Make r fucntion allow zero.

- except global and history ones

.gitattributes

@@ -0,0 +1 @@
+libs/unicode_width/** linguist-vendored

.gitignore

@@ -5,3 +5,6 @@ compile_commands.json
 bin/
 build/
 .cache/
+
+sample.txt
+old*

LICENSE.md

@@ -0,0 +1,660 @@
+# GNU AFFERO GENERAL PUBLIC LICENSE
+
+Version 3, 19 November 2007
+
+Copyright (C) 2007 Free Software Foundation, Inc.
+<https://fsf.org/>
+
+Everyone is permitted to copy and distribute verbatim copies of this
+license document, but changing it is not allowed.
+
+## Preamble
+
+The GNU Affero General Public License is a free, copyleft license for
+software and other kinds of works, specifically designed to ensure
+cooperation with the community in the case of network server software.
+
+The licenses for most software and other practical works are designed
+to take away your freedom to share and change the works. By contrast,
+our General Public Licenses are intended to guarantee your freedom to
+share and change all versions of a program--to make sure it remains
+free software for all its users.
+
+When we speak of free software, we are referring to freedom, not
+price. Our General Public Licenses are designed to make sure that you
+have the freedom to distribute copies of free software (and charge for
+them if you wish), that you receive source code or can get it if you
+want it, that you can change the software or use pieces of it in new
+free programs, and that you know you can do these things.
+
+Developers that use our General Public Licenses protect your rights
+with two steps: (1) assert copyright on the software, and (2) offer
+you this License which gives you legal permission to copy, distribute
+and/or modify the software.
+
+A secondary benefit of defending all users' freedom is that
+improvements made in alternate versions of the program, if they
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+incorporate. Many developers of free software are heartened and
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+software used on network servers, this result may fail to come about.
+The GNU General Public License permits making a modified version and
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+source code to the public.
+
+The GNU Affero General Public License is designed specifically to
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+provide the source code of the modified version running there to the
+users of that server. Therefore, public use of a modified version, on
+a publicly accessible server, gives the public access to the source
+code of the modified version.
+
+An older license, called the Affero General Public License and
+published by Affero, was designed to accomplish similar goals. This is
+a different license, not a version of the Affero GPL, but Affero has
+released a new version of the Affero GPL which permits relicensing
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+
+The precise terms and conditions for copying, distribution and
+modification follow.
+
+## TERMS AND CONDITIONS
+
+### 0. Definitions.
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+"This License" refers to version 3 of the GNU Affero General Public
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+"Copyright" also means copyright-like laws that apply to other kinds
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+### 6. Conveying Non-Source Forms.
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+You may convey a covered work in object code form under the terms of
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+If you convey a covered work, knowingly relying on a patent license,
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+consistent with the requirements of this License, to extend the patent
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+receiving the covered work authorizing them to use, propagate, modify
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+
+A patent license is "discriminatory" if it does not include within the
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+the non-exercise of one or more of the rights that are specifically
+granted under this License. You may not convey a covered work if you
+are a party to an arrangement with a third party that is in the
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+license was granted, prior to 28 March 2007.
+
+Nothing in this License shall be construed as excluding or limiting
+any implied license or other defenses to infringement that may
+otherwise be available to you under applicable patent law.
+
+### 12. No Surrender of Others' Freedom.
+
+If conditions are imposed on you (whether by court order, agreement or
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+excuse you from the conditions of this License. If you cannot convey a
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+consequence you may not convey it at all. For example, if you agree to
+terms that obligate you to collect a royalty for further conveying
+from those to whom you convey the Program, the only way you could
+satisfy both those terms and this License would be to refrain entirely
+from conveying the Program.
+
+### 13. Remote Network Interaction; Use with the GNU General Public License.
+
+Notwithstanding any other provision of this License, if you modify the
+Program, your modified version must prominently offer all users
+interacting with it remotely through a computer network (if your
+version supports such interaction) an opportunity to receive the
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+Corresponding Source shall include the Corresponding Source for any
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+Notwithstanding any other provision of this License, you have
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+License will continue to apply to the part which is the covered work,
+but the work with which it is combined will remain governed by version
+3 of the GNU General Public License.
+
+### 14. Revised Versions of this License.
+
+The Free Software Foundation may publish revised and/or new versions
+of the GNU Affero General Public License from time to time. Such new
+versions will be similar in spirit to the present version, but may
+differ in detail to address new problems or concerns.
+
+Each version is given a distinguishing version number. If the Program
+specifies that a certain numbered version of the GNU Affero General
+Public License "or any later version" applies to it, you have the
+option of following the terms and conditions either of that numbered
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+Foundation. If the Program does not specify a version number of the
+GNU Affero General Public License, you may choose any version ever
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+
+If the Program specifies that a proxy can decide which future versions
+of the GNU Affero General Public License can be used, that proxy's
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+to choose that version for the Program.
+
+Later license versions may give you additional or different
+permissions. However, no additional obligations are imposed on any
+author or copyright holder as a result of your choosing to follow a
+later version.
+
+### 15. Disclaimer of Warranty.
+
+THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY
+APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT
+HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT
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+
+### 16. Limitation of Liability.
+
+IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
+WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR
+CONVEYS THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES,
+INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES
+ARISING OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT
+NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR
+LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM
+TO OPERATE WITH ANY OTHER PROGRAMS), EVEN IF SUCH HOLDER OR OTHER
+PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
+
+### 17. Interpretation of Sections 15 and 16.
+
+If the disclaimer of warranty and limitation of liability provided
+above cannot be given local legal effect according to their terms,
+reviewing courts shall apply local law that most closely approximates
+an absolute waiver of all civil liability in connection with the
+Program, unless a warranty or assumption of liability accompanies a
+copy of the Program in return for a fee.
+
+END OF TERMS AND CONDITIONS
+
+## How to Apply These Terms to Your New Programs
+
+If you develop a new program, and you want it to be of the greatest
+possible use to the public, the best way to achieve this is to make it
+free software which everyone can redistribute and change under these
+terms.
+
+To do so, attach the following notices to the program. It is safest to
+attach them to the start of each source file to most effectively state
+the exclusion of warranty; and each file should have at least the
+"copyright" line and a pointer to where the full notice is found.
+
+        BEd - Better Ed.
+        Copyright (C) 2026 Syed (me@syedm.dev)
+
+        This program is free software: you can redistribute it and/or modify
+        it under the terms of the GNU Affero General Public License as
+        published by the Free Software Foundation, either version 3 of the
+        License, or (at your option) any later version.
+
+        This program is distributed in the hope that it will be useful,
+        but WITHOUT ANY WARRANTY; without even the implied warranty of
+        MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+        GNU Affero General Public License for more details.
+
+        You should have received a copy of the GNU Affero General Public License
+        along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+Also add information on how to contact you by electronic and paper
+mail.
+
+If your software can interact with users remotely through a computer
+network, you should also make sure that it provides a way for users to
+get its source. For example, if your program is a web application, its
+interface could display a "Source" link that leads users to an archive
+of the code. There are many ways you could offer source, and different
+solutions will be better for different programs; see section 13 for
+the specific requirements.
+
+You should also get your employer (if you work as a programmer) or
+school, if any, to sign a "copyright disclaimer" for the program, if
+necessary. For more information on this, and how to apply and follow
+the GNU AGPL, see <https://www.gnu.org/licenses/>.

Makefile

@@ -6,8 +6,8 @@ INCLUDE_DIR := include
 CXX ?= g++
 CC ?= gcc
 
-TARGET_DEBUG := $(BIN_DIR)/crib-dbg
-TARGET_RELEASE := $(BIN_DIR)/crib
+TARGET_DEBUG := $(BIN_DIR)/bed-dbg
+TARGET_RELEASE := $(BIN_DIR)/bed
 
 PCH_DIR_DEBUG := $(OBJ_DIR)/debug/pch
 PCH_DIR_RELEASE := $(OBJ_DIR)/release/pch
@@ -25,13 +25,13 @@ MRUBY_CFLAGS ?= -I./libs/mruby/build/host/include
 MRUBY_LIBS ?= -L./libs/mruby/build/host/lib -lmruby
 
 CFLAGS_DEBUG :=\
-	-std=c++26 -Wall -Wextra -static \
-	-O0 -fno-inline -gsplit-dwarf \
+	-std=c++23 -Wall -Wextra -fno-rtti \
+	-Og -fno-inline -gsplit-dwarf -DDEBUG \
 	-g -fno-omit-frame-pointer -ffast-math \
 	-I./include -I./libs/unicode_width
 
 CFLAGS_RELEASE :=\
-	-std=c++26 -O3 -march=x86-64 -mtune=generic -fno-rtti \
+	-std=c++23 -O3 -mtune=generic -fno-rtti \
 	-fvisibility=hidden -static -ffast-math \
 	-fomit-frame-pointer -DNDEBUG -s \
 	-I./include -I./libs/unicode_width
@@ -77,6 +77,7 @@ $(TARGET_DEBUG): $(PCH_DEBUG) $(OBJ_DEBUG) $(UNICODE_OBJ)
 $(TARGET_RELEASE): $(PCH_RELEASE) $(OBJ_RELEASE) $(UNICODE_OBJ)
 	@mkdir -p $(BIN_DIR)
 	@$(CXX) $(CFLAGS_RELEASE) -o $@ $(OBJ_RELEASE) $(UNICODE_OBJ) $(LIBS)
+	@strip $@
 	@echo "Release build complete: $@"
 
 $(OBJ_DIR)/debug/%.o: $(SRC_DIR)/%.cc $(PCH_DEBUG) $(GENERATED_HEADER)

README.md

@@ -0,0 +1,60 @@
+## BEd
+
+Better ed.<br/>
+An ed implementation (mostly posix compliant) but with:
+- Lsp support for autocomplete suggetions when in ed text mode.
+- Autocomplete for language snippets + other words found near the cursor etc.
+- text mode where arrow keys etc. work as expected.
+- All code printing done with syntax highlighting.
+- Lsp diagnostics command to list global errors/warnings, to print thir lines, jump to their lines, edit them etc.
+- Addressing modes that work by addressing ->
+    - symbol definitions (lsp)
+    - diagnostic points (lsp)
+- Most lsp stuff (like rename symbol, symbol reference count etc.)
+- Inlay hints while editing and printing.
+- A read write command to open a set of lines similar to c command but with the text from before already filled.
+- Code formatters (lsp and others).
+- Ruby based extentions.
+- Custom functions, live ruby code running.
+- Debuggers (dap).
+- Better shell commands/integration.
+- Ruby based configs. (embedded Mruby)
+- Remappable commands/macros.
+- Better history & session saves.
+- Multiple buffers per session support.
+- Indentation engine (with editorconfig loading.).
+- Build systems, npm, nix, make etc integration.
+- More complete & fast regex.
+- Better current line semantics.
+- Full unicode + graphemes support.
+- SSH support for loading files/lsp etc (and fully remote sessions.).
+- Git commands / file diffs show in editor.
+- File operations, directory & files listing.
+- Nerdfonts & themable colorized outputs.
+- Better address marking with ranges.
+- text copy/paste & registers.
+- & A lot more cool stuff.
+
+### Implementation status:
+
+- Internal buffer:
+    - Super fast and memory efficient buffer implementation done.
+    - Loading from files/subshell commands done.
+- Syntax highlighter and block parser system done.
+- All ed addressing modes and block addressing done (also `%`).
+
+#### `lsp`
+
+`lsp` is a generic plug for lsp's.
+<br/>
+<br/>
+It should support:
+- Lsp over ssh or stdin/out or unix sockets etc.
+- Handling multiple lsps at once (including over a single file.)
+- Converting offsets encoding between utf16 - utf8 according to lsp standards.
+- Loading lsp features etc. automatically.
+- Error handling.
+- And more.
+
+Not done yet.
+

flake.nix

@@ -1,5 +1,5 @@
 {
-  description = "Crib - An IDE.";
+  description = "BEd - Better Ed.";
 
   inputs = {
     nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
@@ -47,18 +47,18 @@
         '';
       };
 
-      crib = pkgs.stdenv.mkDerivation {
-        pname = "crib";
+      bed = pkgs.stdenv.mkDerivation {
+        pname = "bed";
         version = "0.1.0";
 
         src = ./.;
 
         nativeBuildInputs = with hostPkgs; [
+          bash
           pkg-config
           gnumake
-          xxd
-          bash
           findutils
+          binutils
         ];
 
         buildInputs = with pkgs; [
@@ -77,19 +77,19 @@
 
         installPhase = ''
           mkdir -p $out/bin
-          cp bin/crib $out/bin/crib
+          cp bin/bed $out/bin/bed
         '';
       };
     in
     {
       packages.${system} = {
-        default = crib;
-        crib = crib;
+        default = bed;
+        bed = bed;
         mruby = mruby;
       };
 
-      devShells.${system}.default = pkgs.mkShell {
-        inputsFrom = [ crib ];
+      devShells.${system}.default = hostPkgs.mkShell {
+        inputsFrom = [ bed ];
 
         packages = [
           hostPkgs.clang-tools
@@ -98,7 +98,6 @@
           hostPkgs.gnumake
           hostPkgs.bear
           hostPkgs.ruby
-          hostPkgs.xxd
           hostPkgs.gdb
           hostPkgs.binutils
           hostPkgs.findutils

include/bed.h

@@ -0,0 +1,55 @@
+#pragma once
+
+#include "definitions.h"
+#include "internal/buffer/buffer.h"
+#include "internal/functions/functions.h"
+#include "internal/functions/suffixes.h"
+#include "internal/io/io.h"
+#include "internal/marks/marks.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::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;
+  internal::io::IO &io;
+  internal::vase::AppendStorage append{"/tmp"};
+
+  bool help_mode = false;
+  bool prompt_mode = true;
+  std::function<std::string(BEd &)> prompt = nullptr;
+  bool suppress_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::Range prev_1;
+  internal::buffer::Range prev_2;
+  internal::marks::MarksEngine marks;
+
+  BEd(std::vector<std::string> args, internal::io::IO &io);
+  ~BEd();
+
+  internal::buffer::Buffer &buffer(const std::string &);
+  internal::buffer::Line &current();
+  internal::buffer::Range &prev();
+  void mark(uint8_t, internal::buffer::Line);
+
+  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

@@ -0,0 +1,31 @@
+#pragma once
+
+#include "internal/vase/vase.h"
+#include "pch.h"
+
+namespace bed {
+struct BEd;
+
+struct fatal_error : std::runtime_error {
+  uint8_t code;
+  fatal_error(std::string msg, uint8_t code)
+      : std::runtime_error(msg), code(code) {}
+};
+
+struct ed_error : std::runtime_error {
+  ed_error(std::string msg) : std::runtime_error(msg) {}
+};
+
+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

include/internal/buffer/buffer.h

@@ -0,0 +1,6 @@
+#pragma once
+
+#include "clip.h"
+#include "decl.h"
+#include "generic.h"
+#include "pch.h"

include/internal/buffer/clip.h

@@ -0,0 +1,35 @@
+#pragma once
+
+#include "decl.h"
+#include "pch.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;
+  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 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/decl.h

@@ -0,0 +1,146 @@
+#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,
+    Null,
+    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(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 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 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/generic.h

@@ -0,0 +1,39 @@
+#pragma once
+
+#include "decl.h"
+#include "pch.h"
+
+namespace bed::internal::buffer {
+struct GenericBuffer : Buffer {
+  vase::Shard *root;
+  std::filesystem::path save_path{};
+  std::string language{};
+  std::optional<syntax::Parser> parser{};
+
+  GenericBuffer(std::string name)
+      : Buffer(name, Kind::Generic), root(nullptr) {};
+  ~GenericBuffer();
+
+  bool waste() 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 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/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

@@ -0,0 +1,26 @@
+#pragma once
+
+#include "pch.h"
+
+namespace bed::internal {
+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 +1,92 @@
+#pragma once
+
+#include "definitions.h"
+#include "pch.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);
+
+  IO();
+  ~IO();
+
+  IO(const IO &) = delete;
+  IO &operator=(const IO &) = delete;
+
+  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);
+
+  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 &);
+
+  std::deque<char> input_queue;
+
+  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/marks/marks.h

@@ -0,0 +1,60 @@
+#pragma once
+
+#include "internal/buffer/buffer.h"
+#include "pch.h"
+
+namespace bed::internal::marks {
+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 +1,114 @@
+#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<ui::Token> *tokens;
+  CompletionContext *completion;
+
+  explicit Parser(
+    std::string_view cmd, BEd &bed, Command *command,
+    std::vector<ui::Token> *tokens, CompletionContext *completion
+  );
+
+  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 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/syntax/decl.h

