string_view s, uint8_t type) : name(s), ev_type(e_t), type(type) {}
+  uint8_t closing;
+  ParseEvent(uint8_t t) : closing(t) {}
 };
 
 struct Language {
   std::function<void *()> none_state;
-  std::function<void(void **, std::string_view, bool, std::vector<Token> *, std::vector<ParseEvent> *)> parse;
+  std::function<void(
+    void **, std::string_view,
+    bool, std::vector<io::Token> *, std::vector<ParseEvent> *
+  )>
+    parse;
   std::function<void *(void *)> copy;
   std::function<bool(void *, void *)> equal;
   std::function<void(void *)> destroy;
 };
 
-struct Symbol {
-  uint32_t definition;
-  uint16_t reference_count;
-  uint8_t type;
-  uint8_t len;
-  // first chars of count len, padded to 4 bytes.
-  // then a set of references. 32bit
-  // references later as modifying at end is faster than shifting the name.
-};
-
 struct ParseState {
   static constexpr uint64_t BRANCH_BIT = 1ull << 63;
   static constexpr uint64_t LINES_MASK = ~BRANCH_BIT;
   uint64_t header;
+  uint16_t height;
+  std::atomic_uint16_t refs;
   bool is_branch() const {
     return header & BRANCH_BIT;
   }
   uint64_t lines() const {
     return header & LINES_MASK;
   }
+  explicit ParseState(bool branch, uint64_t lines, uint16_t height)
+      : height(height), refs(1) {
+    header = lines;
+    header |= branch * BRANCH_BIT;
+  };
+  static void retain(ParseState *node);
+  static void release(Language &lang, ParseState *node);
+  static ParseState *build(Language &lang, ParseState **pieces, uint64_t lo, uint64_t hi);
+  static ParseState *splice(
+    Language &lang, ParseState *node, vase::Shard *vase,
+    uint64_t line, uint64_t original, uint64_t final
+  );
+  static ParseState *concat(Language &lang, ParseState *a, ParseState *b);
+  static void *state_before(Language &lang, ParseState *root, vase::Shard *vase, uint64_t line);
 };
 
 struct ParseStateBranch : ParseState {
   ParseState *left;
   ParseState *right;
+  ParseStateBranch(ParseState *l, ParseState *r)
+      : ParseState(
+          true, l->lines() + r->lines(),
+          1 + std::max(l->height, r->height)
+        ),
+        left(l), right(r) {
+    retain(l);
+    retain(r);
+  }
 };
 
 struct ParseStateLeaf : ParseState {
-  void *state;
-  uint32_t n;
-  uint32_t cap;
-  uint16_t *blocks;
+  static constexpr uint64_t MAX_CHUNK = 512;
+  uint32_t n{0};
   static constexpr uint16_t IS_CLOSING = 0x8000;
   static constexpr uint16_t LINE_MASK = 0x7fff;
+  uint16_t *blocks{nullptr};
+  void *state;
+  ParseStateLeaf(void *state, uint64_t lines, uint32_t n, uint16_t *blocks_)
+      : ParseState(false, lines, 1), n(n), state(state) {
+    blocks = (uint16_t *)malloc(sizeof(uint16_t) * n);
+    memcpy(blocks, blocks_, sizeof(uint16_t) * n);
+  };
+};
+
+struct ParsePieceBuilder {
+  Language &lang;
+  std::vector<ParseState *> pieces;
+  std::vector<uint16_t> blocks;
+  void *piece_state{nullptr};
+  void *prev_state{nullptr};
+  uint64_t chunk_start{0};
+  uint64_t chunk_lines{0};
+  ParsePieceBuilder(Language &lang, uint64_t first_line, void *entry_state)
+      : lang(lang), chunk_start(first_line) {
+    prev_state = lang.copy(entry_state);
+  }
+  ~ParsePieceBuilder() {
+    if (prev_state)
+      lang.destroy(prev_state);
+    if (piece_state)
+      lang.destroy(piece_state);
+  }
+  ParsePieceBuilder(const ParsePieceBuilder &) = delete;
+  ParsePieceBuilder &operator=(const ParsePieceBuilder &) = delete;
+  void add(void *state, uint64_t line, const std::vector<ParseEvent> &events) {
+    if (chunk_lines == 0) {
+      chunk_start = line;
+      piece_state = lang.copy(prev_state);
+    }
+    for (const auto &ev : events) {
+      blocks.push_back(
+        (ev.closing ? ParseStateLeaf::IS_CLOSING : 0)
+        | (line - chunk_start)
+      );
+    }
+    ++chunk_lines;
+    if (prev_state)
+      lang.destroy(prev_state);
+    prev_state = lang.copy(state);
+    if (chunk_lines == ParseStateLeaf::MAX_CHUNK)
+      flush();
+  }
+  void flush() {
+    if (chunk_lines == 0)
+      return;
+    pieces.push_back(new ParseStateLeaf(
+      piece_state,
+      chunk_lines,
+      blocks.size(),
+      blocks.data()
+    ));
+    piece_state = nullptr;
+    blocks.clear();
+    chunk_lines = 0;
+  }
+  ParseState *finish() {
+    flush();
+    if (pieces.empty())
+      return nullptr;
+    ParseState *root = ParseState::build(lang, pieces.data(), 0, pieces.size());
+    pieces.clear();
+    return root;
+  }
 };
 
 struct TreeCursor {
+  Language &lang;
+  ParseState *root;
   ParseStateLeaf *leaf = nullptr;
   ParseStateBranch *stack[64];
   uint8_t depth = 0;
   bool went_left[64];
-  TreeCursor(ParseState *root, uint64_t target_line, uint64_t *relative);
+  TreeCursor(
+    Language &lang, ParseState *root,
+    uint64_t target_line, uint64_t *relative
+  );
+  ~TreeCursor();
+  TreeCursor(const TreeCursor &) = delete;
+  TreeCursor &operator=(const TreeCursor &) = delete;
   void next();
   void prev();
+  ParseState *prefix();
+  ParseState *suffix();
 };
 } // namespace bed::internal::syntax

include/internal/syntax/miniparser.h

@@ -0,0 +1,21 @@
+#pragma once
+
+#include "decl.h"
+
+namespace bed::internal::syntax {
+struct MiniParser {
+  Language ⟨
+  void *start_state;
+  std::vector<std::pair<void *, std::vector<io::Token>>> lines;
+
+  explicit MiniParser(Language &lang, vase::Shard *vase, void *initial_state);
+  ~MiniParser();
+
+  MiniParser(const MiniParser &) = delete;
+  MiniParser &operator=(const MiniParser &) = delete;
+
+  void dirty(vase::Shard *vase, uint64_t start, uint64_t count);
+  void insert(vase::Shard *vase, uint64_t start, uint64_t count);
+  void erase(vase::Shard *vase, uint64_t start, uint64_t count);
+};
+} // namespace bed::internal::syntax

include/internal/syntax/parser.h

@@ -1,49 +1,55 @@
 #pragma once
 
 #include "decl.h"
-#include "internal/vase/vase.h"
 #include "pch.h"
 
 namespace bed::internal::syntax {
-void dump_events(ParseState *node);
+struct ParserSnapshot {
+  ParseState *root = nullptr;
+  Language *lang = nullptr;
+};
 
-struct Parser {
-  static constexpr uint64_t MAX_CHUNK = 512;
+ParserSnapshot make_parser(vase::Shard *vase, uint64_t lines, Language *lang);
+ParserSnapshot retain(const ParserSnapshot &snap);
+void release(ParserSnapshot &snap);
 
-  ParseState *root;
-  Language lang;
+void *state_before(const ParserSnapshot &snap, vase::Shard *vase, uint64_t line);
+uint64_t next_closing(const ParserSnapshot &snap, uint64_t line);
+uint64_t prev_opening(const ParserSnapshot &snap, uint64_t line);
 
-  Parser(vase::Vase &, uint64_t, Language);
-  ~Parser();
-  Parser(const Parser &) = delete;
-  Parser &operator=(const Parser &) = delete;
+struct Iterator {
+  ParserSnapshot snap;
+  std::optional<vase::Iterator> it;
+  void *state;
+  uint64_t at;
+  std::vector<io::Token> tokens;
+  std::vector<ParseEvent> events;
+  Iterator(uint64_t, ParserSnapshot, vase::Shard *);
+  ~Iterator();
+  Iterator(const Iterator &) = delete;
+  Iterator &operator=(const Iterator &) = delete;
+  Iterator(Iterator &&other);
+  Iterator &operator=(Iterator &&other);
+  void next();
+};
 
-  void reset(vase::Vase &, uint64_t, Language);
-  void erase(vase::Vase &, uint64_t, uint64_t);
-  void insert(vase::Vase &, uint64_t, uint64_t);
-  void modify(vase::Vase &, uint64_t, uint64_t);
+std::optional<Iterator> get_hl(const ParserSnapshot &snap, vase::Shard *vase, uint64_t target);
 
-  uint64_t next_closing(uint64_t line);
-  uint64_t prev_opening(uint64_t line);
+void insert(ParserSnapshot &snap, vase::Shard *vase, uint64_t start, uint64_t count);
+void erase(ParserSnapshot &snap, vase::Shard *vase, uint64_t start, uint64_t count);
 
-  std::pair<ParseState *, ParseState *> split_tree(ParseState *node, uint64_t line);
-  ParseState *join_tree(ParseState *a, ParseState *b);
+struct Edit {
+  ParserSnapshot *target;
+  bool dirty = false;
+  uint64_t dirty_start = 0;
+  uint64_t dirty_end = 0;
+  int64_t edit_delta = 0;
 
-  struct Iterator {
-    Parser *p;
-    std::optional<vase::Iterator> it;
-    void *state;
-    uint64_t at;
-    std::vector<Token> tokens;
-    std::vector<ParseEvent> events;
-    Iterator(uint64_t, Parser *, vase::Vase &);
-    ~Iterator();
-    Iterator(const Iterator &) = delete;
-    Iterator &operator=(const Iterator &) = delete;
-    Iterator(Iterator &&other);
-    Iterator &operator=(Iterator &&other);
-    void next();
-  };
-  std::optional<Iterator> get_hl(vase::Vase &, uint64_t);
+  explicit Edit(ParserSnapshot &snap) : target(&snap) {}
+
+  void mark_dirty(uint64_t start, uint64_t end);
+  void insert(uint64_t start, uint64_t count);
+  void erase(uint64_t start, uint64_t count);
+  void commit(vase::Shard *vase);
 };
 } // namespace bed::internal::syntax

include/internal/syntax/ruby/decl.h

@@ -5,15 +5,6 @@
 #include "tries.h"
 
 namespace bed::internal::syntax::ruby {
-enum struct ScopeTypes : uint8_t {
-  None,
-  Comment,
-  Method,
-  Class,
-  Module,
-  Block
-};
-
 struct alignas(2) RubyState {
   struct RubyInternalState {
     uint16_t brace_level;
@@ -33,7 +24,8 @@ struct alignas(2) RubyState {
       DEF_NAME = 0b10,
       MODULE_NAME = 0b11
     };
-    static constexpr uint8_t NEWLINE = 1 << 5;
+    static constexpr uint8_t NEWLINE = 1 << 4;
+    static constexpr uint8_t ALLOW_ESCAPE = 1 << 5;
     static constexpr uint8_t ALLOW_INTERPOLATION = 1 << 6;
     static constexpr uint8_t EXPECTING_EXPRESSION = 1 << 7;
     uint8_t flags = 0;

include/internal/syntax/ruby/parser.h

@@ -104,6 +104,6 @@ struct RubyParser {
 
 void ruby_parse(
   void **v_state, std::string_view line, bool first_line,
-  std::vector<Token> *tokens, std::vector<ParseEvent> *events
+  std::vector<io::Token> *tokens, std::vector<ParseEvent> *events
 );
 } // namespace bed::internal::syntax::ruby

include/internal/syntax/ruby/tries.h

@@ -68,6 +68,11 @@ const static std::vector<std::string> builtins = {
 };
 
 const static std::vector<std::string> methods = {
+  // BEd methods.
+  "handle",
+  "register",
+  "unregister",
+  // Normal:
   "abort",
   "at_exit",
   "binding",

include/internal/theme/theme.h

@@ -5,25 +5,12 @@
 #include "pch.h"
 
 namespace bed::internal::theme {
-struct Highlight {
-  enum : uint8_t {
-    None = 0,
-    Bold = 1 << 0,
-    Italic = 1 << 1,
-    Strikethrough = 1 << 2,
-    Underline = 1 << 3,
-  };
-  uint32_t fg;
-  uint32_t bg;
-  uint8_t flags;
-};
-
 struct Theme {
-  std::array<Highlight, internal::syntax::Token::Count> hl;
+  std::array<io::Highlight, io::Token::Count> hl;
 
   Theme();
 
-  Highlight get(internal::syntax::Token token) const;
+  io::Highlight get(const io::Token::Kind &token) const;
 
   static Theme default_theme();
   static Theme from_name(std::string_view name);

include/internal/trie/trie.h

@@ -6,6 +6,10 @@ namespace bed::internal::trie {
 template <typename T = void>
 struct Trie {
   using V = std::conditional_t<std::is_void_v<T>, std::monostate, T>;
+  using SearchResult = std::conditional_t<
+    std::is_void_v<T>,
+    std::string,
+    std::pair<std::string, V &>>;
 
   struct Node {
     std::string edge;
@@ -113,8 +117,8 @@ struct Trie {
     return true;
   }
 
-  std::vector<std::string> search(std::string_view prefix) {
-    std::vector<std::string> result;
+  std::vector<SearchResult> search(std::string_view prefix) {
+    std::vector<SearchResult> result;
     Node *current = &root;
     std::string key;
     uint64_t pos = 0;
@@ -143,12 +147,17 @@ struct Trie {
   }
 
   static void collect(
-    const Node &node,
+    Node &node,
     std::string &key,
-    std::vector<std::string> &result
+    std::vector<SearchResult> &result
   ) {
-    if (node.value)
-      result.push_back(key);
+    if (node.value) {
+      if constexpr (std::is_void_v<T>) {
+        result.push_back(key);
+      } else {
+        result.emplace_back(key, *node.value);
+      }
+    }
     for (auto *child : node.children) {
       const auto old_size = key.size();
       key += child->edge;
@@ -219,6 +228,44 @@ struct Trie {
     return *current->value;
   }
 
+  V *get_ptr(std::string_view key) {
+    Node *current = &root;
+    uint64_t pos = 0;
+    while (pos < key.size()) {
+      Node *child = find_child(*current, key[pos]);
+      if (!child)
+        return nullptr;
+      const auto remaining = key.substr(pos);
+      const auto common = common_prefix(child->edge, remaining);
+      if (common != child->edge.size())
+        return nullptr;
+      pos += common;
+      current = child;
+    }
+    if (!current->value)
+      return nullptr;
+    return &*current->value;
+  }
+
+  const V *get_ptr(std::string_view key) const {
+    const Node *current = &root;
+    uint64_t pos = 0;
+    while (pos < key.size()) {
+      const Node *child = find_child(*current, key[pos]);
+      if (!child)
+        return nullptr;
+      const auto remaining = key.substr(pos);
+      const auto common = common_prefix(child->edge, remaining);
+      if (common != child->edge.size())
+        return nullptr;
+      pos += common;
+      current = child;
+    }
+    if (!current->value)
+      return nullptr;
+    return &*current->value;
+  }
+
   bool equal_char(char a, char b) const {
     if (case_sensitive)
       return a == b;

include/internal/ui/command.h

@@ -0,0 +1,23 @@
+#pragma once
+
+#include "definitions.h"
+#include "pch.h"
+
+namespace bed::internal::ui {
+struct CommandIO {
+  std::string cmd;
+  uint16_t cursor;
+  std::string prompt;
+  uint16_t start;
+  uint16_t height;
+  uint16_t term_height;
+  uint16_t term_width;
+  BEd &bed;
+
+  CommandIO(BEd &);
+  std::pair<std::string, bool> run();
+  std::pair<std::string, bool> run_pipe();
+  std::pair<std::string, bool> run_terminal();
+  void redraw();
+};
+} // namespace bed::internal::ui

include/internal/ui/text_mode.h

@@ -0,0 +1,31 @@
+#pragma once
+
+#include "internal/syntax/miniparser.h"
+#include "pch.h"
+
+namespace bed::internal::ui::text_mode {
+struct TextMode {
+  struct Row {
+    uint64_t start;
+    uint64_t length;
+  };
+  using Lines = std::vector<Row>;
+  vase::Shard *vase;
+  vase::Point cursor;
+  std::optional<syntax::MiniParser> parser;
+  std::vector<Lines> lines;
+  uint16_t start;
+  uint16_t height;
+  uint16_t term_height;
+  uint16_t term_width;
+  BEd &bed;
+
+  TextMode(BEd &, vase::Shard *, syntax::Language *, void *);
+  std::pair<vase::Shard *, bool> run();
+  std::pair<vase::Shard *, bool> run_pipe();
+  std::pair<vase::Shard *, bool> run_terminal();
+  void grow();
+  void redraw();
+  void layout_lines();
+};
+} // namespace bed::internal::ui::text_mode

include/internal/vase/buffer/original.h

@@ -1,19 +0,0 @@
-#pragma once
-
-#include "buffer.h"
-#include "pch.h"
-
-namespace bed::internal::vase {
-struct OriginalBuffer : Buffer {
-  const char *buf;
-  uint64_t len;
-  int fd = -1;
-
-  OriginalBuffer(std::filesystem::path base_dir);
-  ~OriginalBuffer();
-
-  void initialize();
-  const char *read(uint64_t pos) override;
-  uint64_t length() override;
-};
-} // namespace bed::internal::vase

include/internal/vase/shard.h

@@ -1,9 +1,9 @@
 #pragma once
 
-#include "buffer/buffer.h"
-#include "buffer/original.h"
 #include "constants.h"
 #include "pch.h"
+#include "storage/original.h"
+#include "storage/storage.h"
 
 namespace bed::internal::vase {
 struct Shard {
@@ -12,28 +12,27 @@ struct Shard {
     Petal
   } kind;
 
-  uint8_t height;
+  uint16_t height;
   std::atomic_uint32_t refs;
 
   uint64_t length;
   uint64_t lines;
 
-  Shard(Kind kind, uint64_t length, uint64_t lines, uint8_t height)
+  Shard(Kind kind, uint64_t length, uint64_t lines, uint16_t height)
       : kind(kind), height(height), refs(1), length(length), lines(lines) {};
 
   static void retain(Shard *n);
   static void release(Shard *n);
 
-  static Shard *from_file(std::filesystem::path &path, OriginalBuffer *b, bool posix_ending);
-  static Shard *from_command(const char *cmd, OriginalBuffer *o, bool posix_ending);
-  static std::vector<Shard *> from_swap(std::filesystem::path &path, OriginalBuffer *b);
+  static Shard *from_file(const std::filesystem::path &path);
+  static Shard *from_string(const char *data, uint64_t len);
+  static Shard *from_command(const char *cmd);
 
   static std::pair<Shard *, Shard *> split(Shard *n, uint64_t offset);
   static Shard *concat(Shard *a, Shard *b);
   static Shard *merge_leaves(Shard *a, Shard *b);
   static Shard *append(Shard *root, Shard *leaf);
   static Shard *build(Shard **pieces, uint64_t lo, uint64_t hi);
-  static void dump(Shard *node, int depth = 0);
 };
 
 struct Branch : Shard {
@@ -54,12 +53,13 @@ struct Branch : Shard {
 };
 
 struct Petal : Shard {
-  Buffer *source;
+  Storage *source;
   uint64_t pos;
 
-  Petal(uint64_t length, uint64_t lines, Buffer *source, uint64_t pos)
+  Petal(uint64_t length, uint64_t lines, Storage *source, uint64_t pos)
       : Shard(Kind::Petal, length, lines, 1),
-        source(source), pos(pos) {};
+        source(source), pos(pos) {
+    source->retain();
+  };
 };
-
 } // namespace bed::internal::vase

include/internal/vase/storage/append.h

@@ -1,24 +1,27 @@
 #pragma once
 
 #include "../constants.h"
-#include "buffer.h"
 #include "pch.h"
+#include "storage.h"
 
 namespace bed::internal::vase {
-struct AppendBuffer : Buffer {
+struct AppendStorage : Storage {
   char *buf = nullptr;
   uint64_t allocated_capacity = 0;
   uint64_t current_size = 0;
   int fd = -1;
 
-  AppendBuffer(std::filesystem::path base_dir);
-  ~AppendBuffer();
+  AppendStorage(std::filesystem::path base_dir);
+  ~AppendStorage();
 
   uint64_t append(const char c);
   uint64_t append(const char *text, uint64_t len);
   const char *read(uint64_t pos) override;
   uint64_t length() override;
 
+  void retain() override {}
+  void release() override {}
+
 private:
   void grow(uint64_t len);
 };

include/internal/vase/storage/original.h

@@ -0,0 +1,30 @@
+#pragma once
+
+#include "pch.h"
+#include "storage.h"
+
+namespace bed::internal::vase {
+struct OriginalStorage : Storage {
+  std::atomic_uint64_t refs{0};
+  const char *buf = nullptr;
+  uint64_t len = 0;
+  int fd = -1;
+
+  OriginalStorage(std::filesystem::path base_dir);
+  ~OriginalStorage();
+
+  void initialize();
+  const char *read(uint64_t pos) override;
+  uint64_t length() override;
+
+  void retain() override {
+    refs++;
+  }
+
+  void release() override {
+    if (--refs > 0)
+      return;
+    delete this;
+  }
+};
+} // namespace bed::internal::vase

include/internal/vase/storage/storage.h

@@ -3,9 +3,11 @@
 #include "pch.h"
 
 namespace bed::internal::vase {
-struct Buffer {
+struct Storage {
   virtual const char *read(uint64_t pos) = 0;
   virtual uint64_t length() = 0;
-  virtual ~Buffer() = default;
+  virtual ~Storage() = default;
+  virtual void retain() = 0;
+  virtual void release() = 0;
 };
 } // namespace bed::internal::vase

include/internal/vase/vase.h

@@ -1,11 +1,12 @@
 #pragma once
 
-#include "buffer/append.h"
-#include "buffer/original.h"
 #include "constants.h"
+#include "definitions.h"
 #include "iterators/line.h"
 #include "pch.h"
 #include "shard.h"
+#include "storage/append.h"
+#include "storage/original.h"
 
 namespace bed::internal::vase {
 struct Point {
@@ -18,100 +19,64 @@ struct Range {
   Point end;
 };
 
-struct Vase {
-  struct RegexGroup {
-    uint64_t start{0};
-    uint64_t end{0};
-  };
-
-  struct RegexMatch {
-    uint64_t start;
-    uint64_t end;
-    RegexGroup groups[9]{};
-  };
-
-  struct ReplacePart {
-    enum struct PartType {
-      FullMatch,
-      CaptureGroup,
-      Constant
-    } type;
-
-    std::variant<uint8_t, Shard *> value;
-  };
-
-  OriginalBuffer *original;
-  AppendBuffer *append;
-  Shard *root;
-
-#ifdef _WIN32
-  bool posix_ending = false;
-  bool using_crlf = true;
-#else
-  bool posix_ending = true;
-  bool using_crlf = false;
-#endif
-
-  std::filesystem::path path;
-  std::filesystem::path swapdir;
-
-  Vase(std::filesystem::path path, std::filesystem::path swapdir);
-  Vase(std::string cmd, std::filesystem::path swapdir);
-  Vase(std::filesystem::path swapdir);
-  ~Vase();
-  Vase(Vase &&other) noexcept;
-  Vase &operator=(Vase &&other) noexcept;
-  Vase(const Vase &) = delete;
-  Vase &operator=(const Vase &) = delete;
-
-  uint64_t length();
-  uint64_t lines();
-  std::string to_string();
-  std::string to_string(Range range);
-
-  Iterator iterate(uint64_t line, Direction dir);
-
-  void insert(Point *point, char key);
-  void insert(Point *point, std::string_view str);
-  void insert(Point *point, const char *data, uint64_t len);
-  void erase(Point *point, uint64_t amount, Direction dir);
-  void erase(Range range);
-  void replace(Range range, std::string_view str);
-  void replace(Range range, const char *data, uint64_t len);
-
-  void move_clusters(Point *point, uint64_t amount, Direction dir);
-  void move_lines(Point *point, uint64_t amount, Direction dir);
-  void clamp(Point *point);
-
-  void regex_search_replace(
-    std::string_view pattern, Range range,
-    std::string_view replace, std::string_view options
-  );
-
-  std::vector<Range> regex_search(
-    std::string_view pattern, Range range, std::string_view options
-  );
-
-  bool undo();
-  bool redo();
-  void snapshot();
-  void prune_history(uint64_t n);
-
-  bool save();
-  bool save_swap();
-
-  uint64_t offset_of(Point point);
-  Point point_of(uint64_t offset);
-
-private:
-  std::vector<Shard *> history;
-  uint64_t history_top;
-
-  void _insert(Point *point, const char *data, uint64_t len);
-
-  std::vector<ReplacePart> parse_replace(std::string_view s);
-  std::vector<RegexMatch> _regex_search(
-    std::string_view pattern, Range range, std::string_view options
-  );
+struct RegexGroup {
+  uint64_t start{UINT64_MAX};
+  uint64_t end{UINT64_MAX};
 };
+
+struct RegexMatch {
+  uint64_t start;
+  uint64_t end;
+  RegexGroup groups[9]{};
+};
+
+struct ReplacePart {
+  enum struct PartType {
+    FullMatch,
+    CaptureGroup,
+    Constant
+  } type;
+  std::variant<uint8_t, Shard *> value;
+};
+
+uint64_t offset_of(Shard *root, uint64_t line);
+uint64_t offset_of(Shard *root, Point point);
+Point eof_point(Shard *root);
+
+std::string to_string(Shard *root);
+std::string to_string(Shard *root, Range range);
+
+Shard *insert(AppendStorage *ap, Shard *root, Shard *text, uint64_t line);
+Shard *erase(Shard *root, uint64_t start, uint64_t end);
+Shard *replace(Shard *root, Shard *text, uint64_t start, uint64_t end);
+Shard *join(Shard *root, uint64_t start, uint64_t end);
+Shard *copy(Shard *root, uint64_t start, uint64_t end);
+void write_file(std::filesystem::path path, Shard *text);
+void write_command(const char *cmd, Shard *text);
+
+uint64_t find_next(Shard *root, std::string_view pattern, uint64_t start);
+uint64_t find_prev(Shard *root, std::string_view pattern, uint64_t start);
+
+Shard *substitute(
+  AppendStorage *ap, Shard *root,
+  std::string_view pattern, uint64_t start, uint64_t end,
+  std::string_view replace, std::string_view options,
+  const std::function<void(
+    uint64_t line, uint64_t old_lines, uint64_t new_lines
+  )> &on_edit = nullptr
+);
+
+// internal
+
+void _insert(AppendStorage *ap, Shard **root, Point *point, const char *data, uint64_t len);
+Shard *insert(AppendStorage *ap, Shard *root, Point *point, char key);
+Shard *insert(AppendStorage *ap, Shard *root, Point *point, const char *data, uint64_t len);
+
+Shard *erase(Shard *root, Range range);
+Shard *replace(AppendStorage *ap, Shard *root, Range range, const char *data, uint64_t len);
+
+std::vector<ReplacePart> parse_replace(AppendStorage *ap, std::string_view s);
+std::vector<RegexMatch> _regex_search(
+  Shard *root, std::string_view pattern, uint64_t start_offset, uint64_t end_offset, std::string_view options
+);
 } // namespace bed::internal::vase

include/pch.h

@@ -4,10 +4,29 @@
 
 #include <mruby.h>
 #include <mruby/array.h>
+#include <mruby/boxing_word.h>
+#include <mruby/class.h>
+#include <mruby/common.h>
 #include <mruby/compile.h>
+#include <mruby/data.h>
+#include <mruby/dump.h>
+#include <mruby/error.h>
+#include <mruby/gc.h>
 #include <mruby/hash.h>
+#include <mruby/internal.h>
 #include <mruby/irep.h>
+#include <mruby/numeric.h>
+#include <mruby/object.h>
+#include <mruby/opcode.h>
+#include <mruby/presym.h>
+#include <mruby/proc.h>
+#include <mruby/range.h>
+#include <mruby/re.h>
 #include <mruby/string.h>
+#include <mruby/throw.h>
+#include <mruby/value.h>
+#include <mruby/variable.h>
+#include <mruby/version.h>
 #include <pcre2.h>
 extern "C" {
 #include <grapheme.h>
@@ -29,12 +48,12 @@ extern "C" {
 #include <filesystem>
 #include <fstream>
 #include <functional>
-#include <iostream>
 #include <limits.h>
 #include <map>
 #include <mutex>
 #include <optional>
 #include <poll.h>
+#include <pty.h>
 #include <queue>
 #include <set>
 #include <shared_mutex>

samples/bed.rb

@@ -0,0 +1,3 @@
+register :happy, address: :none do
+  puts "be nice"
+end

samples/depth_sample.rb

@@ -0,0 +1,60 @@
+=begin
+die
+=end
+
+module Outer
+  class User
+    def initialize(name)
+      @name = name
+
+      if @name
+        while @name
+          begin
+            case @name
+            when "admin"
+              puts "admin"
+            else
+              puts "user"
+            end
+          end
+        end
+      else
+        unless name
+          puts "missing"
+        end
+      end
+    end
+
+    def each_item(items)
+      for item in items
+        if item
+          die!
+          puts "ha"
+          puts "ha"
+          item.do_something do
+            puts "ha"
+            puts "ha"
+            puts item
+            puts "ha"
+            puts "ha"
+          end
+          puts "ha"
+          puts "ha"
+        end
+      end
+    end
+  end
+
+  module Inner
+    def run(value)
+      until value == 0
+        case value
+        when 1
+          value -= 1
+        else
+          value -= 2
+        end
+      end
+    end
+  end
+end

src/bed/bed.cc

@@ -0,0 +1,73 @@
+#include "bed.h"
+
+namespace bed {
+BEd::BEd(std::vector<std::string> args)
+    : mrb(this), theme(internal::theme::Theme::default_theme()), io(*this) {
+  std::string prompt_ = "";
+  std::string file = "";
+  bool suppress = false;
+  bool color = true;
+  for (size_t i = 1; i < args.size(); i++) {
+    if (args[i] == "-p") {
+      i++;
+      if (i >= args.size())
+        throw fatal_error("Prompt not specified!", 1);
+      prompt_ = args[i];
+    } else if (args[i] == "-s") {
+      suppress = true;
+    } else if (args[i] == "--no-color") {
+      color = false;
+    } else if (args[i] == "-v" || args[i] == "--verbose") {
+      help_mode = true;
+    } else if (args[i] == "-h" || args[i] == "--help") {
+      print_help();
+      throw fatal_error("", 0);
+    } else {
+      if (file.size())
+        throw fatal_error("Invalid arguments given.", 1);
+      file = args[i];
+    }
+  }
+  if (prompt_ != "")
+    prompt = [p = std::move(prompt_)](BEd &) { return p; };
+  else
+    prompt_mode = false;
+  suppress_mode = suppress;
+  const char *no_color = getenv("NO_COLOR");
+  if (no_color && *no_color != '\0')
+    color = false;
+  const char *colorterm = getenv("COLORTERM");
+  if (colorterm
+      && strcmp(colorterm, "truecolor") != 0
+      && strcmp(colorterm, "24bit") != 0)
+    color = false;
+  color_mode = color;
+  internal::functions::Function::register_posix(*this);
+  internal::functions::Function::register_extented(*this);
+  internal::functions::Suffix::register_suffixes(*this);
+  internal::scripting::register_basic(*this);
+  languages["ruby"] = new internal::syntax::Language(internal::syntax::ruby::lang_ruby());
+  buffers["clip"] = new internal::buffer::ClipBuffer("clip");
+  current() = {"default", 0};
+  try {
+    if (file != "")
+      handle(":default:E " + file, false);
+  } catch (ed_error &e) {
+    io.write_line("?");
+    if (help_mode)
+      io.write_line(e.what());
+    last_help = e.what();
+  }
+}
+
+BEd::~BEd() {
+  for (auto &[_, buffer] : buffers)
+    delete buffer;
+  for (auto &[_, lang] : languages)
+    delete lang;
+}
+
+void BEd::print_help() {
+  io.write("BEd - A line editor.\n");
+}
+} // namespace bed

src/bed/handle.cc

@@ -1,97 +1,115 @@
 #include "bed.h"
-#include "internal/address/address.h"
-#include "internal/commands/commands.h"
+#include "internal/parser/parser.h"
 
 namespace bed {
-void BEd::handle(std::string_view cmd_, bool eof) {
-  using namespace internal::commands;
-  std::string cmd(cmd_);
-  if (eof) {
-    eof_op.handle(*this, {}, "");
+void BEd::handle(std::string_view cmd, bool eof) {
+  if (eof && cmd.empty()) {
+    eof_op.handle(*this, "", nullptr, std::monostate(), nullptr);
     return;
   }
-  uint64_t i = 0;
-  auto skip_space = [&] {
-    while (i < cmd.size() && (cmd[i] == ' ' || cmd[i] == '\t'))
-      ++i;
-  };
-  skip_space();
-  auto addresses = internal::address::Address::handle(*this, cmd, i);
-  if (i >= cmd.size()) {
-    if (!no_op.accept_zero)
-      for (auto l : addresses.span())
-        if (l == 0)
-          throw ed_error("Invalid address given.");
-    switch (no_op.address_mode) {
-    case Command::AddressMode::None:
-      no_op.handle(*this, addresses.span(0), "");
-      break;
-    case Command::AddressMode::Single:
-      no_op.handle(*this, addresses.span(1), "");
-      break;
-    case Command::AddressMode::Range:
-      no_op.handle(*this, addresses.span(2), "");
-      break;
-    }
-    return;
+  internal::parser::Command c = internal::parser::Parser::get_command(cmd, *this);
+  if (c.temp_address) {
+    marks.get(251) = marks.get(250);
+    prev_2 = prev_1;
+    temporary_current = true;
   }
-  uint64_t len = commands.longest_match(cmd.substr(i));
-  if (len == 0)
-    throw ed_error("Command not found.");
-  std::optional<Command> command_opt = commands.get(cmd.substr(i, len));
-  i += len;
-  if (!command_opt)
-    throw ed_error("Command error.");
-  Command command = command_opt.value();
-  std::string argument;
-  Suffix *suffix = nullptr;
-  switch (command.suffix) {
-  case Command::SuffixKind::None:
-    skip_space();
-    if (i < cmd.size())
-      throw ed_error("Command error.");
-    break;
-  case Command::SuffixKind::Suffix:
-    skip_space();
-    if (i < cmd.size()) {
-      if (suffixes[cmd[i] - 'a'].has_value())
-        suffix = &(suffixes[cmd[i++] - 'a'].value());
-      skip_space();
-      std::cout << i << " " << cmd << std::endl;
-      if (i < cmd.size())
-        throw ed_error("Command error.");
+  internal::buffer::Address address;
+  switch (c.function->address_kind) {
+  case internal::functions::Function::AddressKind::None: {
+    auto a = internal::parser::AddressPromise::get_line(*this, c.addresses);
+    if (!a.has_value()) {
+      auto vec = internal::parser::Parser::get_addresses(c.function->default_address, *this);
+      a = internal::parser::AddressPromise::get_line(*this, vec);
+      if (!a.has_value())
+        a = current();
     }
-    break;
-  case Command::SuffixKind::Argument:
-    if (i < cmd.size()) {
-      if (cmd[i] == ' ' || cmd[i] == '\t')
-        skip_space();
-      else
-        throw ed_error("Command Error.");
-      argument = cmd.substr(i);
+    address = a->buffername;
+  } break;
+  case internal::functions::Function::AddressKind::Line: {
+    auto a = internal::parser::AddressPromise::get_line(*this, c.addresses);
+    if (!a.has_value()) {
+      auto vec = internal::parser::Parser::get_addresses(c.function->default_address, *this);
+      a = internal::parser::AddressPromise::get_line(*this, vec);
+      if (!a.has_value())
+        a = current();
     }
-    break;
-  case Command::SuffixKind::Continuation:
-    argument = cmd.substr(i);
-    break;
+    address = *a;
+  } break;
+  case internal::functions::Function::AddressKind::Range: {
+    auto a = internal::parser::AddressPromise::get_range(*this, c.addresses);
+    if (!a.has_value()) {
+      auto vec = internal::parser::Parser::get_addresses(c.function->default_address, *this);
+      a = internal::parser::AddressPromise::get_range(*this, vec);
+      if (!a.has_value())
+        a = internal::buffer::Range(current(), current());
+    }
+    address = *a;
+  } break;
   }
-  if (!command.accept_zero)
-    for (auto l : addresses.span())
-      if (l == 0)
-        throw ed_error("Invalid address given.");
-  switch (command.address_mode) {
-  case Command::AddressMode::None:
-    command.handle(*this, addresses.span(0), argument);
-    break;
-  case Command::AddressMode::Single:
-    command.handle(*this, addresses.span(1), argument);
-    break;
-  case Command::AddressMode::Range:
-    command.handle(*this, addresses.span(2), argument);
-    break;
+  if (std::holds_alternative<internal::buffer::Line>(c.argument)) {
+    if (c.argument_addresses.empty())
+      throw ed_error("Function needs address argument.");
+    auto a = internal::parser::AddressPromise::get_line(*this, c.argument_addresses);
+    if (a.has_value())
+      c.argument = *a;
+    else
+      c.argument = current();
+  } else if (std::holds_alternative<internal::buffer::Range>(c.argument)) {
+    if (c.argument_addresses.empty())
+      throw ed_error("Function needs address argument.");
+    auto a = internal::parser::AddressPromise::get_range(*this, c.argument_addresses);
+    if (a.has_value())
+      c.argument = *a;
+    else
+      c.argument = internal::buffer::Range(current(), current());
+  }
+  if (!c.function->accept_zero) {
+    if (std::holds_alternative<internal::buffer::Line>(address)) {
+      if (std::get<internal::buffer::Line>(address).number == 0)
+        throw ed_error("Line number can't be zero.");
+    } else if (std::holds_alternative<internal::buffer::Range>(address)) {
+      auto r = std::get<internal::buffer::Range>(address);
+      if (r.start == 0 || r.end == 0)
+        throw ed_error("Line number can't be zero.");
+    }
+  }
+  internal::vase::Shard *text = nullptr;
+  if (c.function->input_mode == internal::functions::Function::InputMode::Text) {
+    internal::vase::Shard *vase = nullptr;
+    internal::syntax::Language *lang = nullptr;
+    void *state = nullptr;
+    if (c.function->pre_text_mode)
+      std::tie(vase, lang, state) = c.function->pre_text_mode(*this, address, c.argument);
+    internal::ui::text_mode::TextMode tm(*this, vase, lang, state);
+    auto [a, b] = tm.run();
+    if (!b) {
+      text = a;
+    } else {
+      if (a) {
+        auto p = internal::syntax::make_parser(a, a->lines + 1, lang);
+        auto cancel_buf = new internal::buffer::ReadonlyBuffer("cancel", a, p);
+        internal::syntax::release(p);
+        buffers["cancel"] = cancel_buf;
+        cancel_buf->useless = false;
+        internal::vase::Shard::release(a);
+      }
+      throw ed_error("Operation cancelled.");
+    }
+  }
+  if (c.function->handle)
+    c.function->handle(*this, address, text, c.argument, nullptr);
+  if (c.suffix)
+    c.suffix->handle(*this);
+  if (c.temp_address)
+    temporary_current = false;
+  for (auto it = buffers.begin(); it != buffers.end();) {
+    internal::buffer::Buffer *buf = it->second;
+    if (buf->waste()) {
+      delete buf;
+      it = buffers.erase(it);
+    } else {
+      ++it;
+    }
   }
-  if (suffix)
-    suffix->handle(*this);
-  return;
 }
 } // namespace bed

src/bed/run.cc

@@ -1,54 +1,113 @@
 #include "bed.h"
+#include "internal/parser/parser.h"
 
 namespace bed {
-BEd::BEd(std::vector<std::string> args)
-    : theme(internal::theme::Theme::default_theme()) {
-  internal::commands::Command::register_posix(*this);
-  internal::commands::Suffix::register_suffixes(*this);
-  std::string prompt_ = "";
-  std::string file = "";
-  bool suppress = false;
-  for (size_t i = 1; i < args.size(); i++) {
-    if (args[i] == "-p") {
-      i++;
-      if (i >= args.size())
-        throw fatal_error("Prompt not specified!", 1);
-      prompt_ = args[i];
-    } else if (args[i] == "-s") {
-      suppress = true;
-    } else {
-      if (file.size())
-        throw fatal_error("Invalid arguments given.", 1);
-      file = args[i];
-    }
-  }
-  if (prompt_ != "")
-    prompt = [p = std::move(prompt_)](BEd &) { return p; };
-  else
-    prompt_mode = false;
-  suppress_mode = suppress;
-  active = new internal::buffer::Buffer();
-  buffers.emplace("0", active);
-  if (file != "")
-    handle("E " + file, false);
-}
-
-BEd::~BEd() {
-  for (auto &[_, buffer] : buffers)
-    delete buffer;
-}
-
 void BEd::run() {
   while (true) {
-    std::string cmd;
-    if (prompt_mode)
-      std::cout << prompt(*this);
-    bool eof = !std::getline(std::cin, cmd);
+    internal::ui::CommandIO command(*this);
+    auto [cmd, eof] = command.run();
     try {
       handle(cmd, eof);
-    } catch (ed_error &e) {
-      std::cout << e.what() << std::endl;
+    } catch (const ed_error &e) {
+      io.apply(internal::io::Token::Warning);
+      io.write_line("?");
+      if (help_mode)
+        io.write_line(e.what());
+      io.reset();
+      last_help = e.what();
     }
   }
 }
+
+internal::buffer::Buffer &BEd::buffer(const std::string &name) {
+  if (name.empty())
+    throw ed_error("Can't have empty buffer name");
+  {
+    auto it = buffers.find(name);
+    if (it != buffers.end())
+      return *it->second;
+  }
+  constexpr std::string_view prefix = "history/";
+  if (name == "cancel")
+    throw ed_error("Cancel buffer empty.");
+  if (name.starts_with(prefix)) {
+    std::string_view path{name};
+    path.remove_prefix(prefix.size());
+    auto slash = path.rfind('_');
+    if (slash == std::string_view::npos || slash == 0 || slash == path.size() - 1)
+      throw ed_error("invalid history");
+    std::string bufname(path.substr(0, slash));
+    auto version_str = path.substr(slash + 1);
+    std::size_t version;
+    try {
+      version = std::stoull(std::string(version_str));
+    } catch (...) {
+      throw ed_error("invalid history version");
+    }
+    auto it = buffers.find(bufname);
+    if (it != buffers.end()) {
+      auto &buf_ = *it->second;
+      if (buf_.kind != internal::buffer::Buffer::Kind::Generic)
+        throw ed_error("Only normal buffers can have history.");
+      auto &buf = *(internal::buffer::GenericBuffer *)&buf_;
+      auto *history_buf = buf.get_history(version);
+      buffers.emplace(name, history_buf);
+      return *history_buf;
+    }
+    throw ed_error("Buffer has no history.");
+  }
+  for (auto &c : name)
+    if (!(('0' <= c && c <= '9')
+          || ('a' <= c && c <= 'z')
+          || ('A' <= c && c <= 'Z')
+          || c == '-' || c == '_'
+          || c == '+' || c == '.'
+          || c == ',' || c == '$'
+          || c == '/' || c == '~'))
+      throw ed_error("Invalid buffer name.");
+  auto *buf = new internal::buffer::GenericBuffer(name);
+  buffers.emplace(name, buf);
+  return *buf;
+}
+
+internal::buffer::Line &BEd::current() {
+  return marks.get(250 + temporary_current);
+}
+
+internal::buffer::Range &BEd::prev() {
+  if (temporary_current)
+    return prev_2;
+  else
+    return prev_1;
+}
+
+void BEd::mark(uint8_t m, internal::buffer::Line line) {
+  marks.get(m) = line;
+}
+
+bool BEd::escape_command(std::string &cmd, std::string_view filename) {
+  bool modified = false;
+  if (cmd == "!") {
+    cmd = last_shell;
+    modified = true;
+  }
+  last_shell = cmd;
+  for (size_t i = 0; i < cmd.size();) {
+    if (cmd[i] == '\\') {
+      if (i + 1 >= cmd.size())
+        break;
+      cmd.erase(i++, 1);
+      continue;
+    }
+    if (cmd[i] == '%') {
+      cmd.erase(i, 1);
+      cmd.insert(i, filename);
+      i += filename.size();
+      modified = true;
+      continue;
+    }
+    i++;
+  }
+  return modified;
+}
 } // namespace bed

src/internal/address/address.cc

@@ -1,141 +0,0 @@
-#include "internal/address/address.h"
-
-namespace bed::internal::address {
-Address::Address(std::string &cmd, uint64_t &i) {
-  base = None{};
-  auto skip_space = [&] {
-    while (i < cmd.size() && (cmd[i] == ' ' || cmd[i] == '\t'))
-      ++i;
-  };
-  skip_space();
-  if (i >= cmd.size())
-    return;
-  switch (cmd[i]) {
-  case '.':
-    base = Current();
-    i++;
-    break;
-  case '$':
-    base = Last();
-    i++;
-    break;
-  case ']':
-    base = Block(Direction::Forward);
-    i++;
-    break;
-  case '[':
-    base = Block(Direction::Backward);
-    i++;
-    break;
-  case '\'': {
-    i++;
-    if (i < cmd.size() && 'a' <= cmd[i] && cmd[i] <= 'z')
-      i++;
-    else
-      throw address_error("Invalid mark.");
-    base = Mark(cmd[i]);
-  } break;
-  case '/': {
-    i++;
-    uint64_t start = i;
-    while (true) {
-      if (i >= cmd.size())
-        break;
-      if (cmd[i] == '/')
-        break;
-      else if (cmd[i] == '\\')
-        i += 2;
-      else if (cmd[i] == '[' && i + 1 < cmd.size() && cmd[i + 1] == '[')
-        while (i < cmd.size() && !(cmd[i - 1] == ']' && cmd[i] == ']'))
-          i++;
-      else if (cmd[i] == '[')
-        while (i < cmd.size() && cmd[i] != ']')
-          i++;
-      else
-        i++;
-    }
-    base = RegexLine(Direction::Forward, cmd.substr(start, i - start));
-  } break;
-  case '?': {
-    i++;
-    uint64_t start = i;
-    while (true) {
-      if (i >= cmd.size())
-        break;
-      if (cmd[i] == '?')
-        break;
-      else if (cmd[i] == '\\')
-        i += 2;
-      else if (cmd[i] == '[' && i + 1 < cmd.size() && cmd[i + 1] == '[')
-        while (i < cmd.size() && !(cmd[i - 1] == ']' && cmd[i] == ']'))
-          i++;
-      else if (cmd[i] == '[')
-        while (i < cmd.size() && cmd[i] != ']')
-          i++;
-      else
-        i++;
-    }
-    base = RegexLine(Direction::Backward, cmd.substr(start, i - start));
-  } break;
-  case '+': {
-    base = Current();
-    i++;
-    skip_space();
-    uint64_t start = i;
-    int64_t num = 0;
-    while (i < cmd.size() && '0' <= cmd[i] && cmd[i] <= '9') {
-      num = num * 10 + (cmd[i] - '0');
-      i++;
-    }
-    if (start == i)
-      num = 1;
-    offset += num;
-  } break;
-  case '-': {
-    base = Current();
-    i++;
-    skip_space();
-    uint64_t start = i;
-    int64_t num = 0;
-    while (i < cmd.size() && '0' <= cmd[i] && cmd[i] <= '9') {
-      num = num * 10 + (cmd[i] - '0');
-      i++;
-    }
-    if (start == i)
-      num = 1;
-    offset -= num;
-  } break;
-  default: {
-    if ('0' <= cmd[i] && cmd[i] <= '9') {
-      uint64_t num = 0;
-      while (i < cmd.size() && '0' <= cmd[i] && cmd[i] <= '9') {
-        num = num * 10 + (cmd[i] - '0');
-        i++;
-      }
-      base = Number(num);
-    } else {
-      return;
-    }
-    break;
-  }
-  }
-  skip_space();
-  while (i < cmd.size() && (cmd[i] == '+' || cmd[i] == '-' || ('0' <= cmd[i] && cmd[i] <= '9'))) {
-    bool positive = cmd[i] != '-';
-    if (cmd[i] == '+' || cmd[i] == '-') {
-      i++;
-      skip_space();
-    }
-    uint64_t start = i;
-    int64_t num = 0;
-    while (i < cmd.size() && '0' <= cmd[i] && cmd[i] <= '9') {
-      num = num * 10 + (cmd[i] - '0');
-      i++;
-    }
-    if (start == i)
-      num = 1;
-    offset += positive ? num : -num;
-    skip_space();
-  }
-}
-} // namespace bed::internal::address

src/internal/address/handle.cc

@@ -1,58 +0,0 @@
-#include "bed.h"
-#include "internal/address/address.h"
-
-namespace bed::internal::address {
-Address::Result Address::handle(BEd &ctx, std::string &cmd, uint64_t &i) {
-  bool prev_given = false;
-  Address prev;
-  Address curr;
-  while (i < cmd.size()) {
-    if (cmd[i] == '%') {
-      prev_given = true;
-      prev.base = Number(ctx.active->prev_range.start);
-      prev.offset = 0;
-      curr.base = Number(ctx.active->prev_range.end);
-      curr.offset = 0;
-      i++;
-    } else {
-      curr = Address(cmd, i);
-    }
-    if (i < cmd.size() && (cmd[i] == ',' || cmd[i] == ';')) {
-      if (std::holds_alternative<None>(curr.base)) {
-        if (cmd[i] == ',')
-          curr.base = Number(1);
-        else
-          curr.base = Current();
-        curr.offset = 0;
-        prev_given = false;
-      } else {
-        if (cmd[i] == ';') {
-          uint64_t resolved = curr.resolve(ctx);
-          ctx.active->jump(resolved);
-          curr.base = Number(resolved);
-          curr.offset = 0;
-        }
-        prev_given = true;
-      }
-      i++;
-      prev = std::move(curr);
-    } else {
-      if (std::holds_alternative<None>(curr.base)) {
-        if (std::holds_alternative<std::monostate>(prev.base))
-          return {{}, 0};
-        if (prev_given) {
-          curr = prev;
-        } else {
-          curr.base = Last();
-          curr.offset = 0;
-        }
-        return {{prev.resolve(ctx), curr.resolve(ctx)}, 2};
-      }
-      if (prev_given)
-        return {{prev.resolve(ctx), curr.resolve(ctx)}, 2};
-      return {{curr.resolve(ctx)}, 1};
-    }
-  }
-  return {};
-}
-}; // namespace bed::internal::address

src/internal/address/resolve.cc

@@ -1,55 +0,0 @@
-#include "bed.h"
-#include "internal/address/address.h"
-
-namespace bed::internal::address {
-uint64_t Address::resolve(BEd &ctx) {
-  uint64_t result = std::visit(
-    [&](auto const &addr) -> uint64_t {
-      uint64_t line = 0;
-      using T = std::decay_t<decltype(addr)>;
-      if constexpr (std::is_same_v<T, std::monostate>) {
-        throw address_error("empty address");
-      } else if constexpr (std::is_same_v<T, None>) {
-        throw address_error("no address");
-      } else if constexpr (std::is_same_v<T, Current>) {
-        line = ctx.active->line;
-      } else if constexpr (std::is_same_v<T, Last>) {
-        line = ctx.active->vase.lines();
-      } else if constexpr (std::is_same_v<T, Number>) {
-        line = addr.i;
-      } else if constexpr (std::is_same_v<T, Block>) {
-        if (addr.dir == Direction::Forward) {
-          if (ctx.active->parser) {
-            if (ctx.active->line == 0)
-              ctx.active->line = 1;
-            line = ctx.active->parser->next_closing(ctx.active->line - 1) + 1;
-            if (line > ctx.active->vase.lines())
-              line = ctx.active->vase.lines();
-          } else {
-            line = ctx.active->line + 10;
-          }
-        } else {
-          if (ctx.active->parser) {
-            if (ctx.active->line == 0)
-              ctx.active->line = 1;
-            line = ctx.active->parser->prev_opening(ctx.active->line - 1) + 1;
-          } else {
-            line = ctx.active->line - 10;
-          }
-        }
-      } else {
-        throw ed_error("Unhandled address given.");
-      }
-      if (offset < 0 && line < (uint64_t)-offset)
-        throw address_error("Can't have negative addresses");
-      line += offset;
-      if (line > ctx.active->vase.lines())
-        throw address_error("Line number too high.");
-      return line;
-    },
-    base
-  );
-
-  return result + offset;
-}
-}; // namespace bed::internal::address

src/internal/buffer/buffer.cc

@@ -1,233 +0,0 @@
-#include "internal/buffer/buffer.h"
-#include "bed.h"
-
-namespace bed::internal::buffer {
-Buffer::Buffer() : vase("/tmp") {
-  parser.emplace(vase, vase.lines(), syntax::ruby::lang_ruby());
-  line = vase.lines();
-  modified = false;
-}
-
-Buffer::Buffer(std::string command) : vase(command, "/tmp") {
-  parser.emplace(vase, vase.lines(), syntax::ruby::lang_ruby());
-  line = vase.lines();
-  if (!line)
-    return;
-  prev_range.start = 1;
-  prev_range.end = line;
-  modified = false;
-}
-
-Buffer::Buffer(std::filesystem::path path) : vase(path, "/tmp") {
-  parser.emplace(vase, vase.lines(), syntax::ruby::lang_ruby());
-  line = vase.lines();
-  if (!line)
-    return;
-  prev_range.start = 1;
-  prev_range.end = line;
-  save_path = path;
-  modified = false;
-}
-
-void Buffer::load(std::string command) {
-  vase::Vase new_vase = vase::Vase(command, "/tmp");
-  vase = std::move(new_vase);
-  parser.emplace(vase, vase.lines(), syntax::ruby::lang_ruby());
-  line = vase.lines();
-  if (!line) {
-    prev_range.start = 0;
-    prev_range.end = 0;
-  } else {
-    prev_range.start = 1;
-    prev_range.end = line;
-  }
-  modified = false;
-}
-
-void Buffer::load(std::filesystem::path path) {
-  vase::Vase new_vase = vase::Vase(path, "/tmp");
-  vase = std::move(new_vase);
-  parser.emplace(vase, vase.lines(), syntax::ruby::lang_ruby());
-  line = vase.lines();
-  if (!line) {
-    prev_range.start = 0;
-    prev_range.end = 0;
-  } else {
-    prev_range.start = 1;
-    prev_range.end = line;
-  }
-  save_path = path;
-  modified = false;
-}
-
-void Buffer::jump(uint64_t n_line) {
-  if (n_line > vase.lines())
-    throw ed_error("Line number too high.");
-  line = n_line;
-  prev_range.start = line;
-  prev_range.end = line;
-}
-
-void Buffer::append(std::string text, uint64_t line) {
-  using namespace bed::internal::vase;
-  Point p = {line, 0};
-  if (!vase.lines()) {
-    text.pop_back();
-  } else if (line == vase.lines()) {
-    p.row--;
-    p.col = UINT64_MAX;
-    text = "\n" + text;
-    text.pop_back();
-  }
-  prev_range.start = p.row + 1;
-  vase.insert(&p, text);
-  prev_range.end = p.row + 1;
-  modified = true;
-}
-
-void Buffer::remove(uint64_t start_line, uint64_t end_line) {
-  vase.erase({{start_line - 1, 0}, {end_line, 0}});
-  prev_range.start = start_line;
-  prev_range.end = start_line;
-  modified = true;
-}
-
-void Buffer::join(uint64_t start_line, uint64_t end_line) {
-  vase.regex_search_replace(R"(\n)", {{start_line - 1, 0}, {end_line, 0}}, "", "g");
-  prev_range.start = start_line;
-  prev_range.end = start_line;
-  modified = true;
-}
-
-inline void apply(std::ostream &out, const theme::Highlight &hl) {
-  out << "\x1b[0m";
-  const uint8_t r = (hl.fg >> 16) & 0xff;
-  const uint8_t g = (hl.fg >> 8) & 0xff;
-  const uint8_t b = hl.fg & 0xff;
-  out << "\x1b[38;2;"
-      << (unsigned)r << ';'
-      << (unsigned)g << ';'
-      << (unsigned)b << 'm';
-  if (hl.bg != 0) {
-    const uint8_t br = (hl.bg >> 16) & 0xff;
-    const uint8_t bg = (hl.bg >> 8) & 0xff;
-    const uint8_t bb = hl.bg & 0xff;
-    out << "\x1b[48;2;"
-        << (unsigned)br << ';'
-        << (unsigned)bg << ';'
-        << (unsigned)bb << 'm';
-  }
-  if (hl.flags & theme::Highlight::Bold)
-    out << "\x1b[1m";
-  if (hl.flags & theme::Highlight::Italic)
-    out << "\x1b[3m";
-  if (hl.flags & theme::Highlight::Underline)
-    out << "\x1b[4m";
-  if (hl.flags & theme::Highlight::Strikethrough)
-    out << "\x1b[9m";
-}
-
-inline void reset(std::ostream &out) {
-  out << "\x1b[0m";
-}
-
-void Buffer::print(BEd &ctx, uint64_t start_line, uint64_t end_line) {
-  if (parser) {
-    std::optional<syntax::Parser::Iterator> it_o = parser->get_hl(vase, start_line - 1);
-    auto &it = *it_o;
-    while (start_line <= end_line) {
-      it.next();
-      const std::string &line = it.it->line;
-      const auto &tokens = it.tokens;
-      uint32_t cursor = 0;
-      for (const auto &token : tokens) {
-        const uint32_t start = token.start;
-        const uint32_t end = token.end;
-        if (start > line.size())
-          break;
-        if (end > line.size())
-          break;
-        if (cursor < start) {
-          std::cout.write(
-            line.data() + cursor,
-            start - cursor
-          );
-        }
-        const auto highlight = ctx.theme.get(token);
-        apply(std::cout, highlight);
-        std::cout.write(line.data() + start, end - start);
-        reset(std::cout);
-        cursor = end;
-      }
-      if (cursor < line.size())
-        std::cout.write(line.data() + cursor, line.size() - cursor);
-      std::cout << std::endl;
-      ++start_line;
-    }
-  } else {
-    vase::Iterator it = vase.iterate(start_line - 1, Direction::Forward);
-    while (it.next() && start_line++ <= end_line)
-      std::cout << it.line << std::endl;
-  }
-  prev_range.start = start_line;
-  prev_range.end = end_line;
-}
-
-std::string Buffer::list_string(std::string_view s) {
-  uint32_t width = 80;
-  winsize ws{};
-  if (ioctl(STDOUT_FILENO, TIOCGWINSZ, &ws) == 0 && ws.ws_col != 0)
-    width = ws.ws_col;
-  std::string out;
-  out.reserve(s.size());
-  const uint32_t max_width = width > 1 ? width - 1 : 1;
-  uint32_t column = 0;
-  auto append = [&](std::string_view text) {
-    if (column + text.size() > max_width) {
-      out += "\\\n";
-      column = 0;
-    }
-    out += text;
-    column += text.size();
-  };
-  for (unsigned char c : s) {
-    switch (c) {
-    case '\\':
-      append("\\\\");
-      break;
-    case '$':
-      append("\\$");
-      break;
-    case '\a':
-      append("\\a");
-      break;
-    case '\b':
-      append("\\b");
-      break;
-    case '\f':
-      append("\\f");
-      break;
-    case '\r':
-      append("\\r");
-      break;
-    case '\t':
-      append("\\t");
-      break;
-    case '\v':
-      append("\\v");
-      break;
-    default:
-      if (!std::isprint(c)) {
-        char buf[5];
-        std::snprintf(buf, sizeof(buf), "\\%03o", c);
-        append(buf);
-      } else {
-        append(std::string_view((const char *)&c, 1));
-      }
-      break;
-    }
-  }
-  out += '$';
-  return out;
-}
-} // namespace bed::internal::buffer

src/internal/buffer/generic.cc

@@ -0,0 +1,370 @@
+#include "bed.h"
+#include "internal/buffer/buffer.h"
+
+namespace bed::internal::buffer {
+GenericBuffer::~GenericBuffer() {
+  for (auto &item : undo_stack) {
+    syntax::release(item.parse_state);
+    vase::Shard::release(item.text);
+  }
+  for (auto &item : redo_stack) {
+    syntax::release(item.parse_state);
+    vase::Shard::release(item.text);
+  }
+}
+
+void GenericBuffer::list_history(BEd &ctx) {
+  uint64_t current = base_version + undo_stack.size();
+  uint64_t max_version = current + redo_stack.size();
+  size_t width = std::to_string(max_version).size();
+  for (size_t i = 0; i < undo_stack.size(); ++i) {
+    auto &item = undo_stack[i];
+    uint64_t version = base_version + i;
+    auto time = std::chrono::system_clock::to_time_t(item.timestamp);
+    std::tm tm = *std::localtime(&time);
+    ctx.io.write_line(
+      std::format(
+        "  {:>{}}  {:04}-{:02}-{:02} {:02}:{:02}:{:02} {}",
+        version,
+        width,
+        tm.tm_year + 1900,
+        tm.tm_mon + 1,
+        tm.tm_mday,
+        tm.tm_hour,
+        tm.tm_min,
+        tm.tm_sec,
+        item.summary
+      )
+    );
+  }
+  {
+    auto time = std::chrono::system_clock::to_time_t(timestamp);
+    std::tm tm = *std::localtime(&time);
+    ctx.io.write_line(
+      std::format(
+        "* {:>{}}  {:04}-{:02}-{:02} {:02}:{:02}:{:02} {}",
+        current,
+        width,
+        tm.tm_year + 1900,
+        tm.tm_mon + 1,
+        tm.tm_mday,
+        tm.tm_hour,
+        tm.tm_min,
+        tm.tm_sec,
+        action
+      )
+    );
+  }
+  for (size_t i = 0; i < redo_stack.size(); ++i) {
+    auto &item = redo_stack[redo_stack.size() - 1 - i];
+    uint64_t version = current + i + 1;
+    auto time = std::chrono::system_clock::to_time_t(item.timestamp);
+    std::tm tm = *std::localtime(&time);
+    ctx.io.write_line(
+      std::format(
+        "  {:>{}}  {:04}-{:02}-{:02} {:02}:{:02}:{:02} {}",
+        version,
+        width,
+        tm.tm_year + 1900,
+        tm.tm_mon + 1,
+        tm.tm_mday,
+        tm.tm_hour,
+        tm.tm_min,
+        tm.tm_sec,
+        item.summary
+      )
+    );
+  }
+}
+
+ReadonlyBuffer *GenericBuffer::get_history(uint64_t version) {
+  uint64_t current = base_version + undo_stack.size();
+  if (version < base_version)
+    throw ed_error("History version has been pruned.");
+  if (version < current) {
+    auto &item = undo_stack[version - base_version];
+    return new ReadonlyBuffer(name, item.text, item.parse_state);
+  }
+  if (version == current)
+    return new ReadonlyBuffer(name, root, parse);
+  uint64_t redo_offset = version - current - 1;
+  if (redo_offset >= redo_stack.size())
+    throw ed_error("No such history version.");
+  auto &item = redo_stack[redo_stack.size() - 1 - redo_offset];
+  return new ReadonlyBuffer(name, item.text, item.parse_state);
+}
+
+void GenericBuffer::snapshot(std::string action_) {
+  if (base_version == 0) {
+    base_version++;
+  } else {
+    vase::Shard::retain(root);
+    undo_stack.push_back(
+      HistoryItem{
+        syntax::retain(parse),
+        root,
+        timestamp,
+        action
+      }
+    );
+  }
+  for (auto &item : redo_stack) {
+    syntax::release(item.parse_state);
+    vase::Shard::release(item.text);
+  }
+  redo_stack.clear();
+  timestamp = std::chrono::system_clock::now();
+  action = action_;
+}
+
+bool GenericBuffer::undo(BEd &ctx) {
+  if (undo_stack.empty())
+    return false;
+  HistoryItem prev = undo_stack.back();
+  undo_stack.pop_back();
+  vase::Shard::retain(root);
+  redo_stack.push_back(
+    HistoryItem{
+      syntax::retain(parse),
+      root,
+      timestamp,
+      action
+    }
+  );
+  vase::Shard::release(root);
+  root = prev.text;
+  syntax::release(parse);
+  parse = prev.parse_state;
+  timestamp = prev.timestamp;
+  action = prev.summary;
+  state = Modified;
+  if (!root) {
+    ctx.prev().buffername = name;
+    ctx.prev().start = 0;
+    ctx.prev().end = 0;
+  } else {
+    ctx.prev().buffername = name;
+    ctx.prev().start = 1;
+    ctx.prev().end = root->lines + 1;
+  }
+  return true;
+}
+
+bool GenericBuffer::redo(BEd &ctx) {
+  if (redo_stack.empty())
+    return false;
+  HistoryItem next = redo_stack.back();
+  redo_stack.pop_back();
+  vase::Shard::retain(root);
+  undo_stack.push_back(
+    HistoryItem{
+      syntax::retain(parse),
+      root,
+      timestamp,
+      action
+    }
+  );
+  vase::Shard::release(root);
+  root = next.text;
+  syntax::release(parse);
+  parse = next.parse_state;
+  timestamp = next.timestamp;
+  action = next.summary;
+  state = Modified;
+  if (!root) {
+    ctx.prev().buffername = name;
+    ctx.prev().start = 0;
+    ctx.prev().end = 0;
+  } else {
+    ctx.prev().buffername = name;
+    ctx.prev().start = 1;
+    ctx.prev().end = root->lines + 1;
+  }
+  return true;
+}
+
+uint64_t GenericBuffer::prune(int keep) {
+  size_t drop =
+    undo_stack.size() > (size_t)keep
+      ? undo_stack.size() - keep
+      : 0;
+  for (size_t i = 0; i < drop; ++i) {
+    syntax::release(undo_stack[i].parse_state);
+    vase::Shard::release(undo_stack[i].text);
+  }
+  undo_stack.erase(
+    undo_stack.begin(),
+    undo_stack.begin() + drop
+  );
+  base_version += drop;
+  for (auto &item : redo_stack) {
+    syntax::release(item.parse_state);
+    vase::Shard::release(item.text);
+  }
+  redo_stack.clear();
+  return undo_stack.size();
+}
+
+bool GenericBuffer::waste() {
+  return save_path.empty()
+         && root == nullptr
+         && undo_stack.empty()
+         && parse.lang == nullptr;
+}
+
+void GenericBuffer::saved_hook() {
+  state = buffer::GenericBuffer::Unmodified;
+}
+
+void GenericBuffer::language(BEd &ctx, std::string name) {
+  syntax::Language *lang = nullptr;
+  if (name.size()) {
+    auto it = ctx.languages.find(name);
+    if (it == ctx.languages.end())
+      throw ed_error("Language not found.");
+    lang = it->second;
+  }
+  if (lang == parse.lang)
+    return;
+  snapshot("Change buffer language.");
+  syntax::release(parse);
+  parse = syntax::make_parser(root, lines(), lang);
+}
+
+void GenericBuffer::load(BEd &ctx, vase::Shard *text) {
+  snapshot("Load file.");
+  if (lines())
+    ctx.marks.erase(name, 1, lines());
+  vase::Shard::release(root);
+  vase::Shard::retain(text);
+  root = text;
+  state = buffer::GenericBuffer::Unmodified;
+  if (!text) {
+    ctx.prev().buffername = name;
+    ctx.prev().start = 0;
+    ctx.prev().end = 0;
+  } else {
+    ctx.prev().buffername = name;
+    ctx.prev().start = 1;
+    ctx.prev().end = text->lines + 1;
+  }
+  ctx.current() = {name, lines()};
+  syntax::release(parse);
+  parse = syntax::make_parser(root, lines(), nullptr);
+}
+
+void GenericBuffer::set_filename(std::filesystem::path path) {
+  save_path = path;
+}
+
+std::filesystem::path GenericBuffer::filename() {
+  return save_path;
+};
+
+void GenericBuffer::append(BEd &ctx, vase::Shard *text, uint64_t line) {
+  snapshot(std::format("Insert {} lines after line {}", (text ? text->lines + 1 : 1), line));
+  ctx.prev().buffername = name;
+  ctx.prev().start = line + 1;
+  ctx.prev().end = line + (text ? text->lines + 1 : 1);
+  ctx.current() = {name, line + (text ? text->lines + 1 : 1)};
+  root = vase::insert(&ctx.append, root, text, line);
+  ctx.marks.insert(name, line, (text ? text->lines + 1 : 1));
+  if (parse.lang)
+    syntax::insert(parse, root, line, (text ? text->lines + 1 : 1));
+  state = Modified;
+}
+
+void GenericBuffer::remove(BEd &ctx, uint64_t start_line, uint64_t end_line) {
+  snapshot(std::format("Remove lines {} to {}", start_line, end_line));
+  root = vase::erase(root, start_line, end_line);
+  ctx.prev().buffername = name;
+  uint64_t l = std::min(start_line, lines());
+  ctx.prev().start = l;
+  ctx.prev().end = l;
+  ctx.current() = {name, l};
+  ctx.marks.erase(name, start_line, end_line - start_line + 1);
+  if (parse.lang)
+    syntax::erase(parse, root, start_line, end_line - start_line + 1);
+  state = Modified;
+}
+
+void GenericBuffer::replace(BEd &ctx, vase::Shard *text, uint64_t start_line, uint64_t end_line) {
+  if (!text) {
+    remove(ctx, start_line, end_line);
+    return;
+  }
+  snapshot(std::format("Replace lines {} to {} with {} lines", start_line, end_line, text->lines));
+  ctx.prev().buffername = name;
+  ctx.prev().start = start_line;
+  ctx.prev().end = start_line + text->lines;
+  ctx.current() = {name, start_line + text->lines};
+  uint64_t new_count = text->lines + 1;
+  uint64_t old_count = end_line - start_line + 1;
+  root = vase::replace(root, text, start_line, end_line);
+  if (parse.lang) {
+    syntax::Edit edit(parse);
+    edit.erase(start_line, old_count);
+    edit.insert(start_line, new_count);
+    edit.commit(root);
+  }
+  if (new_count > old_count) {
+    uint64_t diff = new_count - old_count;
+    ctx.marks.insert(name, end_line, diff);
+  } else if (new_count < old_count) {
+    uint64_t diff = old_count - new_count;
+    ctx.marks.collapse(name, start_line + new_count - 1, diff);
+  }
+  state = Modified;
+}
+
+void GenericBuffer::join(BEd &ctx, uint64_t start_line, uint64_t end_line) {
+  snapshot(std::format("Join lines {} to {}", start_line, end_line));
+  root = vase::join(root, start_line, end_line);
+  ctx.prev().buffername = name;
+  ctx.prev().start = start_line;
+  ctx.prev().end = start_line;
+  ctx.current() = {name, start_line};
+  ctx.marks.collapse(name, start_line, end_line - start_line);
+  if (parse.lang)
+    syntax::erase(parse, root, start_line, end_line - start_line);
+  state = Modified;
+}
+
+void GenericBuffer::substitute(
+  BEd &ctx, uint64_t start_line, uint64_t end_line,
+  std::string &regex, std::string &replacement, std::string &options
+) {
+  snapshot(std::format("Substitute /{}/ with /{}/ in lines {} to {}", regex, replacement, start_line, end_line));
+  ctx.prev().buffername = name;
+  ctx.prev().start = start_line;
+  ctx.prev().end = end_line;
+  std::optional<syntax::Edit> edit;
+  if (parse.lang)
+    edit.emplace(parse);
+  root = vase::substitute(
+    &ctx.append,
+    root,
+    regex,
+    start_line,
+    end_line,
+    replacement,
+    options,
+    [&](uint64_t line, uint64_t old_lines, uint64_t new_lines) {
+      if (old_lines) {
+        ctx.marks.erase(name, line, old_lines);
+        if (edit)
+          edit->erase(line, old_lines);
+      }
+      if (new_lines) {
+        ctx.marks.insert(name, line, new_lines);
+        if (edit)
+          edit->insert(line, new_lines);
+      }
+      ctx.current() = {name, line + new_lines};
+    }
+  );
+  if (edit)
+    edit->commit(root);
+  state = Modified;
+}
+} // namespace bed::internal::buffer

src/internal/buffer/shard.cc

@@ -0,0 +1,141 @@
+#include "bed.h"
+#include "internal/buffer/buffer.h"
+
+namespace bed::internal::buffer {
+uint64_t ShardBuffer::lines() {
+  if (root)
+    return root->lines + 1;
+  return 0;
+}
+
+uint64_t ShardBuffer::bytes() {
+  if (root)
+    return root->length + 1;
+  return 0;
+}
+
+vase::Shard *ShardBuffer::copy(uint64_t start_line, uint64_t end_line) {
+  return vase::copy(root, start_line, end_line);
+}
+
+uint64_t ShardBuffer::find_next(std::string_view pattern, uint64_t start) {
+  return vase::find_next(root, pattern, start);
+}
+
+uint64_t ShardBuffer::find_prev(std::string_view pattern, uint64_t start) {
+  return vase::find_prev(root, pattern, start);
+}
+
+uint64_t ShardBuffer::next_closing(uint64_t start) {
+  if (parse.lang) {
+    uint64_t closing = syntax::next_closing(parse, start - 1);
+    return closing + 1;
+  } else {
+    start += 10;
+    if (start > lines())
+      return lines();
+    return start;
+  }
+}
+
+uint64_t ShardBuffer::prev_closing(uint64_t start) {
+  if (parse.lang) {
+    return syntax::prev_opening(parse, start - 1) + 1;
+  } else {
+    if (start > 10)
+      return start - 10;
+    return 0;
+  }
+}
+
+void ShardBuffer::print(BEd &ctx, uint64_t start_line, uint64_t end_line) {
+  ctx.prev().buffername = name;
+  ctx.prev().start = start_line;
+  ctx.prev().end = end_line;
+  if (parse.lang) {
+    auto it_o = syntax::get_hl(parse, root, start_line - 1);
+    if (!it_o)
+      goto h;
+    auto &it = *it_o;
+    while (start_line <= end_line) {
+      it.next();
+      const std::string &line = it.it->line;
+      const auto &tokens = it.tokens;
+      uint32_t cursor = 0;
+      for (const auto &token : tokens) {
+        const uint32_t start = token.start;
+        const uint32_t end = token.end;
+        if (start > line.size() || end > line.size())
+          break;
+        if (cursor < start)
+          ctx.io.write(line.data() + cursor, start - cursor);
+        ctx.io.apply(token.type);
+        ctx.io.write(line.data() + start, end - start);
+        ctx.io.reset();
+        cursor = end;
+      }
+      if (cursor < line.size())
+        ctx.io.write(line.data() + cursor, line.size() - cursor);
+      ctx.io.write_line("");
+      ++start_line;
+    }
+  } else {
+  h:
+    vase::Iterator it(root, start_line - 1, Direction::Forward);
+    while (it.next() && start_line++ <= end_line)
+      ctx.io.write_line(it.line);
+  }
+}
+
+void ShardBuffer::number_print(BEd &ctx, uint64_t start_line, uint64_t end_line) {
+  ctx.prev().buffername = name;
+  ctx.prev().start = start_line;
+  ctx.prev().end = end_line;
+  uint8_t width = 1;
+  for (uint64_t n = end_line; n >= 10; n /= 10)
+    ++width;
+  if (parse.lang) {
+    std::optional<syntax::Iterator> it_o = syntax::get_hl(parse, root, start_line - 1);
+    if (!it_o)
+      goto h;
+    auto &it = *it_o;
+    while (start_line <= end_line) {
+      it.next();
+      ctx.io.write(std::format("{:>{}}\t", start_line, width));
+      const std::string &line = it.it->line;
+      const auto &tokens = it.tokens;
+      uint32_t cursor = 0;
+      for (const auto &token : tokens) {
+        const uint32_t start = token.start;
+        const uint32_t end = token.end;
+        if (start > line.size() || end > line.size())
+          break;
+        if (cursor < start)
+          ctx.io.write(line.data() + cursor, start - cursor);
+        ctx.io.apply(token.type);
+        ctx.io.write(line.data() + start, end - start);
+        ctx.io.reset();
+        cursor = end;
+      }
+      if (cursor < line.size())
+        ctx.io.write(line.data() + cursor, line.size() - cursor);
+      ctx.io.write_line("");
+      ++start_line;
+    }
+  } else {
+  h:
+    vase::Iterator it(root, start_line - 1, Direction::Forward);
+    while (it.next() && start_line <= end_line)
+      ctx.io.write_line(std::format("{:>{}}\t{}", start_line++, width, it.line));
+  }
+}
+
+void ShardBuffer::list_print(BEd &ctx, uint64_t start_line, uint64_t end_line) {
+  ctx.prev().buffername = name;
+  ctx.prev().start = start_line;
+  ctx.prev().end = end_line;
+  vase::Iterator it(root, start_line - 1, Direction::Forward);
+  while (it.next() && start_line++ <= end_line)
+    ctx.io.write_line(list_string(it.line));
+}
+} // namespace bed::internal::buffer

src/internal/buffer/special/clip.cc

@@ -0,0 +1,210 @@
+#include "bed.h"
+#include "internal/buffer/buffer.h"
+
+namespace bed::internal::buffer {
+ClipBuffer::~ClipBuffer() {}
+
+bool ClipBuffer::waste() {
+  return false;
+}
+
+void ClipBuffer::saved_hook() {}
+
+uint64_t ClipBuffer::lines() {
+  auto s = vase::Shard::from_command("xclip -selection clipboard -o");
+  uint64_t lines = s ? s->lines + 1 : 0;
+  vase::Shard::release(s);
+  return lines;
+}
+
+uint64_t ClipBuffer::bytes() {
+  auto s = vase::Shard::from_command("xclip -selection clipboard -o");
+  uint64_t length = s ? s->length + 1 : 0;
+  vase::Shard::release(s);
+  return length;
+}
+
+void ClipBuffer::clip_write(vase::Shard *text) {
+  FILE *pipe = popen("xclip -selection clipboard -i", "w");
+  if (!pipe)
+    throw ed_error("can't access clipboard");
+  auto s = vase::to_string(text);
+  fwrite(s.data(), 1, s.length(), pipe);
+  if (pclose(pipe) != 0)
+    throw ed_error("can't write clipboard");
+}
+
+void ClipBuffer::load(BEd &ctx, vase::Shard *text) {
+  clip_write(text);
+  if (!text) {
+    ctx.prev().buffername = name;
+    ctx.prev().start = 0;
+    ctx.prev().end = 0;
+  } else {
+    ctx.prev().buffername = name;
+    ctx.prev().start = 1;
+    ctx.prev().end = text->lines + 1;
+  }
+}
+
+void ClipBuffer::set_filename(std::filesystem::path) {}
+
+std::filesystem::path ClipBuffer::filename() {
+  return "";
+};
+
+void ClipBuffer::append(BEd &ctx, vase::Shard *text, uint64_t line) {
+  ctx.prev().buffername = name;
+  ctx.prev().start = line + 1;
+  ctx.prev().end = line + (text ? text->lines + 1 : 0);
+  auto s = vase::Shard::from_command("xclip -selection clipboard -o");
+  s = vase::insert(&ctx.append, s, text, line);
+  clip_write(s);
+  vase::Shard::release(s);
+  ctx.marks.insert(name, line, text->lines + 1);
+}
+
+void ClipBuffer::remove(BEd &ctx, uint64_t start_line, uint64_t end_line) {
+  auto s = vase::Shard::from_command("xclip -selection clipboard -o");
+  s = vase::erase(s, start_line, end_line);
+  clip_write(s);
+  ctx.prev().buffername = name;
+  ctx.prev().start = std::min(start_line, s ? s->lines + 1 : 0);
+  ctx.prev().end = std::min(start_line, s ? s->lines + 1 : 0);
+  vase::Shard::release(s);
+  ctx.marks.erase(name, start_line, end_line - start_line + 1);
+}
+
+void ClipBuffer::replace(BEd &ctx, vase::Shard *text, uint64_t start_line, uint64_t end_line) {
+  if (!text) {
+    remove(ctx, start_line, end_line);
+    return;
+  }
+  ctx.prev().buffername = name;
+  ctx.prev().start = start_line;
+  ctx.prev().end = start_line + text->lines;
+  uint64_t new_count = text->lines + 1;
+  uint64_t old_count = end_line - start_line + 1;
+  auto s = vase::Shard::from_command("xclip -selection clipboard -o");
+  s = vase::replace(s, text, start_line, end_line);
+  clip_write(s);
+  vase::Shard::release(s);
+  if (new_count > old_count) {
+    uint64_t diff = new_count - old_count;
+    ctx.marks.insert(name, end_line, diff);
+  } else if (new_count < old_count) {
+    uint64_t diff = old_count - new_count;
+    ctx.marks.collapse(name, start_line + new_count - 1, diff);
+  }
+}
+
+void ClipBuffer::join(BEd &ctx, uint64_t start_line, uint64_t end_line) {
+  auto s = vase::Shard::from_command("xclip -selection clipboard -o");
+  s = vase::join(s, start_line, end_line);
+  clip_write(s);
+  vase::Shard::release(s);
+  ctx.prev().buffername = name;
+  ctx.prev().start = start_line;
+  ctx.prev().end = start_line;
+  ctx.marks.collapse(name, start_line, end_line - start_line);
+}
+
+void ClipBuffer::substitute(
+  BEd &ctx, uint64_t start_line, uint64_t end_line,
+  std::string &regex, std::string &replacement, std::string &options
+) {
+  ctx.prev().buffername = name;
+  ctx.prev().start = start_line;
+  ctx.prev().end = end_line;
+  auto s = vase::Shard::from_command("xclip -selection clipboard -o");
+  s = vase::substitute(
+    &ctx.append,
+    s,
+    regex,
+    start_line,
+    end_line,
+    replacement,
+    options,
+    [&](uint64_t line, uint64_t old_lines, uint64_t new_lines) {
+      if (old_lines)
+        ctx.marks.erase(name, line, old_lines);
+      if (new_lines)
+        ctx.marks.insert(name, line, new_lines);
+    }
+  );
+  clip_write(s);
+  vase::Shard::release(s);
+  ctx.prev().buffername = name;
+}
+
+vase::Shard *ClipBuffer::copy(uint64_t start_line, uint64_t end_line) {
+  auto s = vase::Shard::from_command("xclip -selection clipboard -o");
+  vase::Shard *o = vase::copy(s, start_line, end_line);
+  vase::Shard::release(s);
+  return o;
+}
+
+uint64_t ClipBuffer::find_next(std::string_view pattern, uint64_t start) {
+  auto s = vase::Shard::from_command("xclip -selection clipboard -o");
+  uint64_t line = vase::find_next(s, pattern, start);
+  vase::Shard::release(s);
+  return line;
+}
+
+uint64_t ClipBuffer::find_prev(std::string_view pattern, uint64_t start) {
+  auto s = vase::Shard::from_command("xclip -selection clipboard -o");
+  uint64_t line = vase::find_prev(s, pattern, start);
+  vase::Shard::release(s);
+  return line;
+}
+
+uint64_t ClipBuffer::next_closing(uint64_t start) {
+  start += 10;
+  uint64_t line = lines();
+  if (start > line)
+    return line;
+  return start;
+}
+
+uint64_t ClipBuffer::prev_closing(uint64_t start) {
+  if (start > 10)
+    return start - 10;
+  return 0;
+}
+
+void ClipBuffer::print(BEd &ctx, uint64_t start_line, uint64_t end_line) {
+  ctx.prev().buffername = name;
+  ctx.prev().start = start_line;
+  ctx.prev().end = end_line;
+  auto s = vase::Shard::from_command("xclip -selection clipboard -o");
+  vase::Iterator it(s, start_line - 1, Direction::Forward);
+  while (it.next() && start_line++ <= end_line)
+    ctx.io.write_line(it.line);
+  vase::Shard::release(s);
+}
+
+void ClipBuffer::number_print(BEd &ctx, uint64_t start_line, uint64_t end_line) {
+  ctx.prev().buffername = name;
+  ctx.prev().start = start_line;
+  ctx.prev().end = end_line;
+  uint8_t width = 1;
+  for (uint64_t n = end_line; n >= 10; n /= 10)
+    ++width;
+  auto s = vase::Shard::from_command("xclip -selection clipboard -o");
+  vase::Iterator it(s, start_line - 1, Direction::Forward);
+  while (it.next() && start_line <= end_line)
+    ctx.io.write_line(std::format("{:>{}}\t{}", start_line++, width, it.line));
+  vase::Shard::release(s);
+}
+
+void ClipBuffer::list_print(BEd &ctx, uint64_t start_line, uint64_t end_line) {
+  ctx.prev().buffername = name;
+  ctx.prev().start = start_line;
+  ctx.prev().end = end_line;
+  auto s = vase::Shard::from_command("xclip -selection clipboard -o");
+  vase::Iterator it(s, start_line - 1, Direction::Forward);
+  while (it.next() && start_line++ <= end_line)
+    ctx.io.write_line(list_string(it.line));
+  vase::Shard::release(s);
+}
+} // namespace bed::internal::buffer