@@ -0,0 +1,119 @@
+#pragma once
+
+#include "internal/trie/trie.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 {
+  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 *)> copy;
+  std::function<bool(void *, void *)> equal;
+  std::function<void(void *)> destroy;
+};
+
+struct ParseState {
+  static constexpr uint64_t BRANCH_BIT = 1ull << 63;
+  static constexpr uint64_t LINES_MASK = ~BRANCH_BIT;
+  uint64_t header;
+  bool is_branch() const {
+    return header & BRANCH_BIT;
+  }
+  uint64_t lines() const {
+    return header & LINES_MASK;
+  }
+};
+
+struct ParseStateBranch : ParseState {
+  ParseState *left;
+  ParseState *right;
+};
+
+struct ParseStateLeaf : ParseState {
+  void *state;
+  uint32_t n;
+  uint32_t cap;
+  uint16_t *blocks;
+  static constexpr uint16_t IS_CLOSING = 0x8000;
+  static constexpr uint16_t LINE_MASK = 0x7fff;
+};
+
+struct TreeCursor {
+  ParseStateLeaf *leaf = nullptr;
+  ParseStateBranch *stack[64];
+  uint8_t depth = 0;
+  bool went_left[64];
+  TreeCursor(ParseState *root, uint64_t target_line, uint64_t *relative);
+  void next();
+  void prev();
+};
+} // namespace bed::internal::syntax

include/internal/syntax/parser.h

@@ -0,0 +1,57 @@
+#pragma once
+
+#include "decl.h"
+#include "internal/vase/vase.h"
+#include "pch.h"
+
+namespace bed::internal::syntax {
+struct Parser {
+  static constexpr uint64_t MAX_CHUNK = 512;
+
+  ParseState *root;
+  Language lang;
+  bool in_edit = false;
+  bool dirty = false;
+  uint64_t dirty_start = 0;
+  uint64_t dirty_end = 0;
+
+  Parser(vase::Shard *, uint64_t, Language);
+  ~Parser();
+  Parser(const Parser &) = delete;
+  Parser &operator=(const Parser &) = delete;
+
+  void reset(vase::Shard *, uint64_t, Language);
+  void erase(vase::Shard *, uint64_t, uint64_t);
+  void insert(vase::Shard *, uint64_t, uint64_t);
+  void modify(vase::Shard *, uint64_t, uint64_t);
+
+  void begin_edit();
+  void erase(uint64_t start, uint64_t count);
+  void insert(uint64_t start, uint64_t count);
+  void end_edit(vase::Shard *vase);
+  void mark_dirty(uint64_t start, uint64_t end);
+
+  uint64_t next_closing(uint64_t line);
+  uint64_t prev_opening(uint64_t line);
+
+  std::pair<ParseState *, ParseState *> split_tree(ParseState *node, uint64_t line);
+  ParseState *join_tree(ParseState *a, ParseState *b);
+
+  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::Shard *);
+    ~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::Shard *, uint64_t);
+};
+} // namespace bed::internal::syntax

include/internal/syntax/ruby/decl.h

@@ -0,0 +1,58 @@
+#pragma once
+
+#include "../decl.h"
+#include "pch.h"
+#include "tries.h"
+
+namespace bed::internal::syntax::ruby {
+struct alignas(2) RubyState {
+  struct RubyInternalState {
+    uint16_t brace_level;
+    uint16_t lit_brace_level;
+    enum : uint8_t {
+      NONE,
+      STRING,
+      REGEXP,
+      HEREDOC,
+      COMMENT,
+      END
+    } state;
+    static constexpr uint8_t NAME_MASK = 0b00000011;
+    enum : uint8_t {
+      NONE_NAME = 0b00,
+      CLASS_NAME = 0b01,
+      DEF_NAME = 0b10,
+      MODULE_NAME = 0b11
+    };
+    static constexpr uint8_t NEWLINE = 1 << 5;
+    static constexpr uint8_t ALLOW_INTERPOLATION = 1 << 6;
+    static constexpr uint8_t EXPECTING_EXPRESSION = 1 << 7;
+    uint8_t flags = 0;
+    char delim_start;
+    char delim_end;
+  };
+
+  struct Heredocs {
+    // header masks
+    static constexpr const uint8_t ALLOW_INDENTATION = 0b10000000;
+    static constexpr const uint8_t ALLOW_INTERPOLATION = 0b01000000;
+    static constexpr const uint8_t LEN_MASK = 0b00111111;
+    // the rest will be len number of bytes with the actual name.
+  };
+
+  uint8_t top;
+  uint8_t docs;
+  // the stack (RubyInternalState * top)
+  // the docs queue (docs)
+
+  inline RubyInternalState *stack() {
+    return (RubyInternalState *)(this + 1);
+  }
+
+  inline uint8_t *heredocs() {
+    return (uint8_t *)(stack() + top);
+  }
+};
+
+Language lang_ruby();
+} // namespace bed::internal::syntax::ruby

include/internal/syntax/ruby/parser.h

@@ -0,0 +1,109 @@
+#pragma once
+
+#include "decl.h"
+#include "pch.h"
+
+namespace bed::internal::syntax::ruby {
+struct RubyParser {
+  void **v_state;
+  RubyState *state;
+  std::string_view line;
+  uint32_t i = 0;
+  bool heredoc_start_line = false;
+  bool ending = true;
+  bool op_last = false;
+  bool set_op_last = false;
+
+  RubyParser(void **v_state, std::string_view line)
+      : v_state(v_state), state((RubyState *)*v_state), line(line) {}
+
+  uint32_t len() const {
+    return line.size();
+  }
+
+  RubyState::RubyInternalState &current() {
+    return state->stack()[state->top - 1];
+  }
+
+  char peek(int32_t offset = 0) {
+    uint32_t pos = i + offset;
+    return pos < line.size() ? line[pos] : '\0';
+  }
+
+  std::string_view peek_str(uint32_t len) {
+    return line.substr(i, len);
+  }
+
+  void advance() {
+    ++i;
+  }
+
+  void advance(uint32_t n) {
+    i += n;
+  }
+
+  void push_state() {
+    state->top++;
+    *v_state = (RubyState *)realloc(
+      *v_state,
+      sizeof(RubyState)
+        + sizeof(RubyState::RubyInternalState) * state->top
+        + state->docs
+    );
+    state = (RubyState *)*v_state;
+    memmove(
+      state->heredocs(),
+      state->stack() + state->top - 1,
+      state->docs
+    );
+    current() = {
+      .brace_level = 1,
+      .lit_brace_level = 0,
+      .state = RubyState::RubyInternalState::NONE,
+      .flags = RubyState::RubyInternalState::EXPECTING_EXPRESSION | RubyState::RubyInternalState::NEWLINE,
+      .delim_start = '\0',
+      .delim_end = '\0'
+    };
+  }
+
+  void pop_state() {
+    state->top--;
+    memmove(
+      state->heredocs(),
+      state->stack() + state->top + 1,
+      state->docs
+    );
+  }
+
+  void enqueue_doc(uint8_t header, std::string_view name) {
+    uint32_t bytes = 1 + name.size();
+    uint32_t old_docs = state->docs;
+    state->docs += bytes;
+    *v_state = (RubyState *)realloc(
+      *v_state,
+      sizeof(RubyState)
+        + sizeof(RubyState::RubyInternalState) * state->top
+        + state->docs
+    );
+    state = (RubyState *)*v_state;
+    uint8_t *heredocs = state->heredocs();
+    heredocs[old_docs] = header;
+    memcpy(heredocs + old_docs + 1, name.data(), name.size());
+  }
+
+  bool dequeue_doc(uint8_t heredoc_len) {
+    uint32_t bytes = heredoc_len + 1;
+    uint8_t *heredocs = state->heredocs();
+    if (state->docs -= bytes)
+      memmove(heredocs, heredocs + bytes, state->docs);
+    else
+      return false;
+    return true;
+  }
+};
+
+void ruby_parse(
+  void **v_state, std::string_view line, bool first_line,
+  std::vector<Token> *tokens, std::vector<ParseEvent> *events
+);
+} // namespace bed::internal::syntax::ruby

include/internal/syntax/ruby/tries.h

@@ -0,0 +1,350 @@
+#pragma once
+
+#include "internal/trie/trie.h"
+#include "pch.h"
+
+namespace bed::internal::syntax::ruby {
+const static std::vector<std::string> types = {
+  "BasicObject",
+  "Object",
+  "NilClass",
+  "TrueClass",
+  "FalseClass",
+  "Integer",
+  "Fixnum",
+  "Bignum",
+  "Float",
+  "Rational",
+  "Complex",
+  "Numeric",
+  "String",
+  "Symbol",
+  "Array",
+  "Hash",
+  "Range",
+  "Regexp",
+  "Struct",
+  "Enumarator",
+  "Enumerable",
+  "Time",
+  "Date",
+  "IO",
+  "File",
+  "Dir",
+  "Thread",
+  "Proc",
+  "Method",
+  "Module",
+  "Class",
+  "Mutex",
+  "ConditionVariable",
+  "MatchData",
+  "Encoding",
+  "Fiber",
+};
+
+const static std::vector<std::string> builtins = {
+  "ARGF",
+  "ARGV",
+  "ENV",
+  "STDIN",
+  "STDOUT",
+  "STDERR",
+  "DATA",
+  "TOPLEVEL_BINDING",
+  "RUBY_PLATFORM",
+  "RUBY_VERSION",
+  "RUBY_RELEASE_DATE",
+  "RUBY_PATCHLEVEL",
+  "RUBY_ENGINE",
+  "__LINE__",
+  "__FILE__",
+  "__ENCODING__",
+  "__dir__",
+  "__callee__",
+  "__method__",
+  "__id__",
+  "__send__",
+};
+
+const static std::vector<std::string> methods = {
+  "abort",
+  "at_exit",
+  "binding",
+  "block_given?",
+  "caller",
+  "catch",
+  "chomp",
+  "chomp!",
+  "chop",
+  "chop!",
+  "eval",
+  "exec",
+  "exit",
+  "exit!",
+  "fail",
+  "fork",
+  "format",
+  "gets",
+  "global_variables",
+  "gsub",
+  "gsub!",
+  "iterator?",
+  "lambda",
+  "load",
+  "loop",
+  "open",
+  "print",
+  "printf",
+  "proc",
+  "putc",
+  "puts",
+  "raise",
+  "rand",
+  "readline",
+  "readlines",
+  "require",
+  "require_relative",
+  "select",
+  "sleep",
+  "spawn",
+  "split",
+  "sprintf",
+  "srand",
+  "sub",
+  "sub!",
+  "syscall",
+  "system",
+  "test",
+  "throw",
+  "trace_var",
+  "trap",
+  "untrace_var",
+  "attr",
+  "attr_reader",
+  "attr_writer",
+  "attr_accessor",
+  "class_variable_get",
+  "class_variable_set",
+  "define_method",
+  "instance_variable_get",
+  "instance_variable_set",
+  "private",
+  "protected",
+  "public",
+  "public_class_method",
+  "module_function",
+  "remove_method",
+  "undef_method",
+  "method",
+  "methods",
+  "singleton_methods",
+  "private_methods",
+  "protected_methods",
+  "public_methods",
+  "send",
+  "extend",
+  "include",
+  "prepend",
+  "clone",
+  "dup",
+  "freeze",
+  "taint",
+  "untaint",
+  "trust",
+  "untrust",
+  "untaint?",
+  "trust?",
+  "each",
+  "each_with_index",
+  "each_with_object",
+  "map",
+  "collect",
+  "select",
+  "reject",
+  "reduce",
+  "inject",
+  "find",
+  "detect",
+  "all?",
+  "any?",
+  "none?",
+  "one?",
+  "count",
+  "cycle",
+  "drop",
+  "drop_while",
+  "take",
+  "take_while",
+  "chunk",
+  "chunk_while",
+  "group_by",
+  "partition",
+  "slice_before",
+  "slice_after",
+  "nil?",
+  "is_a?",
+  "kind_of?",
+  "instance_of?",
+  "respond_to?",
+  "equal?",
+  "object_id",
+  "singleton_class",
+  "clone",
+  "freeze",
+  "tap",
+  "then",
+};
+
+const static std::vector<std::string> errors = {
+  "Error",
+  "Exception",
+  "SignalException",
+  "Interrupt",
+  "StopIteration",
+  "Errno",
+  "SystemExit",
+  "fatal",
+};
+
+const static std::vector<std::string> base_keywords = {
+  "else",
+  "rescue",
+  "ensure",
+};
+
+const static std::vector<std::string> expecting_keywords = {
+  "when",
+  "elsif",
+};
+
+const static std::vector<std::string> expecting_end_keywords = {
+  "case",
+  "for",
+};
+
+const static std::vector<std::string> conditional_keywords = {
+  "if",
+  "unless",
+  "while",
+  "until",
+};
+
+const static std::vector<std::string> end_keywords = {
+  "begin",
+  "do",
+};
+
+const static std::vector<std::string> operator_keywords = {
+  "alias",
+  "BEGIN",
+  "break",
+  "catch",
+  "defined?",
+  "in",
+  "next",
+  "redo",
+  "rescue",
+  "retry",
+  "self",
+  "nil",
+  "undef",
+};
+
+const static std::vector<std::string> expecting_operators = {
+  "super",
+  "and",
+  "return",
+  "not",
+  "yield",
+  "or",
+};
+
+const static std::vector<std::string> operators = {
+  "+",
+  "-",
+  "*",
+  "/",
+  "%",
+  "**",
+  "==",
+  "!=",
+  "===",
+  "<=>",
+  ">",
+  ">=",
+  "<",
+  "<=",
+  "&&",
+  "||",
+  "!",
+  "&",
+  "|",
+  "^",
+  "~",
+  "<<",
+  ">>",
+  "=",
+  "+=",
+  "-=",
+  "*=",
+  "/=",
+  "%=",
+  "**=",
+  "&=",
+  "|=",
+  "^=",
+  "<<=",
+  ">>=",
+  "..",
+  "...",
+  "===",
+  "=",
+  "=>",
+  "&",
+  "`",
+  "->",
+  "=~",
+};
+
+struct RubyTries {
+  trie::Trie<void> base_keywords_trie;
+  trie::Trie<void> expecting_keywords_trie;
+  trie::Trie<void> operator_keywords_trie;
+  trie::Trie<void> expecting_operators_trie;
+  trie::Trie<void> operator_trie;
+  trie::Trie<void> types_trie;
+  trie::Trie<void> builtins_trie;
+  trie::Trie<void> methods_trie;
+  trie::Trie<void> errors_trie;
+  trie::Trie<void> expecting_end_keywords_trie;
+  trie::Trie<void> conditional_keywords_trie;
+  trie::Trie<void> end_keywords_trie;
+  RubyTries() {
+    for (auto &keyword : base_keywords)
+      base_keywords_trie.insert(keyword);
+    for (auto &keyword : expecting_keywords)
+      expecting_keywords_trie.insert(keyword);
+    for (auto &keyword : operator_keywords)
+      operator_keywords_trie.insert(keyword);
+    for (auto &keyword : expecting_operators)
+      expecting_operators_trie.insert(keyword);
+    for (auto &keyword : operators)
+      operator_trie.insert(keyword);
+    for (auto &keyword : types)
+      types_trie.insert(keyword);
+    for (auto &keyword : builtins)
+      builtins_trie.insert(keyword);
+    for (auto &keyword : methods)
+      methods_trie.insert(keyword);
+    for (auto &keyword : errors)
+      errors_trie.insert(keyword);
+    for (auto &keyword : expecting_end_keywords)
+      expecting_end_keywords_trie.insert(keyword);
+    for (auto &keyword : conditional_keywords)
+      conditional_keywords_trie.insert(keyword);
+    for (auto &keyword : end_keywords)
+      end_keywords_trie.insert(keyword);
+  }
+};
+} // namespace bed::internal::syntax::ruby

include/internal/theme/theme.h

@@ -0,0 +1,18 @@
+#pragma once
+
+#include "definitions.h"
+#include "internal/syntax/parser.h"
+#include "pch.h"
+
+namespace bed::internal::theme {
+struct Theme {
+  std::array<Highlight, internal::syntax::Token::Count> hl;
+
+  Theme();
+
+  Highlight get(internal::syntax::Token token) const;
+
+  static Theme default_theme();
+  static Theme from_name(std::string_view name);
+};
+} // namespace bed::internal::theme

include/internal/trie/trie.h

@@ -0,0 +1,293 @@
+#pragma once
+
+#include "pch.h"
+
+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;
+    std::optional<V> value{};
+    std::vector<Node *> children;
+    Node(std::string e = {}) : edge(std::move(e)) {}
+    ~Node() {
+      for (auto *c : children)
+        delete c;
+    };
+  } root;
+
+  bool case_sensitive;
+
+  Trie(bool cs = true) : case_sensitive(cs) {}
+
+  void insert(std::string_view key)
+    requires std::is_void_v<T>
+  {
+    _insert(key, std::monostate{});
+  }
+
+  void insert(std::string_view key, V el)
+    requires(!std::is_void_v<T>)
+  {
+    _insert(key, std::move(el));
+  }
+
+  void _insert(std::string_view key, V &&el) {
+    Node *current = &root;
+    uint64_t pos = 0;
+    while (pos < key.size()) {
+      Node *child = find_child(*current, key[pos]);
+      if (!child) {
+        auto *node = new Node(std::string(key.substr(pos)));
+        node->value = std::move(el);
+        current->children.push_back(node);
+        return;
+      }
+      const auto common = common_prefix(child->edge, key.substr(pos));
+      if (common == child->edge.size()) {
+        pos += common;
+        current = child;
+        continue;
+      }
+      auto *split = new Node(child->edge.substr(0, common));
+      child->edge.erase(0, common);
+      split->children.push_back(child);
+      current->children.erase(
+        std::find(current->children.begin(), current->children.end(), child)
+      );
+      current->children.push_back(split);
+      pos += common;
+      if (pos == key.size()) {
+        split->value = std::move(el);
+        return;
+      }
+      auto *node = new Node(std::string(key.substr(pos)));
+      node->value = std::move(el);
+      split->children.push_back(node);
+      return;
+    }
+    current->value = std::move(el);
+  }
+
+  void remove(std::string_view key) {
+    _remove(root, key, 0);
+  }
+
+  bool _remove(Node &node, std::string_view key, uint64_t pos) {
+    if (pos == key.size()) {
+      if (!node.value)
+        return false;
+      node.value.reset();
+      return true;
+    }
+    Node *child = find_child(node, key[pos]);
+    if (!child)
+      return false;
+    const auto remaining = key.substr(pos);
+    const auto common = common_prefix(child->edge, remaining);
+    if (common != child->edge.size())
+      return false;
+    const auto child_pos = pos + common;
+    if (!_remove(*child, key, child_pos))
+      return false;
+    if (!child->value && child->children.empty()) {
+      auto it = std::find(
+        node.children.begin(),
+        node.children.end(),
+        child
+      );
+      node.children.erase(it);
+      delete child;
+      return true;
+    }
+    if (!child->value && child->children.size() == 1) {
+      Node *grandchild = child->children.front();
+      child->edge += grandchild->edge;
+      child->value = std::move(grandchild->value);
+      child->children = std::move(grandchild->children);
+      grandchild->children.clear();
+      delete grandchild;
+    }
+    return true;
+  }
+
+  std::vector<SearchResult> search(std::string_view prefix) {
+    std::vector<SearchResult> result;
+    Node *current = &root;
+    std::string key;
+    uint64_t pos = 0;
+    while (pos < prefix.size()) {
+      Node *child = find_child(*current, prefix[pos]);
+      if (!child)
+        return result;
+      const auto remaining = prefix.substr(pos);
+      const auto common = common_prefix(child->edge, remaining);
+      if (common == 0)
+        return result;
+      if (common < child->edge.size()) {
+        if (common == remaining.size()) {
+          key += child->edge;
+          collect(*child, key, result);
+          return result;
+        }
+        return result;
+      }
+      key += child->edge;
+      pos += common;
+      current = child;
+    }
+    collect(*current, key, result);
+    return result;
+  }
+
+  static void collect(
+    Node &node,
+    std::string &key,
+    std::vector<SearchResult> &result
+  ) {
+    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;
+      collect(*child, key, result);
+      key.resize(old_size);
+    }
+  }
+
+  uint64_t longest_match(std::string_view input) const {
+    const Node *current = &root;
+    uint64_t pos = 0;
+    uint64_t longest = 0;
+    if (current->value)
+      longest = 0;
+    while (pos < input.size()) {
+      const Node *child = find_child(*current, input[pos]);
+      if (!child)
+        break;
+      const auto remaining = input.substr(pos);
+      const auto common = common_prefix(child->edge, remaining);
+      if (common != child->edge.size())
+        break;
+      pos += common;
+      current = child;
+      if (current->value)
+        longest = pos;
+    }
+    return longest;
+  }
+
+  bool matches(std::string_view key) const
+    requires(std::is_void_v<T>)
+  {
+    Node *current = &root;
+    uint64_t pos = 0;
+    while (pos < key.size()) {
+      Node *child = find_child(*current, key[pos]);
+      if (!child)
+        return false;
+      const auto remaining = key.substr(pos);
+      const auto common = common_prefix(child->edge, remaining);
+      if (common != child->edge.size())
+        return false;
+      pos += common;
+      current = child;
+    }
+    return current->value.has_value();
+  }
+
+  std::optional<V> get(std::string_view key) const
+    requires(!std::is_void_v<T>)
+  {
+    const Node *current = &root;
+    uint64_t pos = 0;
+    while (pos < key.size()) {
+      const Node *child = find_child(*current, key[pos]);
+      if (!child)
+        return std::nullopt;
+      const auto remaining = key.substr(pos);
+      const auto common = common_prefix(child->edge, remaining);
+      if (common != child->edge.size())
+        return std::nullopt;
+      pos += common;
+      current = child;
+    }
+    if (!current->value)
+      return std::nullopt;
+    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;
+    return std::tolower((unsigned char)a) == std::tolower((unsigned char)b);
+  }
+
+  uint64_t common_prefix(
+    std::string_view a,
+    std::string_view b
+  ) const {
+    const auto n = std::min(a.size(), b.size());
+    uint64_t i = 0;
+    while (i < n && equal_char(a[i], b[i]))
+      ++i;
+    return i;
+  }
+
+  Node *find_child(const Node &node, char first) const {
+    for (auto *child : node.children)
+      if (equal_char(child->edge.front(), first))
+        return child;
+    return nullptr;
+  }
+};
+} // namespace bed::internal::trie

include/internal/ui/command.h

@@ -0,0 +1,46 @@
+#pragma once
+
+#include "definitions.h"
+#include "pch.h"
+
+namespace bed::internal::ui {
+struct Token {
+  enum struct Type : uint8_t {
+    TempCurrent,      // @
+    AddressSeperator, // ; ,
+    Address,          // . $ % [ ] ^ ~
+    Offset,           // +N -N + -
+    AddressRegex,     // /re/ ?re?
+    AddressSymbol,    // >s> <s< <s>
+    Number,           // 10
+    Mark,             // 'm
+    RubyFunction,     // (func:arg)
+    RubyArg,
+    Function,
+    Any,
+    Shell,
+    Ruby,
+    File,
+    Regex,
+    Replacement,
+    Suffix
+  } type;
+  uint16_t start;
+  uint16_t end;
+};
+
+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();
+  void redraw();
+};
+} // namespace bed::internal::ui

include/internal/ui/text_mode.h

@@ -0,0 +1,21 @@
+#pragma once
+
+#include "definitions.h"
+#include "pch.h"
+
+namespace bed::internal::ui {
+struct TextMode {
+  std::string cmd;
+  uint16_t cursor;
+  uint16_t start;
+  uint16_t height;
+  uint16_t term_height;
+  uint16_t term_width;
+  BEd &bed;
+
+  TextMode(BEd &);
+  std::pair<vase::Shard *, bool> run();
+  void grow(size_t required_height);
+  void redraw();
+};
+} // namespace bed::internal::ui

include/internal/vase/constants.h

@@ -0,0 +1,7 @@
+#pragma once
+
+#include "pch.h"
+
+namespace bed::internal::vase {
+constexpr uint64_t PETAL_SIZE_MAX = 32 * 1024;
+}

include/internal/vase/iterators/line.h

@@ -0,0 +1,73 @@
+#pragma once
+
+#include "../shard.h"
+#include "pch.h"
+#include "petal.h"
+
+namespace bed::internal::vase {
+struct LineIterator {
+  PetalIterator it;
+  const char *chunk;
+  uint64_t len;
+  Direction dir;
+  uint64_t current_offset = 0;
+  uint64_t last_line_offset = 0;
+
+  LineIterator(Shard *root, uint64_t line_num, Direction dir);
+  ~LineIterator() = default;
+
+  bool next(std::string *line);
+  uint64_t byte_offset();
+};
+
+struct Iterator {
+  Shard *root;
+  std::string line;
+
+  Iterator(Shard *root, uint64_t line_num, Direction dir)
+      : root(root), it(root, line_num, dir) {
+    Shard::retain(root);
+  }
+
+  ~Iterator() {
+    Shard::release(root);
+  }
+
+  Iterator(const Iterator &other)
+      : root(other.root), it(other.it) {
+    Shard::retain(root);
+  }
+
+  Iterator &operator=(const Iterator &other) {
+    if (this != &other) {
+      Shard::retain(other.root);
+      Shard::release(root);
+      root = other.root;
+      it = other.it;
+    }
+    return *this;
+  }
+
+  Iterator(Iterator &&other) noexcept
+      : root(other.root), it(std::move(other.it)) {
+    other.root = nullptr;
+  }
+
+  Iterator &operator=(Iterator &&other) noexcept {
+    if (this != &other) {
+      Shard::release(root);
+      root = other.root;
+      it = std::move(other.it);
+      other.root = nullptr;
+    }
+    return *this;
+  }
+
+  bool next() {
+    return it.next(&line);
+  }
+
+private:
+  LineIterator it;
+};
+} // namespace bed::internal::vase

include/internal/vase/iterators/petal.h

@@ -0,0 +1,29 @@
+#pragma once
+
+#include "../shard.h"
+#include "internal/generic.h"
+#include "pch.h"
+
+namespace bed::internal::vase {
+struct PetalIterator {
+  Direction dir;
+  Shard *root = nullptr;
+  std::vector<Shard *> stack;
+  Petal *petal = nullptr;
+  uint64_t global_offset = 0;
+  uint64_t last_offset = 0;
+  uint64_t petal_offset = 0;
+  uint64_t global_line = 0;
+
+  PetalIterator(Shard *r, Direction dir);
+  ~PetalIterator() = default;
+
+  void seek_offset(uint64_t offset);
+  void seek_line(uint64_t offset);
+  bool next(const char **data, uint64_t *out_len);
+  uint64_t byte_offset();
+
+private:
+  Petal *_next(uint64_t *offset);
+};
+} // namespace bed::internal::vase

include/internal/vase/shard.h

@@ -0,0 +1,66 @@
+#pragma once
+
+#include "constants.h"
+#include "pch.h"
+#include "storage/original.h"
+#include "storage/storage.h"
+
+namespace bed::internal::vase {
+struct Shard {
+  enum struct Kind : uint8_t {
+    Branch,
+    Petal
+  } kind;
+
+  uint8_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)
+      : kind(kind), height(height), refs(1), length(length), lines(lines) {};
+
+  static void retain(Shard *n);
+  static void release(Shard *n);
+
+  static Shard *from_file(const std::filesystem::path &path, bool posix_ending);
+  static Shard *from_string(const char *data, uint64_t len, bool posix_ending);
+  static Shard *from_command(const char *cmd, bool posix_ending);
+
+  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);
+};
+
+struct Branch : Shard {
+  Shard *left;
+  Shard *right;
+
+  Branch(Shard *l, Shard *r)
+      : Shard(
+          Kind::Branch,
+          l->length + r->length,
+          l->lines + r->lines,
+          1 + std::max(l->height, r->height)
+        ),
+        left(l), right(r) {
+    retain(left);
+    retain(right);
+  };
+};
+
+struct Petal : Shard {
+  Storage *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->retain();
+  };
+};
+
+} // namespace bed::internal::vase

include/internal/vase/storage/append.h

@@ -0,0 +1,28 @@
+#pragma once
+
+#include "../constants.h"
+#include "pch.h"
+#include "storage.h"
+
+namespace bed::internal::vase {
+struct AppendStorage : Storage {
+  char *buf = nullptr;
+  uint64_t allocated_capacity = 0;
+  uint64_t current_size = 0;
+  int fd = -1;
+
+  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);
+};
+} // namespace bed::internal::vase

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

@@ -0,0 +1,13 @@
+#pragma once
+
+#include "pch.h"
+
+namespace bed::internal::vase {
+struct Storage {
+  virtual const char *read(uint64_t pos) = 0;
+  virtual uint64_t length() = 0;
+  virtual ~Storage() = default;
+  virtual void retain() = 0;
+  virtual void release() = 0;
+};
+} // namespace bed::internal::vase

include/internal/vase/vase.h

@@ -0,0 +1,81 @@
+#pragma once
+
+#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 {
+  uint64_t row;
+  uint64_t col;
+};
+
+struct Range {
+  Point start;
+  Point end;
+};
+
+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 point_of(Shard *root, uint64_t offset);
+
+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 *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/io/file.h

@@ -1,40 +0,0 @@
-#pragma once
-
-#include "pch.h"
-
-inline int read_file(const char *path, char **text, uint32_t *len) {
-  FILE *f = fopen(path, "rb");
-  if (!f)
-    return 0;
-
-  fseek(f, 0, SEEK_END);
-  long size = ftell(f);
-  fseek(f, 0, SEEK_SET);
-
-  if (size < 0 || size > UINT32_MAX) {
-    fclose(f);
-    return 0;
-  }
-
-  *len = (uint32_t)size;
-
-  *text = (char *)malloc(*len + 1);
-  if (!*text) {
-    fclose(f);
-    return 0;
-  }
-
-  size_t read = fread(*text, 1, *len, f);
-  fclose(f);
-
-  if (read != *len) {
-    free(*text);
-    *text = NULL;
-    *len = 0;
-    return 0;
-  }
-
-  (*text)[*len] = '\0'; // handy if treating it as a C string
-
-  return 1;
-}

include/pch.h

@@ -1,7 +1,6 @@
 #pragma once
 
 #define PCRE2_CODE_UNIT_WIDTH 8
-#define PCRE_WORKSPACE_SIZE 512
 
 #include <mruby.h>
 #include <mruby/array.h>
@@ -15,6 +14,7 @@ extern "C" {
 #include <unicode_width.h>
 }
 #include <algorithm>
+#include <assert.h>
 #include <atomic>
 #include <cctype>
 #include <chrono>
@@ -29,21 +29,23 @@ extern "C" {
 #include <filesystem>
 #include <fstream>
 #include <functional>
-#include <immintrin.h>
-#include <iostream>
 #include <limits.h>
 #include <map>
 #include <mutex>
 #include <optional>
 #include <poll.h>
+#include <pty.h>
 #include <queue>
 #include <set>
 #include <shared_mutex>
 #include <signal.h>
 #include <stack>
+#include <stdexcept>
 #include <string.h>
 #include <string>
 #include <sys/ioctl.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
 #include <sys/types.h>
 #include <sys/wait.h>
 #include <termios.h>
@@ -51,6 +53,5 @@ extern "C" {
 #include <unistd.h>
 #include <unordered_map>
 #include <unordered_set>
+#include <variant>
 #include <vector>
-
-using namespace std::chrono_literals;

include/vase/buffer/append.h

@@ -1,37 +0,0 @@
-#pragma once
-
-#include "buffer.h"
-#include "pch.h"
-
-struct AppendBuffer : Buffer {
-  static constexpr uint32_t CHUNK_SIZE = 1 << 16;
-
-  using TChunk = char[CHUNK_SIZE];
-  std::vector<TChunk *> buf;
-  TChunk *t_current;
-  uint32_t current_offset{0};
-  uint32_t t_offset{0};
-
-  using LChunk = uint32_t[CHUNK_SIZE];
-  std::vector<LChunk *> newlines;
-  LChunk *l_current;
-  uint32_t l_offset{0};
-
-  AppendBuffer();
-
-  ~AppendBuffer();
-
-  inline uint32_t key(char c);
-  uint32_t append(const char *text, uint32_t length, uint32_t *line_count);
-
-  const char *read(uint32_t pos, uint32_t *out_len);
-  uint32_t count_lines(uint32_t pos, uint32_t length);
-
-private:
-  inline void new_text_chunk();
-  inline void new_line_chunk();
-
-  inline uint32_t find_newline(uint32_t target, uint32_t low, uint32_t high);
-
-  inline uint32_t _append(const char *text, uint32_t length);
-};