src/internal/commands/commands.cc

@@ -1,162 +0,0 @@
-#include "internal/commands/commands.h"
-#include "bed.h"
-#include "internal/commands/suffixes.h"
-
-namespace bed::internal::commands {
-void Suffix::register_suffixes(BEd &ctx) {
-  ctx.suffixes['p' - 'a'] = Suffix{
-    .desc = "Prints current line.",
-    .handle = [](BEd &ctx) {
-      auto line = ctx.active->line;
-      ctx.active->print(ctx, line, line);
-    }
-  };
-}
-
-void Command::register_posix(BEd &ctx) {
-  ctx.no_op = Command{
-    .address_mode = Command::AddressMode::Single,
-    .suffix = Command::SuffixKind::None,
-    .desc = "Prints a line and jumps to it (default: .+1)",
-    .accept_zero = false,
-    .handle = [](BEd &ctx, std::span<const uint64_t> addresses, std::string_view) {
-      uint64_t line;
-      if (addresses.size())
-        line = addresses[0];
-      else
-        line = ctx.active->line + 1;
-      if (line == 0)
-        throw ed_error("Line 0 is invalid.");
-      ctx.active->jump(line);
-      ctx.active->print(ctx, line, line);
-    }
-  };
-  ctx.eof_op = Command{
-    .address_mode = Command::AddressMode::None,
-    .suffix = Command::SuffixKind::None,
-    .desc = "Try quitting.",
-    .accept_zero = false,
-    .handle = [](BEd &ctx, std::span<const uint64_t>, std::string_view) {
-      for (auto &[name, buffer] : ctx.buffers)
-        if (buffer->modified)
-          throw ed_error("Buffer " + name + " modified.");
-      throw fatal_error("Quitting", 0);
-    }
-  };
-  ctx.commands.insert(
-    "a",
-    Command{
-      .address_mode = Command::AddressMode::Single,
-      .suffix = Command::SuffixKind::Suffix,
-      .desc = "Append lines at address (default: .)",
-      .accept_zero = true,
-      .handle = [](BEd &, std::span<const uint64_t>, std::string_view) {
-        // TODO: start a text editing session, then append its stuff.
-      }
-    }
-  );
-  ctx.commands.insert(
-    "q",
-    Command{
-      .address_mode = Command::AddressMode::None,
-      .suffix = Command::SuffixKind::None,
-      .desc = "Try quitting.",
-      .accept_zero = false,
-      .handle = [](BEd &ctx, std::span<const uint64_t>, std::string_view) {
-        for (auto &[name, buffer] : ctx.buffers)
-          if (buffer->modified)
-            throw ed_error("Buffer " + name + " modified.");
-        throw fatal_error("Quitting", 0);
-      }
-    }
-  );
-  ctx.commands.insert(
-    "Q",
-    Command{
-      .address_mode = Command::AddressMode::None,
-      .suffix = Command::SuffixKind::None,
-      .desc = "Force quitting.",
-      .accept_zero = false,
-      .handle = [](BEd &, std::span<const uint64_t>, std::string_view) {
-        throw fatal_error("Force Quitting", 0);
-      }
-    }
-  );
-  ctx.commands.insert(
-    "p",
-    Command{
-      .address_mode = Command::AddressMode::Range,
-      .suffix = Command::SuffixKind::Suffix,
-      .desc = "Print range (default .,.)",
-      .accept_zero = false,
-      .handle = [](BEd &ctx, std::span<const uint64_t> addresses, std::string_view) {
-        uint64_t start_line = ctx.active->line;
-        uint64_t end_line = ctx.active->line;
-        if (!addresses.size())
-          ctx.active->print(ctx, start_line, end_line);
-        else if (addresses.size() == 1)
-          ctx.active->print(ctx, addresses[0], addresses[0]);
-        else
-          ctx.active->print(ctx, addresses[0], addresses[1]);
-      }
-    }
-  );
-  ctx.commands.insert(
-    "=",
-    Command{
-      .address_mode = Command::AddressMode::Single,
-      .suffix = Command::SuffixKind::Suffix,
-      .desc = "Print line number",
-      .accept_zero = false,
-      .handle = [](BEd &ctx, std::span<const uint64_t> addresses, std::string_view) {
-        if (!addresses.size())
-          std::cout << ctx.active->vase.lines() << std::endl;
-        else
-          std::cout << addresses[0] << std::endl;
-      }
-    }
-  );
-  ctx.commands.insert(
-    "debug",
-    Command{
-      .address_mode = Command::AddressMode::None,
-      .suffix = Command::SuffixKind::None,
-      .desc = "",
-      .accept_zero = false,
-      .handle = [](BEd &ctx, std::span<const uint64_t>, std::string_view) {
-        syntax::dump_events(ctx.active->parser->root);
-      }
-    }
-  );
-  ctx.commands.insert(
-    "E",
-    Command{
-      .address_mode = Command::AddressMode::None,
-      .suffix = Command::SuffixKind::Argument,
-      .desc = "Load a file into the current buffer.",
-      .accept_zero = true,
-      .handle = [](BEd &ctx, std::span<const uint64_t>, std::string_view file) {
-        bool empty = false;
-        if (file.empty())
-          empty = true;
-        uint64_t i = 0;
-        while (i < file.length() && (file[i] == ' ' || file[i] == '\t'))
-          i++;
-        if (i >= file.size())
-          empty = true;
-        if (empty) {
-          if (ctx.active->save_path == "")
-            throw ed_error("Need filename!");
-          ctx.active->load(ctx.active->save_path);
-        } else if (file[i] == '!') {
-          file = file.substr(1);
-          ctx.active->load(file);
-        } else {
-          ctx.active->load(std::filesystem::path(file));
-        }
-        std::cout << ctx.active->vase.length() << std::endl;
-      }
-    }
-  );
-}
-} // namespace bed::internal::commands

src/internal/functions/extended.cc

@@ -0,0 +1,531 @@
+#include "bed.h"
+#include "internal/functions/functions.h"
+#include "internal/functions/suffixes.h"
+
+namespace bed::internal::functions {
+static std::string_view address_kind_str(Function::AddressKind k) {
+  switch (k) {
+  case Function::AddressKind::None:
+    return "none";
+  case Function::AddressKind::Line:
+    return "1 line";
+  case Function::AddressKind::Range:
+    return "range";
+  }
+  return "";
+}
+
+static std::string_view input_mode_str(Function::InputMode m) {
+  switch (m) {
+  case Function::InputMode::None:
+    return "";
+  case Function::InputMode::Text:
+    return "text";
+  case Function::InputMode::Interactive:
+    return "interactive";
+  case Function::InputMode::CommandList:
+    return "command list";
+  }
+  return "";
+}
+
+static std::string_view argument_kind_str(Function::ArgumentKind a) {
+  switch (a) {
+  case Function::ArgumentKind::None:
+    return "";
+  case Function::ArgumentKind::Regex:
+    return "regex";
+  case Function::ArgumentKind::Shell:
+    return "shell command";
+  case Function::ArgumentKind::Any:
+    return "any";
+  case Function::ArgumentKind::File:
+    return "file";
+  case Function::ArgumentKind::Global:
+    return "ed global-style";
+  case Function::ArgumentKind::Mark:
+    return "mark name";
+  case Function::ArgumentKind::Number:
+    return "number";
+  case Function::ArgumentKind::Line:
+    return "address";
+  case Function::ArgumentKind::Range:
+    return "range";
+  case Function::ArgumentKind::Ruby:
+    return "ruby code";
+  }
+  return "";
+}
+
+static void append_field(BEd &ctx, std::string_view label, io::Token::Kind color, std::string_view value) {
+  if (value.empty())
+    return;
+  ctx.io.write("\n");
+  ctx.io.apply(color);
+  ctx.io.write(label);
+  ctx.io.reset();
+  ctx.io.write(": ");
+  ctx.io.write(value);
+}
+
+static void describe_function(BEd &ctx, const Function &func) {
+  ctx.io.write(func.desc);
+  ctx.io.reset();
+  append_field(ctx, "Default address", io::Token::Color1, func.default_address);
+  append_field(ctx, "Address", io::Token::Color2, address_kind_str(func.address_kind));
+  if (func.accept_zero)
+    append_field(ctx, "Zero address", io::Token::Color3, "allowed");
+  append_field(ctx, "Input", io::Token::Color4, input_mode_str(func.input_mode));
+  append_field(ctx, "Argument", io::Token::Color5, argument_kind_str(func.argument_kind));
+  ctx.io.write("\n");
+}
+
+void Function::register_extented(BEd &ctx) {
+  ctx.functions.insert(
+    "*",
+    Function{
+      .address_kind = Function::AddressKind::None,
+      .argument_kind = Function::ArgumentKind::Any,
+      .input_mode = Function::InputMode::None,
+      .desc = "Explain a command",
+      .default_address = "",
+      .accept_zero = false,
+      .pre_text_mode = nullptr,
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &,
+                  vase::Shard *,
+                  const Argument &arg_,
+                  std::vector<buffer::Line> *
+                ) {
+        auto str = std::get<std::string>(arg_);
+        const auto first = str.find_first_not_of(" \t");
+        const auto last = str.find_last_not_of(" \t");
+        if (first == std::string::npos)
+          str.clear();
+        else
+          str = str.substr(first, last - first + 1);
+        if (str.empty()) {
+          describe_function(ctx, ctx.no_op);
+          return;
+        }
+        auto len = ctx.functions.longest_match(str);
+        if (len == str.size()) {
+          describe_function(ctx, *ctx.functions.get_ptr(str));
+          return;
+        }
+        throw ed_error("Not a valid function name.");
+      },
+    }
+  );
+  ctx.functions.insert(
+    "b",
+    Function{
+      .address_kind = Function::AddressKind::None,
+      .argument_kind = Function::ArgumentKind::None,
+      .input_mode = Function::InputMode::None,
+      .desc = "List active buffers",
+      .default_address = "",
+      .accept_zero = false,
+      .pre_text_mode = nullptr,
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *,
+                  const Argument &,
+                  std::vector<buffer::Line> *
+                ) {
+        auto &current = std::get<std::string>(addr_);
+        bool current_real = false;
+        for (auto &[name, _] : ctx.buffers) {
+          if (current == name) {
+            ctx.io.write("* ");
+            current_real = true;
+          } else {
+            ctx.io.write("  ");
+          }
+          ctx.io.write_line(name);
+        }
+        if (!current_real)
+          ctx.io.write_line("* " + current);
+      },
+    }
+  );
+  ctx.functions.insert(
+    "#",
+    Function{
+      .address_kind = Function::AddressKind::None,
+      .argument_kind = Function::ArgumentKind::Any,
+      .input_mode = Function::InputMode::None,
+      .desc = "Write a comment",
+      .default_address = "",
+      .accept_zero = false,
+      .pre_text_mode = nullptr,
+      .handle = [](
+                  BEd &,
+                  const buffer::Address &,
+                  vase::Shard *,
+                  const Argument &,
+                  std::vector<buffer::Line> *
+                ) {},
+    }
+  );
+  ctx.functions.insert(
+    "`",
+    Function{
+      .address_kind = Function::AddressKind::Range,
+      .argument_kind = Function::ArgumentKind::Ruby,
+      .input_mode = Function::InputMode::None,
+      .desc = "Execute given ruby code.",
+      .default_address = "0,0",
+      .accept_zero = true,
+      .pre_text_mode = nullptr,
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *,
+                  const Argument &arg_,
+                  std::vector<buffer::Line> *
+                ) {
+        auto &addr = std::get<buffer::Range>(addr_);
+        auto &arg = std::get<RubyArg>(arg_);
+        auto pre_code = "$START=" + std::to_string(addr.start)
+                        + ";$END=" + std::to_string(addr.end)
+                        + ";$BUFNAME=\"" + addr.buffername + "\"";
+        scripting::run(ctx, pre_code);
+        auto line = scripting::run(ctx, arg.cmd);
+        ctx.io.write("=> ", 3);
+        auto parser = syntax::MiniParser(
+          *ctx.languages["ruby"],
+          vase::Shard::from_string(line.data(), line.size()),
+          nullptr
+        );
+        const auto &tokens = parser.lines[0].second;
+        uint32_t cursor = 0;
+        for (const auto &token : tokens) {
+          const uint32_t start = token.start;
+          const uint32_t end = token.end;
+          if (start > line.size() || end > line.size())
+            break;
+          if (cursor < start)
+            ctx.io.write(line.data() + cursor, start - cursor);
+          ctx.io.apply(token.type);
+          ctx.io.write(line.data() + start, end - start);
+          ctx.io.reset();
+          cursor = end;
+        }
+        if (cursor < line.size())
+          ctx.io.write(line.data() + cursor, line.size() - cursor);
+        ctx.io.write_line("");
+      },
+    }
+  );
+  ctx.functions.insert(
+    "``",
+    Function{
+      .address_kind = Function::AddressKind::Range,
+      .argument_kind = Function::ArgumentKind::None,
+      .input_mode = Function::InputMode::None,
+      .desc = "Execute addressed lines as ruby code.",
+      .default_address = "1,$",
+      .accept_zero = false,
+      .pre_text_mode = nullptr,
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *,
+                  const Argument &,
+                  std::vector<buffer::Line> *
+                ) {
+        auto &addr = std::get<buffer::Range>(addr_);
+        auto &buf = ctx.buffer(addr.buffername);
+        auto code = buf.copy(addr.start, addr.end);
+        ctx.prev().buffername = addr.buffername;
+        ctx.prev().start = addr.start;
+        ctx.prev().end = addr.end;
+        ctx.current() = {addr.buffername, addr.end};
+        auto pre_code = "$START=" + std::to_string(addr.start)
+                        + ";$END=" + std::to_string(addr.end)
+                        + ";$BUFNAME=\"" + addr.buffername + "\"";
+        scripting::run(ctx, pre_code);
+        scripting::run(ctx, vase::to_string(code));
+        vase::Shard::release(code);
+      },
+    }
+  );
+  ctx.functions.insert(
+    "echo",
+    Function{
+      .address_kind = Function::AddressKind::Range,
+      .argument_kind = Function::ArgumentKind::Any,
+      .input_mode = Function::InputMode::None,
+      .desc = "Echo the given message (replacing $1-$4 with address information)",
+      .default_address = "",
+      .accept_zero = true,
+      .pre_text_mode = nullptr,
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *,
+                  const Argument &arg_,
+                  std::vector<buffer::Line> *
+                ) {
+        auto &addr = std::get<buffer::Range>(addr_);
+        auto str = std::get<std::string>(arg_);
+        const auto first = str.find_first_not_of(" \t");
+        const auto last = str.find_last_not_of(" \t");
+        if (first == std::string::npos)
+          str.clear();
+        else
+          str = str.substr(first, last - first + 1);
+        for (size_t i = 0; i < str.size();) {
+          if (str[i] == '\\') {
+            if (i + 1 >= str.size())
+              break;
+            str.erase(i++, 1);
+            if (str[i - 1] == 'n')
+              str[i - 1] = '\n';
+            continue;
+          }
+          if (str[i] == '$' && i + 1 < str.size() && '1' <= str[i + 1] && str[i + 1] <= '4') {
+            char c = str[i + 1];
+            str.erase(i, 2);
+            switch (c) {
+            case '1': {
+              auto start = std::to_string(addr.start);
+              str.insert(i, start);
+              i += start.size();
+            } break;
+            case '2': {
+              auto end = std::to_string(addr.end);
+              str.insert(i, end);
+              i += end.size();
+            } break;
+            case '3': {
+              str.insert(i, addr.buffername);
+              i += addr.buffername.size();
+            } break;
+            case '4': {
+              auto &buf = ctx.buffer(addr.buffername);
+              auto filename = buf.filename().string();
+              str.insert(i, filename);
+              i += filename.size();
+            } break;
+            }
+            continue;
+          }
+          i++;
+        }
+        ctx.io.write_line(str);
+      },
+    }
+  );
+  ctx.functions.insert(
+    "cd",
+    Function{
+      .address_kind = Function::AddressKind::None,
+      .argument_kind = Function::ArgumentKind::Any,
+      .input_mode = Function::InputMode::None,
+      .desc = "Change directory",
+      .default_address = "",
+      .accept_zero = false,
+      .pre_text_mode = nullptr,
+      .handle = [](
+                  BEd &,
+                  const buffer::Address &,
+                  vase::Shard *,
+                  const Argument &arg_,
+                  std::vector<buffer::Line> *
+                ) {
+        auto path = std::get<std::string>(arg_);
+        const auto first = path.find_first_not_of(" \t");
+        const auto last = path.find_last_not_of(" \t");
+        if (first == std::string::npos)
+          path.clear();
+        else
+          path = path.substr(first, last - first + 1);
+        if (path.empty())
+          path = getenv("HOME");
+        if (path == "~")
+          path = getenv("HOME");
+        if (path.starts_with("~/")) {
+          const char *home = getenv("HOME");
+          if (home)
+            path = std::string(home) + path.substr(1);
+        }
+        if (chdir(path.c_str()) == -1)
+          throw ed_error("Can't change directory.");
+      },
+    }
+  );
+  ctx.functions.insert(
+    "pwd",
+    Function{
+      .address_kind = Function::AddressKind::None,
+      .argument_kind = Function::ArgumentKind::None,
+      .input_mode = Function::InputMode::None,
+      .desc = "Print the current working directory",
+      .default_address = "",
+      .accept_zero = false,
+      .pre_text_mode = nullptr,
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &,
+                  vase::Shard *,
+                  const Argument &,
+                  std::vector<buffer::Line> *
+                ) {
+        char cwd[PATH_MAX];
+        if (!getcwd(cwd, sizeof(cwd)))
+          throw ed_error("Can't determine current directory.");
+        ctx.io.write_line(cwd);
+      },
+    }
+  );
+  ctx.functions.insert(
+    "x",
+    Function{
+      .address_kind = Function::AddressKind::Range,
+      .argument_kind = Function::ArgumentKind::Range,
+      .input_mode = Function::InputMode::None,
+      .desc = "Exchange a range of lines for another",
+      .default_address = ".,.",
+      .accept_zero = false,
+      .pre_text_mode = nullptr,
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *,
+                  const Argument &arg_,
+                  std::vector<buffer::Line> *
+                ) {
+        auto addr = std::get<buffer::Range>(addr_);
+        auto arg = std::get<buffer::Range>(arg_);
+        auto text = ctx.buffer(addr.buffername).copy(addr.start, addr.end);
+        try {
+          ctx.buffer(arg.buffername).replace(ctx, text, arg.start, arg.end);
+          vase::Shard::release(text);
+        } catch (...) {
+          vase::Shard::release(text);
+          throw;
+        }
+      },
+    }
+  );
+  ctx.functions.insert(
+    "U",
+    Function{
+      .address_kind = Function::AddressKind::None,
+      .argument_kind = Function::ArgumentKind::None,
+      .input_mode = Function::InputMode::None,
+      .desc = "Redo the last undo modification",
+      .default_address = "",
+      .accept_zero = false,
+      .pre_text_mode = nullptr,
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *,
+                  const Argument &,
+                  std::vector<buffer::Line> *
+                ) {
+        auto &addr = std::get<std::string>(addr_);
+        auto &buf_ = ctx.buffer(addr);
+        if (buf_.kind != buffer::Buffer::Kind::Generic)
+          throw ed_error("Can't redo buffer");
+        auto &buf = *(buffer::GenericBuffer *)&buf_;
+        if (!buf.redo(ctx))
+          throw ed_error("Can't redo buffer.");
+      }
+    }
+  );
+  ctx.functions.insert(
+    "hl",
+    Function{
+      .address_kind = Function::AddressKind::None,
+      .argument_kind = Function::ArgumentKind::None,
+      .input_mode = Function::InputMode::None,
+      .desc = "List available history versions",
+      .default_address = "",
+      .accept_zero = false,
+      .pre_text_mode = nullptr,
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *,
+                  const Argument &,
+                  std::vector<buffer::Line> *
+                ) {
+        auto &addr = std::get<std::string>(addr_);
+        auto &buf_ = ctx.buffer(addr);
+        if (buf_.kind != buffer::Buffer::Kind::Generic)
+          throw ed_error("Can't redo buffer");
+        auto &buf = *(buffer::GenericBuffer *)&buf_;
+        buf.list_history(ctx);
+      }
+    }
+  );
+  ctx.functions.insert(
+    "hp",
+    Function{
+      .address_kind = Function::AddressKind::None,
+      .argument_kind = Function::ArgumentKind::Number,
+      .input_mode = Function::InputMode::None,
+      .desc = "Prune old history versions",
+      .default_address = "",
+      .accept_zero = false,
+      .pre_text_mode = nullptr,
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *,
+                  const Argument &arg_,
+                  std::vector<buffer::Line> *
+                ) {
+        auto &addr = std::get<std::string>(addr_);
+        auto &arg = std::get<int64_t>(arg_);
+        auto &buf_ = ctx.buffer(addr);
+        if (buf_.kind != buffer::Buffer::Kind::Generic)
+          throw ed_error("Can't prune buffer.");
+        auto &buf = *(buffer::GenericBuffer *)&buf_;
+        auto versions = buf.prune(arg);
+        if (!ctx.suppress_mode)
+          ctx.io.write_line(std::format("{} undo versions left.", versions));
+      }
+    }
+  );
+  ctx.functions.insert(
+    "lang",
+    Function{
+      .address_kind = Function::AddressKind::None,
+      .argument_kind = Function::ArgumentKind::Any,
+      .input_mode = Function::InputMode::None,
+      .desc = "Set buffer language",
+      .default_address = "",
+      .accept_zero = false,
+      .pre_text_mode = nullptr,
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *,
+                  const Argument &arg_,
+                  std::vector<buffer::Line> *
+                ) {
+        auto &addr = std::get<std::string>(addr_);
+        auto name = std::get<std::string>(arg_);
+        const auto first = name.find_first_not_of(" \t");
+        const auto last = name.find_last_not_of(" \t");
+        if (first == std::string::npos)
+          name.clear();
+        else
+          name = name.substr(first, last - first + 1);
+        auto &buf_ = ctx.buffer(addr);
+        if (buf_.kind != buffer::Buffer::Kind::Generic)
+          throw ed_error("Can't set language to buffer.");
+        auto &buf = *(buffer::GenericBuffer *)&buf_;
+        buf.language(ctx, name);
+      }
+    }
+  );
+}
+} // namespace bed::internal::functions

src/internal/functions/posix.cc

@@ -0,0 +1,885 @@
+#include "bed.h"
+#include "internal/functions/functions.h"
+#include "internal/functions/suffixes.h"
+
+namespace bed::internal::functions {
+void Suffix::register_suffixes(BEd &ctx) {
+  ctx.suffixes['p' - 'a'] = Suffix{
+    .desc = "Prints current line.",
+    .handle = [](BEd &ctx) {
+      auto &addr = ctx.current();
+      ctx.buffer(addr.buffername).print(ctx, addr.number, addr.number);
+    }
+  };
+  ctx.suffixes['n' - 'a'] = Suffix{
+    .desc = "Prints current line with line number.",
+    .handle = [](BEd &ctx) {
+      auto &addr = ctx.current();
+      ctx.buffer(addr.buffername).number_print(ctx, addr.number, addr.number);
+    }
+  };
+  ctx.suffixes['l' - 'a'] = Suffix{
+    .desc = "Prints current line unambiguously.",
+    .handle = [](BEd &ctx) {
+      auto &addr = ctx.current();
+      ctx.buffer(addr.buffername).list_print(ctx, addr.number, addr.number);
+    }
+  };
+}
+
+void Function::register_posix(BEd &ctx) {
+  ctx.functions.insert(
+    "a",
+    Function{
+      .address_kind = Function::AddressKind::Line,
+      .argument_kind = Function::ArgumentKind::None,
+      .input_mode = Function::InputMode::Text,
+      .desc = "Append text to a line",
+      .default_address = ".",
+      .accept_zero = true,
+      .pre_text_mode = [](
+                         BEd &ctx,
+                         const buffer::Address &addr_,
+                         const Argument &
+                       ) -> std::tuple<vase::Shard *, syntax::Language *, void *> {
+        const auto &addr = std::get<buffer::Line>(addr_);
+        auto &buf_ = ctx.buffer(addr.buffername);
+        if (buf_.kind != buffer::Buffer::Kind::Generic)
+          return {nullptr, nullptr, nullptr};
+        auto &buf = *(buffer::GenericBuffer *)&buf_;
+        void *state = syntax::state_before(buf.parse, buf.root, addr.number);
+        return {nullptr, buf.parse.lang, state};
+      },
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *text,
+                  const Argument &,
+                  std::vector<buffer::Line> *
+                ) {
+        auto addr = std::get<buffer::Line>(addr_);
+        ctx.buffer(addr.buffername).append(ctx, text, addr.number);
+        vase::Shard::release(text); }
+    }
+  );
+  ctx.functions.insert(
+    "c",
+    Function{
+      .address_kind = Function::AddressKind::Range,
+      .argument_kind = Function::ArgumentKind::None,
+      .input_mode = Function::InputMode::Text,
+      .desc = "Change a range of lines",
+      .default_address = ".,.",
+      .accept_zero = false,
+      .pre_text_mode = [](
+                         BEd &ctx,
+                         const buffer::Address &addr_,
+                         const Argument &
+                       ) -> std::tuple<vase::Shard *, syntax::Language *, void *> {
+        const auto &addr = std::get<buffer::Range>(addr_);
+        auto &buf_ = ctx.buffer(addr.buffername);
+        if (buf_.kind != buffer::Buffer::Kind::Generic)
+          return {buf_.copy(addr.start, addr.end), nullptr, nullptr};
+        auto &buf = *(buffer::GenericBuffer *)&buf_;
+        void *state = syntax::state_before(buf.parse, buf.root, addr.start - 1);
+        return {buf.copy(addr.start, addr.end), buf.parse.lang, state};
+      },
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *text,
+                  const Argument &,
+                  std::vector<buffer::Line> *
+                ) {
+        const auto &addr = std::get<buffer::Range>(addr_);
+        ctx.buffer(addr.buffername).replace(ctx, text, addr.start, addr.end);
+        vase::Shard::release(text); }
+    }
+  );
+  ctx.functions.insert(
+    "d",
+    Function{
+      .address_kind = Function::AddressKind::Range,
+      .argument_kind = Function::ArgumentKind::None,
+      .input_mode = Function::InputMode::None,
+      .desc = "Delete a range of lines",
+      .default_address = ".,.",
+      .accept_zero = false,
+      .pre_text_mode = nullptr,
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *,
+                  const Argument &,
+                  std::vector<buffer::Line> *
+                ) {
+        auto addr = std::get<buffer::Range>(addr_);
+        ctx.buffer(addr.buffername).remove(ctx, addr.start, addr.end);
+      }
+    }
+  );
+  ctx.functions.insert(
+    "e",
+    Function{
+      .address_kind = Function::AddressKind::None,
+      .argument_kind = Function::ArgumentKind::File,
+      .input_mode = Function::InputMode::None,
+      .desc = "Load a file into the current buffer, warn once if unsaved changes exist",
+      .default_address = "",
+      .accept_zero = false,
+      .pre_text_mode = nullptr,
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *,
+                  const Argument &arg,
+                  std::vector<buffer::Line> *
+                ) {
+        auto &addr = std::get<std::string>(addr_);
+        auto &buf = ctx.buffer(addr);
+        if (buf.state == buffer::Buffer::Modified) {
+          buf.state = buffer::Buffer::Warned;
+          throw ed_error("Buffer modified.");
+        }
+        vase::Shard *s = nullptr;
+        if (std::holds_alternative<std::filesystem::path>(arg)) {
+          auto path = std::get<std::filesystem::path>(arg);
+          s = vase::Shard::from_file(path);
+          buf.set_filename(path);
+        } else if (std::holds_alternative<ShellArg>(arg)) {
+          auto cmd = std::get<ShellArg>(arg).cmd;
+          ctx.escape_command(cmd, buf.filename().string());
+          s = vase::Shard::from_command(cmd.c_str());
+        } else {
+          auto path = buf.filename();
+          if (path.empty())
+            throw ed_error("Need filename.");
+          s = vase::Shard::from_file(path);
+        };
+        try {
+          buf.load(ctx, s);
+          vase::Shard::release(s);
+        } catch (...) {
+          vase::Shard::release(s);
+          throw;
+        }
+        if (!ctx.suppress_mode)
+          ctx.io.write_line(std::format("{}", buf.bytes()));
+      }
+    }
+  );
+  ctx.functions.insert(
+    "E",
+    Function{
+      .address_kind = Function::AddressKind::None,
+      .argument_kind = Function::ArgumentKind::File,
+      .input_mode = Function::InputMode::None,
+      .desc = "Load a file into the current buffer, discarding unsaved changes",
+      .default_address = "",
+      .accept_zero = false,
+      .pre_text_mode = nullptr,
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *,
+                  const Argument &arg,
+                  std::vector<buffer::Line> *
+                ) {
+        auto &addr = std::get<std::string>(addr_);
+        auto &buf = ctx.buffer(addr);
+        vase::Shard *s = nullptr;
+        if (std::holds_alternative<std::filesystem::path>(arg)) {
+          auto path = std::get<std::filesystem::path>(arg);
+          s = vase::Shard::from_file(path);
+          buf.set_filename(path);
+        } else if (std::holds_alternative<ShellArg>(arg)) {
+          auto cmd = std::get<ShellArg>(arg).cmd;
+          ctx.escape_command(cmd, buf.filename().string());
+          s = vase::Shard::from_command(cmd.c_str());
+        } else {
+          auto path = buf.filename();
+          if (path.empty())
+            throw ed_error("Need filename.");
+          s = vase::Shard::from_file(path);
+        };
+        try {
+          buf.load(ctx, s);
+          vase::Shard::release(s);
+        } catch (...) {
+          vase::Shard::release(s);
+          throw;
+        }
+        if (!ctx.suppress_mode)
+          ctx.io.write_line(std::format("{}", buf.bytes()));
+      }
+    }
+  );
+  ctx.functions.insert(
+    "f",
+    Function{
+      .address_kind = Function::AddressKind::None,
+      .argument_kind = Function::ArgumentKind::File,
+      .input_mode = Function::InputMode::None,
+      .desc = "Set/print a save path",
+      .default_address = "",
+      .accept_zero = false,
+      .pre_text_mode = nullptr,
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *,
+                  const Argument &arg,
+                  std::vector<buffer::Line> *
+                ) {
+        auto &addr = std::get<std::string>(addr_);
+        auto &buf = ctx.buffer(addr);
+        if (std::holds_alternative<std::filesystem::path>(arg))
+          buf.set_filename(std::get<std::filesystem::path>(arg));
+        else if (std::holds_alternative<ShellArg>(arg))
+          throw ed_error("Can't save shell command as save path.");
+        if (buf.filename().empty())
+          throw ed_error("Filename needed.");
+        ctx.io.write_line(buf.filename().string());
+      }
+    }
+  );
+  ctx.functions.insert(
+    "h",
+    Function{
+      .address_kind = Function::AddressKind::None,
+      .argument_kind = Function::ArgumentKind::None,
+      .input_mode = Function::InputMode::None,
+      .desc = "Print last help message",
+      .default_address = "",
+      .accept_zero = false,
+      .pre_text_mode = nullptr,
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &,
+                  vase::Shard *,
+                  const Argument &,
+                  std::vector<buffer::Line> *
+                ) {
+        ctx.io.apply(internal::io::Token::Warning);
+        ctx.io.write_line(ctx.last_help);
+        ctx.io.reset();
+      }
+    }
+  );
+  ctx.functions.insert(
+    "H",
+    Function{
+      .address_kind = Function::AddressKind::None,
+      .argument_kind = Function::ArgumentKind::None,
+      .input_mode = Function::InputMode::None,
+      .desc = "Toggle help mode",
+      .default_address = "",
+      .accept_zero = false,
+      .pre_text_mode = nullptr,
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &,
+                  vase::Shard *,
+                  const Argument &,
+                  std::vector<buffer::Line> *
+                ) {
+        ctx.help_mode = !ctx.help_mode;
+        ctx.io.apply(internal::io::Token::Warning);
+        if (ctx.help_mode)
+          ctx.io.write_line(ctx.last_help);
+        ctx.io.reset();
+      }
+    }
+  );
+  ctx.functions.insert(
+    "i",
+    Function{
+      .address_kind = Function::AddressKind::Line,
+      .argument_kind = Function::ArgumentKind::None,
+      .input_mode = Function::InputMode::Text,
+      .desc = "Insert text before a line",
+      .default_address = ".",
+      .accept_zero = true,
+      .pre_text_mode = [](
+                         BEd &ctx,
+                         const buffer::Address &addr_,
+                         const Argument &
+                       ) -> std::tuple<vase::Shard *, syntax::Language *, void *> {
+        auto addr = std::get<buffer::Line>(addr_);
+        if (addr.number)
+          addr.number--;
+        auto &buf_ = ctx.buffer(addr.buffername);
+        if (buf_.kind != buffer::Buffer::Kind::Generic)
+          return {nullptr, nullptr, nullptr};
+        auto &buf = *(buffer::GenericBuffer *)&buf_;
+        void *state = syntax::state_before(buf.parse, buf.root, addr.number);
+        return {nullptr, buf.parse.lang, state};
+      },
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *text,
+                  const Argument &,
+                  std::vector<buffer::Line> *
+                ) {
+        auto addr = std::get<buffer::Line>(addr_);
+        if (addr.number)
+          addr.number--;
+        ctx.buffer(addr.buffername).append(ctx, text, addr.number);
+        vase::Shard::release(text); }
+    }
+  );
+  ctx.functions.insert(
+    "j",
+    Function{
+      .address_kind = Function::AddressKind::Range,
+      .argument_kind = Function::ArgumentKind::None,
+      .input_mode = Function::InputMode::None,
+      .desc = "Join a range of lines",
+      .default_address = ".,.+1",
+      .accept_zero = false,
+      .pre_text_mode = nullptr,
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *,
+                  const Argument &,
+                  std::vector<buffer::Line> *
+                ) {
+        auto addr = std::get<buffer::Range>(addr_);
+        ctx.buffer(addr.buffername).join(ctx, addr.start, addr.end);
+      }
+    }
+  );
+  ctx.functions.insert(
+    "k",
+    Function{
+      .address_kind = Function::AddressKind::Line,
+      .argument_kind = Function::ArgumentKind::Mark,
+      .input_mode = Function::InputMode::None,
+      .desc = "Mark a line",
+      .default_address = ".",
+      .accept_zero = false,
+      .pre_text_mode = nullptr,
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *,
+                  const Argument &arg,
+                  std::vector<buffer::Line> *
+                ) {
+        auto &addr = std::get<buffer::Line>(addr_);
+        ctx.mark(std::get<char>(arg), addr);
+      }
+    }
+  );
+  ctx.functions.insert(
+    "l",
+    Function{
+      .address_kind = Function::AddressKind::Range,
+      .argument_kind = Function::ArgumentKind::None,
+      .input_mode = Function::InputMode::None,
+      .desc = "Print a range, showing nonprinting characters unambiguously",
+      .default_address = ".,.",
+      .accept_zero = false,
+      .pre_text_mode = nullptr,
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *,
+                  const Argument &,
+                  std::vector<buffer::Line> *
+                ) {
+        auto addr = std::get<buffer::Range>(addr_);
+        ctx.buffer(addr.buffername).list_print(ctx, addr.start, addr.end);
+        ctx.current() = {addr.buffername, addr.end};
+      },
+    }
+  );
+  ctx.functions.insert(
+    "m",
+    Function{
+      .address_kind = Function::AddressKind::Range,
+      .argument_kind = Function::ArgumentKind::Line,
+      .input_mode = Function::InputMode::None,
+      .desc = "Move a range of lines",
+      .default_address = ".,.",
+      .accept_zero = false,
+      .pre_text_mode = nullptr,
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *,
+                  const Argument &arg_,
+                  std::vector<buffer::Line> *
+                ) {
+        auto addr = std::get<buffer::Range>(addr_);
+        auto arg = std::get<buffer::Line>(arg_);
+        if (arg.buffername == addr.buffername
+            && arg.number >= addr.start && arg.number < addr.end)
+          throw ed_error("Can't move lines within themselves.");
+        auto text = ctx.buffer(addr.buffername).copy(addr.start, addr.end);
+        ctx.mark(252, arg);
+        ctx.buffer(addr.buffername).remove(ctx, addr.start, addr.end);
+        arg = ctx.marks.get(252);
+        try {
+          if (arg.number == UINT64_MAX)
+            throw ed_error("Unexpected error when moving lines.");
+          ctx.buffer(arg.buffername).append(ctx, text, arg.number);
+          vase::Shard::release(text);
+        } catch (...) {
+          if (!addr.start) {
+            vase::Shard::release(text);
+            throw;
+          }
+          ctx.buffer(addr.buffername).append(ctx, text, --addr.start);
+          vase::Shard::release(text);
+          throw;
+        }
+      },
+    }
+  );
+  ctx.functions.insert(
+    "n",
+    Function{
+      .address_kind = Function::AddressKind::Range,
+      .argument_kind = Function::ArgumentKind::None,
+      .input_mode = Function::InputMode::None,
+      .desc = "Print a range with line numbers",
+      .default_address = ".,.",
+      .accept_zero = false,
+      .pre_text_mode = nullptr,
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *,
+                  const Argument &,
+                  std::vector<buffer::Line> *
+                ) {
+        auto addr = std::get<buffer::Range>(addr_);
+        ctx.buffer(addr.buffername).number_print(ctx, addr.start, addr.end);
+        ctx.current() = {addr.buffername, addr.end};
+      },
+    }
+  );
+  ctx.functions.insert(
+    "p",
+    Function{
+      .address_kind = Function::AddressKind::Range,
+      .argument_kind = Function::ArgumentKind::None,
+      .input_mode = Function::InputMode::None,
+      .desc = "Print a range",
+      .default_address = ".,.",
+      .accept_zero = false,
+      .pre_text_mode = nullptr,
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *,
+                  const Argument &,
+                  std::vector<buffer::Line> *
+                ) {
+        auto addr = std::get<buffer::Range>(addr_);
+        ctx.buffer(addr.buffername).print(ctx, addr.start, addr.end);
+        ctx.current() = {addr.buffername, addr.end};
+      },
+    }
+  );
+  ctx.functions.insert(
+    "P",
+    Function{
+      .address_kind = Function::AddressKind::None,
+      .argument_kind = Function::ArgumentKind::Any,
+      .input_mode = Function::InputMode::None,
+      .desc = "Toggle/set prompt string",
+      .default_address = "",
+      .accept_zero = false,
+      .pre_text_mode = nullptr,
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &,
+                  vase::Shard *,
+                  const Argument &arg_,
+                  std::vector<buffer::Line> *
+                ) {
+        auto &arg = std::get<std::string>(arg_);
+        if (arg.size()) {
+          ctx.prompt_mode = true;
+          ctx.prompt = [arg](BEd &) { return arg; };
+          return;
+        }
+        ctx.prompt_mode = !ctx.prompt_mode;
+        if (ctx.prompt_mode && !ctx.prompt)
+          ctx.prompt = [](BEd &) { return "*"; };
+      }
+    }
+  );
+  ctx.functions.insert(
+    "q",
+    Function{
+      .address_kind = Function::AddressKind::None,
+      .argument_kind = Function::ArgumentKind::None,
+      .input_mode = Function::InputMode::None,
+      .desc = "Quit, warn once if unsaved changes exist",
+      .default_address = "",
+      .accept_zero = false,
+      .pre_text_mode = nullptr,
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &,
+                  vase::Shard *,
+                  const Argument &,
+                  std::vector<buffer::Line> *
+                ) {
+        std::string modified_buffers;
+        for (auto &[name, buffer] : ctx.buffers) {
+          if (buffer->state == buffer::Buffer::Modified) {
+            buffer->state = buffer::Buffer::Warned;
+            modified_buffers.append(name + ", ");
+          }
+        }
+        if (!modified_buffers.size())
+          throw fatal_error("Quitting", 0);
+        modified_buffers.erase(modified_buffers.size() - 2);
+        throw ed_error("Buffer(s) " + modified_buffers + " modified.");
+      }
+    }
+  );
+  ctx.functions.insert(
+    "Q",
+    Function{
+      .address_kind = Function::AddressKind::None,
+      .argument_kind = Function::ArgumentKind::None,
+      .input_mode = Function::InputMode::None,
+      .desc = "Quit without saving, discarding unsaved changes",
+      .default_address = "",
+      .accept_zero = false,
+      .pre_text_mode = nullptr,
+      .handle = [](
+                  BEd &,
+                  const buffer::Address &,
+                  vase::Shard *,
+                  const Argument &,
+                  std::vector<buffer::Line> *
+                ) {
+        throw fatal_error("Force Quitting", 0);
+      }
+    }
+  );
+  ctx.functions.insert(
+    "r",
+    Function{
+      .address_kind = Function::AddressKind::Line,
+      .argument_kind = Function::ArgumentKind::File,
+      .input_mode = Function::InputMode::None,
+      .desc = "Read a file's contents into the buffer after the given address",
+      .default_address = "$",
+      .accept_zero = true,
+      .pre_text_mode = nullptr,
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *,
+                  const Argument &arg,
+                  std::vector<buffer::Line> *
+                ) {
+        auto &addr = std::get<buffer::Line>(addr_);
+        auto &buf = ctx.buffer(addr.buffername);
+        vase::Shard *s = nullptr;
+        if (std::holds_alternative<std::filesystem::path>(arg)) {
+          auto path = std::get<std::filesystem::path>(arg);
+          s = vase::Shard::from_file(path);
+          if (buf.filename().empty())
+            buf.set_filename(path);
+        } else if (std::holds_alternative<ShellArg>(arg)) {
+          auto cmd = std::get<ShellArg>(arg).cmd;
+          ctx.escape_command(cmd, buf.filename().string());
+          s = vase::Shard::from_command(cmd.c_str());
+        } else {
+          auto path = buf.filename();
+          if (path.empty())
+            throw ed_error("Need filename.");
+          s = vase::Shard::from_file(path);
+        };
+        try {
+          buf.append(ctx, s, addr.number);
+          vase::Shard::release(s);
+        } catch (...) {
+          vase::Shard::release(s);
+          throw;
+        }
+        if (!ctx.suppress_mode)
+          ctx.io.write_line(std::format("{}", s ? s->length + 1 : 0));
+      }
+    }
+  );
+  ctx.functions.insert(
+    "s",
+    Function{
+      .address_kind = Function::AddressKind::Range,
+      .argument_kind = Function::ArgumentKind::Regex,
+      .input_mode = Function::InputMode::None,
+      .desc = "Substitute pattern in range for replacement",
+      .default_address = ".,.",
+      .accept_zero = false,
+      .pre_text_mode = nullptr,
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *,
+                  const Argument &arg_,
+                  std::vector<buffer::Line> *
+                ) {
+        auto &addr = std::get<buffer::Range>(addr_);
+        auto arg = std::get<RegexArg>(arg_);
+        if (arg.expression == "")
+          arg.expression = ctx.last_regex;
+        else
+          ctx.last_regex = arg.expression;
+        if (arg.replacement == "%")
+          arg.replacement = ctx.last_replacement;
+        else
+          ctx.last_replacement = arg.replacement;
+        ctx.buffer(addr.buffername)
+          .substitute(
+            ctx,
+            addr.start,
+            addr.end,
+            arg.expression,
+            arg.replacement,
+            arg.options
+          );
+      }
+    }
+  );
+  ctx.functions.insert(
+    "t",
+    Function{
+      .address_kind = Function::AddressKind::Range,
+      .argument_kind = Function::ArgumentKind::Line,
+      .input_mode = Function::InputMode::None,
+      .desc = "Copy a range of lines",
+      .default_address = ".,.",
+      .accept_zero = false,
+      .pre_text_mode = nullptr,
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *,
+                  const Argument &arg_,
+                  std::vector<buffer::Line> *
+                ) {
+        auto addr = std::get<buffer::Range>(addr_);
+        auto arg = std::get<buffer::Line>(arg_);
+        auto text = ctx.buffer(addr.buffername).copy(addr.start, addr.end);
+        try {
+          ctx.buffer(arg.buffername).append(ctx, text, arg.number);
+          vase::Shard::release(text);
+        } catch (...) {
+          vase::Shard::release(text);
+          throw;
+        }
+      },
+    }
+  );
+  ctx.functions.insert(
+    "u",
+    Function{
+      .address_kind = Function::AddressKind::None,
+      .argument_kind = Function::ArgumentKind::None,
+      .input_mode = Function::InputMode::None,
+      .desc = "Undo the last modification to the buffer",
+      .default_address = "",
+      .accept_zero = false,
+      .pre_text_mode = nullptr,
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *,
+                  const Argument &,
+                  std::vector<buffer::Line> *
+                ) {
+        auto &addr = std::get<std::string>(addr_);
+        auto &buf_ = ctx.buffer(addr);
+        if (buf_.kind != buffer::Buffer::Kind::Generic)
+          throw ed_error("Can't undo buffer");
+        auto &buf = *(buffer::GenericBuffer *)&buf_;
+        if (!buf.undo(ctx))
+          throw ed_error("Can't undo buffer.");
+      }
+    }
+  );
+  ctx.functions.insert(
+    "w",
+    Function{
+      .address_kind = Function::AddressKind::Range,
+      .argument_kind = Function::ArgumentKind::File,
+      .input_mode = Function::InputMode::None,
+      .desc = "Write a range of lines to disk",
+      .default_address = "0,$",
+      .accept_zero = true,
+      .pre_text_mode = nullptr,
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *,
+                  const Argument &arg,
+                  std::vector<buffer::Line> *
+                ) {
+        auto addr = std::get<buffer::Range>(addr_);
+        auto &buf = ctx.buffer(addr.buffername);
+        vase::Shard *text;
+        if (!addr.start && !addr.end) {
+          text = nullptr;
+        } else {
+          if (!addr.start && addr.end)
+            addr.start = 1;
+          text = buf.copy(addr.start, addr.end);
+        }
+        try {
+          if (std::holds_alternative<std::filesystem::path>(arg)) {
+            auto path = std::get<std::filesystem::path>(arg);
+            vase::write_file(path, text);
+            buf.set_filename(path);
+          } else if (std::holds_alternative<ShellArg>(arg)) {
+            auto cmd = std::get<ShellArg>(arg).cmd;
+            ctx.escape_command(cmd, buf.filename().string());
+            vase::write_command(cmd.c_str(), text);
+          } else {
+            auto path = buf.filename();
+            if (path.empty())
+              throw ed_error("Need filename.");
+            vase::write_file(path, text);
+          };
+          vase::Shard::release(text);
+        } catch (...) {
+          vase::Shard::release(text);
+          throw;
+        }
+        buf.saved_hook();
+        if (!ctx.suppress_mode)
+          ctx.io.write(std::format("{}\n", text ? text->length + 1 : 0));
+      }
+    }
+  );
+  ctx.functions.insert(
+    "=",
+    Function{
+      .address_kind = Function::AddressKind::Range,
+      .argument_kind = Function::ArgumentKind::None,
+      .input_mode = Function::InputMode::None,
+      .desc = "Print the line number of the given address",
+      .default_address = "$",
+      .accept_zero = true,
+      .pre_text_mode = nullptr,
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *,
+                  const Argument &,
+                  std::vector<buffer::Line> *
+                ) {
+        auto &addr = std::get<buffer::Range>(addr_);
+        ctx.io.apply(io::Token::BufferName);
+        ctx.io.write(":" + addr.buffername + ":");
+        ctx.io.apply(io::Token::Number);
+        if (addr.start == addr.end) {
+          ctx.io.write_line(std::format(" {}", addr.start));
+        } else {
+          ctx.io.write(std::format(" {}", addr.start));
+          ctx.io.apply(io::Token::AddressSeperator);
+          ctx.io.write(",");
+          ctx.io.apply(io::Token::Number);
+          ctx.io.write_line(std::format("{}", addr.end));
+        }
+        ctx.io.reset();
+        ctx.prev().buffername = addr.buffername;
+        ctx.prev().start = addr.start;
+        ctx.prev().end = addr.end;
+        ctx.current() = {addr.buffername, addr.end};
+      },
+    }
+  );
+  ctx.functions.insert(
+    "!",
+    Function{
+      .address_kind = Function::AddressKind::None,
+      .argument_kind = Function::ArgumentKind::Shell,
+      .input_mode = Function::InputMode::None,
+      .desc = "Run a shell command",
+      .default_address = "",
+      .accept_zero = false,
+      .pre_text_mode = nullptr,
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *,
+                  const Argument &arg_,
+                  std::vector<buffer::Line> *
+                ) {
+        auto &addr = std::get<std::string>(addr_);
+        auto filename = ctx.buffer(addr).filename();
+        auto &arg = std::get<ShellArg>(arg_);
+        auto cmd = arg.cmd;
+        if (ctx.escape_command(cmd, filename.string()))
+          ctx.io.write(cmd + "\n");
+        ctx.io.run_pty(cmd);
+        if (!ctx.suppress_mode)
+          ctx.io.write("!\n");
+      },
+    }
+  );
+  ctx.no_op = Function{
+    .address_kind = Function::AddressKind::Line,
+    .argument_kind = Function::ArgumentKind::None,
+    .input_mode = Function::InputMode::None,
+    .desc = "Print given line and move the cursor to it",
+    .default_address = ".+1",
+    .accept_zero = true,
+    .pre_text_mode = nullptr,
+    .handle = [](
+                BEd &ctx,
+                const buffer::Address &addr_,
+                vase::Shard *,
+                const Argument &,
+                std::vector<buffer::Line> *
+              ) {
+      auto addr = std::get<buffer::Line>(addr_);
+      if (addr.number != 0)
+        ctx.buffer(addr.buffername).print(ctx, addr.number, addr.number);
+      ctx.current() = addr;
+      ctx.prev().buffername = addr.buffername;
+      ctx.prev().start = addr.number;
+      ctx.prev().end = addr.number;
+    }
+  };
+  ctx.eof_op = Function{
+    .address_kind = Function::AddressKind::None,
+    .argument_kind = Function::ArgumentKind::None,
+    .input_mode = Function::InputMode::None,
+    .desc = "Quit, warn once if unsaved changes exist",
+    .default_address = "",
+    .accept_zero = false,
+    .pre_text_mode = nullptr,
+    .handle = [](
+                BEd &ctx,
+                const buffer::Address &,
+                vase::Shard *,
+                const Argument &,
+                std::vector<buffer::Line> *
+              ) {
+      std::string modified_buffers;
+      for (auto &[name, buffer] : ctx.buffers) {
+        if (buffer->state == buffer::Buffer::Modified) {
+          buffer->state = buffer::Buffer::Warned;
+          modified_buffers.append(name + ", ");
+        }
+      }
+      if (!modified_buffers.size())
+        throw fatal_error("Quitting", 0);
+      modified_buffers.erase(modified_buffers.size() - 2);
+      throw ed_error("Buffer(s) " + modified_buffers + " modified.");
+    }
+  };
+}
+} // namespace bed::internal::functions