include/vase/buffer/buffer.h

@@ -1,10 +0,0 @@
-#pragma once
-
-#include "pch.h"
-
-struct Buffer {
-  virtual const char *read(uint32_t pos, uint32_t *out_len) = 0;
-  virtual uint32_t count_lines(uint32_t pos, uint32_t length) = 0;
-
-  virtual ~Buffer() = default;
-};

include/vase/buffer/original.h

@@ -1,30 +0,0 @@
-#pragma once
-
-#include "buffer.h"
-#include "pch.h"
-
-struct OriginalBuffer : Buffer {
-  char *buf;
-  uint32_t length;
-  std::vector<uint32_t> newlines;
-
-  // TODO: replace with file io or even lazy loaded file io for large files/logs etc. later.
-  OriginalBuffer(char *buf, uint32_t length) : buf(buf), length(length) {
-    const char *p = buf;
-    const char *end = buf + length;
-    while (p < end) {
-      p = (const char *)memchr(p, '\n', end - p);
-      if (!p)
-        break;
-      newlines.push_back(uint32_t(p - buf));
-      p++;
-    }
-  }
-
-  ~OriginalBuffer() {
-    free(buf);
-  }
-
-  const char *read(uint32_t pos, uint32_t *out_len);
-  uint32_t count_lines(uint32_t pos, uint32_t length);
-};

include/vase/shard.h

@@ -1,72 +0,0 @@
-#pragma once
-
-#include "buffer/buffer.h"
-#include "pch.h"
-
-struct Shard {
-  enum struct ShardKind {
-    Branch,
-    Petal
-  } kind;
-
-  uint32_t length;
-  uint32_t lines;
-
-  std::atomic_uint32_t refs;
-
-  Shard(ShardKind kind, uint32_t length, uint32_t lines)
-      : kind(kind), length(length), lines(lines), refs(0) {};
-};
-
-struct ShardPtr {
-  Shard *ptr;
-
-  ShardPtr(const ShardPtr &other) : ptr(other.ptr) {
-    if (ptr)
-      ptr->refs++;
-  }
-
-  ShardPtr &operator=(const ShardPtr &other) {
-    if (ptr == other.ptr)
-      return *this;
-    if (ptr && --ptr->refs == 0)
-      delete ptr;
-    ptr = other.ptr;
-    if (ptr)
-      ptr->refs++;
-    return *this;
-  }
-
-  ShardPtr(Shard *p = nullptr) : ptr(p) {
-    if (ptr)
-      ptr->refs++;
-  }
-
-  ~ShardPtr() {
-    if (ptr && --ptr->refs == 0)
-      delete ptr;
-  }
-};
-
-struct Branch : Shard {
-  ShardPtr left;
-  ShardPtr right;
-
-  Branch(Shard *l, Shard *r)
-      : Shard(ShardKind::Branch, l->length + r->length, l->lines + r->lines),
-        left(l), right(r) {};
-};
-
-struct Petal : Shard {
-  Buffer *source;
-
-  uint32_t pos;
-
-  Petal(uint32_t length, uint32_t lines, Buffer *source, uint32_t pos)
-      : Shard(ShardKind::Petal, length, lines), source(source), pos(pos) {};
-};
-
-std::pair<ShardPtr, ShardPtr> split_shard(Shard *n, uint32_t offset);
-ShardPtr concat_shard(ShardPtr left, ShardPtr right);
-
-void print_shard(const Shard *shard, int depth = 0);

include/vase/vase.h

@@ -1,42 +0,0 @@
-#pragma once
-
-#include "buffer/append.h"
-#include "buffer/original.h"
-#include "pch.h"
-#include "shard.h"
-
-struct Vase {
-  OriginalBuffer original;
-  AppendBuffer append;
-
-  std::vector<ShardPtr> undo;
-  uint8_t top; // of the undo stack.
-  uint8_t max; // for redo when no edits have been done after some undo.
-
-  ShardPtr root;
-
-  Vase(char *data, uint32_t length)
-      : original(data, length),
-        append() {
-    root = new Petal(
-      length,
-      original.newlines.size(),
-      &original,
-      0
-    );
-  }
-
-  void insert(uint32_t offset, const char *data, uint32_t len) {
-    uint32_t lines = 0;
-    uint32_t pos = append.append(data, len, &lines);
-
-    ShardPtr inserted = new Petal(len, lines, &append, pos);
-
-    auto [left, right] = split_shard(root.ptr, offset);
-
-    root = concat_shard(
-      concat_shard(left, inserted),
-      right
-    );
-  }
-};

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

samples/sample.rb

@@ -0,0 +1,343 @@
+#!/usr/bin/env ruby
+
+# Unicode / Emoji / CJK stress-test Ruby file
+# Purpose: Test syntax highlighting + width calculation in your editor
+# ---------------------------------------------------------------
+
+# Mixed-width CJKssssssssssssssss LoadErssssssssssssssssssssssss
+cjk_samples = [
+  '漢字テスト',
+  '測試中文字串',
+  '한국어 테스트',
+  'ひらがなカタカナ混合'
+]
+
+# a hex color: #FFFFFF shouldn't hl here: hsl(147rad, 50%, 47%)  as it is not css-style file
+
+0x603010 # another hex color
+
+# Ruby regex with unicode
+$unicode_regex_multiline = /[一-龯ぁ-ん12288ァ
+\-ヶー
+s wow
+
+々〆〤]/
+
+UNICORE = /
+    s
+    {#{ss}}
+    \C-s\u{10}
+  /
+
+UNINITCORE = %(
+
+    {{#{}}}
+
+    test = "A:\x41 B:\101 C:\u0043 D:\u{44 45} NUL:\0 DEL:\c? CTRL_A:\cA META_X:\M-x CTRL_META_X:\C-\M-x MIX:\C-\M-z N:\N{UNICODE NAME}"
+
+  )
+
+# Unicode identifiers (valid in Ruby)
+变量 = 0x5_4eddaee
+π = 0.314_159e+2, ?\u0234, "\,", ?\x0A, 's', true, false, 0
+挨拶 = -> { "こんに \n ちは" }
+
+arr = []
+not_arr = NotABuiltin.new
+
+raise NameError or SystemExit or CustomError or Errno or ErrorNotAtAll
+
+# Method using unicode variable names
+def math_test
+  puts "π * 2 = #{π * 2}"
+end
+
+# Iterate through CJK samples
+cjk_samples.each_with_index do |str, idx:|
+  puts %! CJK[#{idx}] => #{str} (len=#{str.length})\! !
+  symbol = :"
+  a
+  "
+  sym2 = :hello
+end
+
+# Test emoji width behaviors
+puts "Emoji count: #{emojis.length}"
+
+# Multi-line string with unicode
+multi = <<~BASH
+    # Function recursion demo
+    factorial() {
+      local n="$1"
+      if ((n <= 1)); then
+        echo 1
+      else\ns
+        local prev
+        prev=$(factorial $((n - 1)))
+        echo $((n * prev))
+       before #{ interpol
+                 # {'    '}
+                 # comment should be fine heres s
+                 $a / $-s + 0xFF
+              }s#{' '}
+  x
+      a after
+      fi
+    } #{s}
+    log INFO "factorial(5) = $(factorial 5)"
+BASH
+
+puts multi
+
+
+# Arrays mixing everything
+mixed = [
+  '🐍 Ruby + Python? sacrilege! 🐍',
+  '日本語とEnglishと🔧mix',
+  'Spacing test →→→→→→→',
+  'Zero-width joiner test: 👨‍👩‍👧‍👦 family emoji'
+]
+
+two_docs = <<~DOC1, <<~DOC2
+  stuff for doc2
+  rdvajehvbaejbfh
+DOC1
+  stuff for doc 2 with #{!interpolation} and more
+DOC2
+
+p = 0 << 22 # not a heredoc
+
+mixed.each { |m| puts m }
+
+# Unicode in comments — highlight me!
+# コメント：エディタのハイライトを確認します✨
+# Emojis should not break formatting: 🦀🦊🐱‍👤🤖
+
+# Dummy Ruby logic
+5.times do |i|
+  puts "Loop #{i}: 🌟 #{cjk_samples[i % cjk_samples.size]}"
+end
+
+# String escape sequences + unicode
+escaped = "Line1\nLine2\tTabbed 😀"
+puts escaped
+
+p = 0 << 2
+# Frozen string literal test
+# frozen_string_literal: true
+const_str = '定数文字列🔒'.freeze
+puts const_str
+
+# End marker
+puts '--- END OF UNICODE TEST FILE ---'
+
+# Ruby syntax highlighting test
+
+#   This is a multi-line comment.
+#   It spans multiple lines.
+#   Good for testing highlighting.
+#
+# This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped line test, This is a wrapped linetest,
+#
+
+# Constants
+
+PI = 3.14159
+MAX_ITER = 5
+# Module
+module Utilities
+  def self.random_greeting
+    %w[Hello Hi Hey Hola Bonjour Merhaba].sample
+  end
+
+  def self.factorial(n)
+    return 1 if n <= 1
+
+    n * factorial(n - 1)
+  end
+end
+
+# Class
+class TestObject
+  attr_accessor :name, :value
+
+  def initialize(name, value)
+    @name = name
+    @value = value
+  end
+
+  def display
+    puts "#{@name}: #{@value}"
+  end
+
+  private
+
+  def double_value
+    @value * 2
+  end
+end
+
+# Inheritance
+class SpecialObject < TestObject
+  def triple_value
+    @value * 3
+  end
+end
+
+# Lambda
+adder = ->(x, y) { x + y }
+
+# Array and hash
+numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
+hash = { a: 1, b: 2, c: 3 }
+
+# Iteration
+numbers.each do |n|
+  puts "Number: #{n}"
+end
+
+# Hash iteration
+hash.each do |key, value|
+  puts "#{key} => #{value}"
+end
+
+# Conditional
+numbers.each do |n|
+  if n.even?
+    puts "#{n} is even"
+  else
+    puts "#{n} is odd"
+  end
+end
+
+# Method definition
+def greet_person(name)
+  puts "#{Utilities.random_greeting}, #{name}!"
+  return true if name == 'harry'
+
+  's'
+end
+
+h = a / a
+
+# Calling methods
+greet_person('Alice')
+greet_person('Bob')
+
+# Loops
+i = 0
+while i < 5
+  puts "Loop iteration #{i}"
+  i += 1
+end
+
+for j in 1..3
+  puts "For loop #{j}"
+end
+
+# Begin-rescue-ensure
+begin
+  risky = 10 / 2
+  puts "Risky operation succeeded: #{risky}"
+rescue ZeroDivisionError => e
+  puts "Caught an error: #{e}"
+ensure
+  puts 'This runs no matter what'
+end
+
+# Arrays of objects
+objs = []
+5.times do |k|
+  objs << TestObject.new("Obj#{k}", k)
+end
+
+objs.each(&:display)
+
+# Nested arrays
+nested = [[1, 2], [3, 4], [5, 6]]
+nested.each do |arr|
+  arr.each { |x| print "#{x} " }
+  puts
+end
+
+# Case statement
+numbers.each do |n|
+  case n
+  when 1..3
+    puts "#{n} is small"
+  when 4..7
+    puts "#{n} is medium"
+  else
+    puts "#{n} is large"
+  end
+end
+
+# Using factorial
+(0..5).each do |n|
+  puts "Factorial of #{n} is #{Utilities.factorial(n)}"
+end
+
+# Special objects
+so = SpecialObject.new('Special', 10)
+puts "Double: #{so.double_value}, Triple: #{so.triple_value}"
+
+# String interpolation and formatting
+puts "PI is approximately #{PI.round(2)}"
+
+# Multi-line strings
+multi_line = <<~TEXT
+   k kmW ;
+  This is a multi-line string.
+  It spans multiple lines.
+  Gossn sssmss
+  ddsss
+  od for testing highlighting.
+TEXT
+
+puts multi_line
+
+# Symbols and strings
+sym = :my_symbol == __dir__
+str = 'my string'
+puts "Symbol: #{sym}, String: #{str}"
+
+# Random numbers
+rand_nums = Array.new(5) { rand(100) }
+puts "Random numbers: #{rand_nums.join(', ')}"
+
+# More loops
+rand_nums.each_with_index do |num, idx|
+  puts "Index #{idx} has number #{num}"
+end
+
+# Ternary operator
+rand_nums.each do |num|
+  puts num.even? ? "#{num} is even" : "#{num} is odd"
+end
+
+# Block with yield
+def wrapper
+  puts 'Before block'
+  yield if block_given?
+  puts 'After block'
+end
+
+# ss
+
+wrapper { puts 'Inside block' }
+
+# Sorting
+sorted = rand_nums.sort
+puts "Sorted: #{sorted.join(', ')}"
+
+# Regex
+sample_text = 'The quick brown fox jumps over the lazy dog'
+puts "Match 'fox'?" if sample_text =~ /fox/
+
+# End of test script
+puts 'Ruby syntax highlighting test complete.'
+
+__END__
+
+Anything here should be ignored >><<
+{{{}}}[[[]]](((000)))

src/bed/run.cc

@@ -0,0 +1,213 @@
+#include "bed.h"
+#include "internal/parser/parser.h"
+
+namespace bed {
+BEd::BEd(std::vector<std::string> args, internal::io::IO &io)
+    : theme(internal::theme::Theme::default_theme()), io(io) {
+  internal::functions::Function::register_posix(*this);
+  internal::functions::Function::register_extented(*this);
+  internal::functions::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 (args[i] == "-v" || args[i] == "--verbose") {
+      help_mode = 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;
+  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;
+}
+
+void BEd::run() {
+  while (true) {
+    internal::ui::CommandIO command(*this);
+    auto [cmd, eof] = command.run();
+    try {
+      handle(cmd, eof);
+    } catch (ed_error &e) {
+      io.write_line("?");
+      if (help_mode)
+        io.write_line(e.what());
+      last_help = e.what();
+    }
+  }
+}
+
+void BEd::handle(std::string_view cmd, bool eof) {
+  if (eof) {
+    eof_op.handle(*this, "", nullptr, std::monostate(), nullptr);
+    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;
+  }
+  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();
+    }
+    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();
+    }
+    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 (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::ui::TextMode tm(*this);
+    auto [a, b] = tm.run();
+    if (!b)
+      text = a;
+  }
+  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;
+    }
+  }
+}
+
+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;
+  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/buffer/generic.cc

@@ -0,0 +1,270 @@
+#include "bed.h"
+#include "internal/buffer/buffer.h"
+
+namespace bed::internal::buffer {
+GenericBuffer::~GenericBuffer() {
+  vase::Shard::release(root);
+}
+
+bool GenericBuffer::waste() {
+  return save_path.empty()
+         && root == nullptr;
+}
+
+uint64_t GenericBuffer::lines() {
+  if (root)
+    return root->lines + 1;
+  return 0;
+}
+
+uint64_t GenericBuffer::bytes() {
+  if (root)
+    return root->length + 1;
+  return 0;
+}
+
+void GenericBuffer::load(BEd &ctx, vase::Shard *text) {
+  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;
+  }
+  parser.emplace(root, lines(), syntax::ruby::lang_ruby());
+}
+
+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) {
+  ctx.prev().buffername = name;
+  ctx.prev().start = line + 1;
+  ctx.prev().end = line + text->lines + 1;
+  root = vase::insert(&ctx.append, root, text, line);
+  ctx.marks.insert(name, ctx.prev().start, ctx.prev().end);
+  if (parser)
+    parser->insert(root, ctx.prev().start, ctx.prev().end);
+  state = Modified;
+}
+
+void GenericBuffer::remove(BEd &ctx, uint64_t start_line, uint64_t end_line) {
+  root = vase::erase(root, start_line, end_line);
+  ctx.prev().buffername = name;
+  ctx.prev().start = std::min(start_line, lines());
+  ctx.prev().end = std::min(start_line, lines());
+  ctx.marks.erase(name, start_line, end_line - start_line + 1);
+  if (parser)
+    parser->erase(root, start_line, end_line - start_line + 1);
+  state = Modified;
+}
+
+void GenericBuffer::join(BEd &ctx, uint64_t start_line, uint64_t 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.marks.collapse(name, start_line, end_line - start_line);
+  if (parser)
+    parser->erase(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
+) {
+  ctx.prev().buffername = name;
+  ctx.prev().start = start_line;
+  ctx.prev().end = end_line;
+  if (parser)
+    parser->begin_edit();
+  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 (parser)
+          parser->erase(line, old_lines);
+      }
+      if (new_lines) {
+        ctx.marks.insert(name, line, line + new_lines - 1);
+        if (parser)
+          parser->insert(line, line + new_lines - 1);
+      }
+    }
+  );
+  if (parser)
+    parser->end_edit(root);
+  ctx.prev().buffername = name;
+  state = Modified;
+}
+
+vase::Shard *GenericBuffer::copy(uint64_t start_line, uint64_t end_line) {
+  return vase::copy(root, start_line, end_line);
+}
+
+uint64_t GenericBuffer::find_next(std::string_view pattern, uint64_t start) {
+  return vase::find_next(root, pattern, start);
+}
+
+uint64_t GenericBuffer::find_prev(std::string_view pattern, uint64_t start) {
+  return vase::find_prev(root, pattern, start);
+}
+
+uint64_t GenericBuffer::next_closing(uint64_t start) {
+  if (parser.has_value()) {
+    uint64_t closing = parser->next_closing(start - 1);
+    if (closing == UINT64_MAX)
+      return lines();
+    return closing + 1;
+  } else {
+    start += 10;
+    if (start > lines())
+      return lines();
+    return start;
+  }
+}
+
+uint64_t GenericBuffer::prev_closing(uint64_t start) {
+  if (parser.has_value()) {
+    return parser->prev_opening(start - 1) + 1;
+  } else {
+    if (start > 10)
+      return start - 10;
+    return 0;
+  }
+}
+
+inline void apply(io::IO &io, const Highlight &hl) {
+  io.write("\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;
+  io.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;
+    io.write(std::format("\x1b[48;2;{};{};{}m", br, bg, bb));
+  }
+  if (hl.flags & Highlight::Bold)
+    io.write("\x1b[1m");
+  if (hl.flags & Highlight::Italic)
+    io.write("\x1b[3m");
+  if (hl.flags & Highlight::Underline)
+    io.write("\x1b[4m");
+  if (hl.flags & Highlight::Strikethrough)
+    io.write("\x1b[9m");
+}
+
+inline void reset(io::IO &io) {
+  io.write("\x1b[0m");
+}
+
+void GenericBuffer::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 (parser) {
+    auto it_o = parser->get_hl(root, 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() || end > line.size())
+          break;
+        if (cursor < start)
+          ctx.io.write(line.data() + cursor, start - cursor);
+        const auto highlight = ctx.theme.get(token);
+        apply(ctx.io, highlight);
+        ctx.io.write(line.data() + start, end - start);
+        reset(ctx.io);
+        cursor = end;
+      }
+      if (cursor < line.size())
+        ctx.io.write(line.data() + cursor, line.size() - cursor);
+      ctx.io.write_line("");
+      ++start_line;
+    }
+  } else {
+    vase::Iterator it(root, start_line - 1, Direction::Forward);
+    while (it.next() && start_line++ <= end_line)
+      ctx.io.write_line(it.line);
+  }
+}
+
+void GenericBuffer::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 (parser) {
+    std::optional<syntax::Parser::Iterator> it_o = parser->get_hl(root, start_line - 1);
+    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);
+        const auto highlight = ctx.theme.get(token);
+        apply(ctx.io, highlight);
+        ctx.io.write(line.data() + start, end - start);
+        reset(ctx.io);
+        cursor = end;
+      }
+      if (cursor < line.size())
+        ctx.io.write(line.data() + cursor, line.size() - cursor);
+      ctx.io.write_line("");
+      ++start_line;
+    }
+  } else {
+    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 GenericBuffer::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 +1,185 @@
+#include "bed.h"
+#include "internal/buffer/buffer.h"
+
+namespace bed::internal::buffer {
+ClipBuffer::~ClipBuffer() {}
+
+bool ClipBuffer::waste() {
+  return false;
+}
+
+uint64_t ClipBuffer::lines() {
+  auto s = vase::Shard::from_command("xclip -selection clipboard -o", true);
+  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", true);
+  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->lines + 1;
+  auto s = vase::Shard::from_command("xclip -selection clipboard -o", true);
+  s = vase::insert(&ctx.append, s, text, line);
+  clip_write(s);
+  vase::Shard::release(s);
+  ctx.marks.insert(name, ctx.prev().start, ctx.prev().end);
+}
+
+void ClipBuffer::remove(BEd &ctx, uint64_t start_line, uint64_t end_line) {
+  auto s = vase::Shard::from_command("xclip -selection clipboard -o", true);
+  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::join(BEd &ctx, uint64_t start_line, uint64_t end_line) {
+  auto s = vase::Shard::from_command("xclip -selection clipboard -o", true);
+  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", true);
+  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, line + new_lines - 1);
+    }
+  );
+  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", true);
+  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", true);
+  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", true);
+  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", true);
+  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", true);
+  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", true);
+  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/functions/extended.cc

@@ -0,0 +1,58 @@
+#include "bed.h"
+#include "internal/functions/functions.h"
+#include "internal/functions/suffixes.h"
+
+namespace bed::internal::functions {
+void Function::register_extented(BEd &ctx) {
+  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 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);
+      },
+    }
+  );
+}
+} // namespace bed::internal::functions

src/internal/functions/posix.cc

@@ -0,0 +1,657 @@
+#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 = nullptr,
+      .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);
+        ctx.current() = {ctx.prev().buffername, ctx.prev().end};
+        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 set of lines.",
+      .default_address = ".,.",
+      .accept_zero = false,
+      .pre_text_mode = nullptr,
+      .handle = [](BEd &ctx, const buffer::Address &addr_, vase::Shard *text, const Argument &, std::vector<buffer::Line> *) {
+        auto addr = std::get<buffer::Range>(addr_);
+        ctx.buffer(addr.buffername).remove(ctx, addr.start, addr.end);
+        ctx.buffer(addr.buffername).append(ctx, text, addr.start - 1);
+        ctx.current() = {ctx.prev().buffername, ctx.prev().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 set 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.current() = {addr.buffername, addr.start};
+      }
+    }
+  );
+  ctx.functions.insert(
+    "e",
+    Function{
+      .address_kind = Function::AddressKind::None,
+      .argument_kind = Function::ArgumentKind::File,
+      .input_mode = Function::InputMode::None,
+      .desc = "Try load a file into the current buffer.",
+      .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, true);
+          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(), true);
+        } else {
+          auto path = buf.filename();
+          if (path.empty())
+            throw ed_error("Need filename.");
+          s = vase::Shard::from_file(path, true);
+        };
+        try {
+          buf.load(ctx, s);
+          vase::Shard::release(s);
+        } catch (...) {
+          vase::Shard::release(s);
+          throw;
+        }
+        ctx.io.write_line(std::format("{}", buf.bytes()));
+        ctx.current() = {addr, buf.lines()};
+      }
+    }
+  );
+  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.",
+      .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, true);
+          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(), true);
+        } else {
+          auto path = buf.filename();
+          if (path.empty())
+            throw ed_error("Need filename.");
+          s = vase::Shard::from_file(path, true);
+        };
+        try {
+          buf.load(ctx, s);
+          vase::Shard::release(s);
+        } catch (...) {
+          vase::Shard::release(s);
+          throw;
+        }
+        ctx.io.write_line(std::format("{}", buf.bytes()));
+        ctx.current() = {addr, buf.lines()};
+      }
+    }
+  );
+  ctx.functions.insert(
+    "f",
+    Function{
+      .address_kind = Function::AddressKind::None,
+      .argument_kind = Function::ArgumentKind::File,
+      .input_mode = Function::InputMode::None,
+      .desc = "Set 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 (buf_.kind != buffer::Buffer::Kind::Generic)
+          return;
+        auto &buf = *(buffer::GenericBuffer *)&buf_;
+        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.write_line(ctx.last_help);
+      }
+    }
+  );
+  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;
+        if (ctx.help_mode)
+          ctx.io.write_line(ctx.last_help);
+      }
+    }
+  );
+  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 = nullptr,
+      .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);
+        ctx.current() = {ctx.prev().buffername, ctx.prev().end};
+        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 set 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.current() = {addr.buffername, addr.start};
+      }
+    }
+  );
+  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 = "List (print unambiguous) 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).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
+            && addr.start <= arg.number
+            && addr.end < arg.number)
+          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.current() = {arg.buffername, arg.number + addr.end - addr.start + 1};
+      },
+    }
+  );
+  ctx.functions.insert(
+    "n",
+    Function{
+      .address_kind = Function::AddressKind::Range,
+      .argument_kind = Function::ArgumentKind::None,
+      .input_mode = Function::InputMode::None,
+      .desc = "Print 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 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::None,
+      .input_mode = Function::InputMode::None,
+      .desc = "Toggle prompt.",
+      .default_address = "",
+      .accept_zero = false,
+      .pre_text_mode = nullptr,
+      .handle = [](BEd &ctx, const buffer::Address &, vase::Shard *, const Argument &, std::vector<buffer::Line> *) {
+        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 = "Try quitting.",
+      .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 = "Force quit.",
+      .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 from file into buffer.",
+      .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, true);
+          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(), true);
+        } else {
+          auto path = buf.filename();
+          if (path.empty())
+            throw ed_error("Need filename.");
+          s = vase::Shard::from_file(path, true);
+        };
+        try {
+          buf.append(ctx, s, addr.number);
+          ctx.io.write_line(std::format("{}", s ? s->length + 1 : 0));
+          ctx.current() = {addr.buffername, addr.number + (s ? s->lines + 1 : 0)};
+          vase::Shard::release(s);
+        } catch (...) {
+          vase::Shard::release(s);
+          throw;
+        }
+      }
+    }
+  );
+  ctx.functions.insert(
+    "s",
+    Function{
+      .address_kind = Function::AddressKind::Range,
+      .argument_kind = Function::ArgumentKind::Regex,
+      .input_mode = Function::InputMode::None,
+      .desc = "Substitute regex.",
+      .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 (...) {
+          if (!addr.start) {
+            vase::Shard::release(text);
+            throw;
+          }
+          ctx.buffer(addr.buffername).append(ctx, text, --addr.start);
+          vase::Shard::release(text);
+          throw;
+        }
+        ctx.current() = {arg.buffername, arg.number + addr.end - addr.start + 1};
+      },
+    }
+  );
+  ctx.functions.insert(
+    "w",
+    Function{
+      .address_kind = Function::AddressKind::Range,
+      .argument_kind = Function::ArgumentKind::File,
+      .input_mode = Function::InputMode::None,
+      .desc = "Write buffer 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);
+          };
+          ctx.io.write(std::format("{}\n", text ? text->length + 1 : 0));
+          vase::Shard::release(text);
+        } catch (...) {
+          vase::Shard::release(text);
+          throw;
+        }
+      }
+    }
+  );
+  ctx.functions.insert(
+    "=",
+    Function{
+      .address_kind = Function::AddressKind::Range,
+      .argument_kind = Function::ArgumentKind::None,
+      .input_mode = Function::InputMode::None,
+      .desc = "Print line numbers",
+      .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_);
+        if (addr.start == addr.end)
+          ctx.io.write_line(std::format(":{}:{}", addr.buffername, addr.start));
+        else
+          ctx.io.write_line(std::format(":{}:{},{}", addr.buffername, addr.start, 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);
+        ctx.io.write("!\n");
+      },
+    }
+  );
+  ctx.no_op = Function{
+    .address_kind = Function::AddressKind::Line,
+    .argument_kind = Function::ArgumentKind::None,
+    .input_mode = Function::InputMode::None,
+    .desc = "Prints a line and jumps 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.eof_op = Function{
+    .address_kind = Function::AddressKind::None,
+    .argument_kind = Function::ArgumentKind::None,
+    .input_mode = Function::InputMode::None,
+    .desc = "Try quitting.",
+    .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 +1,278 @@
+#include "internal/io/io.h"
+
+namespace bed::internal::io {
+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 +1,180 @@
+#include "internal/io/io.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::IO() {
+  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::enable_mouse() {
+  const char *seq = "\x1b[?1000h";
+  write_all(STDOUT_FILENO, seq, 8);
+}
+
+void IO::disable_mouse() {
+  const char *seq = "\x1b[?1000l";
+  write_all(STDOUT_FILENO, seq, 8);
+}
+
+std::pair<uint16_t, uint16_t> IO::terminal_size() {
+  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() {
+  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)
+    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)
+    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) {
+  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) {
+  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 +1,252 @@
+#include "bed.h"
+#include "internal/parser/parser.h"
+
+namespace bed::internal::parser {
+void Parser::locator(AddressPromise &addr) {
+  addr.base = AddressPromise::None{};
+  switch (peek()) {
+  case '.':
+    advance();
+    addr.base = AddressPromise::Current{};
+    break;
+  case '$':
+    advance();
+    addr.base = AddressPromise::Last{};
+    break;
+  case '%':
+    advance();
+    addr.base = AddressPromise::LastRange{};
+    break;
+  case '[':
+    advance();
+    addr.base = AddressPromise::Block{Direction::Backward};
+    break;
+  case ']':
+    advance();
+    addr.base = AddressPromise::Block{Direction::Forward};
+    break;
+  case '^':
+    advance();
+    addr.base = AddressPromise::Diagnostic{Direction::Backward};
+    break;
+  case '~':
+    advance();
+    addr.base = AddressPromise::Diagnostic{Direction::Forward};
+    break;
+  case '\'':
+    advance();
+    if (('a' <= peek() && peek() <= 'z')
+        || ('A' <= peek() && peek() <= 'Z'))
+      addr.base = AddressPromise::Mark{peek()};
+    else
+      throw ed_error("Valid mark needed after \'");
+    advance();
+    break;
+  case '{': {
+    advance();
+    uint16_t j = 0;
+    std::string func;
+    std::string arg;
+    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);
+        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 + 1);
+  } break;
+  case '/': {
+    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);
+  } break;
+  case '?': {
+    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);
+  } break;
+  case '<': {
+    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);
+  } break;
+  case '>': {
+    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);
+  } break;
+  case '+': {
+    advance();
+    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;
+    advance(j);
+    addr.offset += num;
+  } break;
+  case '-': {
+    advance();
+    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;
+    advance(j);
+    addr.offset -= num;
+  } break;
+  default:
+    if ('0' <= peek() && peek() <= '9') {
+      uint64_t num = 0;
+      while ('0' <= peek() && peek() <= '9') {
+        num = num * 10 + (peek() - '0');
+        advance();
+      }
+      addr.base = AddressPromise::Number{num};
+    }
+  }
+}
+
+int64_t Parser::offset() {
+  int64_t offset = 0;
+  while (peek() == '+' || peek() == '-'
+         || ('0' <= peek() && peek() <= '9')) {
+    bool positive = peek() != '-';
+    if (peek() == '+' || peek() == '-')
+      advance();
+    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);
+    offset += positive ? num : -num;
+    skip_ws();
+  }
+  skip_ws();
+  return offset;
+}
+
+void Parser::address(AddressPromise &addr) {
+  if (peek() == ':') {
+    advance();
+    uint16_t j = 0;
+    while (peek(j) != ':' && peek(j) != '\0')
+      j++;
+    addr.bufname = peek_str(j);
+    advance(j);
+    if (peek() == ':')
+      advance();
+  }
+  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() == ';';
+    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 +1,217 @@
+#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()) {
+      if (curr.bufname->empty()) {
+        bufname = ctx.current().buffername;
+        curr.bufname = bufname;
+      } else {
+        bufname = *curr.bufname;
+      }
+    } else {
+      curr.bufname = bufname;
+    }
+    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;
+      }
+      if (curr.jumping) {
+        buffer::Line resolved = curr.resolve(ctx);
+        ctx.current() = resolved;
+        curr.bufname = resolved.buffername;
+        curr.base = Number(resolved.number);
+        curr.offset = 0;
+      }
+      prev = curr;
+      prev_set = true;
+    } 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()) {
+      if (curr.bufname->empty()) {
+        bufname = ctx.current().buffername;
+        curr.bufname = bufname;
+      } else {
+        bufname = *curr.bufname;
+      }
+    } else {
+      curr.bufname = bufname;
+    }
+    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;
+      }
+      if (curr.jumping) {
+        buffer::Line resolved = curr.resolve(ctx);
+        ctx.current() = resolved;
+        curr.bufname = resolved.buffername;
+        curr.base = Number(resolved.number);
+        curr.offset = 0;
+      }
+      prev = curr;
+      prev_set = true;
+    } 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 +1,208 @@
+#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));
+  advance(len);
+  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.");
+    advance();
+    break;
+  case functions::Function::ArgumentKind::Any:
+    command->argument = std::string(peek_str());
+    advance(peek_str().size());
+    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 '!':
+      advance();
+      command->argument = functions::Function::ShellArg(std::string(peek_str()));
+      advance(peek_str().size());
+      break;
+    case '\0':
+      command->argument = std::monostate();
+      break;
+    default:
+      command->argument = std::filesystem::path(peek_str());
+      advance(peek_str().size());
+      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");
+    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));
+    if (peek(j) != '\0') {
+      advance(j + 1);
+    } else {
+      advance(j);
+    }
+    std::string options;
+    if (peek() != '\0') {
+      options = std::string(peek_str());
+      advance(peek_str().size());
+    }
+    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()));
+    advance(peek_str().size());
+    break;
+  case functions::Function::ArgumentKind::Shell:
+    command->argument = functions::Function::ShellArg(std::string(peek_str()));
+    advance(peek_str().size());
+    break;
+  }
+  if (!suffix) {
+    suffix = peek();
+    advance();
+  }
+  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 +1,65 @@
+#include "internal/parser/parser.h"
+#include "bed.h"
+
+namespace bed::internal::parser {
+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() {
+  while (peek() == ' ' || peek() == '\t')
+    advance();
+}
+
+void Parser::parse() {
+  skip_ws();
+  if (peek() == '@') {
+    advance();
+    command->temp_address = true;
+  } else {
+    command->temp_address = false;
+  }
+  skip_ws();
+  addresses(command->addresses);
+  operation();
+  skip_ws();
+  if (peek() != '\0')
+    throw ed_error("Malformed command");
+}
+
+Parser::Parser(
+  std::string_view cmd, BEd &bed, Command *command,
+  std::vector<ui::Token> *tokens, CompletionContext *completion
+) : bed(bed), cmd(cmd), command(command), tokens(tokens), completion(completion) {
+  i = 0;
+}
+
+Command Parser::get_command(std::string_view cmd, BEd &bed) {
+  Command c;
+  std::vector<ui::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<ui::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/syntax/parser.cc