src/internal/io/input.cc

@@ -0,0 +1,305 @@
+#include "internal/io/io.h"
+
+namespace bed::internal::io {
+std::pair<std::string, bool> IO::read_pipe() {
+  char buf[4096];
+  while (true) {
+    auto pos = pipe_input.find('\n');
+    if (pos != std::string::npos) {
+      std::string line = pipe_input.substr(0, pos);
+      pipe_input.erase(0, pos + 1);
+      return {line, false};
+    }
+    ssize_t n = read(STDIN_FILENO, buf, sizeof(buf));
+    if (n > 0) {
+      pipe_input.append(buf, n);
+      continue;
+    }
+    if (n == 0) {
+      if (pipe_input.empty())
+        return {"", true};
+      std::string line = std::move(pipe_input);
+      pipe_input.clear();
+      return {line, false};
+    }
+    if (errno == EINTR)
+      continue;
+    throw fatal_error("Can't read stdin.", 1);
+  }
+}
+
+KeyEvent::ReadResult IO::get_next_byte(char &out) {
+  if (!input_queue.empty()) {
+    out = input_queue.front();
+    input_queue.pop_front();
+    return KeyEvent::ReadResult::SUCCESS;
+  }
+  if (resized.load())
+    return KeyEvent::ReadResult::RESIZE;
+  ssize_t n = read(STDIN_FILENO, &out, 1);
+  if (n == 1)
+    return KeyEvent::ReadResult::SUCCESS;
+  if (n == -1 && errno == EINTR && resized.load())
+    return KeyEvent::ReadResult::RESIZE;
+  if (n == -1 && errno == EINTR)
+    return get_next_byte(out);
+  return KeyEvent::ReadResult::EOF_;
+}
+
+void IO::enqueue_bytes(const std::string &bytes) {
+  input_queue.insert(input_queue.begin(), bytes.begin(), bytes.end());
+}
+
+int IO::utf8_seq_len(uint8_t byte) {
+  if ((byte & 0x80) == 0x00)
+    return 1;
+  if ((byte & 0xE0) == 0xC0)
+    return 2;
+  if ((byte & 0xF0) == 0xE0)
+    return 3;
+  if ((byte & 0xF8) == 0xF0)
+    return 4;
+  return 1;
+}
+
+KeyEvent::ReadResult IO::read_next_unit(std::string &out) {
+  out.clear();
+  char header;
+  KeyEvent::ReadResult res = get_next_byte(header);
+  if (res != KeyEvent::ReadResult::SUCCESS)
+    return res;
+  if (header == '\x1b') {
+    out.push_back(header);
+    char c;
+    if ((res = get_next_byte(c)) != KeyEvent::ReadResult::SUCCESS)
+      return res;
+    out.push_back(c);
+    if (c != '[')
+      return KeyEvent::ReadResult::SUCCESS;
+    if ((res = get_next_byte(c)) != KeyEvent::ReadResult::SUCCESS)
+      return res;
+    out.push_back(c);
+    if (c == 'M') {
+      for (int i = 0; i < 3; ++i) {
+        if ((res = get_next_byte(c)) != KeyEvent::ReadResult::SUCCESS)
+          return res;
+        out.push_back(c);
+      }
+      return KeyEvent::ReadResult::SUCCESS;
+    }
+    while ((uint8_t)c < 0x40 || (uint8_t)c > 0x7E) {
+      if (out.size() >= 32)
+        break;
+      if ((res = get_next_byte(c)) != KeyEvent::ReadResult::SUCCESS)
+        return res;
+      out.push_back(c);
+    }
+    return KeyEvent::ReadResult::SUCCESS;
+  }
+  int seq_len = utf8_seq_len((uint8_t)header);
+  out.push_back(header);
+  if (seq_len == 1)
+    return KeyEvent::ReadResult::SUCCESS;
+  for (int i = 1; i < seq_len; i++) {
+    char c;
+    if ((res = get_next_byte(c)) != KeyEvent::ReadResult::SUCCESS) {
+      enqueue_bytes(out);
+      out.clear();
+      return res;
+    }
+    out.push_back(c);
+  }
+  uint32_t prev_cp, cur_cp;
+  grapheme_decode_utf8(out.data(), out.size(), &prev_cp);
+  uint16_t state = 0;
+  while (true) {
+    char next_header;
+    if ((res = get_next_byte(next_header)) != KeyEvent::ReadResult::SUCCESS)
+      break;
+    int next_len = utf8_seq_len((uint8_t)next_header);
+    std::string next_seq(1, next_header);
+    bool complete = true;
+    for (int i = 1; i < next_len; i++) {
+      char c;
+      if ((res = get_next_byte(c)) != KeyEvent::ReadResult::SUCCESS) {
+        complete = false;
+        break;
+      }
+      next_seq.push_back(c);
+    }
+    if (!complete) {
+      enqueue_bytes(next_seq);
+      break;
+    }
+    grapheme_decode_utf8(next_seq.data(), next_seq.size(), &cur_cp);
+    if (grapheme_is_character_break(prev_cp, cur_cp, &state)) {
+      enqueue_bytes(next_seq);
+      break;
+    }
+    out += next_seq;
+    prev_cp = cur_cp;
+  }
+  return KeyEvent::ReadResult::SUCCESS;
+}
+
+KeyEvent::ReadResult IO::read_bracketed_paste(std::string &out) {
+  KeyEvent::ReadResult res = KeyEvent::ReadResult::SUCCESS;
+  out.clear();
+  std::string window;
+  while (true) {
+    char c;
+    if ((res = get_next_byte(c)) != KeyEvent::ReadResult::SUCCESS)
+      return res;
+    window.push_back(c);
+    if (window.size() == 5 && window == "\x1b[201") {
+      char tilde;
+      if ((res = get_next_byte(tilde)) != KeyEvent::ReadResult::SUCCESS)
+        return res;
+      if (tilde == '~')
+        return res;
+      out += window;
+      out.push_back(tilde);
+      window.clear();
+      continue;
+    }
+    if (window.size() == 5) {
+      out.push_back(window.front());
+      window.erase(window.begin());
+    }
+  }
+}
+
+KeyEvent IO::parse_mouse(const std::string &buf) {
+  KeyEvent ev;
+  if (buf.size() < 6)
+    return ev;
+  uint8_t code = (uint8_t)buf[3] - 32;
+  uint8_t button = code & 0x03;
+  if (button != 0 && button != 3)
+    return ev;
+  ev.type = KeyEvent::KeyType::MOUSE;
+  ev.mouse_state = (button == 3) ? KeyEvent::MouseState::RELEASE
+                                 : KeyEvent::MouseState::PRESS;
+  ev.mouse_x = (uint8_t)buf[4] - 33;
+  ev.mouse_y = (uint8_t)buf[5] - 33;
+  return ev;
+}
+
+KeyEvent IO::parse_escape(const std::string &buf) {
+  KeyEvent ev;
+  ev.type = KeyEvent::KeyType::SPECIAL;
+  bool has_modifier = buf.size() > 3 && buf[3] == ';';
+  size_t pos;
+  if (!has_modifier) {
+    pos = 2;
+  } else {
+    pos = 5;
+    switch (buf.size() > 4 ? buf[4] : 0) {
+    case '2':
+      ev.modifier = KeyEvent::Modifier::SHIFT;
+      break;
+    case '3':
+      ev.modifier = KeyEvent::Modifier::ALT;
+      break;
+    case '5':
+      ev.modifier = KeyEvent::Modifier::CTRL;
+      break;
+    case '7':
+      ev.modifier = KeyEvent::Modifier::CTRL_ALT;
+      break;
+    default:
+      ev.modifier = KeyEvent::Modifier::NONE;
+      break;
+    }
+  }
+  char key = pos < buf.size() ? buf[pos] : 0;
+  switch (key) {
+  case 'A':
+    ev.special_key = KeyEvent::SpecialKey::UP;
+    break;
+  case 'B':
+    ev.special_key = KeyEvent::SpecialKey::DOWN;
+    break;
+  case 'C':
+    ev.special_key = KeyEvent::SpecialKey::RIGHT;
+    break;
+  case 'D':
+    ev.special_key = KeyEvent::SpecialKey::LEFT;
+    break;
+  case '3':
+    ev.special_key = KeyEvent::SpecialKey::DELETE;
+    break;
+  default:
+    ev.special_key = KeyEvent::SpecialKey::UNKNOWN;
+    break;
+  }
+  return ev;
+}
+
+KeyEvent IO::read_key() {
+  while (true) {
+    std::string buf;
+    auto res = read_next_unit(buf);
+    KeyEvent ev;
+    switch (res) {
+    case KeyEvent::ReadResult::EOF_:
+      ev.type = KeyEvent::KeyType::EOF_;
+      return ev;
+    case KeyEvent::ReadResult::RESIZE:
+      resized.store(false);
+      ev.type = KeyEvent::KeyType::RESIZE;
+      return ev;
+    case KeyEvent::ReadResult::SUCCESS:
+      break;
+    }
+    if (buf.size() >= 6 && buf[0] == '\x1b' && buf[1] == '[' && buf.compare(2, 4, "200~") == 0) {
+      std::string pasted;
+      switch (read_bracketed_paste(pasted)) {
+      case KeyEvent::ReadResult::SUCCESS:
+        ev.type = KeyEvent::KeyType::PASTE;
+        ev.text = std::move(pasted);
+        break;
+      case KeyEvent::ReadResult::EOF_:
+        ev.type = KeyEvent::KeyType::EOF_;
+        break;
+      case KeyEvent::ReadResult::RESIZE:
+        resized.store(false);
+        ev.type = KeyEvent::KeyType::RESIZE;
+        break;
+      }
+      return ev;
+    }
+    if (buf.size() >= 3 && buf[0] == '\x1b' && buf[1] == '[' && buf[2] == 'M') {
+      ev = parse_mouse(buf);
+      if (ev.type == KeyEvent::KeyType::EOF_)
+        continue;
+      return ev;
+    }
+    if (buf.size() >= 2 && buf[0] == '\x1b' && buf[1] == '[')
+      return parse_escape(buf);
+    ev.type = KeyEvent::KeyType::CHAR;
+    ev.modifier = KeyEvent::Modifier::NONE;
+    if (buf.size() == 1) {
+      uint8_t c = (uint8_t)buf[0];
+      if (c >= 1 && c <= 26 && c != '\t' && c != '\n' && c != '\r' && c != '\x08') {
+        ev.modifier = KeyEvent::Modifier::CTRL;
+        ev.text = 'a' + c - 1;
+        return ev;
+      }
+    }
+    if (buf.size() == 2 && (uint8_t)buf[0] == 0x1B) {
+      uint8_t c = (uint8_t)buf[1];
+      if (c >= 1 && c <= 26 && c != '\t' && c != '\n' && c != '\r' && c != '\x08') {
+        ev.modifier = KeyEvent::Modifier::CTRL_ALT;
+        ev.text = 'a' + c - 1;
+        return ev;
+      }
+      ev.modifier = KeyEvent::Modifier::ALT;
+      ev.text = buf.substr(1);
+      return ev;
+    }
+    ev.text = std::move(buf);
+    return ev;
+  }
+}
+} // namespace bed::internal::io

src/internal/io/io.cc

@@ -0,0 +1,228 @@
+#include "internal/io/io.h"
+#include "bed.h"
+
+namespace bed::internal::io {
+termios IO::orig_termios{};
+termios IO::raw_termios{};
+bool IO::cleaned = true;
+volatile std::atomic_bool IO::resized(false);
+IO::Mode IO::mode = IO::Mode::PIPE;
+
+IO::IO(BEd &bed) : bed(bed) {
+  if (!isatty(STDIN_FILENO))
+    return;
+  mode = Mode::TERMINAL;
+  if (tcgetattr(STDIN_FILENO, &orig_termios) == -1)
+    throw fatal_error("Can't get terminal state.", 1);
+  struct sigaction sa{};
+  sa.sa_handler = handle_sigwinch;
+  sigemptyset(&sa.sa_mask);
+  sa.sa_flags = 0;
+  if (sigaction(SIGWINCH, &sa, nullptr) == -1)
+    throw fatal_error("Can't install SIGWINCH handler.", 1);
+  raw_termios = orig_termios;
+  raw_termios.c_iflag &= ~(BRKINT | ISTRIP | IXON);
+  raw_termios.c_cflag |= (CS8);
+  raw_termios.c_lflag &= ~(ECHO | ICANON | ISIG);
+  raw_termios.c_cc[VMIN] = 1;
+  raw_termios.c_cc[VTIME] = 0;
+  enable_raw();
+  atexit(cleanup);
+}
+
+IO::~IO() {
+  cleanup();
+}
+
+void IO::apply(const io::Token::Kind &t) {
+  if (!bed.color_mode)
+    return;
+  write("\x1b[0m");
+  const auto &hl = bed.theme.get(t);
+  const uint8_t r = (hl.fg >> 16) & 0xff;
+  const uint8_t g = (hl.fg >> 8) & 0xff;
+  const uint8_t b = hl.fg & 0xff;
+  write(std::format("\x1b[38;2;{};{};{}m", r, g, b));
+  if (hl.bg != 0) {
+    const uint8_t br = (hl.bg >> 16) & 0xff;
+    const uint8_t bg = (hl.bg >> 8) & 0xff;
+    const uint8_t bb = hl.bg & 0xff;
+    write(std::format("\x1b[48;2;{};{};{}m", br, bg, bb));
+  }
+  if (hl.flags & Highlight::Bold)
+    write("\x1b[1m");
+  if (hl.flags & Highlight::Italic)
+    write("\x1b[3m");
+  if (hl.flags & Highlight::Underline)
+    write("\x1b[4m");
+  if (hl.flags & Highlight::Strikethrough)
+    write("\x1b[9m");
+}
+
+void IO::reset() {
+  if (!bed.color_mode)
+    return;
+  write("\x1b[0m");
+}
+
+void IO::enable_mouse() {
+  if (mode == Mode::PIPE)
+    throw fatal_error("no mouse in pipe mode.", 1);
+  const char *seq = "\x1b[?1000h";
+  write_all(STDOUT_FILENO, seq, 8);
+}
+
+void IO::disable_mouse() {
+  if (mode == Mode::PIPE)
+    throw fatal_error("no mouse in pipe mode.", 1);
+  const char *seq = "\x1b[?1000l";
+  write_all(STDOUT_FILENO, seq, 8);
+}
+
+std::pair<uint16_t, uint16_t> IO::terminal_size() {
+  if (mode == Mode::PIPE)
+    throw fatal_error("no terminal size in pipe mode.", 1);
+  struct winsize ws{};
+  if (ioctl(STDOUT_FILENO, TIOCGWINSZ, &ws) == -1)
+    throw fatal_error("Can't get terminal size.", 1);
+  return {ws.ws_row, ws.ws_col};
+}
+
+std::pair<uint16_t, uint16_t> IO::cursor_position() {
+  if (mode == Mode::PIPE)
+    throw fatal_error("no cursor in pipe mode.", 1);
+  write_all(STDOUT_FILENO, "\x1b[6n", 4);
+  std::string response;
+  char c;
+  if (read(STDIN_FILENO, &c, 1) != 1 || c != '\x1b')
+    throw fatal_error("Invalid cursor position response.", 1);
+  if (read(STDIN_FILENO, &c, 1) != 1 || c != '[')
+    throw fatal_error("Invalid cursor position response.", 1);
+  while (true) {
+    if (read(STDIN_FILENO, &c, 1) != 1)
+      throw fatal_error("Invalid cursor position response.", 1);
+    if (c == 'R')
+      break;
+    response += c;
+  }
+  unsigned row;
+  unsigned col;
+  if (sscanf(response.c_str(), "%u;%u", &row, &col) != 2)
+    throw fatal_error("Invalid cursor position response.", 1);
+  return {(uint16_t)row, (uint16_t)col};
+}
+
+void IO::enable_raw() {
+  if (!cleaned || mode == Mode::PIPE)
+    return;
+  std::string os = "\x1b[?2004h";
+  write_all(STDOUT_FILENO, os.c_str(), os.size());
+  if (tcsetattr(STDIN_FILENO, TCSAFLUSH, &raw_termios) == -1)
+    throw fatal_error("Can't set raw terminal state.", 1);
+  cleaned = false;
+}
+
+void IO::cleanup() {
+  if (cleaned || mode == Mode::PIPE)
+    return;
+  std::string os = "\x1b[?1000l\x1b[?2004l";
+  write_all(STDOUT_FILENO, os.c_str(), os.size());
+  if (tcsetattr(STDIN_FILENO, TCSAFLUSH, &orig_termios) == -1)
+    perror("Can't clean up terminal.");
+  cleaned = true;
+}
+
+void IO::handle_sigwinch(int) {
+  resized.store(true);
+}
+
+void IO::move_cursor(uint16_t row, uint16_t col) {
+  if (mode == Mode::PIPE)
+    return;
+  char buf[32];
+  int n = snprintf(buf, sizeof(buf), "\x1b[%u;%uH", row, col);
+  write_all(STDOUT_FILENO, buf, n);
+}
+
+void IO::write(const char *buf, uint64_t n) {
+  write_all(STDOUT_FILENO, buf, n);
+}
+
+void IO::write(std::string_view s) {
+  write_all(STDOUT_FILENO, s.data(), s.size());
+}
+
+void IO::write_line(std::string_view s) {
+  write(s);
+  write("\n", 1);
+}
+
+void IO::run_pty(const std::string &cmd) {
+  if (mode == Mode::PIPE)
+    throw ed_error("Shell running not allowed in pipe mode.");
+  int master_fd = -1;
+  struct winsize ws{};
+  if (ioctl(STDOUT_FILENO, TIOCGWINSZ, &ws) == -1)
+    throw fatal_error("Can't get terminal size.", 1);
+  pid_t pid = forkpty(
+    &master_fd,
+    nullptr,
+    &orig_termios,
+    &ws
+  );
+  if (pid == -1)
+    throw fatal_error("Can't create PTY.", 1);
+  if (pid == 0) {
+    const char *shell = getenv("BED_SHELL");
+    if (!shell || !*shell)
+      shell = getenv("SHELL");
+    if (!shell || !*shell)
+      shell = "/bin/sh";
+    execl(shell, shell, "-i", "-c", cmd.c_str(), (char *)nullptr);
+    _exit(127);
+  }
+  struct pollfd fds[2];
+  while (true) {
+    fds[0].fd = STDIN_FILENO;
+    fds[0].events = POLLIN;
+    fds[1].fd = master_fd;
+    fds[1].events = POLLIN;
+    int rc = poll(fds, 2, -1);
+    if (rc == -1) {
+      if (errno == EINTR)
+        continue;
+      break;
+    }
+    if (resized.exchange(false)) {
+      struct winsize new_ws{};
+      if (ioctl(STDOUT_FILENO, TIOCGWINSZ, &new_ws) == 0)
+        ioctl(master_fd, TIOCSWINSZ, &new_ws);
+    }
+    if (fds[0].revents & POLLIN) {
+      char buf[4096];
+      ssize_t n = read(STDIN_FILENO, buf, sizeof(buf));
+      if (n > 0)
+        write_all(master_fd, buf, n);
+      else if (n == 0)
+        break;
+    }
+    if (fds[1].revents & POLLIN) {
+      char buf[8192];
+      ssize_t n = read(master_fd, buf, sizeof(buf));
+      if (n > 0)
+        write_all(STDOUT_FILENO, buf, n);
+      else
+        break;
+    }
+    if (fds[0].revents & (POLLERR | POLLHUP | POLLNVAL))
+      break;
+    if (fds[1].revents & (POLLERR | POLLHUP | POLLNVAL))
+      break;
+  }
+  close(master_fd);
+  int status;
+  while (waitpid(pid, &status, 0) == -1)
+    if (errno != EINTR)
+      break;
+}
+} // namespace bed::internal::io

src/internal/parser/address.cc

@@ -0,0 +1,302 @@
+#include "bed.h"
+#include "internal/parser/parser.h"
+
+namespace bed::internal::parser {
+void Parser::locator(AddressPromise &addr) {
+  addr.base = AddressPromise::None{};
+  switch (peek()) {
+  case '.':
+    token(io::Token::AddressSymbol);
+    advance();
+    end_token();
+    addr.base = AddressPromise::Current{};
+    break;
+  case '$':
+    token(io::Token::AddressSymbol);
+    advance();
+    end_token();
+    addr.base = AddressPromise::Last{};
+    break;
+  case '%':
+    token(io::Token::AddressSymbol);
+    advance();
+    end_token();
+    addr.base = AddressPromise::LastRange{};
+    break;
+  case '[':
+    token(io::Token::AddressSymbol);
+    advance();
+    end_token();
+    addr.base = AddressPromise::Block{Direction::Backward};
+    break;
+  case ']':
+    token(io::Token::AddressSymbol);
+    advance();
+    end_token();
+    addr.base = AddressPromise::Block{Direction::Forward};
+    break;
+  case '^':
+    token(io::Token::AddressSymbol);
+    advance();
+    end_token();
+    addr.base = AddressPromise::Diagnostic{Direction::Backward};
+    break;
+  case '~':
+    token(io::Token::AddressSymbol);
+    advance();
+    end_token();
+    addr.base = AddressPromise::Diagnostic{Direction::Forward};
+    break;
+  case '\'':
+    token(io::Token::Mark);
+    advance();
+    if (('a' <= peek() && peek() <= 'z')
+        || ('A' <= peek() && peek() <= 'Z'))
+      addr.base = AddressPromise::Mark{peek()};
+    else
+      throw ed_error("Valid mark needed after \'");
+    advance();
+    end_token();
+    break;
+  case '{': {
+    token(io::Token::AddressSymbol);
+    advance();
+    end_token();
+    uint16_t j = 0;
+    std::string func;
+    std::string arg;
+    token(io::Token::RubyFunction);
+    while (peek(j) != '}') {
+      if (peek(j) == '\0')
+        throw ed_error("Scripted address not terminated");
+      if (peek(j) == '\\')
+        ++j;
+      if (peek(j) == ':') {
+        func = peek_str(j);
+        advance(j + 1);
+        end_token();
+        token(io::Token::RubyArg);
+        j = 0;
+        continue;
+      }
+      ++j;
+    }
+    if (func.size())
+      arg = peek_str(j);
+    else
+      func = peek_str(j);
+    addr.base = AddressPromise::Scripted{std::move(func), std::move(arg)};
+    advance(j);
+    end_token();
+    token(io::Token::AddressSymbol);
+    advance();
+    end_token();
+  } break;
+  case '/': {
+    token(io::Token::Regexp);
+    advance();
+    uint64_t j = 0;
+    while (true) {
+      if (peek(j) == '\0')
+        break;
+      if (peek(j) == '/')
+        break;
+      else if (peek(j) == '\\')
+        j += 2;
+      else if (peek(j) == '[')
+        while (peek(j) != '\0' && cmd[i] != ']')
+          j++;
+      else
+        j++;
+    }
+    addr.base = AddressPromise::Regex(
+      Direction::Forward,
+      std::string(peek_str(j))
+    );
+    advance(j + 1);
+    end_token();
+  } break;
+  case '?': {
+    token(io::Token::Regexp);
+    advance();
+    uint16_t j = 0;
+    while (true) {
+      if (peek(j) == '\0')
+        break;
+      if (peek(j) == '?')
+        break;
+      else if (peek(j) == '\\')
+        j += 2;
+      else if (peek(j) == '[')
+        while (peek(j) != '\0' && cmd[i] != ']')
+          j++;
+      else
+        j++;
+    }
+    addr.base = AddressPromise::Regex(
+      Direction::Backward,
+      std::string(peek_str(j))
+    );
+    advance(j + 1);
+    end_token();
+  } break;
+  case '<': {
+    token(io::Token::Label);
+    advance();
+    uint16_t j = 0;
+    while (peek(j) != '>'
+           && peek(j) != '<'
+           && peek(j) != '\0')
+      j++;
+    switch (peek(j)) {
+    case '\0':
+    case '>':
+      addr.base = AddressPromise::SymbolDefinition{
+        std::string(peek_str(j))
+      };
+      break;
+    case '<':
+      addr.base = AddressPromise::SymbolReference{
+        Direction::Backward,
+        std::string(peek_str(j))
+      };
+      break;
+    }
+    advance(j + 1);
+    end_token();
+  } break;
+  case '>': {
+    token(io::Token::Label);
+    advance();
+    uint16_t j = 0;
+    while (peek(j) != '>' && peek(j) != '\0')
+      j++;
+    switch (peek(j)) {
+    case '\0':
+      throw ed_error("Unterminated symbol reference addressing.");
+    case '>':
+      addr.base = AddressPromise::SymbolReference{
+        Direction::Forward,
+        std::string(peek_str(j))
+      };
+      break;
+    }
+    advance(j + 1);
+    end_token();
+  } break;
+  case '+': {
+    token(io::Token::AddressSymbol);
+    advance();
+    end_token();
+    token(io::Token::Number);
+    addr.base = AddressPromise::Current{};
+    uint16_t j = 0;
+    uint64_t num = 0;
+    while ('0' <= peek(j) && peek(j) <= '9') {
+      num = num * 10 + (peek(j) - '0');
+      j++;
+    }
+    if (j == 0)
+      num = 1;
+    addr.offset += num;
+    advance(j);
+    end_token();
+  } break;
+  case '-': {
+    token(io::Token::AddressSymbol);
+    advance();
+    end_token();
+    token(io::Token::Number);
+    addr.base = AddressPromise::Current{};
+    uint16_t j = 0;
+    uint64_t num = 0;
+    while ('0' <= peek(j) && peek(j) <= '9') {
+      num = num * 10 + (peek(j) - '0');
+      j++;
+    }
+    if (j == 0)
+      num = 1;
+    addr.offset -= num;
+    advance(j);
+    end_token();
+  } break;
+  default:
+    if ('0' <= peek() && peek() <= '9') {
+      token(io::Token::Number);
+      uint64_t num = 0;
+      while ('0' <= peek() && peek() <= '9') {
+        num = num * 10 + (peek() - '0');
+        advance();
+      }
+      addr.base = AddressPromise::Number{num};
+      end_token();
+    }
+  }
+}
+
+int64_t Parser::offset() {
+  int64_t offset = 0;
+  while (peek() == '+' || peek() == '-'
+         || ('0' <= peek() && peek() <= '9')) {
+    bool positive = peek() != '-';
+    token(io::Token::AddressSymbol);
+    if (peek() == '+' || peek() == '-')
+      advance();
+    end_token();
+    token(io::Token::Number);
+    uint16_t j = 0;
+    int64_t num = 0;
+    while ('0' <= peek(j) && peek(j) <= '9')
+      num = num * 10 + (peek(j++) - '0');
+    if (j == 0)
+      num = 1;
+    advance(j);
+    end_token();
+    offset += positive ? num : -num;
+    skip_ws();
+  }
+  skip_ws();
+  return offset;
+}
+
+void Parser::address(AddressPromise &addr) {
+  if (peek() == ':') {
+    token(io::Token::BufferName);
+    advance();
+    uint16_t j = 0;
+    while (peek(j) != ':' && peek(j) != '\0')
+      j++;
+    addr.bufname = peek_str(j);
+    advance(j);
+    if (peek() == ':')
+      advance();
+    end_token();
+  }
+  skip_ws();
+  if (peek() == '\0')
+    return;
+  locator(addr);
+  skip_ws();
+  addr.offset += offset();
+}
+
+void Parser::addresses(std::vector<AddressPromise> &addresses) {
+  skip_ws();
+  addresses.push_back({});
+  auto *addr = &addresses.back();
+  address(*addr);
+  while (peek() == ',' || peek() == ';') {
+    addr->jumping = peek() == ';';
+    token(io::Token::AddressSeperator);
+    advance();
+    skip_ws();
+    addresses.push_back({});
+    addr = &addresses.back();
+    address(*addr);
+  }
+  if (addresses.size() == 1
+      && addr->offset == 0 && !addr->bufname.has_value()
+      && std::holds_alternative<AddressPromise::None>(addr->base))
+    addresses.pop_back();
+}
+} // namespace bed::internal::parser

src/internal/parser/address_promise.cc

@@ -0,0 +1,205 @@
+#include "bed.h"
+#include "internal/parser/parser.h"
+#include "internal/vase/vase.h"
+
+namespace bed::internal::parser {
+buffer::Line AddressPromise::resolve(BEd &ctx) {
+  buffer::Line result = std::visit(
+    [&](auto const &addr) -> buffer::Line {
+      if (!bufname.has_value() || bufname->empty())
+        throw ed_error("Buffer name can't be empty.");
+      buffer::Line line = {*bufname, 0};
+      auto &buf = ctx.buffer(line.buffername);
+      using T = std::decay_t<decltype(addr)>;
+      if constexpr (std::is_same_v<T, None>) {
+        if (line.buffername == ctx.current().buffername)
+          line.number = ctx.current().number;
+        else
+          line.number = buf.lines();
+      } else if constexpr (std::is_same_v<T, Current>) {
+        if (line.buffername == ctx.current().buffername)
+          line.number = ctx.current().number;
+        else
+          line.number = buf.lines();
+      } else if constexpr (std::is_same_v<T, Last>) {
+        line.number = buf.lines();
+      } else if constexpr (std::is_same_v<T, Number>) {
+        line.number = addr.i;
+      } else if constexpr (std::is_same_v<T, Mark>) {
+        line = ctx.marks.get(addr.m);
+        if (line.number == UINT64_MAX)
+          throw ed_error("Mark not set.");
+      } else if constexpr (std::is_same_v<T, Regex>) {
+        if (line.buffername == ctx.current().buffername)
+          line.number = ctx.current().number;
+        else
+          line.number = buf.lines();
+        if (buf.lines() > 0 && line.number == 0)
+          line.number = 1;
+        if (line.number == 0)
+          throw ed_error("Can't search empty buffer.");
+        std::string_view re = addr.re;
+        if (re.size() == 0)
+          re = ctx.last_regex;
+        if (re.size() == 0)
+          throw ed_error("No regex given.");
+        if (addr.dir == Direction::Forward)
+          line.number = buf.find_next(re, line.number);
+        else
+          line.number = buf.find_prev(re, line.number);
+        ctx.last_regex = re;
+      } else if constexpr (std::is_same_v<T, Block>) {
+        if (line.buffername == ctx.current().buffername)
+          line.number = ctx.current().number;
+        else
+          line.number = buf.lines();
+        if (buf.lines() > 0 && line.number == 0)
+          line.number = 1;
+        if (addr.dir == Direction::Forward)
+          line.number = buf.next_closing(line.number);
+        else
+          line.number = buf.prev_closing(line.number);
+      } else {
+        throw ed_error("Unhandled address given.");
+      }
+      if (offset < 0 && line.number < (uint64_t)-offset)
+        throw ed_error("Can't have negative addresses");
+      line.number += offset;
+      if (line.number > ctx.buffer(line.buffername).lines())
+        throw ed_error("Line number too high.");
+      return line;
+    },
+    base
+  );
+  return result;
+}
+
+std::optional<buffer::Line> AddressPromise::get_line(BEd &ctx, std::vector<AddressPromise> &list) {
+  std::string bufname = ctx.current().buffername;
+  bool prev_given = false;
+  bool prev_set = false;
+  AddressPromise prev;
+  for (std::size_t idx = 0; idx < list.size(); idx++) {
+    AddressPromise &curr = list[idx];
+    if (!curr.bufname.has_value())
+      curr.bufname = bufname;
+    else if (curr.bufname->empty())
+      curr.bufname = bufname = ctx.current().buffername;
+    bool is_final = idx + 1 == list.size();
+    if (!is_final) {
+      if (std::holds_alternative<None>(curr.base)) {
+        if (!curr.jumping)
+          curr.base = Number(1);
+        else
+          curr.base = Current();
+        curr.offset = 0;
+        prev_given = false;
+      } else if (std::holds_alternative<LastRange>(curr.base)) {
+        curr.bufname = ctx.prev().buffername;
+        curr.base = Number(ctx.prev().end);
+        prev_given = true;
+      } else {
+        prev_given = true;
+      }
+      buffer::Line resolved = curr.resolve(ctx);
+      if (curr.jumping)
+        ctx.current() = resolved;
+      curr.bufname = resolved.buffername;
+      curr.base = Number(resolved.number);
+      curr.offset = 0;
+      prev = curr;
+      prev_set = true;
+      bufname = *curr.bufname;
+    } else {
+      if (std::holds_alternative<None>(curr.base)) {
+        if (prev_set) {
+          if (prev_given) {
+            curr.base = prev.base;
+            curr.offset = prev.offset;
+          } else {
+            curr.base = Last();
+            curr.offset = 0;
+          }
+        }
+      } else if (std::holds_alternative<LastRange>(curr.base)) {
+        curr.bufname = ctx.prev().buffername;
+        curr.base = Number(ctx.prev().end);
+      }
+      return curr.resolve(ctx);
+    }
+  }
+  return std::nullopt;
+}
+
+std::optional<buffer::Range> AddressPromise::get_range(BEd &ctx, std::vector<AddressPromise> &list) {
+  std::string bufname = ctx.current().buffername;
+  bool prev_given = false;
+  bool prev_set = false;
+  AddressPromise prev;
+  for (std::size_t idx = 0; idx < list.size(); idx++) {
+    AddressPromise &curr = list[idx];
+    if (!curr.bufname.has_value())
+      curr.bufname = bufname;
+    else if (curr.bufname->empty())
+      curr.bufname = bufname = ctx.current().buffername;
+    bool is_final = idx + 1 == list.size();
+    if (!is_final) {
+      if (std::holds_alternative<None>(curr.base)) {
+        if (!curr.jumping)
+          curr.base = Number(1);
+        else
+          curr.base = Current();
+        curr.offset = 0;
+        prev_given = false;
+      } else if (std::holds_alternative<LastRange>(curr.base)) {
+        curr.bufname = ctx.prev().buffername;
+        curr.base = Number(ctx.prev().end);
+        prev_given = true;
+      } else {
+        prev_given = true;
+      }
+      buffer::Line resolved = curr.resolve(ctx);
+      curr.bufname = resolved.buffername;
+      curr.base = Number(resolved.number);
+      curr.offset = 0;
+      if (curr.jumping)
+        ctx.current() = resolved;
+      prev = curr;
+      prev_set = true;
+      bufname = *curr.bufname;
+    } else {
+      if (std::holds_alternative<None>(curr.base)) {
+        if (prev_set) {
+          if (prev_given) {
+            curr.base = prev.base;
+            curr.offset = prev.offset;
+          } else {
+            curr.base = Last();
+            curr.offset = 0;
+          }
+          return buffer::Range(prev.resolve(ctx), curr.resolve(ctx));
+        }
+      } else if (std::holds_alternative<LastRange>(curr.base)) {
+        auto previous = ctx.prev();
+        auto &buf = ctx.buffer(previous.buffername);
+        if (curr.offset < 0 && previous.start < (uint64_t)-curr.offset)
+          throw ed_error("Can't have negative addresses");
+        previous.start += curr.offset;
+        if (previous.start > buf.lines())
+          throw ed_error("Line number too high.");
+        if (curr.offset < 0 && previous.end < (uint64_t)-curr.offset)
+          throw ed_error("Can't have negative addresses");
+        previous.end += curr.offset;
+        if (previous.end > buf.lines())
+          throw ed_error("Line number too high.");
+        return previous;
+      }
+      if (prev_given)
+        return buffer::Range(prev.resolve(ctx), curr.resolve(ctx));
+      buffer::Line only = curr.resolve(ctx);
+      return buffer::Range(only, only);
+    }
+  }
+  return std::nullopt;
+}
+} // namespace bed::internal::parser