@@ -0,0 +1,391 @@
+#include "internal/syntax/parser.h"
+
+namespace bed::internal::syntax {
+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::Shard *vase, uint64_t lines, Language lang)
+    : root(nullptr), lang(lang) {
+  reset(vase, lines, lang);
+}
+
+Parser::~Parser() {
+  destroy_tree(root, lang);
+}
+
+void Parser::reset(vase::Shard *vase, uint64_t lines, Language lang_) {
+  destroy_tree(root, lang);
+  root = nullptr;
+  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);
+}
+
+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};
+  }
+}
+
+ParseState *Parser::join_tree(ParseState *a, ParseState *b) {
+  // TODO: balance
+  return make_branch(a, b);
+}
+
+void Parser::erase(vase::Shard *vase, uint64_t start, uint64_t count) {
+  begin_edit();
+  erase(start, count);
+  end_edit(vase);
+}
+
+void Parser::insert(vase::Shard *vase, uint64_t start, uint64_t count) {
+  begin_edit();
+  insert(start, count);
+  end_edit(vase);
+}
+
+void Parser::modify(vase::Shard *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, 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) {
+      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++] = ev.closing << 15 | (at - chunk_start);
+    }
+    at++;
+  }
+  lang.destroy(state);
+}
+
+void Parser::begin_edit() {
+  in_edit = true;
+}
+
+void Parser::mark_dirty(uint64_t start, uint64_t end) {
+  if (!dirty) {
+    dirty_start = start;
+    dirty_end = end;
+    dirty = true;
+  } else {
+    dirty_start = std::min(dirty_start, start);
+    dirty_end = std::max(dirty_end, end);
+  }
+}
+
+void Parser::erase(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);
+  mark_dirty(start, start + 1);
+}
+
+void Parser::insert(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);
+  mark_dirty(start, start + count);
+}
+
+void Parser::end_edit(vase::Shard *vase) {
+  in_edit = false;
+  if (!dirty)
+    return;
+  uint64_t count = dirty_end > dirty_start ? dirty_end - dirty_start : 1;
+  modify(vase, dirty_start, count);
+  dirty = false;
+}
+
+uint64_t Parser::next_closing(uint64_t line) {
+  if (!root)
+    return UINT64_MAX;
+  uint64_t relative = 0;
+  TreeCursor c(root, line, &relative);
+  uint64_t line_offset = line - relative;
+  int level = 0;
+  bool first_leaf = true;
+  while (c.leaf) {
+    auto *leaf = c.leaf;
+    for (uint32_t i = 0; i < leaf->n; ++i) {
+      uint16_t block = leaf->blocks[i];
+      uint32_t pos = block & ParseStateLeaf::LINE_MASK;
+      if (first_leaf && pos <= relative)
+        continue;
+      bool closing = block & ParseStateLeaf::IS_CLOSING;
+      if (closing) {
+        if (level == 0)
+          return line_offset + pos;
+        --level;
+      } else {
+        ++level;
+      }
+    }
+    line_offset += leaf->lines();
+    c.next();
+    first_leaf = false;
+  }
+  return UINT64_MAX;
+}
+
+uint64_t Parser::prev_opening(uint64_t line) {
+  if (!root)
+    return 0;
+  uint64_t relative = 0;
+  TreeCursor c(root, line, &relative);
+  uint64_t line_offset = line - relative;
+  int level = 0;
+  bool first_leaf = true;
+  while (c.leaf) {
+    auto *leaf = c.leaf;
+    for (int32_t i = (int32_t)leaf->n - 1; i >= 0; --i) {
+      uint16_t block = leaf->blocks[i];
+      uint32_t pos = block & ParseStateLeaf::LINE_MASK;
+      if (first_leaf && pos >= relative)
+        continue;
+      bool closing = block & ParseStateLeaf::IS_CLOSING;
+      if (!closing) {
+        if (level == 0)
+          return line_offset + pos;
+        --level;
+      } else {
+        ++level;
+      }
+    }
+    c.prev();
+    first_leaf = false;
+    if (c.leaf)
+      line_offset -= c.leaf->lines();
+  }
+  return 0;
+}
+
+std::optional<Parser::Iterator> Parser::get_hl(vase::Shard *vase, uint64_t target) {
+  if (!root)
+    return std::nullopt;
+  return Parser::Iterator(target, this, vase);
+}
+
+Parser::Iterator::Iterator(uint64_t target, Parser *p, vase::Shard *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);
+  } 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::Iterator(vase, at, Direction::Forward);
+  while (at < target) {
+    it->next();
+    tokens.clear();
+    events.clear();
+    p->lang.parse(&state, it->line, at == 0, &tokens, &events);
+    at++;
+  }
+}
+
+Parser::Iterator::~Iterator() {
+  if (state)
+    p->lang.destroy(state);
+}
+
+Parser::Iterator::Iterator(Iterator &&other)
+    : p(other.p),
+      it(std::move(other.it)),
+      state(other.state),
+      tokens(std::move(other.tokens)) {
+  other.state = nullptr;
+}
+
+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 Parser::Iterator::next() {
+  it->next();
+  tokens.clear();
+  events.clear();
+  p->lang.parse(&state, it->line, at++ == 0, &tokens, &events);
+}
+} // namespace bed::internal::syntax

src/internal/syntax/ruby/ruby.cc

@@ -0,0 +1,44 @@
+#include "internal/syntax/ruby/parser.h"
+
+namespace bed::internal::syntax::ruby {
+Language lang_ruby() {
+  return Language{
+    .none_state = []() {
+      RubyState *st = (RubyState *)malloc(
+        sizeof(RubyState)
+        + sizeof(RubyState::RubyInternalState)
+      );
+      st->top = 1;
+      st->docs = 0;
+      st->stack()[0] = {
+        .brace_level = 1,
+        .lit_brace_level = 0,
+        .state = RubyState::RubyInternalState::NONE,
+        .flags = RubyState::RubyInternalState::EXPECTING_EXPRESSION | RubyState::RubyInternalState::NEWLINE,
+        .delim_start = '\0',
+        .delim_end = '\0'
+      };
+      return st; },
+    .parse = ruby_parse,
+    .copy = [](void *v_i_st) {
+      RubyState *i_st = (RubyState *)v_i_st;
+      uint32_t bytes = sizeof(RubyState)
+                       + sizeof(RubyState::RubyInternalState) * i_st->top
+                       + i_st->docs;
+      RubyState *o_st = (RubyState *)malloc(bytes);
+      memcpy(o_st, i_st, bytes);
+      return o_st; },
+    .equal = [](void *v_a_st, void *v_b_st) {
+      RubyState *a_st = (RubyState *)v_a_st;
+      uint32_t a_bytes = sizeof(RubyState)
+                         + sizeof(RubyState::RubyInternalState) * a_st->top
+                         + a_st->docs;
+      RubyState *b_st = (RubyState *)v_b_st;
+      uint32_t b_bytes = sizeof(RubyState)
+                         + sizeof(RubyState::RubyInternalState) * b_st->top
+                         + b_st->docs;
+      return a_bytes == b_bytes && memcmp(a_st, b_st, a_bytes) == 0; },
+    .destroy = [](void *v_st) { free(v_st); },
+  };
+}
+} // namespace bed::internal::syntax::ruby

src/internal/syntax/tree_cursor.cc

@@ -0,0 +1,66 @@
+#include "internal/syntax/decl.h"
+
+namespace bed::internal::syntax {
+TreeCursor::TreeCursor(ParseState *root, uint64_t target_line, uint64_t *relative) {
+  ParseState *node = root;
+  while (node->is_branch()) {
+    auto *branch = (ParseStateBranch *)node;
+    auto *left = branch->left;
+    stack[depth] = branch;
+    if (target_line < left->lines()) {
+      went_left[depth] = true;
+      ++depth;
+      node = left;
+    } else {
+      target_line -= left->lines();
+      went_left[depth] = false;
+      ++depth;
+      node = branch->right;
+    }
+  }
+  *relative = target_line;
+  leaf = (ParseStateLeaf *)node;
+}
+
+void TreeCursor::next() {
+  while (depth > 0) {
+    auto *branch = stack[depth - 1];
+    bool from_left = went_left[depth - 1];
+    --depth;
+    if (!from_left)
+      continue;
+    ParseState *node = branch->right;
+    while (node->is_branch()) {
+      auto *b = (ParseStateBranch *)node;
+      stack[depth] = b;
+      went_left[depth] = true;
+      ++depth;
+      node = b->left;
+    }
+    leaf = (ParseStateLeaf *)node;
+    return;
+  }
+  leaf = nullptr;
+}
+
+void TreeCursor::prev() {
+  while (depth > 0) {
+    auto *branch = stack[depth - 1];
+    bool from_left = went_left[depth - 1];
+    --depth;
+    if (from_left)
+      continue;
+    ParseState *node = branch->left;
+    while (node->is_branch()) {
+      auto *b = (ParseStateBranch *)node;
+      stack[depth] = b;
+      went_left[depth] = false;
+      ++depth;
+      node = b->right;
+    }
+    leaf = (ParseStateLeaf *)node;
+    return;
+  }
+  leaf = nullptr;
+}
+} // namespace bed::internal::syntax

src/internal/theme/theme.cc

@@ -0,0 +1,162 @@
+#include "internal/theme/theme.h"
+
+namespace bed::internal::theme {
+Theme::Theme() {
+  hl.fill({
+    .fg = 0xF0F0F0,
+    .bg = 0x000000,
+    .flags = Highlight::None,
+  });
+}
+
+Highlight Theme::get(internal::syntax::Token token) const {
+  return hl[token.type];
+}
+
+Theme Theme::default_theme() {
+  Theme theme;
+  theme.hl[internal::syntax::Token::Shebang] = {
+    .fg = 0x7DCFFF,
+    .bg = 0x000000,
+    .flags = Highlight::None,
+  };
+  theme.hl[internal::syntax::Token::Error] = {
+    .fg = 0xEF5168,
+    .bg = 0x000000,
+    .flags = Highlight::None,
+  };
+  theme.hl[internal::syntax::Token::Comment] = {
+    .fg = 0xAAAAAA,
+    .bg = 0x000000,
+    .flags = Highlight::Italic,
+  };
+  theme.hl[internal::syntax::Token::String] = {
+    .fg = 0xAAD94C,
+    .bg = 0x000000,
+    .flags = Highlight::None,
+  };
+  theme.hl[internal::syntax::Token::Escape] = {
+    .fg = 0x7DCFFF,
+    .bg = 0x000000,
+    .flags = 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] = {
+    .fg = 0xEF5168,
+    .bg = 0x000000,
+    .flags = Highlight::None,
+  };
+  theme.hl[internal::syntax::Token::Char] = {
+    .fg = 0xFFAF70,
+    .bg = 0x000000,
+    .flags = Highlight::None,
+  };
+  theme.hl[internal::syntax::Token::Keyword] = {
+    .fg = 0xFF8F40,
+    .bg = 0x000000,
+    .flags = Highlight::None,
+  };
+  theme.hl[internal::syntax::Token::KeywordOperator] = {
+    .fg = 0xF07178,
+    .bg = 0x000000,
+    .flags = Highlight::None,
+  };
+  theme.hl[internal::syntax::Token::Operator] = {
+    .fg = 0xFFFFFF,
+    .bg = 0x000000,
+    .flags = Highlight::Italic,
+  };
+  theme.hl[internal::syntax::Token::Function] = {
+    .fg = 0xFFAF70,
+    .bg = 0x000000,
+    .flags = Highlight::None,
+  };
+  theme.hl[internal::syntax::Token::Type] = {
+    .fg = 0xF07178,
+    .bg = 0x000000,
+    .flags = Highlight::None,
+  };
+  theme.hl[internal::syntax::Token::Constant] = {
+    .fg = 0x7DCFFF,
+    .bg = 0x000000,
+    .flags = Highlight::None,
+  };
+  theme.hl[internal::syntax::Token::VariableInstance] = {
+    .fg = 0x95E6CB,
+    .bg = 0x000000,
+    .flags = Highlight::None,
+  };
+  theme.hl[internal::syntax::Token::VariableGlobal] = {
+    .fg = 0xF07178,
+    .bg = 0x000000,
+    .flags = Highlight::None,
+  };
+  theme.hl[internal::syntax::Token::Annotation] = {
+    .fg = 0x7DCFFF,
+    .bg = 0x000000,
+    .flags = Highlight::None,
+  };
+  theme.hl[internal::syntax::Token::Directive] = {
+    .fg = 0xFF8F40,
+    .bg = 0x000000,
+    .flags = Highlight::None,
+  };
+  theme.hl[internal::syntax::Token::Label] = {
+    .fg = 0xD2A6FF,
+    .bg = 0x000000,
+    .flags = Highlight::None,
+  };
+  theme.hl[internal::syntax::Token::Brace1] = {
+    .fg = 0xD2A6FF,
+    .bg = 0x000000,
+    .flags = Highlight::None,
+  };
+  theme.hl[internal::syntax::Token::Brace2] = {
+    .fg = 0xFFAFAF,
+    .bg = 0x000000,
+    .flags = Highlight::None,
+  };
+  theme.hl[internal::syntax::Token::Brace3] = {
+    .fg = 0xFFFF00,
+    .bg = 0x000000,
+    .flags = Highlight::None,
+  };
+  theme.hl[internal::syntax::Token::Brace4] = {
+    .fg = 0x0FFF0F,
+    .bg = 0x000000,
+    .flags = Highlight::None,
+  };
+  theme.hl[internal::syntax::Token::Brace5] = {
+    .fg = 0xFF0F0F,
+    .bg = 0x000000,
+    .flags = Highlight::None,
+  };
+  return theme;
+}
+
+Theme Theme::from_name(std::string_view name) {
+  if (name == "default")
+    return default_theme();
+  throw std::runtime_error("Unknown theme: " + std::string(name));
+}
+
+} // namespace bed::internal::theme