src/internal/parser/operation.cc

@@ -0,0 +1,240 @@
+#include "bed.h"
+#include "internal/parser/parser.h"
+
+namespace bed::internal::parser {
+void Parser::operation() {
+  if (peek() == '\0') {
+    command->function = &bed.no_op;
+    return;
+  }
+  uint64_t len = bed.functions.longest_match(peek_str());
+  if (len == 0)
+    throw ed_error("Function not found.");
+  functions::Function *function = bed.functions.get_ptr(peek_str(len));
+  token(io::Token::Function);
+  advance(len);
+  end_token();
+  command->function = function;
+  char suffix = '\0';
+  switch (command->function->argument_kind) {
+  case functions::Function::ArgumentKind::None:
+    break;
+  case functions::Function::ArgumentKind::Number:
+    skip_ws();
+    command->argument = offset();
+    break;
+  case functions::Function::ArgumentKind::Mark:
+    if (('a' <= peek() && peek() <= 'z')
+        || ('A' <= peek() && peek() <= 'Z'))
+      command->argument = peek();
+    else
+      throw ed_error("Valid mark needed.");
+    token(io::Token::Mark);
+    advance();
+    end_token();
+    break;
+  case functions::Function::ArgumentKind::Any:
+    command->argument = std::string(peek_str());
+    token(io::Token::Data);
+    advance(peek_str().size());
+    end_token();
+    break;
+  case functions::Function::ArgumentKind::Global: {
+    char delim;
+    std::string val;
+    switch (peek()) {
+    case '\0':
+      throw ed_error("Command needs a delimited value.");
+    case '{': {
+      advance();
+      delim = '}';
+      uint16_t j = 0;
+      while (peek(j) != '}' && peek(j) != '\0') {
+        if (peek(j) == '\\')
+          j++;
+        j++;
+      }
+      switch (peek(j)) {
+      case '\0':
+        throw ed_error("Unterminated {");
+      case '}':
+        val = peek_str(j);
+        break;
+      }
+      advance(j + 1);
+    } break;
+    case '<': {
+      advance();
+      delim = '<';
+      uint16_t j = 0;
+      while (peek(j) != '>' || peek(j) != '\0') {
+        if (peek(j) == '\\')
+          j++;
+        j++;
+      }
+      switch (peek(j)) {
+      case '\0':
+        throw ed_error("Unterminated <");
+      case '>':
+        val = peek_str(j);
+        break;
+      }
+      advance(j + 1);
+    } break;
+    case '^':
+    case '~':
+      advance();
+      delim = '^';
+      break;
+    default:
+      delim = peek();
+      advance();
+      uint64_t j = 0;
+      while (true) {
+        if (peek(j) == '\0')
+          break;
+        if (peek(j) == delim)
+          break;
+        else if (peek(j) == '\\')
+          j += 2;
+        else if (peek(j) == '[')
+          while (peek(j) != '\0' && cmd[i] != ']')
+            j++;
+        else
+          j++;
+      }
+      val = peek_str(j);
+      advance(j + 1);
+    }
+    command->argument = functions::Function::GlobalArg(delim, std::move(val));
+  } break;
+  case functions::Function::ArgumentKind::File:
+    if (!(peek() == '\t' || peek() == ' ' || peek() == '\0'))
+      throw ed_error("Incorrect file input usage.");
+    skip_ws();
+    switch (peek()) {
+    case '!':
+      token(io::Token::Error);
+      advance();
+      end_token();
+      token(io::Token::Shell);
+      command->argument = functions::Function::ShellArg(std::string(peek_str()));
+      advance(peek_str().size());
+      end_token();
+      break;
+    case '\0':
+      command->argument = std::monostate();
+      break;
+    default:
+      token(io::Token::File);
+      command->argument = std::filesystem::path(peek_str());
+      advance(peek_str().size());
+      end_token();
+      break;
+    }
+    break;
+  case functions::Function::ArgumentKind::Line:
+    command->argument = buffer::Line();
+    addresses(command->argument_addresses);
+    break;
+  case functions::Function::ArgumentKind::Range:
+    command->argument = buffer::Range();
+    addresses(command->argument_addresses);
+    break;
+  case functions::Function::ArgumentKind::Regex: {
+    char delim = peek();
+    if (delim == '\0')
+      throw ed_error("regex expected");
+    token(io::Token::Regexp);
+    advance();
+    uint16_t j = 0;
+    while (true) {
+      if (peek(j) == '\0')
+        throw ed_error("Unterminated regex");
+      if (peek(j) == delim)
+        break;
+      else if (peek(j) == '\\')
+        j += 2;
+      else if (peek(j) == '[')
+        while (peek(j) != '\0' && peek(j) != ']')
+          j++;
+      else
+        j++;
+    }
+    std::string expression(peek_str(j));
+    advance(j + 1);
+    j = 0;
+    while (true) {
+      if (peek(j) == '\0')
+        break;
+      if (peek(j) == delim)
+        break;
+      else if (peek(j) == '\\')
+        j += 2;
+      else if (peek(j) == '[')
+        while (peek(j) != '\0' && peek(j) != ']')
+          j++;
+      else
+        j++;
+    }
+    std::string replacement(peek_str(j));
+    std::string options;
+    if (peek(j) != '\0') {
+      advance(j + 1);
+    } else {
+      advance(j);
+      options = "p";
+    }
+    end_token();
+    token(io::Token::Suffix);
+    if (peek() != '\0') {
+      options = std::string(peek_str());
+      advance(peek_str().size());
+    }
+    end_token();
+    std::erase_if(options, [&](char c) {
+      if (bed.suffixes[c - 'a'].has_value()) {
+        suffix = c;
+        return true;
+      }
+      return false;
+    });
+    command->argument = functions::Function::RegexArg(expression, replacement, options);
+  } break;
+  case functions::Function::ArgumentKind::Ruby: {
+    command->argument = functions::Function::RubyArg(std::string(peek_str()));
+    auto *ruby_parser = bed.languages["ruby"];
+    void *state = ruby_parser->none_state();
+    std::vector<syntax::ParseEvent> events;
+    std::vector<io::Token> tokens_;
+    ruby_parser->parse(&state, peek_str(), false, &tokens_, &events);
+    for (auto &token : tokens_) {
+      token.start += i;
+      token.end += i;
+      tokens->push_back(token);
+    }
+    ruby_parser->destroy(state);
+    advance(peek_str().size());
+  } break;
+  case functions::Function::ArgumentKind::Shell:
+    command->argument = functions::Function::ShellArg(std::string(peek_str()));
+    token(io::Token::Shell);
+    advance(peek_str().size());
+    end_token();
+    break;
+  }
+  if (!suffix) {
+    suffix = peek();
+    token(io::Token::Suffix);
+    advance();
+    end_token();
+  }
+  if (suffix) {
+    auto &s = bed.suffixes[suffix - 'a'];
+    if (s.has_value())
+      command->suffix = &s.value();
+    else
+      throw ed_error("Invalid suffix.");
+  }
+}
+} // namespace bed::internal::parser

src/internal/parser/parser.cc

@@ -0,0 +1,102 @@
+#include "internal/parser/parser.h"
+#include "bed.h"
+
+namespace bed::internal::parser {
+void Parser::token(io::Token::Kind k) {
+  end_token();
+  tokens->push_back({.start = i, .end = 0, .type = k});
+}
+
+void Parser::end_token() {
+  if (tokens->empty())
+    return;
+  auto &b = tokens->back();
+  if (!b.end)
+    b.end = i;
+}
+
+char Parser::peek(uint16_t o) {
+  return i + o < cmd.size() ? cmd[i + o] : '\0';
+}
+
+std::string_view Parser::peek_str(uint16_t len) {
+  return cmd.substr(i, len);
+}
+
+void Parser::advance(uint16_t c) {
+  i += c;
+}
+
+void Parser::skip_ws() {
+  end_token();
+  while (peek() == ' ' || peek() == '\t')
+    advance();
+}
+
+void Parser::parse() {
+  try {
+    skip_ws();
+    if (peek() == '@') {
+      token(io::Token::TempCurrent);
+      advance();
+      command->temp_address = true;
+    } else {
+      command->temp_address = false;
+    }
+    skip_ws();
+    addresses(command->addresses);
+    operation();
+    skip_ws();
+    if (peek() != '\0') {
+      token(io::Token::Error);
+      throw ed_error("Malformed command");
+    }
+    advance(cmd.size() - i);
+    end_token();
+  } catch (const ed_error &e) {
+    advance(cmd.size() - i);
+    end_token();
+    throw;
+  }
+}
+
+Parser::Parser(
+  std::string_view cmd, BEd &bed, Command *command,
+  std::vector<io::Token> *tokens, CompletionContext *completion
+) : bed(bed), cmd(cmd), command(command), tokens(tokens), completion(completion) {
+  i = 0;
+}
+
+std::vector<io::Token> Parser::get_highlight(std::string_view cmd, BEd &bed) {
+  Command c;
+  std::vector<io::Token> tokens;
+  CompletionContext completion;
+  try {
+    Parser p(cmd, bed, &c, &tokens, &completion);
+    p.parse();
+  } catch (const ed_error &e) {
+  }
+  return tokens;
+}
+
+Command Parser::get_command(std::string_view cmd, BEd &bed) {
+  Command c;
+  std::vector<io::Token> tokens;
+  CompletionContext completion;
+  Parser p(cmd, bed, &c, &tokens, &completion);
+  p.parse();
+  return c;
+}
+
+std::vector<AddressPromise> Parser::get_addresses(std::string_view cmd, BEd &bed) {
+  std::vector<AddressPromise> result;
+  std::vector<io::Token> tokens;
+  CompletionContext completion;
+  Parser p(cmd, bed, nullptr, &tokens, &completion);
+  p.addresses(result);
+  p.skip_ws();
+  if (p.peek() != '\0')
+    throw ed_error("Malformed address");
+  return result;
+}
+} // namespace bed::internal::parser

src/internal/scripting/ruby.cc

@@ -0,0 +1,149 @@
+#include "internal/scripting/ruby.h"
+#include "bed.h"
+
+namespace bed::internal::scripting {
+static mrb_value mrb_bed_exit(mrb_state *mrb, mrb_value) {
+  mrb_raise(mrb, E_RUNTIME_ERROR, "Use `handle(\"q\")` to quit.");
+  return mrb_nil_value();
+}
+
+static void raise_fatal(mrb_state *mrb, const fatal_error &e) {
+  struct RClass *klass = mrb_class_get(mrb, "FatalError");
+  mrb_value exc = mrb_exc_new_str(mrb, klass, mrb_str_new_cstr(mrb, e.what()));
+  mrb_iv_set(mrb, exc, mrb_intern_lit(mrb, "@code"), mrb_fixnum_value(e.code));
+  mrb_exc_raise(mrb, exc);
+}
+
+static mrb_value mrb_bed_handle(mrb_state *mrb, mrb_value) {
+  auto &ctx = *(BEd *)mrb->ud;
+  const char *command;
+  mrb_int len;
+  mrb_get_args(mrb, "s", &command, &len);
+  std::string_view cmd(command, len);
+  try {
+    ctx.handle(cmd, false);
+  } catch (const ed_error &e) {
+    mrb_raise(mrb, mrb_class_get(mrb, "EdError"), e.what());
+  } catch (const fatal_error &f) {
+    raise_fatal(mrb, f);
+  }
+  return mrb_nil_value();
+}
+
+static mrb_value hash_get(mrb_state *mrb, mrb_value hash, const char *name) {
+  if (mrb_nil_p(hash))
+    return mrb_nil_value();
+  return mrb_hash_get(mrb, hash, mrb_symbol_value(mrb_intern_cstr(mrb, name)));
+}
+
+static functions::Function::AddressKind parse_address_kind(mrb_state *mrb, mrb_value value) {
+  if (mrb_nil_p(value))
+    return functions::Function::AddressKind::None;
+  if (!mrb_symbol_p(value))
+    mrb_raise(mrb, E_TYPE_ERROR, "address must be a Symbol");
+  auto name = mrb_sym_name(mrb, mrb_symbol(value));
+  if (strcmp(name, "none") == 0)
+    return functions::Function::AddressKind::None;
+  if (strcmp(name, "line") == 0)
+    return functions::Function::AddressKind::Line;
+  if (strcmp(name, "range") == 0)
+    return functions::Function::AddressKind::Range;
+  mrb_raisef(mrb, E_ARGUMENT_ERROR, "invalid address type: :%s", name);
+  return functions::Function::AddressKind::None;
+}
+
+static mrb_value mrb_bed_register(mrb_state *mrb, mrb_value) {
+  auto &ctx = *(BEd *)mrb->ud;
+  mrb_sym r_cmd_name;
+  mrb_value proc;
+  mrb_value opts = mrb_nil_value();
+  mrb_get_args(mrb, "n&|H", &r_cmd_name, &proc, &opts);
+  mrb_int cmd_name_len;
+  const char *name = mrb_sym_name_len(mrb, r_cmd_name, &cmd_name_len);
+  std::string_view cmd_name(name, cmd_name_len);
+  std::string desc;
+  mrb_value r_desc = hash_get(mrb, opts, "desc");
+  if (mrb_string_p(r_desc))
+    desc.assign(RSTRING_PTR(r_desc), RSTRING_LEN(r_desc));
+  std::string default_address;
+  mrb_value r_default_address = hash_get(mrb, opts, "default");
+  if (mrb_string_p(r_default_address))
+    default_address.assign(RSTRING_PTR(r_default_address), RSTRING_LEN(r_default_address));
+  ctx.functions.insert(
+    cmd_name,
+    functions::Function{
+      .address_kind = parse_address_kind(mrb, hash_get(mrb, opts, "address")),
+      .argument_kind = functions::Function::ArgumentKind::None,
+      .input_mode = functions::Function::InputMode::None,
+      .desc = desc,
+      .default_address = default_address,
+      .accept_zero = true,
+      .pre_text_mode = nullptr,
+      .handle = [b = Block(mrb, proc)](
+                  BEd &,
+                  const buffer::Address &,
+                  vase::Shard *,
+                  const functions::Function::Argument &,
+                  std::vector<buffer::Line> *
+                ) {
+        b.call();
+      }
+    }
+  );
+  return mrb_nil_value();
+}
+
+static mrb_value mrb_bed_unregister(mrb_state *mrb, mrb_value) {
+  auto &ctx = *(BEd *)mrb->ud;
+  mrb_sym r_cmd_name;
+  mrb_get_args(mrb, "n", &r_cmd_name);
+  mrb_int cmd_name_len;
+  const char *name = mrb_sym_name_len(mrb, r_cmd_name, &cmd_name_len);
+  std::string_view cmd_name(name, cmd_name_len);
+  ctx.functions.remove(cmd_name);
+  return mrb_nil_value();
+}
+
+void register_basic(BEd &ctx) {
+  auto mrb = ctx.mrb.state;
+  auto *bed_error =
+    mrb_define_class(mrb, "EdError", mrb_exc_get_id(mrb, MRB_ERROR_SYM(RuntimeError)));
+  mrb_define_class(mrb, "FatalError", bed_error);
+  mrb_define_method(mrb, mrb->kernel_module, "exit", mrb_bed_exit, MRB_ARGS_NONE());
+  mrb_define_method(mrb, mrb->kernel_module, "handle", mrb_bed_handle, MRB_ARGS_REQ(1));
+  mrb_define_method(mrb, mrb->kernel_module, "register", mrb_bed_register, MRB_ARGS_REQ(1) | MRB_ARGS_OPT(1) | MRB_ARGS_BLOCK());
+  mrb_define_method(mrb, mrb->kernel_module, "unregister", mrb_bed_unregister, MRB_ARGS_REQ(1));
+}
+
+std::string run(BEd &ctx, const std::string &str) {
+  mrb_state *mrb = ctx.mrb.state;
+  mrb_value result = mrb_load_nstring(mrb, str.data(), str.size());
+  if (!mrb->exc) {
+    mrb_value inspected = mrb_funcall(mrb, result, "inspect", 0);
+    std::string output(RSTRING_PTR(inspected), RSTRING_LEN(inspected));
+    return output;
+  }
+  mrb_value exc = mrb_obj_value(mrb->exc);
+  mrb_value msg = mrb_funcall(mrb, exc, "message", 0);
+  std::string error;
+  if (mrb_string_p(msg))
+    error.assign(RSTRING_PTR(msg), RSTRING_LEN(msg));
+  auto *fatal_class = mrb_class_get(mrb, "FatalError");
+  if (mrb_obj_is_kind_of(mrb, exc, fatal_class)) {
+    mrb_value code =
+      mrb_iv_get(mrb, exc, mrb_intern_lit(mrb, "@code"));
+    mrb->exc = nullptr;
+    int c = 1;
+    if (mrb_fixnum_p(code))
+      c = mrb_fixnum(code);
+    throw fatal_error(error, c);
+  }
+  auto *ed_class = mrb_class_get(mrb, "EdError");
+  if (mrb_obj_is_kind_of(mrb, exc, ed_class)) {
+    mrb->exc = nullptr;
+    throw ed_error(error);
+  }
+  mrb->exc = nullptr;
+  throw ed_error("Ruby Exception: " + error);
+}
+} // namespace bed::internal::scripting

src/internal/syntax/iterator.cc

@@ -0,0 +1,48 @@
+#include "internal/syntax/parser.h"
+
+namespace bed::internal::syntax {
+Iterator::Iterator(uint64_t target, ParserSnapshot p, vase::Shard *vase)
+    : snap(p), at(target) {
+  at = target;
+  if (snap.lang)
+    state = ParseState::state_before(*snap.lang, snap.root, vase, at);
+  it = vase::Iterator(vase, at, Direction::Forward);
+}
+
+Iterator::~Iterator() {
+  if (state)
+    snap.lang->destroy(state);
+  release(snap);
+}
+
+Iterator::Iterator(Iterator &&other)
+    : snap(other.snap),
+      it(std::move(other.it)),
+      state(other.state),
+      tokens(std::move(other.tokens)) {
+  other.snap = {};
+  other.state = nullptr;
+}
+
+Iterator &Iterator::operator=(Iterator &&other) {
+  if (this == &other)
+    return *this;
+  if (state)
+    snap.lang->destroy(state);
+  snap = other.snap;
+  it = std::move(other.it);
+  state = other.state;
+  tokens = std::move(other.tokens);
+  other.state = nullptr;
+  return *this;
+}
+
+void Iterator::next() {
+  if (!state)
+    return;
+  it->next();
+  tokens.clear();
+  events.clear();
+  snap.lang->parse(&state, it->line, at++ == 0, &tokens, &events);
+}
+} // namespace bed::internal::syntax

src/internal/syntax/miniparser.cc

@@ -0,0 +1,120 @@
+#include "internal/syntax/miniparser.h"
+
+namespace bed::internal::syntax {
+MiniParser::MiniParser(Language &lang, vase::Shard *vase, void *initial_state)
+    : lang(lang),
+      start_state(initial_state ? lang.copy(initial_state) : lang.none_state()) {
+  vase::Iterator it(vase, 0, Direction::Forward);
+  void *state = lang.copy(start_state);
+  std::vector<io::Token> tokens;
+  std::vector<ParseEvent> events;
+  const uint64_t count = vase ? vase->lines + 1 : 1;
+  lines.reserve(count);
+  for (uint64_t i = 0; i < count; ++i) {
+    it.next();
+    tokens.clear();
+    events.clear();
+    lang.parse(&state, it.line, i == 0, &tokens, &events);
+    lines.emplace_back(lang.copy(state), std::move(tokens));
+  }
+  lang.destroy(state);
+}
+
+MiniParser::~MiniParser() {
+  if (start_state)
+    lang.destroy(start_state);
+  for (auto &[state, tokens] : lines)
+    if (state)
+      lang.destroy(state);
+}
+
+void MiniParser::dirty(vase::Shard *vase, uint64_t start, uint64_t count) {
+  vase::Iterator it(vase, start, Direction::Forward);
+  void *state = start ? lang.copy(lines[start - 1].first)
+                      : lang.copy(start_state);
+  std::vector<ParseEvent> events;
+  uint64_t i = start;
+  for (; i < start + count; i++) {
+    it.next();
+    auto &line = lines[i];
+    line.second.clear();
+    events.clear();
+    lang.parse(&state, it.line, i == 0, &line.second, &events);
+    lang.destroy(line.first);
+    line.first = lang.copy(state);
+  }
+  while (it.next()) {
+    auto &line = lines[i++];
+    line.second.clear();
+    events.clear();
+    lang.parse(&state, it.line, false, &line.second, &events);
+    if (lang.equal(line.first, state))
+      break;
+    lang.destroy(line.first);
+    line.first = lang.copy(state);
+  }
+  lang.destroy(state);
+}
+
+void MiniParser::insert(vase::Shard *vase, uint64_t start, uint64_t count) {
+  vase::Iterator it(vase, start, Direction::Forward);
+  void *state = start ? lang.copy(lines[start - 1].first)
+                      : lang.copy(start_state);
+  std::vector<ParseEvent> events;
+  std::vector<std::pair<void *, std::vector<io::Token>>> lines_new;
+  std::vector<io::Token> tokens;
+  lines_new.reserve(count);
+  for (uint64_t i = 0; i < count; ++i) {
+    it.next();
+    tokens.clear();
+    events.clear();
+    lang.parse(&state, it.line, start + i == 0, &tokens, &events);
+    lines_new.emplace_back(lang.copy(state), std::move(tokens));
+  }
+  uint64_t i = start;
+  while (it.next()) {
+    auto &line = lines[i++];
+    line.second.clear();
+    events.clear();
+    lang.parse(&state, it.line, i == 0, &line.second, &events);
+    if (lang.equal(line.first, state))
+      break;
+    lang.destroy(line.first);
+    line.first = lang.copy(state);
+  }
+  lines.insert(
+    lines.begin() + start,
+    std::make_move_iterator(lines_new.begin()),
+    std::make_move_iterator(lines_new.end())
+  );
+  lang.destroy(state);
+}
+
+void MiniParser::erase(vase::Shard *vase, uint64_t start, uint64_t count) {
+  if (count == 0)
+    return;
+  void *state = start ? lang.copy(lines[start - 1].first)
+                      : lang.copy(start_state);
+  std::vector<ParseEvent> events;
+  for (uint64_t i = start; i < start + count; ++i)
+    if (lines[i].first)
+      lang.destroy(lines[i].first);
+  lines.erase(
+    lines.begin() + start,
+    lines.begin() + start + count
+  );
+  vase::Iterator it(vase, start, Direction::Forward);
+  uint64_t i = start;
+  while (i < lines.size() && it.next()) {
+    auto &line = lines[i];
+    line.second.clear();
+    events.clear();
+    lang.parse(&state, it.line, i++ == 0, &line.second, &events);
+    if (lang.equal(line.first, state))
+      break;
+    lang.destroy(line.first);
+    line.first = lang.copy(state);
+  }
+  lang.destroy(state);
+}
+} // namespace bed::internal::syntax

src/internal/syntax/parser.cc

@@ -1,268 +1,38 @@
 #include "internal/syntax/parser.h"
 
 namespace bed::internal::syntax {
-void dump_events(ParseState *root) {
-  if (!root)
-    return;
-  uint64_t offset = 0;
-  TreeCursor c(root, 0, &offset);
-  uint64_t line_offset = 0;
-  int depth = 0;
-  while (c.leaf) {
-    auto *leaf = c.leaf;
-    for (uint32_t i = 0; i < leaf->n; ++i) {
-      uint32_t block = leaf->blocks[i];
-      uint32_t pos = block & ParseStateLeaf::LINE_MASK;
-      bool closing = block & ParseStateLeaf::IS_CLOSING;
-      if (closing) {
-        if (depth > 0)
-          --depth;
-        else
-          std::cout << "!! UNMATCHED CLOSE !! ";
-      }
-      std::cout << std::string(static_cast<size_t>(depth) * 2, ' ')
-                << (closing ? "}" : "{")
-                << " line " << (line_offset + pos)
-                << '\n';
-      if (!closing)
-        ++depth;
-    }
-    line_offset += leaf->lines();
-    c.next();
-  }
-  if (depth != 0) {
-    std::cout << "!! UNBALANCED: depth = "
-              << depth
-              << " !!\n";
-  }
-}
-
-static void destroy_tree(ParseState *node, Language &lang) {
-  if (!node)
-    return;
-  if (node->is_branch()) {
-    auto *branch = (ParseStateBranch *)node;
-    destroy_tree(branch->left, lang);
-    destroy_tree(branch->right, lang);
-    free(branch);
-  } else {
-    auto *leaf = (ParseStateLeaf *)node;
-    if (leaf->state)
-      lang.destroy(leaf->state);
-    if (leaf->blocks)
-      free(leaf->blocks);
-    free(leaf);
-  }
-}
-
-static ParseState *make_branch(ParseState *left, ParseState *right) {
-  if (!left)
-    return right;
-  if (!right)
-    return left;
-  auto *branch = (ParseStateBranch *)malloc(sizeof(ParseStateBranch));
-  branch->header = ParseState::BRANCH_BIT + left->lines() + right->lines();
-  branch->left = left;
-  branch->right = right;
-  return branch;
-}
-
-static ParseState *build_tree(std::vector<ParseStateLeaf *> &leaves, size_t begin, size_t end) {
-  const size_t count = end - begin;
-  if (count == 0)
-    return nullptr;
-  if (count == 1)
-    return leaves[begin];
-  const size_t mid = begin + count / 2;
-  ParseState *left = build_tree(leaves, begin, mid);
-  ParseState *right = build_tree(leaves, mid, end);
-  return make_branch(left, right);
-}
-
-Parser::Parser(vase::Vase &vase, uint64_t lines, Language lang)
-    : root(nullptr), lang(lang) {
-  reset(vase, lines, lang);
-}
-
-Parser::~Parser() {
-  destroy_tree(root, lang);
-}
-
-void Parser::reset(vase::Vase &vase, uint64_t lines, Language lang_) {
-  destroy_tree(root, lang);
-  root = nullptr;
+ParserSnapshot make_parser(vase::Shard *vase, uint64_t lines, Language *lang) {
+  ParserSnapshot snap{nullptr, lang};
   if (lines == 0)
-    return;
-  lang = std::move(lang_);
-  std::vector<ParseStateLeaf *> leaves;
-  leaves.reserve((lines + MAX_CHUNK - 1) / MAX_CHUNK);
-  uint64_t consumed = 0;
-  while (consumed < lines) {
-    auto *leaf = (ParseStateLeaf *)malloc(sizeof(ParseStateLeaf));
-    leaf->state = nullptr;
-    leaf->blocks = nullptr;
-    leaf->n = 0;
-    leaf->cap = 0;
-    uint64_t chunk = std::min(MAX_CHUNK, lines - consumed);
-    leaf->header = chunk;
-    consumed += chunk;
-    leaves.push_back(leaf);
-  }
-  root = build_tree(leaves, 0, leaves.size());
-  modify(vase, 0, lines);
+    return snap;
+  if (lang)
+    snap.root = ParseState::splice(*lang, nullptr, vase, 0, 0, lines);
+  return snap;
 }
 
-std::pair<ParseState *, ParseState *> Parser::split_tree(ParseState *node, uint64_t line) {
-  if (!node)
-    return {nullptr, nullptr};
-  if (line == 0)
-    return {nullptr, node};
-  if (line >= node->lines())
-    return {node, nullptr};
-  if (node->is_branch()) {
-    auto *branch = (ParseStateBranch *)node;
-    uint64_t left_lines = branch->left->lines();
-    if (line < left_lines) {
-      auto [a, b] = split_tree(branch->left, line);
-      ParseState *right = join_tree(b, branch->right);
-      free(branch);
-      return {a, right};
-    }
-    if (line == left_lines) {
-      ParseState *left = branch->left;
-      ParseState *right = branch->right;
-      free(branch);
-      return {left, right};
-    }
-    auto [a, b] = split_tree(branch->right, line - left_lines);
-    ParseState *left = join_tree(branch->left, a);
-    free(branch);
-    return {left, b};
-  } else {
-    auto *leaf = (ParseStateLeaf *)node;
-    uint64_t lines = leaf->lines();
-    auto *right = (ParseStateLeaf *)malloc(sizeof(ParseStateLeaf));
-    right->header = lines - line;
-    right->state = nullptr;
-    right->blocks = nullptr;
-    right->n = 0;
-    right->cap = 0;
-    leaf->header = line;
-    leaf->n = 0;
-    return {leaf, right};
-  }
+ParserSnapshot retain(const ParserSnapshot &snap) {
+  if (snap.root)
+    ParseState::retain(snap.root);
+  return snap;
 }
 
-ParseState *Parser::join_tree(ParseState *a, ParseState *b) {
-  // TODO: balance
-  return make_branch(a, b);
+void release(ParserSnapshot &snap) {
+  if (snap.root && snap.lang)
+    ParseState::release(*snap.lang, snap.root);
+  snap.root = nullptr;
 }
 
-void Parser::erase(vase::Vase &vase, uint64_t start, uint64_t count) {
-  if (count == 0 || !root)
-    return;
-  auto [a, remaining] = split_tree(root, start);
-  auto [waste, b] = split_tree(remaining, count);
-  destroy_tree(waste, lang);
-  root = join_tree(a, b);
-  modify(vase, start, 1);
+void *state_before(const ParserSnapshot &snap, vase::Shard *vase, uint64_t line) {
+  if (!snap.lang)
+    return nullptr;
+  return ParseState::state_before(*snap.lang, snap.root, vase, line);
 }
 
-void Parser::insert(vase::Vase &vase, uint64_t start, uint64_t count) {
-  if (count == 0)
-    return;
-  std::vector<ParseStateLeaf *> leaves;
-  leaves.reserve((count + MAX_CHUNK - 1) / MAX_CHUNK);
-  uint64_t consumed = 0;
-  while (consumed < count) {
-    auto *leaf = (ParseStateLeaf *)malloc(sizeof(ParseStateLeaf));
-    leaf->state = nullptr;
-    leaf->blocks = nullptr;
-    leaf->n = 0;
-    leaf->cap = 0;
-    uint64_t chunk = std::min(MAX_CHUNK, count - consumed);
-    leaf->header = chunk;
-    consumed += chunk;
-    leaves.push_back(leaf);
-  }
-  ParseState *subtree = build_tree(leaves, 0, leaves.size());
-  auto [left, right] = split_tree(root, start);
-  root = join_tree(join_tree(left, subtree), right);
-  modify(vase, start, count);
-}
-
-void Parser::modify(vase::Vase &vase, uint64_t target, uint64_t count) {
-  if (count == 0 || !root)
-    return;
-  std::vector<Token> tokens;
-  std::vector<ParseEvent> events;
-  uint64_t offset;
-  TreeCursor c = TreeCursor(root, target, &offset);
-  uint64_t at = target - offset;
-  void *state = nullptr;
-  if (c.leaf->state) {
-    state = lang.copy(c.leaf->state);
-  } else {
-    while (!c.leaf->state) {
-      c.prev();
-      if (!c.leaf) {
-        at = 0;
-        break;
-      }
-      at -= c.leaf->lines();
-    }
-    if (c.leaf) {
-      state = lang.copy(c.leaf->state);
-    } else {
-      state = lang.none_state();
-      c = TreeCursor(root, 0, &offset);
-    }
-  }
-  vase::Iterator it = vase.iterate(at, Direction::Forward);
-  uint64_t chunk_start = at;
-  uint64_t next_boundary = at + c.leaf->lines();
-  c.leaf->n = 0;
-  while (true) {
-    it.next();
-    if (at == next_boundary) {
-      c.next();
-      if (!c.leaf)
-        break;
-      c.leaf->n = 0;
-      chunk_start = at;
-      next_boundary += c.leaf->lines();
-      if (at >= target + count
-          && c.leaf->state != nullptr
-          && lang.equal(state, c.leaf->state))
-        break;
-      if (c.leaf->state)
-        lang.destroy(c.leaf->state);
-      c.leaf->state = lang.copy(state);
-    }
-    tokens.clear();
-    events.clear();
-    lang.parse(&state, it.line, at == 0, &tokens, &events);
-    for (const auto &ev : events) {
-      const auto t = uint8_t(ev.ev_type);
-      if (t > ParseEvent::Closing)
-        continue;
-      if (c.leaf->n == c.leaf->cap) {
-        uint32_t cap = c.leaf->cap ? c.leaf->cap * 2 : 8;
-        c.leaf->blocks = (uint16_t *)realloc(c.leaf->blocks, cap * sizeof(uint16_t));
-        c.leaf->cap = cap;
-      }
-      c.leaf->blocks[c.leaf->n++] = t << 15 | (at - chunk_start);
-    }
-    at++;
-  }
-  lang.destroy(state);
-}
-
-uint64_t Parser::next_closing(uint64_t line) {
-  if (!root)
-    return UINT64_MAX;
+uint64_t next_closing(const ParserSnapshot &snap, uint64_t line) {
+  if (!snap.root || !snap.lang)
+    return line + 10;
   uint64_t relative = 0;
-  TreeCursor c(root, line, &relative);
+  TreeCursor c(*snap.lang, snap.root, line, &relative);
   uint64_t line_offset = line - relative;
   int level = 0;
   bool first_leaf = true;
@@ -286,14 +56,14 @@ uint64_t Parser::next_closing(uint64_t line) {
     c.next();
     first_leaf = false;
   }
-  return UINT64_MAX;
+  return (snap.root->lines() - line > 10 ? line + 10 : snap.root->lines() - 1);
 }
 
-uint64_t Parser::prev_opening(uint64_t line) {
-  if (!root)
+uint64_t prev_opening(const ParserSnapshot &snap, uint64_t line) {
+  if (!snap.root || !snap.lang)
     return 0;
   uint64_t relative = 0;
-  TreeCursor c(root, line, &relative);
+  TreeCursor c(*snap.lang, snap.root, line, &relative);
   uint64_t line_offset = line - relative;
   int level = 0;
   bool first_leaf = true;
@@ -318,77 +88,66 @@ uint64_t Parser::prev_opening(uint64_t line) {
     if (c.leaf)
       line_offset -= c.leaf->lines();
   }
-  return 0;
+  return (line > 10 ? line - 10 : 0);
 }
 
-std::optional<Parser::Iterator> Parser::get_hl(vase::Vase &vase, uint64_t target) {
-  if (!root)
+std::optional<Iterator> get_hl(const ParserSnapshot &snap, vase::Shard *vase, uint64_t target) {
+  if (!snap.root || !snap.lang)
     return std::nullopt;
-  return Parser::Iterator(target, this, vase);
+  return Iterator(target, retain(snap), vase);
 }
 
-Parser::Iterator::Iterator(uint64_t target, Parser *p, vase::Vase &vase) : p(p) {
-  uint64_t offset;
-  TreeCursor c = TreeCursor(p->root, target, &offset);
-  at = target - offset;
-  if (c.leaf->state) {
-    state = p->lang.copy(c.leaf->state);
+void Edit::mark_dirty(uint64_t start, uint64_t end) {
+  if (!dirty) {
+    dirty_start = start;
+    dirty_end = end;
+    dirty = true;
   } else {
-    while (!c.leaf->state) {
-      c.prev();
-      if (!c.leaf) {
-        at = 0;
-        break;
-      }
-      at -= c.leaf->lines();
-    }
-    if (c.leaf) {
-      state = p->lang.copy(c.leaf->state);
-    } else {
-      state = p->lang.none_state();
-      c = TreeCursor(p->root, 0, &offset);
-    }
-  }
-  it = vase.iterate(at, Direction::Forward);
-  while (at < target) {
-    it->next();
-    tokens.clear();
-    events.clear();
-    p->lang.parse(&state, it->line, at == 0, &tokens, &events);
-    at++;
+    dirty_start = std::min(dirty_start, start);
+    dirty_end = std::max(dirty_end, end);
   }
 }
 
-Parser::Iterator::~Iterator() {
-  if (state)
-    p->lang.destroy(state);
+void Edit::insert(uint64_t start, uint64_t count) {
+  if (count == 0)
+    return;
+  uint64_t orig_pos = (uint64_t)((int64_t)start - edit_delta);
+  mark_dirty(orig_pos, orig_pos);
+  edit_delta += (int64_t)count;
 }
 
-Parser::Iterator::Iterator(Iterator &&other)
-    : p(other.p),
-      it(std::move(other.it)),
-      state(other.state),
-      tokens(std::move(other.tokens)) {
-  other.state = nullptr;
+void Edit::erase(uint64_t start, uint64_t count) {
+  if (count == 0 || !target->root)
+    return;
+  uint64_t orig_start = (uint64_t)((int64_t)start - edit_delta);
+  uint64_t orig_end = orig_start + count;
+  mark_dirty(orig_start, orig_end);
+  edit_delta -= (int64_t)count;
 }
 
-Parser::Iterator &Parser::Iterator::operator=(Iterator &&other) {
-  if (this == &other)
-    return *this;
-  if (state)
-    p->lang.destroy(state);
-  p = other.p;
-  it = std::move(other.it);
-  state = other.state;
-  tokens = std::move(other.tokens);
-  other.state = nullptr;
-  return *this;
+void Edit::commit(vase::Shard *vase) {
+  if (!dirty || !target->lang)
+    return;
+  uint64_t line = dirty_start;
+  uint64_t original = dirty_end - dirty_start;
+  uint64_t final = (uint64_t)((int64_t)original + edit_delta);
+  ParseState *new_root =
+    ParseState::splice(*target->lang, target->root, vase, line, original, final);
+  release(*target);
+  target->root = new_root;
+  dirty = false;
+  edit_delta = 0;
 }
 
-void Parser::Iterator::next() {
-  it->next();
-  tokens.clear();
-  events.clear();
-  p->lang.parse(&state, it->line, at++ == 0, &tokens, &events);
+void insert(ParserSnapshot &snap, vase::Shard *vase, uint64_t start, uint64_t count) {
+  Edit e(snap);
+  e.insert(start, count);
+  e.commit(vase);
+}
+
+void erase(ParserSnapshot &snap, vase::Shard *vase, uint64_t start, uint64_t count) {
+  Edit e(snap);
+  e.erase(start, count);
+  e.commit(vase);
 }
 } // namespace bed::internal::syntax

src/internal/syntax/parser_state.cc

@@ -0,0 +1,219 @@
+#include "internal/syntax/parser.h"
+
+namespace bed::internal::syntax {
+void ParseState::retain(ParseState *n) {
+  if (n)
+    n->refs++;
+};
+
+void ParseState::release(Language &lang, ParseState *n) {
+  if (!n || --n->refs > 0)
+    return;
+  if (n->is_branch()) {
+    auto *branch = (ParseStateBranch *)n;
+    release(lang, branch->left);
+    release(lang, branch->right);
+    delete branch;
+  } else {
+    auto *leaf = (ParseStateLeaf *)n;
+    if (leaf->state)
+      lang.destroy(leaf->state);
+    if (leaf->blocks)
+      free(leaf->blocks);
+    delete leaf;
+  }
+}
+
+int height(ParseState *n) {
+  return n ? n->height : 0;
+}
+
+int balance_factor(ParseState *n) {
+  ParseStateBranch *b = (ParseStateBranch *)n;
+  return height(b->left) - height(b->right);
+}
+
+ParseState *rotate_right(Language &lang, ParseStateBranch *z) {
+  ParseStateBranch *y = (ParseStateBranch *)z->left;
+  ParseState *middle = new ParseStateBranch(y->right, z->right);
+  ParseState *out = new ParseStateBranch(y->left, middle);
+  ParseState::release(lang, middle);
+  ParseState::release(lang, z);
+  return out;
+}
+
+ParseState *rotate_left(Language &lang, ParseStateBranch *z) {
+  ParseStateBranch *y = (ParseStateBranch *)z->right;
+  ParseState *middle = new ParseStateBranch(z->left, y->left);
+  ParseState *out = new ParseStateBranch(middle, y->right);
+  ParseState::release(lang, middle);
+  ParseState::release(lang, z);
+  return out;
+}
+
+ParseState *balance(Language &lang, ParseState *node) {
+  if (!node || !node->is_branch())
+    return node;
+  ParseStateBranch *b = (ParseStateBranch *)node;
+  int bf = balance_factor(node);
+  if (bf > 1) {
+    ParseStateBranch *left = (ParseStateBranch *)b->left;
+    if (balance_factor(left) < 0) {
+      ParseState::retain(left);
+      auto new_left = rotate_left(lang, left);
+      auto rebuilt = new ParseStateBranch(new_left, b->right);
+      auto result = rotate_right(lang, (ParseStateBranch *)rebuilt);
+      ParseState::release(lang, new_left);
+      ParseState::release(lang, b);
+      return result;
+    }
+    return rotate_right(lang, b);
+  }
+  if (bf < -1) {
+    ParseStateBranch *right = (ParseStateBranch *)b->right;
+    if (balance_factor(right) > 0) {
+      ParseState::retain(right);
+      auto new_right = rotate_right(lang, right);
+      auto rebuilt = new ParseStateBranch(b->left, new_right);
+      auto result = rotate_left(lang, (ParseStateBranch *)rebuilt);
+      ParseState::release(lang, new_right);
+      ParseState::release(lang, b);
+      return result;
+    }
+    return rotate_left(lang, b);
+  }
+  return node;
+}
+
+ParseState *ParseState::build(Language &lang, ParseState **pieces, uint64_t lo, uint64_t hi) {
+  if (hi - lo == 1)
+    return pieces[lo];
+  uint64_t mid = lo + (hi - lo) / 2;
+  ParseState *left = build(lang, pieces, lo, mid);
+  ParseState *right = build(lang, pieces, mid, hi);
+  ParseState *node = concat(lang, left, right);
+  release(lang, left);
+  release(lang, right);
+  return node;
+}
+
+ParseState *ParseState::splice(
+  Language &lang, ParseState *root, vase::Shard *vase,
+  uint64_t line, uint64_t original, uint64_t final
+) {
+  if (!vase)
+    return nullptr;
+  if (!root || (line == 0 && root->lines() == original)) {
+    vase::Iterator it(vase, 0, Direction::Forward);
+    void *state = lang.none_state();
+    std::vector<io::Token> tokens;
+    std::vector<ParseEvent> events;
+    ParsePieceBuilder builder(lang, 0, state);
+    for (uint64_t at = 0; at < final; ++at) {
+      it.next();
+      tokens.clear();
+      events.clear();
+      lang.parse(&state, it.line, at == 0, &tokens, &events);
+      builder.add(state, at, events);
+    }
+    lang.destroy(state);
+    return builder.finish();
+  }
+  uint64_t at;
+  void *state;
+  ParseState *prefix;
+  {
+    uint64_t offset;
+    TreeCursor c = TreeCursor(lang, root, line, &offset);
+    prefix = c.prefix();
+    at = line - offset;
+    state = lang.copy(c.leaf->state);
+  }
+  vase::Iterator it(vase, at, Direction::Forward);
+  std::vector<io::Token> tokens;
+  std::vector<ParseEvent> events;
+  uint64_t end_in_tree = line + original;
+  uint64_t end_extra;
+  TreeCursor c = TreeCursor(lang, root, end_in_tree, &end_extra);
+  uint64_t end_in_vase = line + final;
+  ParsePieceBuilder builder(lang, at, state);
+  while (at < end_in_vase + end_extra) {
+    it.next();
+    tokens.clear();
+    events.clear();
+    lang.parse(&state, it.line, at == 0, &tokens, &events);
+    builder.add(state, at, events);
+    ++at;
+  }
+  c.next();
+  while (c.leaf) {
+    if (lang.equal(state, c.leaf->state))
+      break;
+    for (uint64_t i = 0; i < c.leaf->lines(); ++i) {
+      it.next();
+      tokens.clear();
+      events.clear();
+      lang.parse(&state, it.line, at == 0, &tokens, &events);
+      builder.add(state, at, events);
+      ++at;
+    }
+    c.next();
+  }
+  lang.destroy(state);
+  ParseState *suffix = c.suffix();
+  ParseState *new_stuff = builder.finish();
+  auto a = concat(lang, prefix, new_stuff);
+  release(lang, prefix);
+  release(lang, new_stuff);
+  auto result = concat(lang, a, suffix);
+  release(lang, a);
+  release(lang, suffix);
+  return result;
+}
+
+ParseState *ParseState::concat(Language &lang, ParseState *a, ParseState *b) {
+  if (!a)
+    return (retain(b), b);
+  if (!b)
+    return (retain(a), a);
+  if (a->height > b->height + 1) {
+    ParseStateBranch *ba = (ParseStateBranch *)a;
+    ParseState *r = concat(lang, ba->right, b);
+    ParseState *out = balance(lang, new ParseStateBranch(ba->left, r));
+    release(lang, r);
+    return out;
+  }
+  if (b->height > a->height + 1) {
+    ParseStateBranch *bb = (ParseStateBranch *)b;
+    ParseState *l = concat(lang, a, bb->left);
+    ParseState *out = balance(lang, new ParseStateBranch(l, bb->right));
+    release(lang, l);
+    return out;
+  }
+  return balance(lang, new ParseStateBranch(a, b));
+}
+
+void *ParseState::state_before(Language &lang, ParseState *root, vase::Shard *vase, uint64_t line) {
+  uint64_t offset;
+  uint64_t at;
+  void *state;
+  if (!root) {
+    at = 0;
+    state = lang.none_state();
+  } else {
+    TreeCursor c = TreeCursor(lang, root, line, &offset);
+    at = line - offset;
+    state = lang.copy(c.leaf->state);
+  }
+  vase::Iterator it(vase, at, Direction::Forward);
+  std::vector<io::Token> tokens;
+  std::vector<ParseEvent> events;
+  for (; at < line; ++at) {
+    it.next();
+    tokens.clear();
+    events.clear();
+    lang.parse(&state, it.line, at == 0, &tokens, &events);
+  }
+  return state;
+}
+} // namespace bed::internal::syntax

src/internal/syntax/ruby/parse.cc

@@ -34,75 +34,87 @@ inline uint8_t utf8_codepoint_width(unsigned char c) {
   return 1;
 }
 
-bool handle_escapes(RubyParser &p, std::vector<Token> *tokens, uint32_t &start, bool string = true) {
-  if (p.peek() == '\\') {
-    if (string)
-      tokens->push_back({start, p.i, Token::String});
-    else
-      tokens->push_back({start, p.i, Token::Regexp});
-    start = p.i;
+bool handle_escapes(RubyParser &p, std::vector<io::Token> *tokens, uint32_t &start, bool string = true) {
+  if (p.peek() != '\\')
+    return false;
+  if (!(p.current().flags & RubyState::RubyInternalState::ALLOW_ESCAPE)) {
     p.advance();
-    if (p.peek() == 'x') {
-      p.advance();
-      if (is_hex(p.peek()))
-        p.advance();
-      if (is_hex(p.peek()))
-        p.advance();
-    } else if (p.peek() == 'u') {
-      p.advance();
-      if (p.peek() == '{') {
-        p.advance();
-        while (p.peek() != '}' && p.peek() != '\0')
-          p.advance();
-        if (p.peek() == '}')
-          p.advance();
-      } else {
-        if (is_hex(p.peek()))
-          p.advance();
-        if (is_hex(p.peek()))
-          p.advance();
-        if (is_hex(p.peek()))
-          p.advance();
-        if (is_hex(p.peek()))
-          p.advance();
-      }
-    } else if ('0' <= p.peek() && p.peek() <= '7') {
-      p.advance();
-      if ('0' <= p.peek() && p.peek() <= '7')
-        p.advance();
-      if ('0' <= p.peek() && p.peek() <= '7')
-        p.advance();
-    } else if (p.peek() == 'c') {
-      p.advance();
-      if (p.peek() != '\\')
-        p.advance();
-    } else if (p.peek() == 'M' || p.peek() == 'C') {
-      p.advance();
-      if (p.peek() == '-') {
-        p.advance();
-        if (p.peek() != '\\')
-          p.advance();
-      }
-    } else if (p.peek() == 'N') {
-      p.advance();
-      if (p.peek() == '{') {
-        p.advance();
-        while (p.peek() != '}' && p.peek() != '\0')
-          p.advance();
-        if (p.peek() == '}')
-          p.advance();
-      }
-    } else {
-      p.advance();
-    }
-    tokens->push_back({start, p.i, Token::Escape});
+    if (p.peek() != '\'' && p.peek() != '\\')
+      return false;
+    if (string)
+      tokens->push_back({start, p.i - 1, io::Token::String});
+    else
+      tokens->push_back({start, p.i - 1, io::Token::Regexp});
+    p.advance();
+    tokens->push_back({p.i - 2, p.i, io::Token::Escape});
     start = p.i;
     return true;
   }
-  return false;
+  if (string)
+    tokens->push_back({start, p.i, io::Token::String});
+  else
+    tokens->push_back({start, p.i, io::Token::Regexp});
+  start = p.i;
+  p.advance();
+  if (p.peek() == 'x') {
+    p.advance();
+    if (is_hex(p.peek()))
+      p.advance();
+    if (is_hex(p.peek()))
+      p.advance();
+  } else if (p.peek() == 'u') {
+    p.advance();
+    if (p.peek() == '{') {
+      p.advance();
+      while (p.peek() != '}' && p.peek() != '\0')
+        p.advance();
+      if (p.peek() == '}')
+        p.advance();
+    } else {
+      if (is_hex(p.peek()))
+        p.advance();
+      if (is_hex(p.peek()))
+        p.advance();
+      if (is_hex(p.peek()))
+        p.advance();
+      if (is_hex(p.peek()))
+        p.advance();
+    }
+  } else if ('0' <= p.peek() && p.peek() <= '7') {
+    p.advance();
+    if ('0' <= p.peek() && p.peek() <= '7')
+      p.advance();
+    if ('0' <= p.peek() && p.peek() <= '7')
+      p.advance();
+  } else if (p.peek() == 'c') {
+    p.advance();
+    if (p.peek() != '\\')
+      p.advance();
+  } else if (p.peek() == 'M' || p.peek() == 'C') {
+    p.advance();
+    if (p.peek() == '-') {
+      p.advance();
+      if (p.peek() != '\\')
+        p.advance();
+    }
+  } else if (p.peek() == 'N') {
+    p.advance();
+    if (p.peek() == '{') {
+      p.advance();
+      while (p.peek() != '}' && p.peek() != '\0')
+        p.advance();
+      if (p.peek() == '}')
+        p.advance();
+    }
+  } else {
+    p.advance();
+  }
+  tokens->push_back({start, p.i, io::Token::Escape});
+  start = p.i;
+  return true;
 };
 
-bool handle_heredoc(RubyParser &p, std::vector<Token> *tokens) {
+bool handle_heredoc(RubyParser &p, std::vector<io::Token> *tokens, std::vector<ParseEvent> *events) {
   uint8_t *heredocs = p.state->heredocs();
   uint32_t start = p.i;
   if (start == 0) {
@@ -114,21 +126,22 @@ bool handle_heredoc(RubyParser &p, std::vector<Token> *tokens) {
         && memcmp(p.line.data() + start, heredocs + 1, heredoc_len) == 0) {
       if (!p.dequeue_doc(heredoc_len))
         p.current().state = RubyState::RubyInternalState::NONE;
-      tokens->push_back({p.i, p.len(), Token::Annotation});
+      events->push_back(true);
+      tokens->push_back({p.i, p.len(), io::Token::Annotation});
       p.current().flags |= RubyState::RubyInternalState::EXPECTING_EXPRESSION;
       return true;
     }
   }
   if (!(heredocs[0] & RubyState::Heredocs::ALLOW_INTERPOLATION)) {
-    tokens->push_back({p.i, p.len(), Token::String});
+    tokens->push_back({p.i, p.len(), io::Token::String});
     return true;
   } else {
     while (p.i < p.len()) {
       if (handle_escapes(p, tokens, start))
         continue;
       if (p.peek_str(2) == "#{") {
-        tokens->push_back({start, p.i, Token::String});
-        tokens->push_back({p.i, p.i + 2, Token::Interpolation});
+        tokens->push_back({start, p.i, io::Token::String});
+        tokens->push_back({p.i, p.i + 2, io::Token::Interpolation});
         p.advance(2);
         p.push_state();
         return false;
@@ -136,20 +149,20 @@ bool handle_heredoc(RubyParser &p, std::vector<Token> *tokens) {
       p.advance();
     }
     if (p.i >= p.len())
-      tokens->push_back({start, p.len(), Token::String});
+      tokens->push_back({start, p.len(), io::Token::String});
     return true;
   }
 }
 
-void handle_string(RubyParser &p, std::vector<Token> *tokens) {
+void handle_string(RubyParser &p, std::vector<io::Token> *tokens) {
   uint32_t start = p.i;
   while (p.i < p.len()) {
     if (handle_escapes(p, tokens, start))
       continue;
     if ((p.current().flags & RubyState::RubyInternalState::ALLOW_INTERPOLATION)
         && p.peek_str(2) == "#{") {
-      tokens->push_back({start, p.i, Token::String});
-      tokens->push_back({p.i, p.i + 2, Token::Interpolation});
+      tokens->push_back({start, p.i, io::Token::String});
+      tokens->push_back({p.i, p.i + 2, io::Token::Interpolation});
       p.advance(2);
       p.push_state();
       return;
@@ -160,7 +173,7 @@ void handle_string(RubyParser &p, std::vector<Token> *tokens) {
     if (p.peek() == p.current().delim_end) {
       if (p.current().delim_start == p.current().delim_end) {
         p.advance();
-        tokens->push_back({start, p.i, Token::String});
+        tokens->push_back({start, p.i, io::Token::String});
         p.current().state = RubyState::RubyInternalState::NONE;
         p.current().flags &= ~RubyState::RubyInternalState::EXPECTING_EXPRESSION;
         return;
@@ -168,7 +181,7 @@ void handle_string(RubyParser &p, std::vector<Token> *tokens) {
         p.current().lit_brace_level--;
         if (p.current().lit_brace_level == 0) {
           p.advance();
-          tokens->push_back({start, p.i, Token::String});
+          tokens->push_back({start, p.i, io::Token::String});
           p.current().state = RubyState::RubyInternalState::NONE;
           p.current().flags &= ~RubyState::RubyInternalState::EXPECTING_EXPRESSION;
           return;
@@ -178,18 +191,18 @@ void handle_string(RubyParser &p, std::vector<Token> *tokens) {
     p.advance();
   }
   if (p.i >= p.len())
-    tokens->push_back({start, p.len(), Token::String});
+    tokens->push_back({start, p.len(), io::Token::String});
 }
 
-void handle_regex(RubyParser &p, std::vector<Token> *tokens) {
+void handle_regex(RubyParser &p, std::vector<io::Token> *tokens) {
   uint32_t start = p.i;
   while (p.i < p.len()) {
     if (handle_escapes(p, tokens, start, false))
       continue;
     if ((p.current().flags & RubyState::RubyInternalState::ALLOW_INTERPOLATION)
         && p.peek_str(2) == "#{") {
-      tokens->push_back({start, p.i, Token::Regexp});
-      tokens->push_back({p.i, p.i + 2, Token::Interpolation});
+      tokens->push_back({start, p.i, io::Token::Regexp});
+      tokens->push_back({p.i, p.i + 2, io::Token::Interpolation});
       p.advance(2);
       p.push_state();
       return;
@@ -200,7 +213,7 @@ void handle_regex(RubyParser &p, std::vector<Token> *tokens) {
     if (p.peek() == p.current().delim_end) {
       if (p.current().delim_start == p.current().delim_end) {
         p.advance();
-        tokens->push_back({start, p.i, Token::Regexp});
+        tokens->push_back({start, p.i, io::Token::Regexp});
         p.current().state = RubyState::RubyInternalState::NONE;
         p.current().flags &= ~RubyState::RubyInternalState::EXPECTING_EXPRESSION;
         return;
@@ -208,7 +221,7 @@ void handle_regex(RubyParser &p, std::vector<Token> *tokens) {
         p.current().lit_brace_level--;
         if (p.current().lit_brace_level == 0) {
           p.advance();
-          tokens->push_back({start, p.i, Token::Regexp});
+          tokens->push_back({start, p.i, io::Token::Regexp});
           p.current().state = RubyState::RubyInternalState::NONE;
           p.current().flags &= ~RubyState::RubyInternalState::EXPECTING_EXPRESSION;
           return;
@@ -218,15 +231,15 @@ void handle_regex(RubyParser &p, std::vector<Token> *tokens) {
     p.advance();
   }
   if (p.i >= p.len())
-    tokens->push_back({start, p.len(), Token::Regexp});
+    tokens->push_back({start, p.len(), io::Token::Regexp});
 }
 
-bool handle_line_markers(RubyParser &p, std::vector<Token> *tokens, std::vector<ParseEvent> *events) {
+bool handle_line_markers(RubyParser &p, std::vector<io::Token> *tokens, std::vector<ParseEvent> *events) {
   if (p.len() == 6 && p.peek_str(6) == "=begin") {
     p.current().state = RubyState::RubyInternalState::COMMENT;
     p.current().flags &= ~RubyState::RubyInternalState::EXPECTING_EXPRESSION;
-    events->push_back(ParseEvent::Opening);
-    tokens->push_back({0, p.len(), Token::Comment});
+    events->push_back(false);
+    tokens->push_back({0, p.len(), io::Token::Comment});
     return true;
   }
   if (p.len() == 7 && p.peek_str(7) == "__END__") {
@@ -237,20 +250,20 @@ bool handle_line_markers(RubyParser &p, std::vector<Token> *tokens, std::vector<
   return false;
 }
 
-bool handle_comment(RubyParser &p, std::vector<Token> *tokens, bool first_line) {
+bool handle_comment(RubyParser &p, std::vector<io::Token> *tokens, bool first_line) {
   if (p.peek() == '#') {
     p.current().flags &= ~RubyState::RubyInternalState::EXPECTING_EXPRESSION;
     if (first_line && p.i == 0 && p.peek(1) == '!') {
-      tokens->push_back({0, p.len(), Token::Shebang});
+      tokens->push_back({0, p.len(), io::Token::Shebang});
       return true;
     }
-    tokens->push_back({p.i, p.len(), Token::Comment});
+    tokens->push_back({p.i, p.len(), io::Token::Comment});
     return true;
   }
   return false;
 }
 
-bool handle_syntax(RubyParser &p, std::vector<Token> *tokens, std::vector<ParseEvent> *events) {
+bool handle_syntax(RubyParser &p, std::vector<io::Token> *tokens, std::vector<ParseEvent> *events) {
   static const RubyTries tries = RubyTries();
   if (p.peek() == ' ' || p.peek() == '\t') {
     while (p.peek() == ' ' || p.peek() == '\t')
@@ -266,7 +279,7 @@ bool handle_syntax(RubyParser &p, std::vector<Token> *tokens, std::vector<ParseE
     case RubyState::RubyInternalState::CLASS_NAME: {
       if (p.peek() == '<' && p.peek(1) == '<') {
         p.advance(2);
-        events->push_back(ParseEvent::Opening);
+        events->push_back(false);
         p.current().flags = (p.current().flags & ~RubyState::RubyInternalState::NAME_MASK);
         p.current().flags |= RubyState::RubyInternalState::EXPECTING_EXPRESSION;
         return false;
@@ -276,7 +289,7 @@ bool handle_syntax(RubyParser &p, std::vector<Token> *tokens, std::vector<ParseE
         j++;
         while (identifier_char(p.peek(j)))
           j++;
-        tokens->push_back({p.i, p.i + j, Token::Constant});
+        tokens->push_back({p.i, p.i + j, io::Token::Constant});
         p.advance(j);
         while (p.peek() == ' ' || p.peek() == '\t')
           p.advance();
@@ -285,7 +298,7 @@ bool handle_syntax(RubyParser &p, std::vector<Token> *tokens, std::vector<ParseE
           return false;
         }
       }
-      events->push_back(ParseEvent::Opening);
+      events->push_back(false);
       p.current().flags = (p.current().flags & ~RubyState::RubyInternalState::NAME_MASK);
       return false;
     }
@@ -298,11 +311,11 @@ bool handle_syntax(RubyParser &p, std::vector<Token> *tokens, std::vector<ParseE
         if (p.peek(j) == '!' || p.peek(j) == '?')
           j++;
         if ('A' <= p.peek() && p.peek() <= 'Z')
-          tokens->push_back({p.i, p.i + j, Token::Constant});
+          tokens->push_back({p.i, p.i + j, io::Token::Constant});
         else if (j == 4 && p.peek_str(4) == "self")
-          tokens->push_back({p.i, p.i + j, Token::Keyword});
+          tokens->push_back({p.i, p.i + j, io::Token::Keyword});
         else
-          tokens->push_back({p.i, p.i + j, Token::Function});
+          tokens->push_back({p.i, p.i + j, io::Token::Function});
         p.advance(j);
         while (p.peek() == ' ' || p.peek() == '\t')
           p.advance();
@@ -311,7 +324,7 @@ bool handle_syntax(RubyParser &p, std::vector<Token> *tokens, std::vector<ParseE
           return false;
         }
       }
-      events->push_back(ParseEvent::Opening);
+      events->push_back(false);
       p.current().flags = (p.current().flags & ~RubyState::RubyInternalState::NAME_MASK);
       return false;
     }
@@ -321,7 +334,7 @@ bool handle_syntax(RubyParser &p, std::vector<Token> *tokens, std::vector<ParseE
         j++;
         while (identifier_char(p.peek(j)))
           j++;
-        tokens->push_back({p.i, p.i + j, Token::Constant});
+        tokens->push_back({p.i, p.i + j, io::Token::Constant});
         p.advance(j);
         while (p.peek() == ' ' || p.peek() == '\t')
           p.advance();
@@ -330,7 +343,7 @@ bool handle_syntax(RubyParser &p, std::vector<Token> *tokens, std::vector<ParseE
           return false;
         }
       }
-      events->push_back(ParseEvent::Opening);
+      events->push_back(false);
       p.current().flags = (p.current().flags & ~RubyState::RubyInternalState::NAME_MASK);
       return false;
     }
@@ -343,7 +356,7 @@ bool handle_syntax(RubyParser &p, std::vector<Token> *tokens, std::vector<ParseE
       indented = true;
     if (p.peek(j) == '~' || p.peek(j) == '-')
       j++;
-    tokens->push_back({p.i, p.i + j, Token::Operator});
+    tokens->push_back({p.i, p.i + j, io::Token::Operator});
     if (p.i + j >= p.len())
       return false;
     std::string delim;
@@ -366,7 +379,8 @@ bool handle_syntax(RubyParser &p, std::vector<Token> *tokens, std::vector<ParseE
       return false;
     p.current().flags &= ~RubyState::RubyInternalState::EXPECTING_EXPRESSION;
     if (!delim.empty()) {
-      tokens->push_back({s, p.i + j, Token::Annotation});
+      events->push_back(false);
+      tokens->push_back({s, p.i + j, io::Token::Annotation});
       uint8_t header = delim.size();
       if (interpolation)
         header |= RubyState::Heredocs::ALLOW_INTERPOLATION;
@@ -380,7 +394,7 @@ bool handle_syntax(RubyParser &p, std::vector<Token> *tokens, std::vector<ParseE
     return false;
   }
   if (p.peek() == '/' && p.current().flags & RubyState::RubyInternalState::EXPECTING_EXPRESSION) {
-    tokens->push_back({p.i, p.i + 1, Token::Regexp});
+    tokens->push_back({p.i, p.i + 1, io::Token::Regexp});
     p.current().state = RubyState::RubyInternalState::REGEXP;
     p.current().flags &= ~RubyState::RubyInternalState::EXPECTING_EXPRESSION;
     p.current().flags |= RubyState::RubyInternalState::ALLOW_INTERPOLATION;
@@ -399,7 +413,7 @@ bool handle_syntax(RubyParser &p, std::vector<Token> *tokens, std::vector<ParseE
       if (p.peek() == '.')
         p.advance();
     }
-    tokens->push_back({start, p.i, Token::Operator});
+    tokens->push_back({start, p.i, io::Token::Operator});
     return false;
   }
   case ':': {
@@ -407,17 +421,17 @@ bool handle_syntax(RubyParser &p, std::vector<Token> *tokens, std::vector<ParseE
     uint32_t start = p.i;
     p.advance();
     if (p.i >= p.len()) {
-      tokens->push_back({start, p.i, Token::Operator});
+      tokens->push_back({start, p.i, io::Token::Operator});
       p.current().flags |= RubyState::RubyInternalState::EXPECTING_EXPRESSION;
       return false;
     }
     if (p.peek() == ':') {
       p.advance();
-      tokens->push_back({start, p.i, Token::Operator});
+      tokens->push_back({start, p.i, io::Token::Operator});
       return false;
     }
     if (p.peek() == '\'' || p.peek() == '"') {
-      tokens->push_back({start, p.i, Token::Label});
+      tokens->push_back({start, p.i, io::Token::Label});
       p.current().flags |= RubyState::RubyInternalState::EXPECTING_EXPRESSION;
       return false;
     }
@@ -428,12 +442,12 @@ bool handle_syntax(RubyParser &p, std::vector<Token> *tokens, std::vector<ParseE
         p.advance();
       while (identifier_char(p.peek()))
         p.advance();
-      tokens->push_back({start, p.i, Token::Label});
+      tokens->push_back({start, p.i, io::Token::Label});
       return false;
     }
     uint32_t op_len = tries.operator_trie.longest_match(p.peek_str(p.len() - p.i));
     if (op_len > 0) {
-      tokens->push_back({start, p.i + op_len, Token::Label});
+      tokens->push_back({start, p.i + op_len, io::Token::Label});
       p.advance(op_len);
       return false;
     }
@@ -443,10 +457,10 @@ bool handle_syntax(RubyParser &p, std::vector<Token> *tokens, std::vector<ParseE
         p.advance();
       if (p.peek() == '!' || p.peek() == '?')
         p.advance();
-      tokens->push_back({start, p.i, Token::Label});
+      tokens->push_back({start, p.i, io::Token::Label});
       return false;
     }
-    tokens->push_back({start, p.i, Token::Operator});
+    tokens->push_back({start, p.i, io::Token::Operator});
     return false;
   }
   case '@': {
@@ -463,7 +477,7 @@ bool handle_syntax(RubyParser &p, std::vector<Token> *tokens, std::vector<ParseE
       return false;
     while (identifier_char(p.peek()))
       p.advance();
-    tokens->push_back({start, p.i, Token::VariableInstance});
+    tokens->push_back({start, p.i, io::Token::VariableInstance});
     return false;
   }
   case '$': {
@@ -510,7 +524,7 @@ bool handle_syntax(RubyParser &p, std::vector<Token> *tokens, std::vector<ParseE
         return false;
       }
     }
-    tokens->push_back({start, p.i, Token::VariableGlobal});
+    tokens->push_back({start, p.i, io::Token::VariableGlobal});
     return false;
   }
   case '?': {
@@ -526,7 +540,7 @@ bool handle_syntax(RubyParser &p, std::vector<Token> *tokens, std::vector<ParseE
           p.advance();
         if (is_hex(p.peek()))
           p.advance();
-        tokens->push_back({start, p.i, Token::Char});
+        tokens->push_back({start, p.i, io::Token::Char});
         return false;
       } else if (p.peek() == 'u') {
         p.advance();
@@ -546,7 +560,7 @@ bool handle_syntax(RubyParser &p, std::vector<Token> *tokens, std::vector<ParseE
           if (is_hex(p.peek()))
             p.advance();
         }
-        tokens->push_back({start, p.i, Token::Char});
+        tokens->push_back({start, p.i, io::Token::Char});
         return false;
       } else if ('0' <= p.peek() && p.peek() <= '7') {
         p.advance();
@@ -554,7 +568,7 @@ bool handle_syntax(RubyParser &p, std::vector<Token> *tokens, std::vector<ParseE
           p.advance();
         if ('0' <= p.peek() && p.peek() <= '7')
           p.advance();
-        tokens->push_back({start, p.i, Token::Char});
+        tokens->push_back({start, p.i, io::Token::Char});
         return false;
       } else if (p.peek() == 'c') {
         p.advance();
@@ -562,7 +576,7 @@ bool handle_syntax(RubyParser &p, std::vector<Token> *tokens, std::vector<ParseE
           p.advance();
         else
           goto combination;
-        tokens->push_back({start, p.i, Token::Char});
+        tokens->push_back({start, p.i, io::Token::Char});
         return false;
       } else if (p.peek() == 'M' || p.peek() == 'C') {
         p.advance();
@@ -573,7 +587,7 @@ bool handle_syntax(RubyParser &p, std::vector<Token> *tokens, std::vector<ParseE
           else
             goto combination;
         }
-        tokens->push_back({start, p.i, Token::Char});
+        tokens->push_back({start, p.i, io::Token::Char});
         return false;
       } else if (p.peek() == 'N') {
         p.advance();
@@ -584,28 +598,28 @@ bool handle_syntax(RubyParser &p, std::vector<Token> *tokens, std::vector<ParseE
           if (p.peek() == '}')
             p.advance();
         }
-        tokens->push_back({start, p.i, Token::Char});
+        tokens->push_back({start, p.i, io::Token::Char});
         return false;
       } else {
         p.advance();
-        tokens->push_back({start, p.i, Token::Char});
+        tokens->push_back({start, p.i, io::Token::Char});
         return false;
       }
     } else if (p.peek() != '\0' && p.peek() != ' ' && p.peek() != '\t') {
       p.advance();
-      tokens->push_back({start, p.i, Token::Char});
+      tokens->push_back({start, p.i, io::Token::Char});
       return false;
     } else {
       p.current().flags &= ~RubyState::RubyInternalState::EXPECTING_EXPRESSION;
-      tokens->push_back({start, p.i, Token::Operator});
+      tokens->push_back({start, p.i, io::Token::Operator});
       return false;
     }
   }
   case '{': {
     p.current().flags |= RubyState::RubyInternalState::EXPECTING_EXPRESSION;
     uint8_t brace_color =
-      (uint8_t)Token::Brace1 + (p.current().brace_level % 5);
-    tokens->push_back({p.i, p.i + 1, (Token::Kind)brace_color});
+      (uint8_t)io::Token::Brace1 + (p.current().brace_level % 5);
+    tokens->push_back({p.i, p.i + 1, (io::Token::Kind)brace_color});
     p.current().brace_level++;
     p.advance();
     return false;
@@ -614,11 +628,11 @@ bool handle_syntax(RubyParser &p, std::vector<Token> *tokens, std::vector<ParseE
     p.current().flags &= ~RubyState::RubyInternalState::EXPECTING_EXPRESSION;
     if (!--p.current().brace_level && p.state->top > 1) {
       p.pop_state();
-      tokens->push_back({p.i, p.i + 1, Token::Interpolation});
+      tokens->push_back({p.i, p.i + 1, io::Token::Interpolation});
     } else {
       uint8_t brace_color =
-        (uint8_t)Token::Brace1 + (p.current().brace_level % 5);
-      tokens->push_back({p.i, p.i + 1, (Token::Kind)brace_color});
+        (uint8_t)io::Token::Brace1 + (p.current().brace_level % 5);
+      tokens->push_back({p.i, p.i + 1, (io::Token::Kind)brace_color});
     }
     p.advance();
     return false;
@@ -626,8 +640,8 @@ bool handle_syntax(RubyParser &p, std::vector<Token> *tokens, std::vector<ParseE
   case '(': {
     p.current().flags |= RubyState::RubyInternalState::EXPECTING_EXPRESSION;
     uint8_t brace_color =
-      (uint8_t)Token::Brace1 + (p.current().brace_level % 5);
-    tokens->push_back({p.i, p.i + 1, (Token::Kind)brace_color});
+      (uint8_t)io::Token::Brace1 + (p.current().brace_level % 5);
+    tokens->push_back({p.i, p.i + 1, (io::Token::Kind)brace_color});
     p.current().brace_level++;
     p.advance();
     return false;
@@ -636,16 +650,16 @@ bool handle_syntax(RubyParser &p, std::vector<Token> *tokens, std::vector<ParseE
     p.current().flags &= ~RubyState::RubyInternalState::EXPECTING_EXPRESSION;
     p.current().brace_level--;
     uint8_t brace_color =
-      (uint8_t)Token::Brace1 + (p.current().brace_level % 5);
-    tokens->push_back({p.i, p.i + 1, (Token::Kind)brace_color});
+      (uint8_t)io::Token::Brace1 + (p.current().brace_level % 5);
+    tokens->push_back({p.i, p.i + 1, (io::Token::Kind)brace_color});
     p.advance();
     return false;
   }
   case '[': {
     p.current().flags |= RubyState::RubyInternalState::EXPECTING_EXPRESSION;
     uint8_t brace_color =
-      (uint8_t)Token::Brace1 + (p.current().brace_level % 5);
-    tokens->push_back({p.i, p.i + 1, (Token::Kind)brace_color});
+      (uint8_t)io::Token::Brace1 + (p.current().brace_level % 5);
+    tokens->push_back({p.i, p.i + 1, (io::Token::Kind)brace_color});
     p.current().brace_level++;
     p.advance();
     return false;
@@ -654,34 +668,36 @@ bool handle_syntax(RubyParser &p, std::vector<Token> *tokens, std::vector<ParseE
     p.current().flags &= ~RubyState::RubyInternalState::EXPECTING_EXPRESSION;
     p.current().brace_level--;
     uint8_t brace_color =
-      (uint8_t)Token::Brace1 + (p.current().brace_level % 5);
-    tokens->push_back({p.i, p.i + 1, (Token::Kind)brace_color});
+      (uint8_t)io::Token::Brace1 + (p.current().brace_level % 5);
+    tokens->push_back({p.i, p.i + 1, (io::Token::Kind)brace_color});
     p.advance();
     return false;
   }
   case '\'': {
     p.current().flags &= ~RubyState::RubyInternalState::EXPECTING_EXPRESSION;
-    tokens->push_back({p.i, p.i + 1, Token::String});
+    tokens->push_back({p.i, p.i + 1, io::Token::String});
     p.current().state = RubyState::RubyInternalState::STRING;
     p.current().delim_start = '\'';
     p.current().delim_end = '\'';
     p.current().flags &= ~RubyState::RubyInternalState::ALLOW_INTERPOLATION;
+    p.current().flags &= ~RubyState::RubyInternalState::ALLOW_ESCAPE;
     p.advance();
     return false;
   }
   case '"': {
     p.current().flags &= ~RubyState::RubyInternalState::EXPECTING_EXPRESSION;
-    tokens->push_back({p.i, p.i + 1, Token::String});
+    tokens->push_back({p.i, p.i + 1, io::Token::String});
     p.current().state = RubyState::RubyInternalState::STRING;
     p.current().delim_start = '"';
     p.current().delim_end = '"';
     p.current().flags |= RubyState::RubyInternalState::ALLOW_INTERPOLATION;
+    p.current().flags |= RubyState::RubyInternalState::ALLOW_ESCAPE;
     p.advance();
     return false;
   }
   case '`': {
     p.current().flags &= ~RubyState::RubyInternalState::EXPECTING_EXPRESSION;
-    tokens->push_back({p.i, p.i + 1, Token::String});
+    tokens->push_back({p.i, p.i + 1, io::Token::String});
     p.current().state = RubyState::RubyInternalState::STRING;
     p.current().delim_start = '`';
     p.current().delim_end = '`';
@@ -691,7 +707,7 @@ bool handle_syntax(RubyParser &p, std::vector<Token> *tokens, std::vector<ParseE
   }
   case '%': {
     if (p.i + 1 >= p.len()) {
-      tokens->push_back({p.i, p.i + 1, Token::Operator});
+      tokens->push_back({p.i, p.i + 1, io::Token::Operator});
       p.advance();
       p.current().flags |= RubyState::RubyInternalState::EXPECTING_EXPRESSION;
       return false;
@@ -701,6 +717,7 @@ bool handle_syntax(RubyParser &p, std::vector<Token> *tokens, std::vector<ParseE
     char delim_start = '\0';
     char delim_end = '\0';
     bool allow_interp = true;
+    bool allow_escape = true;
     int prefix_len = 1;
     bool is_regexp = false;
     switch (type) {
@@ -714,6 +731,7 @@ bool handle_syntax(RubyParser &p, std::vector<Token> *tokens, std::vector<ParseE
     case 'I':
     case 'W':
       allow_interp = true;
+      allow_escape = true;
       prefix_len = 2;
       break;
     case 'w':
@@ -721,22 +739,24 @@ bool handle_syntax(RubyParser &p, std::vector<Token> *tokens, std::vector<ParseE
     case 'i':
     case 's':
       allow_interp = false;
+      allow_escape = false;
       prefix_len = 2;
       break;
     default:
       allow_interp = true;
+      allow_escape = true;
       prefix_len = 1;
       break;
     }
     if (p.i + prefix_len >= p.len()) {
-      tokens->push_back({p.i, p.i + 1, Token::Operator});
+      tokens->push_back({p.i, p.i + 1, io::Token::Operator});
       p.advance(prefix_len);
       p.current().flags |= RubyState::RubyInternalState::EXPECTING_EXPRESSION;
       return false;
     }
     delim_start = p.peek(prefix_len);
     if (identifier_char(delim_start) || delim_start == ' ') {
-      tokens->push_back({p.i, p.i + 1, Token::Operator});
+      tokens->push_back({p.i, p.i + 1, io::Token::Operator});
       p.advance(prefix_len);
       p.current().flags |= RubyState::RubyInternalState::EXPECTING_EXPRESSION;
       return false;
@@ -758,7 +778,7 @@ bool handle_syntax(RubyParser &p, std::vector<Token> *tokens, std::vector<ParseE
       delim_end = delim_start;
       break;
     }
-    tokens->push_back({p.i, p.i + prefix_len + 1, (is_regexp ? Token::Regexp : Token::String)});
+    tokens->push_back({p.i, p.i + prefix_len + 1, (is_regexp ? io::Token::Regexp : io::Token::String)});
     p.current().state = is_regexp
                           ? RubyState::RubyInternalState::REGEXP
                           : RubyState::RubyInternalState::STRING;
@@ -766,6 +786,8 @@ bool handle_syntax(RubyParser &p, std::vector<Token> *tokens, std::vector<ParseE
     p.current().delim_end = delim_end;
     if (allow_interp)
       p.current().flags |= RubyState::RubyInternalState::ALLOW_INTERPOLATION;
+    if (allow_escape)
+      p.current().flags |= RubyState::RubyInternalState::ALLOW_ESCAPE;
     p.current().lit_brace_level = 1;
     p.advance(prefix_len + 1);
     return false;
@@ -780,11 +802,6 @@ bool handle_syntax(RubyParser &p, std::vector<Token> *tokens, std::vector<ParseE
       p.ending = false;
     p.advance();
     return false;
-  case '\0':
-    if (p.ending)
-      p.current().flags |= RubyState::RubyInternalState::EXPECTING_EXPRESSION;
-    p.advance();
-    return false;
   default:
     if ('0' <= p.peek() && p.peek() <= '9') {
       p.current().flags &= ~RubyState::RubyInternalState::EXPECTING_EXPRESSION;
@@ -860,7 +877,7 @@ bool handle_syntax(RubyParser &p, std::vector<Token> *tokens, std::vector<ParseE
           }
         }
       }
-      tokens->push_back({start, p.i, Token::Number});
+      tokens->push_back({start, p.i, io::Token::Number});
       return false;
     } else if (identifier_start_char(p.peek())) {
       uint32_t j = 1;
@@ -870,93 +887,93 @@ bool handle_syntax(RubyParser &p, std::vector<Token> *tokens, std::vector<ParseE
         j++;
       if (j == tries.base_keywords_trie.longest_match(p.peek_str(j))) {
         p.current().flags &= ~RubyState::RubyInternalState::EXPECTING_EXPRESSION;
-        tokens->push_back({p.i, p.i + j, Token::Keyword});
+        tokens->push_back({p.i, p.i + j, io::Token::Keyword});
         p.advance(j);
         return false;
       } else if (j == tries.expecting_keywords_trie.longest_match(p.peek_str(j))) {
         p.current().flags |= RubyState::RubyInternalState::EXPECTING_EXPRESSION;
-        tokens->push_back({p.i, p.i + j, Token::Keyword});
+        tokens->push_back({p.i, p.i + j, io::Token::Keyword});
         p.advance(j);
         return false;
       } else if (j == tries.operator_keywords_trie.longest_match(p.peek_str(j))) {
         p.current().flags &= ~RubyState::RubyInternalState::EXPECTING_EXPRESSION;
-        tokens->push_back({p.i, p.i + j, Token::KeywordOperator});
+        tokens->push_back({p.i, p.i + j, io::Token::KeywordOperator});
         p.advance(j);
         return false;
       } else if (j == tries.expecting_operators_trie.longest_match(p.peek_str(j))) {
         p.current().flags |= RubyState::RubyInternalState::EXPECTING_EXPRESSION;
-        tokens->push_back({p.i, p.i + j, Token::KeywordOperator});
+        tokens->push_back({p.i, p.i + j, io::Token::KeywordOperator});
         p.advance(j);
         return false;
       } else if (j == tries.types_trie.longest_match(p.peek_str(j))) {
         p.current().flags |= RubyState::RubyInternalState::EXPECTING_EXPRESSION;
-        tokens->push_back({p.i, p.i + j, Token::Type});
+        tokens->push_back({p.i, p.i + j, io::Token::Type});
         p.advance(j);
         return false;
       } else if (j == tries.methods_trie.longest_match(p.peek_str(j))) {
         p.current().flags &= ~RubyState::RubyInternalState::EXPECTING_EXPRESSION;
-        tokens->push_back({p.i, p.i + j, Token::Function});
+        tokens->push_back({p.i, p.i + j, io::Token::Function});
         p.advance(j);
         return false;
       } else if (j == tries.expecting_end_keywords_trie.longest_match(p.peek_str(j))) {
-        events->push_back(ParseEvent::Opening);
+        events->push_back(false);
         p.current().flags |= RubyState::RubyInternalState::EXPECTING_EXPRESSION;
-        tokens->push_back({p.i, p.i + j, Token::Keyword});
+        tokens->push_back({p.i, p.i + j, io::Token::Keyword});
         p.advance(j);
         return false;
       } else if (j == tries.conditional_keywords_trie.longest_match(p.peek_str(j))) {
         if (p.current().flags & RubyState::RubyInternalState::NEWLINE || p.op_last)
-          events->push_back(ParseEvent::Opening);
+          events->push_back(false);
         p.current().flags |= RubyState::RubyInternalState::EXPECTING_EXPRESSION;
-        tokens->push_back({p.i, p.i + j, Token::Keyword});
+        tokens->push_back({p.i, p.i + j, io::Token::Keyword});
         p.advance(j);
         return false;
       } else if (j == tries.end_keywords_trie.longest_match(p.peek_str(j))) {
         p.current().flags |= RubyState::RubyInternalState::EXPECTING_EXPRESSION;
-        events->push_back(ParseEvent::Opening);
-        tokens->push_back({p.i, p.i + j, Token::Keyword});
+        events->push_back(false);
+        tokens->push_back({p.i, p.i + j, io::Token::Keyword});
         p.advance(j);
         return false;
       } else if (j == tries.builtins_trie.longest_match(p.peek_str(j))) {
         p.current().flags &= ~RubyState::RubyInternalState::EXPECTING_EXPRESSION;
-        tokens->push_back({p.i, p.i + j, Token::Constant});
+        tokens->push_back({p.i, p.i + j, io::Token::Constant});
         p.advance(j);
         return false;
       } else if (j == tries.errors_trie.longest_match(p.peek_str(j))) {
         p.current().flags &= ~RubyState::RubyInternalState::EXPECTING_EXPRESSION;
-        tokens->push_back({p.i, p.i + j, Token::Error});
+        tokens->push_back({p.i, p.i + j, io::Token::Error});
         p.advance(j);
         return false;
       } else if ('A' <= p.peek() && p.peek() <= 'Z' && !(p.peek(j) == '!' || p.peek(j) == '?')) {
         p.current().flags &= ~RubyState::RubyInternalState::EXPECTING_EXPRESSION;
         if (j >= 5 && p.peek_str(j).substr(j - 5) == "Error") {
-          tokens->push_back({p.i, p.i + j, Token::Error});
+          tokens->push_back({p.i, p.i + j, io::Token::Error});
           p.advance(j);
           return false;
         }
-        tokens->push_back({p.i, p.i + j, Token::Constant});
+        tokens->push_back({p.i, p.i + j, io::Token::Constant});
         p.advance(j);
         return false;
       } else {
         p.current().flags &= ~RubyState::RubyInternalState::EXPECTING_EXPRESSION;
         if (j == 4 && p.peek_str(4) == "true") {
-          tokens->push_back({p.i, p.i + j, Token::True});
+          tokens->push_back({p.i, p.i + j, io::Token::True});
           p.advance(4);
           return false;
         }
         if (j == 5 && p.peek_str(5) == "false") {
-          tokens->push_back({p.i, p.i + j, Token::False});
+          tokens->push_back({p.i, p.i + j, io::Token::False});
           p.advance(5);
           return false;
         }
         if (j == 3 && p.peek_str(3) == "end") {
-          events->push_back(ParseEvent::Closing);
-          tokens->push_back({p.i, p.i + j, Token::Keyword});
+          events->push_back(true);
+          tokens->push_back({p.i, p.i + j, io::Token::Keyword});
           p.advance(3);
           return false;
         }
         if (j == 5 && p.peek_str(5) == "class") {
-          tokens->push_back({p.i, p.i + j, Token::Keyword});
+          tokens->push_back({p.i, p.i + j, io::Token::Keyword});
           p.advance(5);
           p.current().flags =
             (p.current().flags & ~RubyState::RubyInternalState::NAME_MASK)
@@ -964,7 +981,7 @@ bool handle_syntax(RubyParser &p, std::vector<Token> *tokens, std::vector<ParseE
           return false;
         }
         if (j == 6 && p.peek_str(6) == "module") {
-          tokens->push_back({p.i, p.i + j, Token::Keyword});
+          tokens->push_back({p.i, p.i + j, io::Token::Keyword});
           p.advance(6);
           p.current().flags =
             (p.current().flags & ~RubyState::RubyInternalState::NAME_MASK)
@@ -972,27 +989,33 @@ bool handle_syntax(RubyParser &p, std::vector<Token> *tokens, std::vector<ParseE
           return false;
         }
         if (j == 3 && p.peek_str(3) == "def") {
-          tokens->push_back({p.i, p.i + j, Token::Keyword});
+          tokens->push_back({p.i, p.i + j, io::Token::Keyword});
           p.advance(3);
           p.current().flags =
             (p.current().flags & ~RubyState::RubyInternalState::NAME_MASK)
             | RubyState::RubyInternalState::DEF_NAME;
           return false;
         }
+        if (j > 3 && p.peek_str(3) == "to_") {
+          p.current().flags &= ~RubyState::RubyInternalState::EXPECTING_EXPRESSION;
+          tokens->push_back({p.i, p.i + j, io::Token::Function});
+          p.advance(j);
+        }
         uint32_t start = p.i;
-        p.advance(j);
-        if (p.peek() == ':') {
+        if (p.peek(j) == ':') {
+          p.advance(j);
           p.advance();
-          tokens->push_back({start, p.i, Token::Label});
+          tokens->push_back({start, p.i, io::Token::Label});
           return false;
-        } else if (p.peek(-1) == '!' || p.peek(-1) == '?') {
-          p.advance();
-          tokens->push_back({start, p.i, Token::Function});
+        } else if (p.peek(j - 1) == '!' || p.peek(j - 1) == '?') {
+          p.advance(j);
+          tokens->push_back({start, p.i, io::Token::Function});
           return false;
         } else {
-          uint32_t j = 0;
+          p.advance(j);
+          j = 0;
           if (p.peek(j) == '(' || p.peek(j) == '{') {
-            tokens->push_back({start, p.i, Token::Function});
+            tokens->push_back({start, p.i, io::Token::Function});
             return false;
           } else if (p.peek(j) == ' ' || p.peek(j) == '\t') {
             j++;
@@ -1005,8 +1028,9 @@ bool handle_syntax(RubyParser &p, std::vector<Token> *tokens, std::vector<ParseE
             return false;
           if (p.peek(j) == '&'
               || p.peek(j) == '%'
-              || p.peek(j) == ':') {
-            if (p.peek(j + 1) == ' ' || p.peek(j + 1) == '>')
+              || p.peek(j) == ':'
+              || p.peek(j) == '?') {
+            if (p.peek(j + 1) == ' ' || p.peek(j + 1) == '\0')
               return false;
           } else if (p.peek(j) == '-') {
             if (p.peek(j + 1) != '>')
@@ -1022,22 +1046,22 @@ bool handle_syntax(RubyParser &p, std::vector<Token> *tokens, std::vector<ParseE
             || p.peek(j) == '*'
             || p.peek(j) == '/'
             || p.peek(j) == '='
-            || p.peek(j) == '?'
             || p.peek(j) == '|'
             || p.peek(j) == '^'
             || p.peek(j) == '<'
             || p.peek(j) == '>'
+            || p.peek(j) == '#'
           ) {
             return false;
           }
-          tokens->push_back({start, p.i, Token::Function});
+          tokens->push_back({start, p.i, io::Token::Function});
           return false;
         }
       }
     } else {
       uint32_t op_len;
       if ((op_len = tries.operator_trie.longest_match(p.peek_str(p.len() - p.i)))) {
-        tokens->push_back({p.i, p.i + op_len, Token::Operator});
+        tokens->push_back({p.i, p.i + op_len, io::Token::Operator});
         p.advance(op_len);
         p.current().flags |= RubyState::RubyInternalState::EXPECTING_EXPRESSION;
         p.set_op_last = true;
@@ -1053,26 +1077,26 @@ void ruby_parse(
   void **v_state,
   std::string_view line,
   bool fl,
-  std::vector<Token> *tokens,
+  std::vector<io::Token> *tokens,
   std::vector<ParseEvent> *events
 ) {
   RubyParser p(v_state, line);
-  while (p.i <= p.len()) {
+  while (p.i < p.len()) {
     p.op_last = p.set_op_last;
     p.set_op_last = false;
     if (p.current().state == RubyState::RubyInternalState::END)
       return;
     if (p.current().state == RubyState::RubyInternalState::COMMENT) {
-      tokens->push_back({p.i, p.len(), Token::Comment});
+      tokens->push_back({p.i, p.len(), io::Token::Comment});
       if (p.i == 0 && p.peek_str(4) == "=end") {
         p.current().state = RubyState::RubyInternalState::NONE;
-        events->push_back(ParseEvent::Closing);
+        events->push_back(true);
       }
       return;
     }
     if (!p.heredoc_start_line
         && p.current().state == RubyState::RubyInternalState::HEREDOC) {
-      if (handle_heredoc(p, tokens))
+      if (handle_heredoc(p, tokens, events))
         return;
       else
         continue;
@@ -1095,6 +1119,13 @@ void ruby_parse(
       return;
     if (!handle_syntax(p, tokens, events))
       p.current().flags &= ~RubyState::RubyInternalState::NEWLINE;
+    if (p.peek() == '\0') {
+      if (p.ending)
+        p.current().flags |= RubyState::RubyInternalState::EXPECTING_EXPRESSION;
+      p.advance();
+      p.current().flags &= ~RubyState::RubyInternalState::NEWLINE;
+      break;
+    }
     continue;
   }
   if (p.ending)

src/internal/syntax/tree_cursor.cc

@@ -1,7 +1,19 @@
 #include "internal/syntax/decl.h"
 
 namespace bed::internal::syntax {
-TreeCursor::TreeCursor(ParseState *root, uint64_t target_line, uint64_t *relative) {
+TreeCursor::~TreeCursor() {
+  ParseState::release(lang, root);
+}
+
+TreeCursor::TreeCursor(
+  Language &lang, ParseState *root,
+  uint64_t target_line, uint64_t *relative
+) : lang(lang), root(root) {
+  if (!root) {
+    *relative = 0;
+    return;
+  }
+  ParseState::retain(root);
   ParseState *node = root;
   while (node->is_branch()) {
     auto *branch = (ParseStateBranch *)node;
@@ -63,4 +75,42 @@ void TreeCursor::prev() {
   }
   leaf = nullptr;
 }
+
+ParseState *TreeCursor::prefix() {
+  ParseState *result = nullptr;
+  for (uint8_t i = 0; i < depth; ++i) {
+    if (went_left[i])
+      continue;
+    auto *branch = stack[i];
+    ParseState *piece = branch->left;
+    if (!result) {
+      ParseState::retain(piece);
+      result = piece;
+    } else {
+      ParseState *next = ParseState::concat(lang, result, piece);
+      ParseState::release(lang, result);
+      result = next;
+    }
+  }
+  return result;
+}
+
+ParseState *TreeCursor::suffix() {
+  ParseState *result = nullptr;
+  for (uint8_t i = depth; i-- > 0;) {
+    if (!went_left[i])
+      continue;
+    auto *branch = stack[i];
+    ParseState *piece = branch->right;
+    if (!result) {
+      ParseState::retain(piece);
+      result = piece;
+    } else {
+      ParseState *next = ParseState::concat(lang, result, piece);
+      ParseState::release(lang, result);
+      result = next;
+    }
+  }
+  return result;
+}
 } // namespace bed::internal::syntax

src/internal/theme/theme.cc

@@ -5,150 +5,248 @@ Theme::Theme() {
   hl.fill({
     .fg = 0xF0F0F0,
     .bg = 0x000000,
-    .flags = Highlight::None,
+    .flags = io::Highlight::None,
   });
 }
 