src/internal/ui/command/command.cc

@@ -0,0 +1,157 @@
+#include "internal/ui/command.h"
+#include "bed.h"
+
+namespace bed::internal::ui {
+/*template <typename F>
+static void for_each_cluster(std::string_view s, F &&f) {
+  unicode_width_state_t state;
+  unicode_width_init(&state);
+  size_t i = 0;
+  while (i < s.size()) {
+    unsigned char c = static_cast<unsigned char>(s[i]);
+    size_t bytes = 1;
+    int width = 0;
+    if (c < 128) {
+      width = unicode_width_process(&state, c);
+    } else {
+      uint_least32_t cp;
+      size_t decoded = grapheme_decode_utf8(s.data() + i, s.size() - i, &cp);
+      bytes = decoded > 0 ? decoded : 1;
+      width = unicode_width_process(&state, cp);
+    }
+    if (width < 0)
+      width = 0;
+    f(i, bytes, width);
+    i += bytes;
+  }
+}
+
+static int display_width(std::string_view s) {
+  int w = 0;
+  for_each_cluster(s, [&](size_t, size_t, int cw) { w += cw; });
+  return w;
+}
+
+static uint16_t count_clusters(std::string_view s) {
+  uint16_t n = 0;
+  for_each_cluster(s, [&](size_t, size_t, int) { ++n; });
+  return n;
+}
+
+static std::vector<uint16_t> wrap_offsets(std::string_view line, uint16_t avail) {
+  std::vector<uint16_t> offsets{0};
+  int col = 0;
+  for_each_cluster(line, [&](uint16_t i, uint16_t, int w) {
+    if (col + w > avail && col > 0) {
+      offsets.push_back(i);
+      col = 0;
+    }
+    col += w;
+  });
+  return offsets;
+}
+
+// The word under/before `byte_pos`, split on plain ASCII spaces. Used to
+// pick what prefix to hand the suggestion trie.
+// TODO: change to use libgrapheme word break here.
+static std::string current_word(const std::string &line, size_t byte_pos) {
+  size_t start = (byte_pos == 0) ? std::string::npos : line.rfind(' ', byte_pos - 1);
+  start = (start == std::string::npos) ? 0 : start + 1;
+  if (byte_pos < start)
+    byte_pos = start;
+  return line.substr(start, byte_pos - start);
+}*/
+
+CommandIO::CommandIO(BEd &bed) : bed(bed) {
+  if (bed.prompt_mode)
+    prompt = bed.prompt(bed);
+  cursor = 0;
+}
+
+std::pair<std::string, bool> CommandIO::run() {
+  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);
+  bed.io.write(cmd);
+  bed.io.move_cursor(start, prompt.size() + cursor + 1);
+}
+} // namespace bed::internal::ui

src/internal/ui/text_mode/text_mode.cc

@@ -0,0 +1,188 @@
+#include "internal/ui/text_mode.h"
+#include "bed.h"
+
+namespace bed::internal::ui {
+TextMode::TextMode(BEd &bed) : bed(bed) {
+  cursor = 0;
+}
+
+std::pair<vase::Shard *, bool> TextMode::run() {
+  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;
+  cmd.clear();
+  cursor = 0;
+  redraw();
+  bool running = true;
+
+  while (running) {
+    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:
+        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') {
+          size_t lines = 1 + std::count(cmd.begin(), cmd.end(), '\n');
+          grow(lines + 1);
+          cmd.insert(cursor++, 1, '\n');
+        } else {
+          cmd.insert(cursor, res.text);
+          cursor += res.text.size();
+        }
+        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:
+        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::UP: {
+        size_t line_start =
+          cmd.rfind('\n', cursor == 0 ? 0 : cursor - 1);
+        if (line_start == std::string::npos)
+          line_start = 0;
+        else
+          ++line_start;
+        size_t col = cursor - line_start;
+        if (line_start == 0)
+          break;
+        size_t prev_end = line_start - 1;
+        size_t prev_start =
+          cmd.rfind('\n', prev_end == 0 ? 0 : prev_end - 1);
+        if (prev_start == std::string::npos)
+          prev_start = 0;
+        else
+          ++prev_start;
+        size_t prev_len = prev_end - prev_start;
+        cursor = prev_start + std::min(col, prev_len);
+        break;
+      }
+      case io::KeyEvent::SpecialKey::DOWN: {
+        size_t line_start =
+          cmd.rfind('\n', cursor == 0 ? 0 : cursor - 1);
+        if (line_start == std::string::npos)
+          line_start = 0;
+        else
+          ++line_start;
+        size_t col = cursor - line_start;
+        size_t line_end = cmd.find('\n', cursor);
+        if (line_end == std::string::npos)
+          line_end = cmd.size();
+        if (line_end == cmd.size())
+          break;
+        size_t next_start = line_end + 1;
+        size_t next_end = cmd.find('\n', next_start);
+        if (next_end == std::string::npos)
+          next_end = cmd.size();
+        size_t next_len = next_end - next_start;
+        cursor = next_start + std::min(col, next_len);
+        break;
+      }
+      case io::KeyEvent::SpecialKey::DELETE:
+        if (cursor < cmd.size())
+          cmd.erase(cursor, 1);
+        break;
+      }
+      break;
+    }
+    redraw();
+    if (cmd.size() >= 3 && cmd.compare(cmd.size() - 3, 3, "\n.\n") == 0) {
+      cmd.erase(cmd.size() - 3);
+      cursor = cmd.size();
+      running = false;
+    }
+  }
+
+  size_t total_lines = 1 + std::count(cmd.begin(), cmd.end(), '\n');
+  uint16_t last_row = start + total_lines;
+  bed.io.move_cursor(last_row, 1);
+  bed.io.write("\n", 1);
+  return {vase::Shard::from_string(cmd.data(), cmd.length(), true), false};
+}
+
+void TextMode::grow(size_t required_height) {
+  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", 1);
+  start -= overflow;
+  if (start < 1)
+    start = 1;
+}
+
+void TextMode::redraw() {
+  auto [rows, cols] = bed.io.terminal_size();
+  term_height = rows;
+  term_width = cols;
+  for (uint16_t i = 0; i < height; ++i) {
+    bed.io.move_cursor(start + i, 1);
+    bed.io.write("\x1b[2K", 4);
+  }
+  size_t line = 0;
+  size_t line_start = 0;
+  for (size_t i = 0; i < cursor; ++i) {
+    if (cmd[i] == '\n') {
+      ++line;
+      line_start = i + 1;
+    }
+  }
+  size_t col = cursor - line_start;
+  size_t pos = 0;
+  uint16_t screen_line = start;
+  while (pos <= cmd.size()) {
+    size_t end = cmd.find('\n', pos);
+    if (end == std::string::npos)
+      end = cmd.size();
+    if (screen_line < start + height) {
+      size_t len = std::min(end - pos, size_t(term_width));
+      bed.io.move_cursor(screen_line, 1);
+      bed.io.write(cmd.substr(pos, len));
+    }
+    if (end == cmd.size())
+      break;
+    pos = end + 1;
+    ++screen_line;
+  }
+  size_t vis_col = std::min(col, size_t(term_width - 1));
+  bed.io.move_cursor(start + line, vis_col + 1);
+}
+} // namespace bed::internal::ui

src/internal/vase/iterators/line.cc

@@ -0,0 +1,75 @@
+#include "internal/vase/vase.h"
+
+namespace bed::internal::vase {
+LineIterator::LineIterator(Shard *root, uint64_t line_num, Direction dir)
+    : it(root, dir), dir(dir) {
+  it.seek_line(line_num);
+  it.next(&chunk, &len);
+  current_offset = it.byte_offset();
+  last_line_offset = current_offset;
+}
+
+bool LineIterator::next(std::string *line) {
+  if (!line || !chunk)
+    return false;
+  last_line_offset = current_offset;
+  line->clear();
+  if (dir == Direction::Forward) {
+  retry_forward:
+    const char *nl = (const char *)memchr(chunk, '\n', len);
+    if (!nl) {
+      if (len && chunk[len - 1] == '\r')
+        len--;
+      line->append(chunk, len);
+      current_offset += len;
+      if (!it.next(&chunk, &len))
+        return true;
+      goto retry_forward;
+    }
+    const char *end = nl;
+    if (end - chunk > 0 && *(end - 1) == '\r')
+      end--;
+    line->append(chunk, end);
+    size_t consumed = (nl - chunk) + 1;
+    chunk += consumed;
+    len -= consumed;
+    current_offset += consumed;
+    return true;
+  } else {
+  retry_backward:
+#if defined(__GLIBC__) || defined(__APPLE__) || defined(__FreeBSD__)
+    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);
+      current_offset -= len;
+      if (!it.next(&chunk, &len))
+        return true;
+      goto retry_backward;
+    }
+    const char *start = nl + 1;
+    const char *line_end = chunk + len;
+    const size_t consumed = line_end - nl;
+    const char *end = line_end;
+    if (end > start && *(end - 1) == '\r')
+      end--;
+    if (end > start)
+      line->insert(0, start, end - start);
+    len = nl - chunk;
+    current_offset -= consumed;
+    return true;
+  }
+}
+
+uint64_t LineIterator::byte_offset() {
+  return last_line_offset;
+}
+} // namespace bed::internal::vase

src/internal/vase/iterators/petal.cc

@@ -0,0 +1,171 @@
+#include "internal/vase/vase.h"
+
+namespace bed::internal::vase {
+PetalIterator::PetalIterator(Shard *r, Direction dir)
+    : dir(dir), root(r) {
+  if (!root)
+    return;
+}
+
+void PetalIterator::seek_offset(uint64_t offset) {
+  stack.clear();
+  petal = nullptr;
+  global_offset = 0;
+  last_offset = 0;
+  global_line = 0;
+  if (!root)
+    return;
+  if (offset >= root->length)
+    offset = root->length - 1;
+  uint64_t target = offset;
+  Shard *curr = root;
+  while (curr) {
+    if (curr->kind == Shard::Kind::Petal) {
+      petal = (Petal *)curr;
+      petal_offset = target;
+      global_offset += target;
+      last_offset = global_offset;
+      return;
+    } else {
+      auto *b = (Branch *)curr;
+      uint64_t left_len = b->left->length;
+      if (target < left_len) {
+        if (dir == Direction::Forward)
+          stack.push_back(b->right);
+        curr = b->left;
+      } else {
+        target -= left_len;
+        if (dir == Direction::Backward)
+          stack.push_back(b->left);
+        global_offset += left_len;
+        global_line += b->left->lines;
+        curr = b->right;
+      }
+    }
+  }
+  std::unreachable();
+}
+
+void PetalIterator::seek_line(uint64_t line) {
+  stack.clear();
+  petal = nullptr;
+  global_offset = 0;
+  last_offset = 0;
+  bool last_line = false;
+  if (!root)
+    return;
+  if (line > root->lines)
+    line = root->lines;
+  if (line == root->lines)
+    last_line = true;
+  if (!last_line && dir == Direction::Backward)
+    line++;
+  Shard *curr = root;
+  while (curr) {
+    if (curr->kind == Shard::Kind::Petal) {
+      petal = (Petal *)curr;
+      if (last_line && dir == Direction::Backward) {
+        petal_offset = petal->length;
+        global_offset += petal->length;
+      } else {
+        const char *text = petal->source->read(petal->pos);
+        uint64_t offset = 0;
+        while (line) {
+          const char *c = (const char *)memchr(text, '\n', petal->length - offset);
+          if (!c)
+            throw std::runtime_error("leaf line count is wrong.");
+          offset += (c - text) + 1;
+          text = c + 1;
+          line--;
+        }
+        if (dir == Direction::Backward)
+          --offset;
+        petal_offset = offset;
+        global_offset += offset;
+      }
+      last_offset = global_offset;
+      return;
+    } else {
+      auto *b = (Branch *)curr;
+      uint64_t left_lines = b->left->lines;
+      if (line <= left_lines) {
+        if (dir == Direction::Forward)
+          stack.push_back(b->right);
+        curr = b->left;
+      } else {
+        line -= left_lines;
+        if (dir == Direction::Backward)
+          stack.push_back(b->left);
+        global_offset += b->left->length;
+        curr = b->right;
+      }
+    }
+  }
+  std::unreachable();
+}
+
+Petal *PetalIterator::_next(uint64_t *offset) {
+  while (true) {
+    if (petal) {
+      if (dir == Direction::Forward) {
+        if (petal_offset == petal->length) {
+          petal = nullptr;
+          continue;
+        }
+      } else {
+        if (petal_offset == 0) {
+          petal = nullptr;
+          continue;
+        }
+      }
+      auto ret = petal;
+      last_offset = global_offset;
+      if (dir == Direction::Forward)
+        global_offset += petal_offset;
+      else
+        global_offset -= petal_offset;
+      petal = nullptr;
+      *offset = petal_offset;
+      return ret;
+    }
+    if (stack.empty())
+      return nullptr;
+    auto s = stack.back();
+    stack.pop_back();
+    while (s->kind == Shard::Kind::Branch) {
+      Branch *b = (Branch *)s;
+      if (dir == Direction::Forward) {
+        stack.push_back(b->right);
+        s = b->left;
+      } else {
+        stack.push_back(b->left);
+        s = b->right;
+      }
+    }
+    petal = (Petal *)s;
+    petal_offset = dir == Direction::Forward ? 0 : petal->length;
+  }
+}
+
+bool PetalIterator::next(const char **data, uint64_t *out_len) {
+  uint64_t offset = 0;
+  Petal *p = _next(&offset);
+  if (!p) {
+    *data = nullptr;
+    *out_len = 0;
+    return false;
+  }
+  if (dir == Direction::Forward) {
+    *out_len = p->length - offset;
+    *data = p->source->read(p->pos + offset);
+  } else {
+    *out_len = offset;
+    *data = p->source->read(p->pos);
+  }
+  return true;
+}
+
+uint64_t PetalIterator::byte_offset() {
+  return last_offset;
+}
+} // namespace bed::internal::vase

src/internal/vase/regex/api.cc

@@ -0,0 +1,308 @@
+#include "internal/vase/vase.h"
+
+namespace bed::internal::vase {
+std::vector<ReplacePart> parse_replace(AppendStorage *ap, std::string_view s) {
+  std::vector<ReplacePart> parts;
+  std::string constant;
+  auto flush_constant = [&]() {
+    if (!constant.empty()) {
+      uint64_t lines = 0;
+      const char *p = constant.data();
+      const char *end = p + constant.size();
+      while ((p = (const char *)memchr(p, '\n', end - p))) {
+        ++lines;
+        ++p;
+      }
+      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, ap, pos)
+        }
+      );
+      constant.clear();
+    }
+  };
+  for (size_t i = 0; i < s.size(); ++i) {
+    char c = s[i];
+    if (c == '\\' && i + 1 < s.size()) {
+      char next = s[i + 1];
+      if (next == '0') {
+        flush_constant();
+        parts.push_back(
+          ReplacePart{
+            .type = ReplacePart::PartType::FullMatch,
+            .value = (uint8_t)0
+          }
+        );
+      } else if (next >= '1' && next <= '9') {
+        flush_constant();
+        parts.push_back(
+          ReplacePart{
+            .type = ReplacePart::PartType::CaptureGroup,
+            .value = (uint8_t)(next - '0')
+          }
+        );
+      } 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);
+  }
+  flush_constant();
+  return parts;
+}
+
+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
+) {
+  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 root;
+  std::vector<ReplacePart> replace_parts = parse_replace(ap, replace);
+  struct Edit {
+    uint64_t line;
+    uint64_t old_lines;
+    uint64_t new_lines;
+  };
+  uint64_t orig_line = start;
+  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) {
+      auto [keep, rest] = Shard::split(remaining, gap);
+      Shard::release(remaining);
+      pieces.push_back(keep);
+      remaining = rest;
+      orig_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 *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 != UINT64_MAX) {
+            uint64_t ls = group.start - match.start;
+            uint64_t le = group.end - match.start;
+            auto [a, b] = Shard::split(dropped, ls);
+            auto [g, c] = Shard::split(b, le - ls);
+            Shard::release(a);
+            Shard::release(b);
+            Shard::release(c);
+            pieces.push_back(g);
+            new_lines += g ? g->lines : 0;
+          }
+        }
+        break;
+      }
+      }
+    }
+    Shard::release(dropped);
+    if (old_lines || new_lines) {
+      uint64_t report_line = (uint64_t)((int64_t)orig_line + line_delta);
+      if (on_edit)
+        on_edit(report_line, old_lines, new_lines);
+      line_delta += (int64_t)new_lines - (int64_t)old_lines;
+    }
+    orig_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) {
+    if (p && p->length > 0)
+      compact.push_back(p);
+    else if (p)
+      Shard::release(p);
+  }
+  Shard *new_root = compact.empty() ? nullptr : Shard::build(compact.data(), 0, compact.size());
+  Shard::release(root);
+  return new_root;
+}
+
+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