-Highlight Theme::get(internal::syntax::Token token) const {
-  return hl[token.type];
+io::Highlight Theme::get(const io::Token::Kind &token) const {
+  return hl[token];
 }
 
 Theme Theme::default_theme() {
   Theme theme;
-  theme.hl[internal::syntax::Token::Shebang] = {
-    .fg = 0x7DCFFF,
+
+  constexpr uint32_t PINK = 0xECA1AE;
+  constexpr uint32_t GREY = 0xAFB7D3;
+  constexpr uint32_t BLUE = 0x799EDB;
+  constexpr uint32_t LIGHT_BLUE = 0xB5BFFE;
+  constexpr uint32_t RED = 0xF38CAA;
+  constexpr uint32_t YELLOW = 0xF9E3B1;
+  constexpr uint32_t PURPLE = 0xA286C7;
+  constexpr uint32_t CYAN = 0x89DBEA;
+  constexpr uint32_t LIGHT_GREEN = 0x98CE94;
+  constexpr uint32_t TURQUOISE = 0x00BDB7;
+  constexpr uint32_t BRIGHT_GREEN = 0x4AF6CA;
+
+  theme.hl[io::Token::TempCurrent] = {
+    .fg = PINK,
     .bg = 0x000000,
-    .flags = Highlight::None,
+    .flags = io::Highlight::None,
   };
-  theme.hl[internal::syntax::Token::Error] = {
-    .fg = 0xEF5168,
+  theme.hl[io::Token::BufferName] = {
+    .fg = PURPLE,
     .bg = 0x000000,
-    .flags = Highlight::None,
+    .flags = io::Highlight::None,
   };
-  theme.hl[internal::syntax::Token::Comment] = {
-    .fg = 0xAAAAAA,
+  theme.hl[io::Token::AddressSeperator] = {
+    .fg = GREY,
     .bg = 0x000000,
-    .flags = Highlight::Italic,
+    .flags = io::Highlight::None,
   };
-  theme.hl[internal::syntax::Token::String] = {
+  theme.hl[io::Token::AddressSymbol] = {
+    .fg = BLUE,
+    .bg = 0x000000,
+    .flags = io::Highlight::None,
+  };
+  theme.hl[io::Token::Mark] = {
+    .fg = LIGHT_BLUE,
+    .bg = 0x000000,
+    .flags = io::Highlight::None,
+  };
+  theme.hl[io::Token::RubyFunction] = {
+    .fg = RED,
+    .bg = 0x000000,
+    .flags = io::Highlight::None,
+  };
+  theme.hl[io::Token::RubyArg] = {
+    .fg = LIGHT_GREEN,
+    .bg = 0x000000,
+    .flags = io::Highlight::None,
+  };
+  theme.hl[io::Token::Shell] = {
+    .fg = BRIGHT_GREEN,
+    .bg = 0x000000,
+    .flags = io::Highlight::None,
+  };
+  theme.hl[io::Token::File] = {
+    .fg = GREY,
+    .bg = 0x000000,
+    .flags = io::Highlight::None,
+  };
+  theme.hl[io::Token::Suffix] = {
+    .fg = TURQUOISE,
+    .bg = 0x000000,
+    .flags = io::Highlight::None,
+  };
+  theme.hl[io::Token::Color1] = {
+    .fg = 0x7AA2F7,
+    .bg = 0x000000,
+    .flags = io::Highlight::None,
+  };
+  theme.hl[io::Token::Color2] = {
     .fg = 0xAAD94C,
     .bg = 0x000000,
-    .flags = Highlight::None,
+    .flags = io::Highlight::None,
   };
-  theme.hl[internal::syntax::Token::Escape] = {
+  theme.hl[io::Token::Color3] = {
+    .fg = 0xFF9E64,
+    .bg = 0x000000,
+    .flags = io::Highlight::None,
+  };
+  theme.hl[io::Token::Color4] = {
+    .fg = 0xBB9AF7,
+    .bg = 0x000000,
+    .flags = io::Highlight::None,
+  };
+  theme.hl[io::Token::Color5] = {
+    .fg = 0xFF757F,
+    .bg = 0x000000,
+    .flags = io::Highlight::None,
+  };
+  theme.hl[io::Token::Warning] = {
+    .fg = 0xF1C55A,
+    .bg = 0x000000,
+    .flags = io::Highlight::None,
+  };
+  theme.hl[io::Token::Data] = {
+    .fg = GREY,
+    .bg = 0x000000,
+    .flags = io::Highlight::None,
+  };
+  theme.hl[io::Token::Shebang] = {
     .fg = 0x7DCFFF,
     .bg = 0x000000,
-    .flags = Highlight::None,
+    .flags = io::Highlight::None,
   };
-  theme.hl[internal::syntax::Token::Interpolation] = {
-    .fg = 0x7DCFFF,
-    .bg = 0x000000,
-    .flags = Highlight::None,
-  };
-  theme.hl[internal::syntax::Token::Regexp] = {
-    .fg = 0xD2A6FF,
-    .bg = 0x000000,
-    .flags = Highlight::None,
-  };
-  theme.hl[internal::syntax::Token::Number] = {
-    .fg = 0xE6C08A,
-    .bg = 0x000000,
-    .flags = Highlight::None,
-  };
-  theme.hl[internal::syntax::Token::True] = {
-    .fg = 0x7AE93C,
-    .bg = 0x000000,
-    .flags = Highlight::None,
-  };
-  theme.hl[internal::syntax::Token::False] = {
+  theme.hl[io::Token::Error] = {
     .fg = 0xEF5168,
     .bg = 0x000000,
-    .flags = Highlight::None,
+    .flags = io::Highlight::None,
   };
-  theme.hl[internal::syntax::Token::Char] = {
+  theme.hl[io::Token::Comment] = {
+    .fg = 0xAAAAAA,
+    .bg = 0x000000,
+    .flags = io::Highlight::Italic,
+  };
+  theme.hl[io::Token::String] = {
+    .fg = 0xAAD94C,
+    .bg = 0x000000,
+    .flags = io::Highlight::None,
+  };
+  theme.hl[io::Token::Escape] = {
+    .fg = 0x7DCFFF,
+    .bg = 0x000000,
+    .flags = io::Highlight::None,
+  };
+  theme.hl[io::Token::Interpolation] = {
+    .fg = 0x7DCFFF,
+    .bg = 0x000000,
+    .flags = io::Highlight::None,
+  };
+  theme.hl[io::Token::Regexp] = {
+    .fg = 0x7DCFFF,
+    .bg = 0x000000,
+    .flags = io::Highlight::None,
+  };
+  theme.hl[io::Token::Number] = {
+    .fg = 0xE6C08A,
+    .bg = 0x000000,
+    .flags = io::Highlight::None,
+  };
+  theme.hl[io::Token::True] = {
+    .fg = 0x7AE93C,
+    .bg = 0x000000,
+    .flags = io::Highlight::None,
+  };
+  theme.hl[io::Token::False] = {
+    .fg = 0xEF5168,
+    .bg = 0x000000,
+    .flags = io::Highlight::None,
+  };
+  theme.hl[io::Token::Char] = {
     .fg = 0xFFAF70,
     .bg = 0x000000,
-    .flags = Highlight::None,
+    .flags = io::Highlight::None,
   };
-  theme.hl[internal::syntax::Token::Keyword] = {
+  theme.hl[io::Token::Keyword] = {
     .fg = 0xFF8F40,
     .bg = 0x000000,
-    .flags = Highlight::None,
+    .flags = io::Highlight::None,
   };
-  theme.hl[internal::syntax::Token::KeywordOperator] = {
+  theme.hl[io::Token::KeywordOperator] = {
     .fg = 0xF07178,
     .bg = 0x000000,
-    .flags = Highlight::None,
+    .flags = io::Highlight::None,
   };
-  theme.hl[internal::syntax::Token::Operator] = {
+  theme.hl[io::Token::Operator] = {
     .fg = 0xFFFFFF,
     .bg = 0x000000,
-    .flags = Highlight::Italic,
+    .flags = io::Highlight::Italic,
   };
-  theme.hl[internal::syntax::Token::Function] = {
+  theme.hl[io::Token::Function] = {
     .fg = 0xFFAF70,
     .bg = 0x000000,
-    .flags = Highlight::None,
+    .flags = io::Highlight::None,
   };
-  theme.hl[internal::syntax::Token::Type] = {
+  theme.hl[io::Token::Type] = {
     .fg = 0xF07178,
     .bg = 0x000000,
-    .flags = Highlight::None,
+    .flags = io::Highlight::None,
   };
-  theme.hl[internal::syntax::Token::Constant] = {
+  theme.hl[io::Token::Constant] = {
     .fg = 0x7DCFFF,
     .bg = 0x000000,
-    .flags = Highlight::None,
+    .flags = io::Highlight::None,
   };
-  theme.hl[internal::syntax::Token::VariableInstance] = {
+  theme.hl[io::Token::VariableInstance] = {
     .fg = 0x95E6CB,
     .bg = 0x000000,
-    .flags = Highlight::None,
+    .flags = io::Highlight::None,
   };
-  theme.hl[internal::syntax::Token::VariableGlobal] = {
+  theme.hl[io::Token::VariableGlobal] = {
     .fg = 0xF07178,
     .bg = 0x000000,
-    .flags = Highlight::None,
+    .flags = io::Highlight::None,
   };
-  theme.hl[internal::syntax::Token::Annotation] = {
+  theme.hl[io::Token::Annotation] = {
     .fg = 0x7DCFFF,
     .bg = 0x000000,
-    .flags = Highlight::None,
+    .flags = io::Highlight::None,
   };
-  theme.hl[internal::syntax::Token::Directive] = {
+  theme.hl[io::Token::Directive] = {
     .fg = 0xFF8F40,
     .bg = 0x000000,
-    .flags = Highlight::None,
+    .flags = io::Highlight::None,
   };
-  theme.hl[internal::syntax::Token::Label] = {
+  theme.hl[io::Token::Label] = {
     .fg = 0xD2A6FF,
     .bg = 0x000000,
-    .flags = Highlight::None,
+    .flags = io::Highlight::None,
   };
-  theme.hl[internal::syntax::Token::Brace1] = {
-    .fg = 0xD2A6FF,
+  theme.hl[io::Token::Brace1] = {
+    .fg = BRIGHT_GREEN,
     .bg = 0x000000,
-    .flags = Highlight::None,
+    .flags = io::Highlight::None,
   };
-  theme.hl[internal::syntax::Token::Brace2] = {
-    .fg = 0xFFAFAF,
+  theme.hl[io::Token::Brace2] = {
+    .fg = YELLOW,
     .bg = 0x000000,
-    .flags = Highlight::None,
+    .flags = io::Highlight::None,
   };
-  theme.hl[internal::syntax::Token::Brace3] = {
+  theme.hl[io::Token::Brace3] = {
     .fg = 0xFFFF00,
     .bg = 0x000000,
-    .flags = Highlight::None,
+    .flags = io::Highlight::None,
   };
-  theme.hl[internal::syntax::Token::Brace4] = {
-    .fg = 0x0FFF0F,
+  theme.hl[io::Token::Brace4] = {
+    .fg = CYAN,
     .bg = 0x000000,
-    .flags = Highlight::None,
+    .flags = io::Highlight::None,
   };
-  theme.hl[internal::syntax::Token::Brace5] = {
+  theme.hl[io::Token::Brace5] = {
     .fg = 0xFF0F0F,
     .bg = 0x000000,
-    .flags = Highlight::None,
+    .flags = io::Highlight::None,
   };
   return theme;
 }
@@ -156,7 +254,6 @@ Theme Theme::default_theme() {
 Theme Theme::from_name(std::string_view name) {
   if (name == "default")
     return default_theme();
-  throw std::runtime_error("Unknown theme: " + std::string(name));
+  throw ed_error("Unknown theme: " + std::string(name));
 }
-
 } // namespace bed::internal::theme

src/internal/ui/command/command.cc

@@ -0,0 +1,124 @@
+#include "internal/ui/command.h"
+#include "bed.h"
+#include "internal/parser/parser.h"
+
+namespace bed::internal::ui {
+CommandIO::CommandIO(BEd &bed) : bed(bed) {
+  if (bed.prompt_mode)
+    prompt = bed.prompt(bed);
+  cursor = 0;
+}
+
+std::pair<std::string, bool> CommandIO::run() {
+  if (!bed.io.interactive())
+    return run_pipe();
+  return run_terminal();
+}
+
+std::pair<std::string, bool> CommandIO::run_pipe() {
+  bed.io.write(prompt);
+  return bed.io.read_pipe();
+}
+
+std::pair<std::string, bool> CommandIO::run_terminal() {
+  auto [row, col] = bed.io.cursor_position();
+  auto [rows, cols] = bed.io.terminal_size();
+  if (row > rows)
+    throw fatal_error("Invalid cursor position.", 1);
+  start = row;
+  height = rows - row + 1;
+  term_width = cols;
+  term_height = rows;
+  redraw();
+
+  io::KeyEvent res;
+  bool running = true;
+  while (running) {
+    res = bed.io.read_key();
+    switch (res.type) {
+    case io::KeyEvent::KeyType::EOF_:
+      running = false;
+      break;
+    case io::KeyEvent::KeyType::MOUSE:
+    case io::KeyEvent::KeyType::RESIZE:
+      break;
+    case io::KeyEvent::KeyType::CHAR:
+      switch (res.modifier) {
+      case io::KeyEvent::Modifier::SHIFT:
+      case io::KeyEvent::Modifier::ALT:
+      case io::KeyEvent::Modifier::CTRL_ALT:
+      case io::KeyEvent::Modifier::CTRL:
+        break;
+      case io::KeyEvent::Modifier::NONE:
+        if (res.text[0] == '\b' || res.text[0] == 0x7f) {
+          if (cursor > 0)
+            cmd.erase(--cursor, 1);
+        } else if (res.text[0] == '\n') {
+          running = false;
+        } else {
+          cmd.insert(cursor++, res.text);
+        }
+        break;
+      }
+      break;
+    case io::KeyEvent::KeyType::PASTE:
+      cmd.insert(cursor, res.text);
+      cursor += res.text.size();
+      break;
+    case io::KeyEvent::KeyType::SPECIAL:
+      switch (res.special_key) {
+      case io::KeyEvent::SpecialKey::UNKNOWN:
+      case io::KeyEvent::SpecialKey::UP:
+      case io::KeyEvent::SpecialKey::DOWN:
+        break;
+      case io::KeyEvent::SpecialKey::RIGHT:
+        if (cursor < cmd.size())
+          cursor++;
+        break;
+      case io::KeyEvent::SpecialKey::LEFT:
+        if (cursor > 0)
+          cursor--;
+        break;
+      case io::KeyEvent::SpecialKey::DELETE:
+        if (cursor < cmd.size())
+          cmd.erase(cursor, 1);
+        break;
+      }
+      break;
+    }
+    redraw();
+  }
+
+  for (uint16_t i = 1; i < height; ++i) {
+    bed.io.move_cursor(start + i, 1);
+    bed.io.write("\x1b[2K", 4);
+  }
+  bed.io.move_cursor(start, 1);
+  bed.io.write("\n", 1);
+  return {cmd, false};
+}
+
+void CommandIO::redraw() {
+  bed.io.move_cursor(start, 1);
+  bed.io.write("\x1b[2K", 4);
+  bed.io.move_cursor(start, 1);
+  bed.io.write(prompt);
+  const auto tokens = parser::Parser::get_highlight(cmd, bed);
+  uint32_t pos = 0;
+  for (const auto &token : tokens) {
+    const uint32_t tstart = token.start;
+    const uint32_t tend = token.end;
+    if (tstart > cmd.size())
+      break;
+    if (pos < tstart)
+      bed.io.write(cmd.data() + pos, tstart - pos);
+    bed.io.apply(token.type);
+    bed.io.write(cmd.data() + tstart, tend - tstart);
+    bed.io.reset();
+    pos = tend;
+  }
+  if (pos < cmd.size())
+    bed.io.write(cmd.data() + pos, cmd.size() - pos);
+  bed.io.move_cursor(start, prompt.size() + cursor + 1);
+}
+} // namespace bed::internal::ui

src/internal/ui/text_mode/text_mode.cc

@@ -0,0 +1,428 @@
+#include "internal/ui/text_mode.h"
+#include "bed.h"
+
+namespace bed::internal::ui::text_mode {
+// TODO: make this into a proper layout engine, in order to avoid so many expensive calculations repeatedly.
+
+template <typename F>
+static void for_each_cluster(std::string_view s, F &&f) {
+  size_t cluster_start = 0;
+  while (cluster_start < s.size()) {
+    size_t cluster_len =
+      grapheme_next_character_break_utf8(
+        s.data() + cluster_start,
+        s.size() - cluster_start
+      );
+    if (cluster_len == 0)
+      break;
+    size_t cluster_end = cluster_start + cluster_len;
+    unicode_width_state_t state;
+    unicode_width_init(&state);
+    size_t i = cluster_start;
+    int width = 0;
+    while (i < cluster_end) {
+      uint_least32_t cp;
+      size_t decoded =
+        grapheme_decode_utf8(s.data() + i, cluster_end - i, &cp);
+      if (decoded == 0)
+        decoded = 1;
+      int w = unicode_width_process(&state, cp);
+      if (w > width)
+        width = w;
+      i += decoded;
+    }
+    if (width < 0)
+      width = 0;
+    if (!f(cluster_start, cluster_len, width))
+      return;
+    cluster_start = cluster_end;
+  }
+}
+
+static size_t previous_cluster(std::string_view line, size_t col) {
+  size_t previous = 0;
+  for_each_cluster(line, [&](size_t start, size_t len, int) {
+    if (start >= col)
+      return false;
+    previous = start;
+    return start + len < col;
+  });
+  return previous;
+}
+
+static size_t next_cluster(std::string_view line, size_t col) {
+  size_t next = line.size();
+  for_each_cluster(line, [&](size_t start, size_t len, int) {
+    if (start >= col) {
+      next = start + len;
+      return false;
+    }
+    return true;
+  });
+  return next;
+}
+
+static size_t visual_column(std::string_view line, size_t col) {
+  size_t width = 0;
+  for_each_cluster(line, [&](size_t start, size_t, int cluster_width) {
+    if (start >= col)
+      return false;
+    width += cluster_width;
+    return true;
+  });
+  return width;
+}
+
+static size_t byte_column(std::string_view line, size_t target_width) {
+  size_t width = 0;
+  size_t col = 0;
+  for_each_cluster(line, [&](size_t start, size_t len, int cluster_width) {
+    if (width + cluster_width > target_width)
+      return false;
+    width += cluster_width;
+    col = start + len;
+    if (width == target_width)
+      return false;
+    return true;
+  });
+  return col;
+}
+
+static std::vector<std::pair<size_t, size_t>> wrap_line(std::string_view line, size_t avail) {
+  std::vector<std::pair<size_t, size_t>> result;
+  if (avail == 0) {
+    result.push_back({0, line.size()});
+    return result;
+  }
+  size_t begin = 0;
+  size_t end = 0;
+  int col = 0;
+  for_each_cluster(line, [&](size_t i, size_t len, int width) {
+    if (col > 0 && col + width > int(avail)) {
+      result.push_back({begin, i});
+      begin = i;
+      col = 0;
+    }
+    col += width;
+    end = i + len;
+    return true;
+  });
+  if (begin < line.size() || result.empty())
+    result.push_back({begin, end});
+  return result;
+}
+
+void TextMode::layout_lines() {
+  vase::Iterator it(vase, 0, Direction::Forward);
+  lines.clear();
+  while (it.next()) {
+    auto wrapped = wrap_line(it.line, term_width);
+    lines.push_back({});
+    for (auto [begin, end] : wrapped)
+      lines.back().push_back({begin, end - begin});
+  }
+}
+
+TextMode::TextMode(
+  BEd &bed, vase::Shard *vase, syntax::Language *lang, void *state
+) : vase(vase), bed(bed) {
+  if (lang)
+    parser.emplace(*lang, vase, state);
+  cursor = vase::eof_point(vase);
+}
+
+std::pair<vase::Shard *, bool> TextMode::run() {
+  if (!bed.io.interactive())
+    return run_pipe();
+  return run_terminal();
+}
+
+std::pair<vase::Shard *, bool> TextMode::run_pipe() {
+  vase::Shard::release(vase);
+  vase = nullptr;
+  while (true) {
+    auto [str, eof] = bed.io.read_pipe();
+    if (str == "." || eof)
+      break;
+    vase = vase::insert(&bed.append, vase, &cursor, str.data(), str.length());
+    vase = vase::insert(&bed.append, vase, &cursor, '\n');
+  }
+  return {vase, false};
+}
+
+std::pair<vase::Shard *, bool> TextMode::run_terminal() {
+  auto [row, col] = bed.io.cursor_position();
+  auto [rows, cols] = bed.io.terminal_size();
+  if (row > rows)
+    throw ed_error("Invalid cursor position.");
+  start = row;
+  height = rows - row + 1;
+  term_width = cols;
+  term_height = rows;
+  redraw();
+  bool running = true;
+  bool cancelled = false;
+
+  while (running) {
+    redraw();
+    io::KeyEvent res = bed.io.read_key();
+    switch (res.type) {
+    case io::KeyEvent::KeyType::EOF_:
+      running = false;
+      break;
+    case io::KeyEvent::KeyType::MOUSE:
+    case io::KeyEvent::KeyType::RESIZE:
+      break;
+    case io::KeyEvent::KeyType::CHAR:
+      switch (res.modifier) {
+      case io::KeyEvent::Modifier::SHIFT:
+      case io::KeyEvent::Modifier::ALT:
+      case io::KeyEvent::Modifier::CTRL_ALT:
+      case io::KeyEvent::Modifier::CTRL:
+        if (res.text[0] == 'c') {
+          cancelled = true;
+          running = false;
+        }
+        break;
+      case io::KeyEvent::Modifier::NONE:
+        if (res.text[0] == '\b' || res.text[0] == 0x7f) {
+          if (!vase)
+            break;
+          if (cursor.row || cursor.col) {
+            auto last = cursor;
+            if (last.col) {
+              vase::Iterator it(vase, last.row, Direction::Forward);
+              if (!it.next())
+                throw ed_error("Invalid cursor position.");
+              last.col = previous_cluster(it.line, last.col);
+            } else if (last.row) {
+              --last.row;
+              vase::Iterator it(vase, last.row, Direction::Forward);
+              if (!it.next())
+                throw ed_error("Invalid cursor position.");
+              last.col = it.line.size();
+            } else {
+              break;
+            }
+            vase::Range r = {last, cursor};
+            vase = vase::erase(vase, r);
+            if (parser) {
+              if (cursor.row == last.row) {
+                parser->dirty(vase, cursor.row, 1);
+              } else {
+                parser->erase(vase, cursor.row, 1);
+                parser->dirty(vase, last.row, 1);
+              }
+            }
+            cursor = last;
+          }
+        } else if (res.text[0] == '\n') {
+          if (vase && cursor.row == vase->lines) {
+            vase::Iterator it(vase, vase->lines, Direction::Backward);
+            if (it.next() && it.line == ".") {
+              vase = vase::erase(vase, vase->lines + 1, vase->lines + 1);
+              running = false;
+              break;
+            }
+          }
+          vase = vase::insert(&bed.append, vase, &cursor, '\n');
+          if (parser)
+            parser->insert(vase, cursor.row - 1, 1);
+        } else {
+          vase = vase::insert(&bed.append, vase, &cursor, res.text.data(), res.text.size());
+          if (parser)
+            parser->dirty(vase, cursor.row, 1);
+        }
+        break;
+      }
+      break;
+    case io::KeyEvent::KeyType::PASTE: {
+      auto lines = std::count(res.text.begin(), res.text.end(), '\n');
+      vase = vase::insert(&bed.append, vase, &cursor, res.text.data(), res.text.size());
+      if (parser) {
+        if (lines) {
+          parser->insert(vase, cursor.row - lines, lines);
+          parser->dirty(vase, cursor.row - lines, 1);
+        } else {
+          parser->dirty(vase, cursor.row, 1);
+        }
+      }
+    } break;
+    case io::KeyEvent::KeyType::SPECIAL:
+      if (!vase)
+        break;
+      switch (res.special_key) {
+      case io::KeyEvent::SpecialKey::UNKNOWN:
+        break;
+      case io::KeyEvent::SpecialKey::RIGHT: {
+        vase::Iterator it(vase, cursor.row, Direction::Forward);
+        if (!it.next())
+          throw ed_error("Invalid cursor position.");
+        cursor.col = next_cluster(it.line, cursor.col);
+      } break;
+      case io::KeyEvent::SpecialKey::LEFT: {
+        vase::Iterator it(vase, cursor.row, Direction::Forward);
+        if (!it.next())
+          throw ed_error("Invalid cursor position.");
+        cursor.col = previous_cluster(it.line, cursor.col);
+      } break;
+      case io::KeyEvent::SpecialKey::UP: {
+        if (!cursor.row)
+          break;
+        vase::Iterator current(vase, cursor.row, Direction::Forward);
+        if (!current.next())
+          throw ed_error("Invalid cursor position.");
+        size_t wanted = visual_column(current.line, cursor.col);
+        --cursor.row;
+        vase::Iterator previous(vase, cursor.row, Direction::Forward);
+        if (!previous.next())
+          throw ed_error("Invalid cursor position.");
+        cursor.col = byte_column(previous.line, wanted);
+      } break;
+      case io::KeyEvent::SpecialKey::DOWN: {
+        if (cursor.row >= vase->lines)
+          break;
+        vase::Iterator current(vase, cursor.row, Direction::Forward);
+        if (!current.next())
+          throw ed_error("Invalid cursor position.");
+        size_t wanted = visual_column(current.line, cursor.col);
+        ++cursor.row;
+        vase::Iterator previous(vase, cursor.row, Direction::Forward);
+        if (!previous.next())
+          throw ed_error("Invalid cursor position.");
+        cursor.col = byte_column(previous.line, wanted);
+      } break;
+      case io::KeyEvent::SpecialKey::DELETE:
+        auto next = cursor;
+        vase::Iterator it(vase, cursor.row, Direction::Forward);
+        if (!it.next())
+          break;
+        if (cursor.col < it.line.size()) {
+          vase::Iterator it(vase, next.row, Direction::Forward);
+          if (!it.next())
+            throw ed_error("Invalid cursor position.");
+          next.col = next_cluster(it.line, cursor.col);
+        } else if (cursor.row < vase->lines) {
+          ++next.row;
+          next.col = 0;
+        } else {
+          break;
+        }
+        vase::Range r = {cursor, next};
+        vase = vase::erase(vase, r);
+        if (parser) {
+          if (cursor.row != next.row)
+            parser->erase(vase, cursor.row + 1, 1);
+          parser->dirty(vase, cursor.row, 1);
+        }
+      }
+      break;
+    }
+  }
+
+  layout_lines();
+  size_t required_height = 0;
+  for (const auto &elem : lines)
+    required_height += elem.size();
+  uint16_t last_row = start + required_height;
+  bed.io.move_cursor(last_row, 1);
+  bed.io.write("\n");
+  return {vase, cancelled};
+}
+
+void TextMode::grow() {
+  size_t required_height = 0;
+  for (const auto &elem : lines)
+    required_height += elem.size();
+  auto [rows, cols] = bed.io.terminal_size();
+  term_height = rows;
+  term_width = cols;
+  if (required_height > height)
+    height = required_height;
+  long overflow = long(start) + long(height) - 1 - long(rows);
+  if (overflow <= 0)
+    return;
+  bed.io.move_cursor(rows, 1);
+  for (long i = 0; i < overflow; ++i)
+    bed.io.write("\n");
+  start -= overflow;
+  if (start < 1)
+    start = 1;
+}
+
+void TextMode::redraw() {
+  layout_lines();
+  grow();
+  bed.io.write("\x1b[?25l", 6);
+  for (uint16_t i = 0; i < height; ++i) {
+    bed.io.move_cursor(start + i, 1);
+    bed.io.write("\x1b[2K", 4);
+  }
+  uint16_t screen_line = start;
+  uint64_t line = 0;
+  size_t cursor_screen_row = start;
+  size_t cursor_screen_col = 0;
+  vase::Iterator it(vase, line, Direction::Forward);
+  while (it.next()) {
+    if (screen_line >= start + height)
+      break;
+    std::string_view l(it.line);
+    const std::vector<io::Token> *tokens = nullptr;
+    if (parser && parser->lines.size() > line)
+      tokens = &parser->lines[line].second;
+    size_t token_index = 0;
+    for (auto &row : lines[line]) {
+      const size_t row_start = row.start;
+      const size_t row_end = row.start + row.length;
+      bed.io.move_cursor(screen_line, 1);
+      if (tokens) {
+        while (token_index < tokens->size() && (*tokens)[token_index].end <= row_start)
+          ++token_index;
+        size_t pos = row_start;
+        for (size_t i = token_index; i < tokens->size(); ++i) {
+          const auto &token = (*tokens)[i];
+          if (token.start >= row_end)
+            break;
+          const size_t begin = std::max<size_t>(
+            token.start,
+            row_start
+          );
+          const size_t end = std::min<size_t>(
+            token.end,
+            row_end
+          );
+          if (begin > pos)
+            bed.io.write(l.data() + pos, begin - pos);
+          if (begin < end) {
+            bed.io.apply(token.type);
+            bed.io.write(l.data() + begin, end - begin);
+            bed.io.reset();
+            pos = end;
+          }
+        }
+        if (pos < row_end)
+          bed.io.write(l.data() + pos, row_end - pos);
+        bed.io.reset();
+      } else {
+        bed.io.write(l.substr(row_start, row.length));
+      }
+      if (line == cursor.row && cursor.col >= row_start && cursor.col <= row_end) {
+        cursor_screen_row = screen_line;
+        cursor_screen_col = 0;
+        for_each_cluster(
+          l.substr(row_start, cursor.col - row_start),
+          [&](size_t, size_t, int width) {
+            cursor_screen_col += width;
+            return true;
+          }
+        );
+      }
+      ++screen_line;
+    }
+    ++line;
+  }
+  cursor_screen_col = std::min(cursor_screen_col, size_t(term_width - 1));
+  bed.io.move_cursor(cursor_screen_row, cursor_screen_col + 1);
+  bed.io.write("\x1b[?25h", 6);
+}
+} // namespace bed::internal::ui::text_mode

src/internal/vase/regex/api.cc

@@ -1,7 +1,7 @@
 #include "internal/vase/vase.h"
 
 namespace bed::internal::vase {
-std::vector<Vase::ReplacePart> Vase::parse_replace(std::string_view s) {
+std::vector<ReplacePart> parse_replace(AppendStorage *ap, std::string_view s) {
   std::vector<ReplacePart> parts;
   std::string constant;
   auto flush_constant = [&]() {
@@ -13,11 +13,11 @@ std::vector<Vase::ReplacePart> Vase::parse_replace(std::string_view s) {
         ++lines;
         ++p;
       }
-      uint64_t pos = append->append(constant.data(), (uint64_t)constant.size());
+      uint64_t pos = ap->append(constant.data(), (uint64_t)constant.size());
       parts.push_back(
         ReplacePart{
           .type = ReplacePart::PartType::Constant,
-          .value = new Petal((uint64_t)constant.size(), lines, append, pos)
+          .value = new Petal((uint64_t)constant.size(), lines, ap, pos)
         }
       );
       constant.clear();
@@ -25,12 +25,7 @@ std::vector<Vase::ReplacePart> Vase::parse_replace(std::string_view s) {
   };
   for (size_t i = 0; i < s.size(); ++i) {
     char c = s[i];
-    if (c == '\\' && i + 1 < s.size() && s[i + 1] == '$') {
-      constant.push_back('$');
-      ++i;
-      continue;
-    }
-    if (c == '$' && i + 1 < s.size()) {
+    if (c == '\\' && i + 1 < s.size()) {
       char next = s[i + 1];
       if (next == '0') {
         flush_constant();
@@ -40,10 +35,7 @@ std::vector<Vase::ReplacePart> Vase::parse_replace(std::string_view s) {
             .value = (uint8_t)0
           }
         );
-        ++i;
-        continue;
-      }
-      if (next >= '1' && next <= '9') {
+      } else if (next >= '1' && next <= '9') {
         flush_constant();
         parts.push_back(
           ReplacePart{
@@ -51,9 +43,22 @@ std::vector<Vase::ReplacePart> Vase::parse_replace(std::string_view s) {
             .value = (uint8_t)(next - '0')
           }
         );
-        ++i;
-        continue;
+      } else if (next == 'n') {
+        constant.push_back('\n');
+      } else {
+        constant.push_back(next);
       }
+      ++i;
+      continue;
+    }
+    if (c == '&') {
+      flush_constant();
+      parts.push_back(
+        ReplacePart{
+          .type = ReplacePart::PartType::FullMatch,
+          .value = (uint8_t)0
+        }
+      );
     }
     constant.push_back(c);
   }
@@ -61,23 +66,37 @@ std::vector<Vase::ReplacePart> Vase::parse_replace(std::string_view s) {
   return parts;
 }
 
-void Vase::regex_search_replace(
-  std::string_view pattern, Range range,
-  std::string_view replace, std::string_view options
+Shard *substitute(
+  AppendStorage *ap, Shard *root,
+  std::string_view pattern, uint64_t start, uint64_t end,
+  std::string_view replace, std::string_view options,
+  const std::function<void(uint64_t line, uint64_t old_lines, uint64_t new_lines)> &on_edit
 ) {
-  std::vector<RegexMatch> matches = _regex_search(pattern, range, options);
+  if (!start || !end)
+    throw ed_error("Invalid range.");
+  start--;
+  end--;
+  if (!root)
+    throw ed_error("line range out of bounds");
+  uint64_t line_count = root->lines + 1;
+  if (start > end || end >= line_count)
+    throw ed_error("line range out of bounds");
+  uint64_t start_offset = offset_of(root, start);
+  uint64_t end_offset =
+    (end + 1 == line_count)
+      ? root->length
+      : offset_of(root, end + 1) - 1;
+  std::vector<RegexMatch> matches = _regex_search(root, pattern, start_offset, end_offset, options);
   if (matches.empty())
-    return;
-
-  std::vector<ReplacePart> replace_parts = parse_replace(replace);
-
+    return root;
+  std::vector<ReplacePart> replace_parts = parse_replace(ap, replace);
+  uint64_t current_line = 1;
+  int64_t line_delta = 0;
   std::vector<Shard *> pieces;
   pieces.reserve(matches.size() * 2 + 1);
-
   Shard *remaining = root;
   Shard::retain(remaining);
   uint64_t cursor = 0;
-
   for (const RegexMatch &match : matches) {
     uint64_t gap = match.start - cursor;
     if (gap > 0) {
@@ -85,28 +104,33 @@ void Vase::regex_search_replace(
       Shard::release(remaining);
       pieces.push_back(keep);
       remaining = rest;
+      current_line += keep ? keep->lines : 0;
     }
-
     auto [dropped, rest2] = Shard::split(remaining, match.end - match.start);
     Shard::release(remaining);
     remaining = rest2;
-
+    uint64_t old_lines = dropped ? dropped->lines : 0;
+    uint64_t new_lines = 0;
     for (size_t i = 0; i < replace_parts.size(); ++i) {
       const ReplacePart &part = replace_parts[i];
       switch (part.type) {
-      case ReplacePart::PartType::Constant:
-        Shard::retain(std::get<Shard *>(part.value));
-        pieces.push_back(std::get<Shard *>(part.value));
+      case ReplacePart::PartType::Constant: {
+        Shard *c = std::get<Shard *>(part.value);
+        Shard::retain(c);
+        pieces.push_back(c);
+        new_lines += c ? c->lines : 0;
         break;
+      }
       case ReplacePart::PartType::FullMatch:
         Shard::retain(dropped);
         pieces.push_back(dropped);
+        new_lines += dropped ? dropped->lines : 0;
         break;
       case ReplacePart::PartType::CaptureGroup: {
         uint8_t idx = std::get<uint8_t>(part.value);
         if (idx <= 9) {
           const RegexGroup &group = match.groups[idx - 1];
-          if (group.start > group.end) {
+          if (group.start != UINT64_MAX) {
             uint64_t ls = group.start - match.start;
             uint64_t le = group.end - match.start;
             auto [a, b] = Shard::split(dropped, ls);
@@ -115,6 +139,7 @@ void Vase::regex_search_replace(
             Shard::release(b);
             Shard::release(c);
             pieces.push_back(g);
+            new_lines += g ? g->lines : 0;
           }
         }
         break;
@@ -122,14 +147,17 @@ void Vase::regex_search_replace(
       }
     }
     Shard::release(dropped);
+    uint64_t report_line = (uint64_t)((int64_t)current_line + line_delta);
+    if (on_edit)
+      on_edit(report_line, old_lines, new_lines);
+    line_delta += (int64_t)new_lines - (int64_t)old_lines;
+    current_line += old_lines;
     cursor = match.end;
   }
   pieces.push_back(remaining);
-
   for (auto &part : replace_parts)
     if (part.type == ReplacePart::PartType::Constant)
       Shard::release(std::get<Shard *>(part.value));
-
   std::vector<Shard *> compact;
   compact.reserve(pieces.size());
   for (Shard *p : pieces) {
@@ -138,22 +166,136 @@ void Vase::regex_search_replace(
     else if (p)
       Shard::release(p);
   }
-
   Shard *new_root = compact.empty() ? nullptr : Shard::build(compact.data(), 0, compact.size());
   Shard::release(root);
-  root = new_root;
+  return new_root;
 }
 
-std::vector<Range> Vase::regex_search(
-  std::string_view pattern, Range range, std::string_view options
-) {
-  std::vector<RegexMatch> matches = _regex_search(pattern, range, options);
-  if (matches.empty())
-    return {};
-  std::vector<Range> result;
-  result.reserve(matches.size());
-  for (auto match : matches)
-    result.push_back({point_of(match.start), point_of(match.end)});
-  return result;
+uint64_t find_next(Shard *root, std::string_view pattern, uint64_t start) {
+  if (!root)
+    throw ed_error("Invalid line number.");
+  if (start == 0 || start > root->lines + 1)
+    throw ed_error("Invalid line number.");
+  start--;
+  std::vector<RegexMatch> results;
+  int errornumber;
+  PCRE2_SIZE erroroffset;
+  pcre2_code *re = pcre2_compile(
+    (PCRE2_SPTR)pattern.data(),
+    pattern.size(),
+    PCRE2_UTF | PCRE2_EXTENDED,
+    &errornumber,
+    &erroroffset,
+    NULL
+  );
+  if (re == NULL)
+    throw ed_error("Can't compile regex.");
+  pcre2_match_data *match_data = pcre2_match_data_create_from_pattern(re, nullptr);
+  if (!match_data) {
+    pcre2_code_free(re);
+    throw ed_error("Can't create regex match data.");
+  }
+  uint64_t at = (start + 1) % (root->lines + 1);
+  LineIterator it(root, at, Direction::Forward);
+  std::string line;
+  while (it.next(&line)) {
+    int rc = pcre2_match(re, (PCRE2_SPTR)line.data(), line.size(), 0, 0, match_data, nullptr);
+    if (rc >= 0) {
+      pcre2_match_data_free(match_data);
+      pcre2_code_free(re);
+      return at + 1;
+    }
+    if (rc != PCRE2_ERROR_NOMATCH) {
+      pcre2_match_data_free(match_data);
+      pcre2_code_free(re);
+      throw ed_error("Regex matching failed.");
+    }
+    at++;
+  }
+  at = 0;
+  LineIterator it2(root, at, Direction::Forward);
+  while (it2.next(&line)) {
+    if (at > start)
+      break;
+    int rc = pcre2_match(re, (PCRE2_SPTR)line.data(), line.size(), 0, 0, match_data, nullptr);
+    if (rc >= 0) {
+      pcre2_match_data_free(match_data);
+      pcre2_code_free(re);
+      return at + 1;
+    }
+    if (rc != PCRE2_ERROR_NOMATCH) {
+      pcre2_match_data_free(match_data);
+      pcre2_code_free(re);
+      throw ed_error("Regex matching failed.");
+    }
+    at++;
+  }
+  pcre2_match_data_free(match_data);
+  pcre2_code_free(re);
+  throw ed_error("No line matched.");
+}
+
+uint64_t find_prev(Shard *root, std::string_view pattern, uint64_t start) {
+  if (!root)
+    throw ed_error("Invalid line number.");
+  if (start == 0 || start > root->lines + 1)
+    throw ed_error("Invalid line number.");
+  start--;
+  std::vector<RegexMatch> results;
+  int errornumber;
+  PCRE2_SIZE erroroffset;
+  pcre2_code *re = pcre2_compile(
+    (PCRE2_SPTR)pattern.data(),
+    pattern.size(),
+    PCRE2_UTF | PCRE2_EXTENDED,
+    &errornumber,
+    &erroroffset,
+    NULL
+  );
+  if (re == NULL)
+    throw ed_error("Can't compile regex.");
+  pcre2_match_data *match_data = pcre2_match_data_create_from_pattern(re, nullptr);
+  if (!match_data) {
+    pcre2_code_free(re);
+    throw ed_error("Can't create regex match data.");
+  }
+  uint64_t at = (start == 0 ? root->lines : start - 1);
+  LineIterator it(root, at, Direction::Backward);
+  std::string line;
+  while (it.next(&line)) {
+    int rc = pcre2_match(re, (PCRE2_SPTR)line.data(), line.size(), 0, 0, match_data, nullptr);
+    if (rc >= 0) {
+      pcre2_match_data_free(match_data);
+      pcre2_code_free(re);
+      return at + 1;
+    }
+    if (rc != PCRE2_ERROR_NOMATCH) {
+      pcre2_match_data_free(match_data);
+      pcre2_code_free(re);
+      throw ed_error("Regex matching failed.");
+    }
+    at--;
+  }
+  at = root->lines;
+  LineIterator it2(root, at, Direction::Backward);
+  while (it2.next(&line)) {
+    if (at < start)
+      break;
+    int rc = pcre2_match(re, (PCRE2_SPTR)line.data(), line.size(), 0, 0, match_data, nullptr);
+    if (rc >= 0) {
+      pcre2_match_data_free(match_data);
+      pcre2_code_free(re);
+      return at + 1;
+    }
+    if (rc != PCRE2_ERROR_NOMATCH) {
+      pcre2_match_data_free(match_data);
+      pcre2_code_free(re);
+      throw ed_error("Regex matching failed.");
+    }
+    at--;
+  }
+  pcre2_match_data_free(match_data);
+  pcre2_code_free(re);
+  throw ed_error("No line matched.");
 }
 } // namespace bed::internal::vase

src/internal/vase/regex/core.cc

@@ -1,8 +1,8 @@
 #include "internal/vase/vase.h"
 
 namespace bed::internal::vase {
-std::vector<Vase::RegexMatch> Vase::_regex_search(
-  std::string_view pattern, Range range, std::string_view options
+std::vector<RegexMatch> _regex_search(
+  Shard *root, std::string_view pattern, uint64_t start_offset, uint64_t end_offset, std::string_view options
 ) {
   bool global = false;
   uint64_t flags = PCRE2_MULTILINE | PCRE2_UTF;
@@ -52,9 +52,6 @@ std::vector<Vase::RegexMatch> Vase::_regex_search(
 
   pcre2_match_data *match_data = pcre2_match_data_create_from_pattern(re, NULL);
 
-  uint64_t start_offset = offset_of(range.start);
-  uint64_t end_offset = offset_of(range.end);
-
   PetalIterator it(root, Direction::Forward);
   it.seek_offset(start_offset);
 
@@ -67,7 +64,7 @@ std::vector<Vase::RegexMatch> Vase::_regex_search(
   uint64_t offset = UINT64_MAX;
 
   auto record_match = [&](int rc, PCRE2_SIZE *ovector) {
-    if (global_offset + (uint64_t)ovector[1] > end_offset || ovector[0] == ovector[1])
+    if (global_offset + (uint64_t)ovector[1] > end_offset)
       return;
     RegexMatch match{
       .start = global_offset + (uint64_t)ovector[0],
@@ -77,8 +74,8 @@ std::vector<Vase::RegexMatch> Vase::_regex_search(
       PCRE2_SIZE s = ovector[2 * i];
       PCRE2_SIZE e = ovector[2 * i + 1];
       if (s != PCRE2_UNSET) {
-        match.groups[i].start = global_offset + (uint64_t)s;
-        match.groups[i].end = global_offset + (uint64_t)e;
+        match.groups[i - 1].start = global_offset + (uint64_t)s;
+        match.groups[i - 1].end = global_offset + (uint64_t)e;
       }
     }
     results.push_back(std::move(match));

src/internal/vase/shard.cc

@@ -1,3 +1,4 @@
+#include "internal/io/io.h"
 #include "internal/vase/vase.h"
 
 namespace bed::internal::vase {
@@ -14,6 +15,7 @@ void Shard::release(Shard *n) {
     release(((Branch *)n)->right);
     delete (Branch *)n;
   } else {
+    ((Petal *)n)->source->release();
     delete (Petal *)n;
   }
 }
@@ -191,53 +193,38 @@ Shard *Shard::append(Shard *root, Shard *leaf) {
 Shard *Shard::build(Shard **pieces, uint64_t lo, uint64_t hi) {
   if (hi - lo == 1)
     return pieces[lo];
-  size_t mid = lo + (hi - lo) / 2;
+  uint64_t mid = lo + (hi - lo) / 2;
   Shard *left = build(pieces, lo, mid);
   Shard *right = build(pieces, mid, hi);
-  Shard *node = new Branch(left, right);
+  Shard *node = Shard::concat(left, right);
   Shard::release(left);
   Shard::release(right);
   return node;
 }
 
-static bool write_all(int fd, const void *data, size_t len) {
-  const char *p = (const char *)data;
-  while (len > 0) {
-    ssize_t n = write(fd, p, len);
-    if (n > 0) {
-      p += n;
-      len -= (size_t)n;
-      continue;
-    }
-    if (n == -1 && errno == EINTR)
-      continue;
-    return false;
-  }
-  return true;
-}
-
-Shard *Shard::from_command(const char *cmd, OriginalBuffer *o, bool posix_ending) {
+Shard *Shard::from_command(const char *cmd) {
+  auto o = new OriginalStorage("/tmp");
   int dest_fd = o->fd;
-  if (dest_fd == -1)
+  if (dest_fd == -1) {
+    delete o;
     return nullptr;
-
+  }
+  io::IO::cleanup();
   FILE *pipe = popen(cmd, "r");
-  if (!pipe)
+  if (!pipe) {
+    delete o;
+    io::IO::enable_raw();
     return nullptr;
-
+  }
   std::vector<Shard *> pieces;
   pieces.reserve(16);
-
   uint64_t pos = 0;
   char buf[PETAL_SIZE_MAX];
   uint64_t buf_cursor = 0;
-
   char ending[2] = {'\0', '\0'};
-
   while (true) {
     size_t got = fread(buf + buf_cursor, 1, sizeof(buf) - buf_cursor, pipe);
     buf_cursor += got;
-
     if (buf_cursor == PETAL_SIZE_MAX || feof(pipe)) {
       if (buf_cursor == 0)
         break;
@@ -260,6 +247,8 @@ Shard *Shard::from_command(const char *cmd, OriginalBuffer *o, bool posix_ending
       }
       if (!write_all(dest_fd, buf, buf_cursor)) {
         pclose(pipe);
+        delete o;
+        io::IO::enable_raw();
         return nullptr;
       }
       pieces.push_back(new Petal(buf_cursor, lines, o, pos));
@@ -267,81 +256,97 @@ Shard *Shard::from_command(const char *cmd, OriginalBuffer *o, bool posix_ending
     }
     if (feof(pipe))
       break;
-    if (ferror(pipe))
+    if (ferror(pipe)) {
+      delete o;
+      io::IO::enable_raw();
       return nullptr;
-  }
-
-  int status = pclose(pipe);
-  if (status == -1)
-    return nullptr;
-  if (!WIFEXITED(status) || WEXITSTATUS(status) != 0)
-    return nullptr;
-
-  if (pieces.empty())
-    return nullptr;
-
-  if (posix_ending) {
-    if (ending[1] == '\n') {
-      Petal *last = (Petal *)pieces.back();
-      last->lines--;
-      last->length--;
-      if (last->length == 0) {
-        Shard::release(last);
-        pieces.pop_back();
-        last = nullptr;
-        if (!pieces.empty())
-          last = (Petal *)pieces.back();
-      }
-      if (last && ending[0] == '\r')
-        last->length--;
     }
   }
-
+  int status = pclose(pipe);
+  if (status == -1) {
+    delete o;
+    io::IO::enable_raw();
+    return nullptr;
+  }
+  if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
+    delete o;
+    io::IO::enable_raw();
+    return nullptr;
+  }
+  if (pieces.empty()) {
+    delete o;
+    io::IO::enable_raw();
+    return nullptr;
+  }
+  if (ending[1] == '\n') {
+    Petal *last = (Petal *)pieces.back();
+    last->lines--;
+    last->length--;
+    if (last->length == 0) {
+      Shard::release(last);
+      pieces.pop_back();
+      last = nullptr;
+      if (!pieces.empty())
+        last = (Petal *)pieces.back();
+      else
+        return nullptr;
+    }
+    if (last && ending[0] == '\r')
+      last->length--;
+  }
   o->initialize();
-
+  io::IO::enable_raw();
   if (pieces.size() == 1)
     return pieces[0];
-
   return build(pieces.data(), 0, pieces.size());
 }
 
-Shard *Shard::from_file(std::filesystem::path &path, OriginalBuffer *o, bool posix_ending) {
+Shard *Shard::from_file(const std::filesystem::path &path) {
+  auto o = new OriginalStorage("/tmp");
   int dest_fd = o->fd;
-  if (dest_fd == -1)
+  if (dest_fd == -1) {
+    delete o;
     return nullptr;
+  }
   int src_fd = open(path.c_str(), O_RDONLY);
-  if (src_fd == -1)
-    return nullptr;
-
+  if (src_fd == -1) {
+    delete o;
+    throw ed_error("Couldn't open file.");
+  }
   uint64_t total = std::filesystem::file_size(path);
-  if (posix_ending && total > 0) {
+  if (total > 0) {
     char last;
-    if (pread(src_fd, &last, 1, (off_t)(total - 1)) != 1)
+    if (pread(src_fd, &last, 1, (off_t)(total - 1)) != 1) {
+      delete o;
       return nullptr;
+    }
     if (last == '\n') {
       total--;
       if (total > 0) {
         char s_last;
-        if (pread(src_fd, &s_last, 1, (off_t)(total - 1)) != 1)
+        if (pread(src_fd, &s_last, 1, (off_t)(total - 1)) != 1) {
+          delete o;
           return nullptr;
+        }
         if (s_last == '\r')
           total--;
       }
     }
   }
-  if (total == 0)
+  if (total == 0) {
+    delete o;
     return nullptr;
-
+  }
   std::vector<Shard *> pieces;
   uint64_t pos = 0;
   pieces.reserve((total + PETAL_SIZE_MAX - 1) / PETAL_SIZE_MAX);
   char buf[PETAL_SIZE_MAX];
-
   while (pos < total) {
     uint64_t want = std::min(PETAL_SIZE_MAX, total - pos);
     ssize_t got = pread(src_fd, buf, want, pos);
     if (got <= 0) {
       close(src_fd);
+      delete o;
       return nullptr;
     }
     uint64_t take = (uint64_t)got;
@@ -357,71 +362,72 @@ Shard *Shard::from_file(std::filesystem::path &path, OriginalBuffer *o, bool pos
     }
     if (!write_all(dest_fd, buf, take)) {
       close(src_fd);
+      delete o;
       return nullptr;
     }
     pieces.push_back(new Petal(take, lines, o, pos));
     pos += take;
   }
-
   close(src_fd);
-
-  if (pieces.empty())
+  if (pieces.empty()) {
+    delete o;
     return nullptr;
-
+  }
   o->initialize();
-
   if (pieces.size() == 1)
     return pieces[0];
   return build(pieces.data(), 0, pieces.size());
 }
 
-void Shard::dump(Shard *node, int depth) {
-  if (!node) {
-    std::cout << std::string(depth * 2, ' ') << "<null>\n";
-    return;
+Shard *Shard::from_string(const char *data, uint64_t len) {
+  auto o = new OriginalStorage("/tmp");
+  int dest_fd = o->fd;
+  if (dest_fd == -1 || data == nullptr) {
+    delete o;
+    return nullptr;
   }
-  std::string indent(depth * 2, ' ');
-  std::cout << indent
-            << "Shard@" << node
-            << " kind=";
-  switch (node->kind) {
-  case Shard::Kind::Branch:
-    std::cout << "Branch";
-    break;
-  case Shard::Kind::Petal:
-    std::cout << "Petal";
-    break;
+  uint64_t total = len;
+  if (total > 0) {
+    if (data[total - 1] == '\n') {
+      total--;
+      if (total > 0 && data[total - 1] == '\r')
+        total--;
+    }
   }
-  std::cout
-    << " height=" << unsigned(node->height)
-    << " length=" << node->length
-    << " lines=" << node->lines
-    << " refs=" << node->refs.load()
-    << "\n";
-  if (node->kind == Shard::Kind::Branch) {
-    auto *branch = (Branch *)node;
-    std::cout << indent << "  left:\n";
-    dump(branch->left, depth + 2);
-    std::cout << indent << "  right:\n";
-    dump(branch->right, depth + 2);
-  } else {
-    auto *petal = static_cast<Petal *>(node);
-    constexpr auto clean = [](const std::string &text) {
-      std::string result = text;
-      size_t pos = 0;
-      while ((pos = result.find('\n', pos)) != std::string::npos) {
-        result.replace(pos, 1, "\\n");
-        pos += 2;
-      }
-      return result;
-    };
-    std::cout
-      << indent << "  source=" << petal->source
-      << " pos=" << petal->pos
-      << " length=" << petal->length
-      << " lines=" << petal->lines
-      << " text=\"" << clean(std::string(petal->source->read(petal->pos), petal->length))
-      << "\"\n";
+  if (total == 0) {
+    delete o;
+    return nullptr;
   }
+  std::vector<Shard *> pieces;
+  uint64_t pos = 0;
+  pieces.reserve((total + PETAL_SIZE_MAX - 1) / PETAL_SIZE_MAX);
+  while (pos < total) {
+    uint64_t take = std::min(PETAL_SIZE_MAX, total - pos);
+    const char *buf = data + pos;
+    uint64_t lines = 0;
+    const char *p = buf;
+    const char *end = buf + take;
+    while (p < end) {
+      const void *nl = memchr(p, '\n', end - p);
+      if (!nl)
+        break;
+      lines++;
+      p = (const char *)nl + 1;
+    }
+    if (!write_all(dest_fd, buf, take)) {
+      delete o;
+      return nullptr;
+    }
+    pieces.push_back(new Petal(take, lines, o, pos));
+    pos += take;
+  }
+  if (pieces.empty()) {
+    delete o;
+    return nullptr;
+  }
+  o->initialize();
+  if (pieces.size() == 1)
+    return pieces[0];
+  return build(pieces.data(), 0, pieces.size());
 }
 } // namespace bed::internal::vase

src/internal/vase/storage/append.cc

@@ -1,7 +1,7 @@
 #include "internal/vase/vase.h"
 
 namespace bed::internal::vase {
-AppendBuffer::AppendBuffer(std::filesystem::path base_dir) {
+AppendStorage::AppendStorage(std::filesystem::path base_dir) {
   base_dir /= "tapp.XXXXXX";
   char *s = strdup(base_dir.c_str());
   fd = mkstemp(s);
@@ -17,14 +17,14 @@ AppendBuffer::AppendBuffer(std::filesystem::path base_dir) {
     throw std::runtime_error("mmap failed");
 }
 
-AppendBuffer::~AppendBuffer() {
+AppendStorage::~AppendStorage() {
   if (buf && buf != MAP_FAILED)
     munmap(buf, allocated_capacity);
   if (fd != -1)
     close(fd);
 }
 
-void AppendBuffer::grow(uint64_t len) {
+void AppendStorage::grow(uint64_t len) {
   if (current_size + len > allocated_capacity) {
     uint64_t new_capacity = allocated_capacity * 2;
     if (new_capacity < current_size + len)
@@ -46,13 +46,13 @@ void AppendBuffer::grow(uint64_t len) {
   }
 }
 
-uint64_t AppendBuffer::append(const char c) {
+uint64_t AppendStorage::append(const char c) {
   grow(1);
   buf[current_size++] = c;
   return current_size - 1;
 }
 
-uint64_t AppendBuffer::append(const char *text, uint64_t len) {
+uint64_t AppendStorage::append(const char *text, uint64_t len) {
   grow(len);
   memcpy(buf + current_size, text, len);
   uint64_t old_pos = current_size;
@@ -60,13 +60,13 @@ uint64_t AppendBuffer::append(const char *text, uint64_t len) {
   return old_pos;
 }
 
-const char *AppendBuffer::read(uint64_t pos) {
+const char *AppendStorage::read(uint64_t pos) {
   if (pos >= current_size)
     return nullptr;
   return buf + pos;
 }
 
-uint64_t AppendBuffer::length() {
+uint64_t AppendStorage::length() {
   return current_size;
 }
 } // namespace bed::internal::vase

src/internal/vase/storage/original.cc

@@ -1,7 +1,7 @@
 #include "internal/vase/vase.h"
 
 namespace bed::internal::vase {
-OriginalBuffer::OriginalBuffer(std::filesystem::path base_dir) {
+OriginalStorage::OriginalStorage(std::filesystem::path base_dir) {
   if (!std::filesystem::exists(base_dir) || !std::filesystem::is_directory(base_dir))
     throw std::runtime_error("Swap directory does not exist or is not a directory.");
   base_dir /= "tbuf.XXXXXX";
@@ -13,14 +13,14 @@ OriginalBuffer::OriginalBuffer(std::filesystem::path base_dir) {
   free(s);
 }
 
-OriginalBuffer::~OriginalBuffer() {
+OriginalStorage::~OriginalStorage() {
   if (buf)
     munmap((char *)buf, len);
   if (fd != -1)
     close(fd);
 }
 
-void OriginalBuffer::initialize() {
+void OriginalStorage::initialize() {
   struct stat st;
   if (fstat(fd, &st) == -1)
     throw std::runtime_error("fstat failed");
@@ -35,13 +35,13 @@ void OriginalBuffer::initialize() {
   fd = -1;
 }
 
-const char *OriginalBuffer::read(uint64_t pos) {
+const char *OriginalStorage::read(uint64_t pos) {
   if (pos >= len)
     return nullptr;
   return buf + pos;
 }
 
-uint64_t OriginalBuffer::length() {
+uint64_t OriginalStorage::length() {
   return len;
 }
 } // namespace bed::internal::vase

src/internal/vase/vase.cc

@@ -1,108 +1,8 @@
 #include "internal/vase/vase.h"
+#include "internal/io/io.h"
 
 namespace bed::internal::vase {
-Vase::Vase(std::filesystem::path path, std::filesystem::path swapdir)
-    : path(path), swapdir(swapdir) {
-  if (!std::filesystem::exists(swapdir) || !std::filesystem::is_directory(swapdir))
-    throw std::runtime_error("Swap directory does not exist or is not a directory.");
-  append = new AppendBuffer(swapdir);
-  original = new OriginalBuffer(swapdir);
-  if (std::filesystem::is_regular_file(path))
-    root = Shard::from_file(path, original, posix_ending);
-  else
-    root = nullptr;
-  history_top = 0;
-  history.push_back(root);
-  Shard::retain(root);
-}
-
-Vase::Vase(std::string cmd, std::filesystem::path swapdir)
-    : path(""), swapdir(swapdir) {
-  if (!std::filesystem::exists(swapdir) || !std::filesystem::is_directory(swapdir))
-    throw std::runtime_error("Swap directory does not exist or is not a directory.");
-  append = new AppendBuffer(swapdir);
-  original = new OriginalBuffer(swapdir);
-  root = Shard::from_command(cmd.c_str(), original, posix_ending);
-  history_top = 0;
-  history.push_back(root);
-  Shard::retain(root);
-}
-
-Vase::Vase(std::filesystem::path swapdir)
-    : path(""), swapdir(swapdir) {
-  if (!std::filesystem::exists(swapdir) || !std::filesystem::is_directory(swapdir))
-    throw std::runtime_error("Swap directory does not exist or is not a directory.");
-  append = new AppendBuffer(swapdir);
-  original = new OriginalBuffer(swapdir);
-  root = nullptr;
-  history_top = 0;
-  history.push_back(root);
-  Shard::retain(root);
-}
-
-Vase::~Vase() {
-  Shard::release(root);
-  for (auto s : history)
-    Shard::release(s);
-  if (original)
-    delete original;
-  if (append)
-    delete append;
-}
-
-Vase::Vase(Vase &&other) noexcept
-    : original(other.original),
-      append(other.append),
-      root(other.root),
-      posix_ending(other.posix_ending),
-      using_crlf(other.using_crlf),
-      path(std::move(other.path)),
-      swapdir(std::move(other.swapdir)),
-      history(std::move(other.history)),
-      history_top(other.history_top) {
-  other.original = nullptr;
-  other.append = nullptr;
-  other.root = nullptr;
-  other.history_top = 0;
-}
-
-Vase &Vase::operator=(Vase &&other) noexcept {
-  if (this == &other)
-    return *this;
-  Shard::release(root);
-  for (auto s : history)
-    Shard::release(s);
-  delete original;
-  delete append;
-  original = other.original;
-  append = other.append;
-  root = other.root;
-  posix_ending = other.posix_ending;
-  using_crlf = other.using_crlf;
-  path = std::move(other.path);
-  swapdir = std::move(other.swapdir);
-  history = std::move(other.history);
-  history_top = other.history_top;
-  other.original = nullptr;
-  other.append = nullptr;
-  other.root = nullptr;
-  other.history_top = 0;
-  return *this;
-}
-
-uint64_t Vase::length() {
-  if (!root)
-    return 0;
-  return root->length + posix_ending;
-}
-
-uint64_t Vase::lines() {
-  if (!root)
-    return 0;
-  return root->lines + 1;
-}
-
-std::string Vase::to_string() {
+std::string to_string(Shard *root) {
   std::string out;
   if (!root)
     return out;
@@ -112,23 +12,19 @@ std::string Vase::to_string() {
   uint64_t len;
   while (it.next(&data, &len))
     out.append(data, len);
-  if (posix_ending)
-    out.append("\n");
   return out;
 }
 
-std::string Vase::to_string(Range range) {
-  clamp(&range.start);
-  clamp(&range.end);
+std::string to_string(Shard *root, Range range) {
   std::string out;
   if (!root)
     return out;
   PetalIterator it(root, Direction::Forward);
-  uint64_t start = offset_of(range.start);
+  uint64_t start = offset_of(root, range.start);
   it.seek_offset(start);
   const char *data;
   uint64_t len;
-  uint64_t remaining = offset_of(range.end) - start;
+  uint64_t remaining = offset_of(root, range.end) - start;
   while (remaining && it.next(&data, &len)) {
     uint64_t n = std::min(len, remaining);
     out.append(data, n);
@@ -137,85 +33,10 @@ std::string Vase::to_string(Range range) {
   return out;
 }
 
-Iterator Vase::iterate(uint64_t line, Direction dir) {
-  return Iterator(root, line, dir);
-}
-
-bool Vase::undo() {
-  if (history_top == 0)
-    return false;
-  Shard::release(root);
-  history_top--;
-  root = history[history_top];
-  Shard::retain(root);
-  return true;
-}
-
-bool Vase::redo() {
-  if (history_top + 1 >= history.size())
-    return false;
-  Shard::release(root);
-  history_top++;
-  root = history[history_top];
-  Shard::retain(root);
-  return true;
-}
-
-void Vase::snapshot() {
-  if (history[history_top] == root)
-    return;
-  while (history.size() > history_top + 1) {
-    Shard::release(history.back());
-    history.pop_back();
-  }
-  Shard::retain(root);
-  history.push_back(root);
-  history_top++;
-}
-
-void Vase::prune_history(uint64_t n) {
-  uint64_t keep = std::min(history.size(), n + 1);
-  if (keep == history.size())
-    return;
-  uint64_t remove = history.size() - keep;
-  for (uint64_t i = 0; i < remove; ++i)
-    Shard::release(history[i]);
-  history.erase(history.begin(), history.begin() + remove);
-  history_top -= remove;
-}
-
-bool Vase::save() {
-  if (!root)
-    return true;
-  if (path == "")
-    return false;
-  std::ofstream file(path, std::ios::binary);
-  if (!file)
-    return false;
-  PetalIterator it(root, Direction::Forward);
-  it.seek_offset(0);
-  const char *data;
-  uint64_t len;
-  while (it.next(&data, &len)) {
-    file.write(data, len);
-    if (!file)
-      return false;
-  }
-  if (posix_ending)
-    file.write("\n", 1);
-  if (!file)
-    return false;
-  return true;
-}
-
-bool Vase::save_swap() {
-  return false;
-}
-
-void Vase::insert(Point *point, char key) {
-  uint64_t pos = append->append(key);
-  Shard *inserted = new Petal(1, key == '\n', append, pos);
-  auto [left, right] = Shard::split(root, offset_of(*point));
+Shard *insert(AppendStorage *ap, Shard *root, Point *point, char key) {
+  uint64_t pos = ap->append(key);
+  Shard *inserted = new Petal(1, key == '\n', ap, pos);
+  auto [left, right] = Shard::split(root, offset_of(root, *point));
   Shard *left2 = Shard::append(left, inserted);
   Shard::release(left);
   Shard::release(inserted);
@@ -223,31 +44,28 @@ void Vase::insert(Point *point, char key) {
   Shard::release(left2);
   Shard::release(right);
   Shard::release(root);
-  root = new_root;
   if (key == '\n')
     *point = {point->row + 1, 0};
   else
     point->col++;
+  return new_root;
 }
 
-void Vase::insert(Point *point, std::string_view str) {
-  insert(point, str.data(), str.size());
-}
-
-void Vase::insert(Point *point, const char *data, uint64_t len) {
+Shard *insert(AppendStorage *ap, Shard *root, Point *point, const char *data, uint64_t len) {
   while (len) {
     uint64_t chunk_size = std::min<uint64_t>(len, PETAL_SIZE_MAX);
-    _insert(point, data, chunk_size);
+    _insert(ap, &root, point, data, chunk_size);
     len -= chunk_size;
     data += chunk_size;
   }
+  return root;
 }
 
-void Vase::_insert(Point *point, const char *data, uint64_t len) {
+void _insert(AppendStorage *ap, Shard **root, Point *point, const char *data, uint64_t len) {
   if (len == 0)
     return;
-  uint64_t offset = offset_of(*point);
-  uint64_t pos = append->append(data, len);
+  uint64_t offset = offset_of(*root, *point);
+  uint64_t pos = ap->append(data, len);
   uint64_t lines = 0;
   const char *start = data;
   const char *last_line = start;
@@ -256,64 +74,30 @@ void Vase::_insert(Point *point, const char *data, uint64_t len) {
     ++lines;
     last_line = ++data;
   }
-  uint64_t col = 0;
-  uint64_t remaining = end - last_line;
-  while (remaining) {
-    uint64_t n = grapheme_next_character_break_utf8(last_line, remaining);
-    last_line += n;
-    remaining -= n;
-    ++col;
-  }
+  uint64_t col = end - last_line;
   if (lines) {
     point->row += lines;
     point->col = col;
   } else {
     point->col += col;
   }
-  Shard *inserted = new Petal(len, lines, append, pos);
-  auto [left, right] = Shard::split(root, offset);
+  Shard *inserted = new Petal(len, lines, ap, pos);
+  auto [left, right] = Shard::split(*root, offset);
   Shard *left2 = Shard::append(left, inserted);
   Shard::release(left);
   Shard::release(inserted);
   Shard *new_root = Shard::concat(left2, right);
   Shard::release(left2);
   Shard::release(right);
-  Shard::release(root);
-  root = new_root;
+  Shard::release(*root);
+  *root = new_root;
 }
 
-void Vase::erase(Point *point, uint64_t amount, Direction dir) {
-  if (amount == 0)
-    return;
-  Point start = *point;
-  Point end = *point;
-  if (dir == Direction::Forward)
-    move_clusters(&end, amount, Direction::Forward);
-  else
-    move_clusters(&start, amount, Direction::Backward);
-  uint64_t start_offset = offset_of(start);
-  uint64_t end_offset = offset_of(end);
-  if (start_offset > end_offset)
-    std::swap(start_offset, end_offset);
-  uint64_t count = end_offset - start_offset;
-  auto [a, b] = Shard::split(root, start_offset);
-  auto [d, c] = Shard::split(b, count);
-  Shard *new_root = Shard::concat(a, c);
-  Shard::release(a);
-  Shard::release(b);
-  Shard::release(c);
-  Shard::release(d);
-  Shard::release(root);
-  root = new_root;
-  if (dir == Direction::Backward)
-    *point = start;
-}
-
-void Vase::erase(Range range) {
+Shard *erase(Shard *root, Range range) {
   Point start = range.start;
   Point end = range.end;
-  uint64_t start_offset = offset_of(start);
-  uint64_t end_offset = offset_of(end);
+  uint64_t start_offset = offset_of(root, start);
+  uint64_t end_offset = offset_of(root, end);
   uint64_t count = end_offset - start_offset;
   auto [a, b] = Shard::split(root, start_offset);
   auto [d, c] = Shard::split(b, count);
@@ -323,188 +107,258 @@ void Vase::erase(Range range) {
   Shard::release(c);
   Shard::release(d);
   Shard::release(root);
-  root = new_root;
+  return new_root;
 }
 
-void Vase::replace(Range range, std::string_view str) {
-  replace(range, str.data(), str.size());
+Shard *replace(AppendStorage *ap, Shard *root, Range range, const char *data, uint64_t len) {
+  root = erase(root, range);
+  return insert(ap, root, &range.start, data, len);
 }
 
-void Vase::replace(Range range, const char *data, uint64_t len) {
-  erase(range);
-  insert(&range.start, data, len);
+Point eof_point(Shard *root) {
+  if (!root)
+    return {0, 0};
+  Point result{
+    .row = root->lines,
+    .col = 0
+  };
+  PetalIterator it(root, Direction::Forward);
+  it.seek_line(root->lines);
+  const char *data;
+  uint64_t len;
+  while (it.next(&data, &len))
+    result.col += len;
+  return result;
 }
 
-uint64_t Vase::offset_of(Point point) {
-  clamp(&point);
-  LineIterator it(root, point.row, Direction::Forward);
-  std::string line;
+uint64_t offset_of(Shard *root, Point point) {
+  return offset_of(root, point.row) + point.col;
+}
+
+uint64_t offset_of(Shard *root, uint64_t line) {
+  if (!root)
+    return 0;
+  if (line == 0)
+    return 0;
+  if (line == root->lines + 1)
+    return root->length;
+  if (line > root->lines + 1)
+    throw ed_error("line out of range");
   uint64_t offset = 0;
-  if (it.next(&line)) {
-    const char *ptr = line.data();
-    uint64_t remaining = line.length();
-    while (point.col && remaining) {
-      uint64_t next_len = grapheme_next_character_break_utf8(ptr, remaining);
-      remaining -= next_len;
-      ptr += next_len;
-      offset += next_len;
-      point.col--;
+  Shard *curr = root;
+  while (curr->kind == Shard::Kind::Branch) {
+    auto *b = (Branch *)curr;
+    if (line <= b->left->lines) {
+      curr = b->left;
+    } else {
+      line -= b->left->lines;
+      offset += b->left->length;
+      curr = b->right;
     }
   }
-  return it.byte_offset() + offset;
+  auto *petal = (Petal *)curr;
+  if (line == 0)
+    return offset;
+  const char *text = petal->source->read(petal->pos);
+  uint64_t local = 0;
+  while (line--) {
+    const char *nl = (const char *)memchr(text + local, '\n', petal->length - local);
+    if (!nl)
+      throw std::runtime_error("leaf line count is wrong.");
+    local = (nl - text) + 1;
+  }
+  return offset + local;
 }
 
-Point Vase::point_of(uint64_t offset) {
-  PetalIterator it(root, Direction::Backward);
-  it.seek_offset(offset);
-  Point p;
-  p.row = it.global_line;
-  std::string line;
-  const char *chunk;
-  uint64_t len = 0;
-  if (!it.next(&chunk, &len))
-    return p;
-  while (true) {
-#if defined(__GLIBC__) || defined(__APPLE__)
-    const char *nl = (const char *)memrchr(chunk, '\n', len);
-#else
-    const char *nl = nullptr;
-    const char *p = chunk + len;
-    while (!nl && p != chunk)
-      if (*(--p) == '\n')
-        nl = p;
-#endif
-    if (!nl) {
-      if (len && chunk[len - 1] == '\r')
-        --len;
-      line.insert(0, chunk, len);
-      if (!it.next(&chunk, &len))
-        break;
-      continue;
-    }
-    const char *end = chunk + len;
-    const char *start = nl + 1;
-    const char *line_end = end;
-    if (line_end > start && *(line_end - 1) == '\r')
-      --line_end;
-    line.insert(0, start, line_end - start);
-    break;
-  }
-  const char *ptr = line.data();
-  uint64_t remaining = line.length();
-  while (remaining) {
-    uint64_t next_len = grapheme_next_character_break_utf8(ptr, remaining);
-    remaining -= next_len;
-    ptr += next_len;
-    p.col++;
-  }
-  clamp(&p);
-  return p;
+static Shard *newline(AppendStorage *ap) {
+  uint64_t pos = ap->append('\n');
+  return new Petal(1, true, ap, pos);
 }
 
-void Vase::move_clusters(Point *point, uint64_t amount, Direction dir) {
-  if (amount == 0)
-    return;
-  if (dir == Direction::Backward) {
-    LineIterator it(root, point->row, Direction::Backward);
-    while (amount) {
-      std::string line;
-      if (!it.next(&line))
-        return;
-      std::vector<uint64_t> clusters;
-      const char *ptr = line.data();
-      uint64_t remaining = line.size();
-      uint64_t byte = 0;
-      while (remaining) {
-        clusters.push_back(byte);
-        uint64_t len =
-          grapheme_next_character_break_utf8(ptr, remaining);
-        ptr += len;
-        remaining -= len;
-        byte += len;
-      }
-      while (amount && point->col) {
-        point->col--;
-        amount--;
-      }
-      if (amount == 0)
-        return;
-      if (point->row == 0)
-        return;
-      point->row--;
-      point->col = clusters.size();
-      amount--;
-    }
-  } else {
-    LineIterator it(root, point->row, Direction::Forward);
-    while (amount) {
-      std::string line;
-      if (!it.next(&line))
-        return;
-      if (point->col || amount) {
-        const char *ptr = line.data();
-        uint64_t remaining = line.size();
-        uint64_t col = 0;
-        while (col < point->col && remaining) {
-          uint64_t len = grapheme_next_character_break_utf8(ptr, remaining);
-          ptr += len;
-          remaining -= len;
-          col++;
-        }
-        while (amount && remaining) {
-          uint64_t len = grapheme_next_character_break_utf8(ptr, remaining);
-          ptr += len;
-          remaining -= len;
-          point->col++;
-          amount--;
-        }
-      }
-      if (amount) {
-        point->row++;
-        point->col = 0;
-        amount--;
-      }
-    }
-  }
-  clamp(point);
-}
-
-void Vase::clamp(Point *point) {
+Shard *insert(AppendStorage *ap, Shard *root, Shard *text, uint64_t line) {
   if (!root) {
-    point->row = 0;
-    point->col = 0;
-    return;
+    if (line != 0)
+      throw ed_error("line out of range");
+    Shard::retain(text);
+    return text;
   }
-  if (point->row > root->lines) {
-    point->row = root->lines;
-    point->col = UINT64_MAX;
+  if (line > root->lines + 1)
+    throw ed_error("line out of range");
+  Shard::retain(text);
+  Shard *nl = newline(ap);
+  if (line <= root->lines) {
+    uint64_t offset = offset_of(root, line);
+    auto [left, right] = Shard::split(root, offset);
+    Shard *middle = Shard::concat(text, nl);
+    Shard::release(text);
+    Shard::release(nl);
+    Shard *new_root = Shard::concat(left, middle);
+    Shard::release(left);
+    Shard::release(middle);
+    middle = Shard::concat(new_root, right);
+    Shard::release(new_root);
+    Shard::release(right);
+    Shard::release(root);
+    return middle;
   }
-  LineIterator it(root, point->row, Direction::Forward);
-  std::string line;
-  uint64_t clusters = 0;
-  if (it.next(&line)) {
-    const char *ptr = line.data();
-    uint64_t remaining = line.length();
-    while (remaining) {
-      uint64_t next_len = grapheme_next_character_break_utf8(ptr, remaining);
-      remaining -= next_len;
-      ptr += next_len;
-      clusters++;
-    }
-  }
-  if (point->col > clusters)
-    point->col = clusters;
+  Shard *new_root = Shard::concat(root, nl);
+  Shard::release(root);
+  Shard::release(nl);
+  Shard *result = Shard::concat(new_root, text);
+  Shard::release(new_root);
+  Shard::release(text);
+  return result;
 }
 
-void Vase::move_lines(Point *point, uint64_t amount, Direction dir) {
-  if (dir == Direction::Forward) {
-    point->row += amount;
-  } else {
-    if (amount > point->row)
-      point->row = 0;
-    else
-      point->row -= amount;
+Shard *replace(Shard *root, Shard *text, uint64_t start, uint64_t end) {
+  if (!start || !end)
+    throw ed_error("Invalid range.");
+  start--;
+  end--;
+  if (!root)
+    throw ed_error("line range out of bounds");
+  uint64_t line_count = root->lines + 1;
+  if (start > end || end >= line_count)
+    throw ed_error("line range out of bounds");
+  uint64_t start_offset = offset_of(root, start);
+  uint64_t end_offset =
+    (end + 1 == line_count)
+      ? root->length
+      : offset_of(root, end + 1) - 1;
+  auto [left, rest] = Shard::split(root, start_offset);
+  auto [middle, right] = Shard::split(rest, end_offset - start_offset);
+  Shard *a = Shard::concat(left, text);
+  Shard *new_root = Shard::concat(a, right);
+  Shard::release(left);
+  Shard::release(rest);
+  Shard::release(middle);
+  Shard::release(right);
+  Shard::release(a);
+  Shard::release(root);
+  return new_root;
+}
+
+Shard *erase(Shard *root, uint64_t start, uint64_t end) {
+  if (!start || !end)
+    throw ed_error("Invalid range.");
+  start--;
+  end--;
+  if (!root)
+    throw ed_error("line range out of bounds");
+  uint64_t line_count = root->lines + 1;
+  if (start > end || end >= line_count)
+    throw ed_error("line range out of bounds");
+  uint64_t start_offset = offset_of(root, start);
+  uint64_t end_offset = offset_of(root, end + 1);
+  if (end == root->lines && start_offset)
+    start_offset--;
+  auto [left, rest] = Shard::split(root, start_offset);
+  auto [middle, right] = Shard::split(rest, end_offset - start_offset);
+  Shard *new_root = Shard::concat(left, right);
+  Shard::release(left);
+  Shard::release(rest);
+  Shard::release(middle);
+  Shard::release(right);
+  Shard::release(root);
+  return new_root;
+}
+
+Shard *join(Shard *root, uint64_t start, uint64_t end) {
+  if (!start || !end)
+    throw ed_error("Invalid range.");
+  start--;
+  end--;
+  if (!root)
+    throw ed_error("line range out of bounds");
+  uint64_t line_count = root->lines + 1;
+  if (start >= end || end >= line_count)
+    throw ed_error("line range out of bounds");
+  uint64_t offset = offset_of(root, start);
+  std::vector<Shard *> pieces;
+  pieces.reserve(end - start + 3);
+  auto [a, b] = Shard::split(root, offset);
+  pieces.push_back(a);
+  for (uint64_t line = start; line < end; line++) {
+    uint64_t nl_pos = offset_of(b, 1) - 1;
+    auto [content, rest] = Shard::split(b, nl_pos);
+    Shard::release(b);
+    auto [nl, next_b] = Shard::split(rest, 1);
+    Shard::release(rest);
+    Shard::release(nl);
+    pieces.push_back(content);
+    b = next_b;
   }
-  clamp(point);
+  pieces.push_back(b);
+  Shard *joined = Shard::build(pieces.data(), 0, pieces.size());
+  Shard::release(root);
+  return joined;
+}
+
+Shard *copy(Shard *root, uint64_t start, uint64_t end) {
+  if (!start || !end)
+    throw ed_error("Invalid range.");
+  start--;
+  end--;
+  if (!root)
+    throw ed_error("line range out of bounds");
+  uint64_t line_count = root->lines + 1;
+  if (start > end || end >= line_count)
+    throw ed_error("line range out of bounds");
+  uint64_t start_offset = offset_of(root, start);
+  uint64_t end_offset =
+    (end + 1 == line_count)
+      ? root->length
+      : offset_of(root, end + 1) - 1;
+  auto [left, rest] = Shard::split(root, start_offset);
+  auto [middle, right] = Shard::split(rest, end_offset - start_offset);
+  Shard::release(left);
+  Shard::release(rest);
+  Shard::release(right);
+  return middle;
+}
+
+void write_file(std::filesystem::path path, Shard *text) {
+  std::ofstream file(path, std::ios::binary);
+  if (!text)
+    return;
+  PetalIterator it(text, Direction::Forward);
+  it.seek_offset(0);
+  const char *data;
+  uint64_t len;
+  while (it.next(&data, &len)) {
+    if (!file)
+      throw ed_error("Failed while writing file: " + path.string());
+    file.write(data, len);
+  }
+  file.write("\n", 1);
+  if (!file)
+    throw ed_error("Failed while writing file: " + path.string());
+}
+
+void write_command(const char *cmd, Shard *text) {
+  io::IO::cleanup();
+  FILE *pipe = popen(cmd, "w");
+  if (!pipe) {
+    io::IO::enable_raw();
+    throw ed_error("Failed to start command: " + std::string(cmd));
+  }
+  if (!text) {
+    int status = pclose(pipe);
+    if (status == -1)
+      throw ed_error("Failed to wait for command: " + std::string(cmd));
+    return;
+  }
+  PetalIterator it(text, Direction::Forward);
+  it.seek_offset(0);
+  const char *data;
+  uint64_t len;
+  while (it.next(&data, &len))
+    fwrite(data, 1, len, pipe);
+  fwrite("\n", 1, 1, pipe);
+  int status = pclose(pipe);
+  io::IO::enable_raw();
+  if (status == -1)
+    throw ed_error("Failed to wait for command: " + std::string(cmd));
+  return;
 }
 } // namespace bed::internal::vase

src/main.cc

@@ -8,12 +8,12 @@ int main(int argc, char *argv[]) {
     ed.run();
   } catch (bed::fatal_error &e) {
     if (e.code)
-      std::cout << "Fatal error: " << e.what() << std::endl;
+      printf("Fatal error: %s\n", e.what());
     return e.code;
   }
 #ifndef DEBUG
   catch (...) {
-    std::cout << "Unexpected error." << std::endl;
+    printf("Unexpected error.\n");
     return 1;
   }
 #endif