@@ -0,0 +1,244 @@
+#include "internal/vase/vase.h"
+
+namespace bed::internal::vase {
+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;
+
+  for (char c : options) {
+    switch (c) {
+    case 'g':
+      global = true;
+      break;
+    case 'i':
+      flags |= PCRE2_CASELESS;
+      break;
+    case 's':
+      flags |= PCRE2_DOTALL;
+      break;
+    case 'x':
+      flags |= PCRE2_EXTENDED;
+      break;
+    case 'U':
+      flags |= PCRE2_UNGREEDY;
+      break;
+    case 'n':
+      flags |= PCRE2_NO_AUTO_CAPTURE;
+      break;
+    case 'm':
+      flags &= ~PCRE2_MULTILINE;
+      break;
+    }
+  }
+
+  std::vector<RegexMatch> results;
+
+  int errornumber;
+  PCRE2_SIZE erroroffset;
+
+  pcre2_code *re = pcre2_compile(
+    (PCRE2_SPTR)pattern.data(),
+    pattern.size(),
+    flags,
+    &errornumber,
+    &erroroffset,
+    NULL
+  );
+
+  if (re == NULL)
+    return results;
+
+  pcre2_match_data *match_data = pcre2_match_data_create_from_pattern(re, NULL);
+
+  PetalIterator it(root, Direction::Forward);
+  it.seek_offset(start_offset);
+
+  const char *data;
+  uint64_t length;
+
+  char buf[2048];
+
+  uint64_t global_offset = start_offset;
+  uint64_t offset = UINT64_MAX;
+
+  auto record_match = [&](int rc, PCRE2_SIZE *ovector) {
+    if (global_offset + (uint64_t)ovector[1] > end_offset)
+      return;
+    RegexMatch match{
+      .start = global_offset + (uint64_t)ovector[0],
+      .end = global_offset + (uint64_t)ovector[1]
+    };
+    for (int i = 1; i < rc && i <= 9; ++i) {
+      PCRE2_SIZE s = ovector[2 * i];
+      PCRE2_SIZE e = ovector[2 * i + 1];
+      if (s != PCRE2_UNSET) {
+        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));
+  };
+
+  auto skip_to_next_line = [&](const char *&data, uint64_t &length, uint64_t &offset, uint64_t &global_offset) {
+    while (true) {
+      const char *p = (const char *)memchr(data + offset, '\n', length - offset);
+      if (p) {
+        uint64_t nl = p - data;
+        offset = nl + 1;
+        return;
+      }
+      global_offset += length;
+      offset = -1;
+      if (!it.next(&data, &length))
+        return;
+      offset = 0;
+    }
+  };
+
+  while (global_offset < end_offset) {
+    if (offset == UINT64_MAX) {
+      bool more = it.next(&data, &length);
+      if (!more)
+        break;
+      offset = 0;
+    }
+
+    while (offset < length) {
+      if (offset == UINT64_MAX)
+        break;
+
+      int rc = pcre2_match(
+        re,
+        (PCRE2_SPTR)data,
+        (size_t)length,
+        offset,
+        PCRE2_PARTIAL_HARD,
+        match_data,
+        NULL
+      );
+
+      if (rc == PCRE2_ERROR_PARTIAL) {
+        uint64_t buflen = 0;
+
+        PCRE2_SIZE *ovector = pcre2_get_ovector_pointer(match_data);
+        uint64_t partial_start = ovector[0];
+        uint64_t partial_length = length - partial_start;
+
+        if (partial_length >= 2048) {
+          global_offset += offset;
+          offset = UINT64_MAX;
+          continue;
+        }
+
+        global_offset += partial_start;
+
+        memcpy(buf, data + partial_start, partial_length);
+        buflen += partial_length;
+
+        offset = UINT64_MAX;
+        bool exhausted = false;
+
+        while (true) {
+          if (buflen >= 2048)
+            break;
+
+          bool more = it.next(&data, &length);
+          if (!more) {
+            exhausted = true;
+            break;
+          }
+          uint64_t l = std::min(length, 2048 - buflen);
+          memcpy(buf + buflen, data, l);
+          buflen += l;
+
+          int rc = pcre2_match(
+            re,
+            (PCRE2_SPTR)buf,
+            (size_t)buflen,
+            0,
+            PCRE2_PARTIAL_HARD,
+            match_data,
+            NULL
+          );
+
+          if (rc == PCRE2_ERROR_PARTIAL) {
+            continue;
+          } else if (rc > 0) {
+            PCRE2_SIZE *ovector = pcre2_get_ovector_pointer(match_data);
+            record_match(rc, ovector);
+            global_offset += buflen - l;
+            offset = l - (buflen - ovector[1]);
+            if (!global)
+              skip_to_next_line(data, length, offset, global_offset);
+            break;
+          } else if (rc == PCRE2_ERROR_NOMATCH) {
+            global_offset += buflen - l;
+            offset = 0;
+            break;
+          } else {
+            break;
+          }
+        }
+
+        if (exhausted) {
+          uint64_t search_from = 0;
+          while (search_from <= buflen) {
+            int rc = pcre2_match(
+              re,
+              (PCRE2_SPTR)buf,
+              (size_t)buflen,
+              search_from,
+              0,
+              match_data,
+              NULL
+            );
+            if (rc <= 0)
+              break;
+            PCRE2_SIZE *ov = pcre2_get_ovector_pointer(match_data);
+            record_match(rc, ov);
+            if (global) {
+              search_from = (ov[1] == ov[0]) ? (uint64_t)ov[1] + 1 : (uint64_t)ov[1];
+            } else {
+              const void *p = memchr(buf + ov[1], '\n', buflen - ov[1]);
+              if (!p)
+                break;
+              search_from = (const char *)p - buf + 1;
+            }
+          }
+          offset = UINT64_MAX;
+        }
+
+        continue;
+      } else if (rc > 0) {
+        PCRE2_SIZE *ovector = pcre2_get_ovector_pointer(match_data);
+        record_match(rc, ovector);
+        if (global) {
+          if (ovector[1] == offset)
+            offset++;
+          else
+            offset = ovector[1];
+        } else {
+          offset = ovector[1];
+          skip_to_next_line(data, length, offset, global_offset);
+        }
+      } else if (rc == PCRE2_ERROR_NOMATCH) {
+        offset = length;
+        break;
+      } else {
+        offset = length;
+        break;
+      }
+    }
+
+    global_offset += offset;
+    offset = UINT64_MAX;
+  }
+
+  pcre2_match_data_free(match_data);
+  pcre2_code_free(re);
+
+  return results;
+}
+} // namespace bed::internal::vase

src/internal/vase/shard.cc

@@ -0,0 +1,433 @@
+#include "internal/io/io.h"
+#include "internal/vase/vase.h"
+
+namespace bed::internal::vase {
+void Shard::retain(Shard *n) {
+  if (n)
+    n->refs++;
+};
+
+void Shard::release(Shard *n) {
+  if (!n || --n->refs > 0)
+    return;
+  if (n->kind == Shard::Kind::Branch) {
+    release(((Branch *)n)->left);
+    release(((Branch *)n)->right);
+    delete (Branch *)n;
+  } else {
+    ((Petal *)n)->source->release();
+    delete (Petal *)n;
+  }
+}
+
+int height(Shard *n) {
+  return n ? n->height : 0;
+}
+
+int balance_factor(Shard *n) {
+  Branch *b = (Branch *)n;
+  return height(b->left) - height(b->right);
+}
+
+Shard *rotate_right(Branch *z) {
+  Branch *y = (Branch *)z->left;
+
+  Shard *middle = new Branch(y->right, z->right);
+  Shard *out = new Branch(y->left, middle);
+
+  Shard::release(middle);
+  Shard::release(z);
+
+  return out;
+}
+
+Shard *rotate_left(Branch *z) {
+  Branch *y = (Branch *)z->right;
+
+  Shard *middle = new Branch(z->left, y->left);
+  Shard *out = new Branch(middle, y->right);
+
+  Shard::release(middle);
+  Shard::release(z);
+
+  return out;
+}
+
+Shard *balance(Shard *node) {
+  if (!node || node->kind == Shard::Kind::Petal)
+    return node;
+
+  Branch *b = (Branch *)node;
+  int bf = balance_factor(node);
+
+  if (bf > 1) {
+    Branch *left = (Branch *)b->left;
+    if (balance_factor(left) < 0) {
+      Shard::retain(left);
+      auto new_left = rotate_left(left);
+      auto rebuilt = new Branch(new_left, b->right);
+      auto result = rotate_right((Branch *)rebuilt);
+      Shard::release(new_left);
+      Shard::release(b);
+      return result;
+    }
+    return rotate_right(b);
+  }
+
+  if (bf < -1) {
+    Branch *right = (Branch *)b->right;
+    if (balance_factor(right) > 0) {
+      Shard::retain(right);
+      auto new_right = rotate_right(right);
+      auto rebuilt = new Branch(b->left, new_right);
+      auto result = rotate_left((Branch *)rebuilt);
+      Shard::release(new_right);
+      Shard::release(b);
+      return result;
+    }
+    return rotate_left(b);
+  }
+
+  return node;
+}
+
+Shard *Shard::concat(Shard *a, Shard *b) {
+  if (!a)
+    return (Shard::retain(b), b);
+  if (!b)
+    return (Shard::retain(a), a);
+  if (a->height > b->height + 1) {
+    Branch *ba = (Branch *)a;
+    Shard *r = concat(ba->right, b);
+    Shard *out = balance(new Branch(ba->left, r));
+    Shard::release(r);
+    return out;
+  }
+  if (b->height > a->height + 1) {
+    Branch *bb = (Branch *)b;
+    Shard *l = concat(a, bb->left);
+    Shard *out = balance(new Branch(l, bb->right));
+    Shard::release(l);
+    return out;
+  }
+  return balance(new Branch(a, b));
+}
+
+std::pair<Shard *, Shard *> Shard::split(Shard *n, uint64_t offset) {
+  if (!n)
+    return {nullptr, nullptr};
+  if (offset == 0) {
+    Shard::retain(n);
+    return {nullptr, n};
+  }
+  if (offset == n->length) {
+    Shard::retain(n);
+    return {n, nullptr};
+  }
+  if (n->kind == Shard::Kind::Branch) {
+    Branch *b = (Branch *)n;
+    if (offset < b->left->length) {
+      auto [a, b2] = split(b->left, offset);
+      Shard *right = concat(b2, b->right);
+      Shard::release(b2);
+      return {a, right};
+    } else {
+      auto [a, b2] = split(b->right, offset - b->left->length);
+      Shard *left = concat(b->left, a);
+      Shard::release(a);
+      return {left, b2};
+    }
+  } else {
+    Petal *p = (Petal *)n;
+    uint64_t count[2]{0};
+    const char *c = p->source->read(p->pos);
+    const char *start = c;
+    const char *end = c + p->length;
+    while (c < end) {
+      const char *nl = (const char *)memchr(c, '\n', end - c);
+      if (!nl)
+        break;
+      if ((uint64_t)(nl - start) < offset)
+        count[0]++;
+      else
+        count[1]++;
+      c = nl + 1;
+    }
+    auto left = new Petal(offset, count[0], p->source, p->pos);
+    auto right = new Petal(p->length - offset, count[1], p->source, p->pos + offset);
+    return {left, right};
+  }
+}
+
+Shard *Shard::merge_leaves(Shard *a, Shard *b) {
+  if (a->kind != Shard::Kind::Petal || b->kind != Shard::Kind::Petal)
+    return concat(a, b);
+  if (a->length + b->length > PETAL_SIZE_MAX)
+    return concat(a, b);
+  Petal *pa = (Petal *)a;
+  Petal *pb = (Petal *)b;
+  if (!(pa->source == pb->source && pa->pos + pa->length == pb->pos))
+    return concat(a, b);
+  return new Petal(
+    pa->length + pb->length,
+    pa->lines + pb->lines,
+    pa->source,
+    pa->pos
+  );
+}
+
+Shard *Shard::append(Shard *root, Shard *leaf) {
+  if (!root) {
+    Shard::retain(leaf);
+    return leaf;
+  }
+  if (root->kind == Shard::Kind::Petal)
+    return merge_leaves(root, leaf);
+  Branch *b = (Branch *)root;
+  auto new_right = append(b->right, leaf);
+  auto out = balance(new Branch(b->left, new_right));
+  Shard::release(new_right);
+  return out;
+}
+
+Shard *Shard::build(Shard **pieces, uint64_t lo, uint64_t hi) {
+  if (hi - lo == 1)
+    return pieces[lo];
+  uint64_t mid = lo + (hi - lo) / 2;
+  Shard *left = build(pieces, lo, mid);
+  Shard *right = build(pieces, mid, hi);
+  Shard *node = Shard::concat(left, right);
+  Shard::release(left);
+  Shard::release(right);
+  return node;
+}
+
+Shard *Shard::from_command(const char *cmd, bool posix_ending) {
+  auto o = new OriginalStorage("/tmp");
+  int dest_fd = o->fd;
+  if (dest_fd == -1) {
+    delete o;
+    return nullptr;
+  }
+  io::IO::cleanup();
+  FILE *pipe = popen(cmd, "r");
+  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;
+      uint64_t lines = 0;
+      const char *p = buf;
+      const char *end = p + buf_cursor;
+      while (p < end) {
+        const void *nl = memchr(p, '\n', end - p);
+        if (!nl)
+          break;
+        lines++;
+        p = (const char *)nl + 1;
+      }
+      if (buf_cursor >= 2) {
+        ending[0] = buf[buf_cursor - 2];
+        ending[1] = buf[buf_cursor - 1];
+      } else if (buf_cursor == 1) {
+        ending[0] = ending[1];
+        ending[1] = buf[0];
+      }
+      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));
+      pos += buf_cursor;
+    }
+    if (feof(pipe))
+      break;
+    if (ferror(pipe)) {
+      delete o;
+      io::IO::enable_raw();
+      return nullptr;
+    }
+  }
+  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 (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--;
+    }
+  }
+  o->initialize();
+  io::IO::enable_raw();
+  if (pieces.size() == 1)
+    return pieces[0];
+  return build(pieces.data(), 0, pieces.size());
+}
+
+Shard *Shard::from_file(const std::filesystem::path &path, bool posix_ending) {
+  auto o = new OriginalStorage("/tmp");
+  int dest_fd = o->fd;
+  if (dest_fd == -1) {
+    delete o;
+    return nullptr;
+  }
+  int src_fd = open(path.c_str(), O_RDONLY);
+  if (src_fd == -1) {
+    delete o;
+    return nullptr;
+  }
+  uint64_t total = std::filesystem::file_size(path);
+  if (posix_ending && total > 0) {
+    char last;
+    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) {
+          delete o;
+          return nullptr;
+        }
+        if (s_last == '\r')
+          total--;
+      }
+    }
+  }
+  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;
+    uint64_t lines = 0;
+    const char *p = buf;
+    const char *end = p + 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)) {
+      close(src_fd);
+      delete o;
+      return nullptr;
+    }
+    pieces.push_back(new Petal(take, lines, o, pos));
+    pos += take;
+  }
+  close(src_fd);
+  if (pieces.empty()) {
+    delete o;
+    return nullptr;
+  }
+  o->initialize();
+  if (pieces.size() == 1)
+    return pieces[0];
+  return build(pieces.data(), 0, pieces.size());
+}
+
+Shard *Shard::from_string(const char *data, uint64_t len, bool posix_ending) {
+  auto o = new OriginalStorage("/tmp");
+  int dest_fd = o->fd;
+  if (dest_fd == -1 || data == nullptr) {
+    delete o;
+    return nullptr;
+  }
+  uint64_t total = len;
+  if (posix_ending && total > 0) {
+    if (data[total - 1] == '\n') {
+      total--;
+      if (total > 0 && data[total - 1] == '\r')
+        total--;
+    }
+  }
+  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

@@ -0,0 +1,72 @@
+#include "internal/vase/vase.h"
+
+namespace bed::internal::vase {
+AppendStorage::AppendStorage(std::filesystem::path base_dir) {
+  base_dir /= "tapp.XXXXXX";
+  char *s = strdup(base_dir.c_str());
+  fd = mkstemp(s);
+  if (fd == -1)
+    throw std::runtime_error("mkstemp failed");
+  unlink(s);
+  free(s);
+  allocated_capacity = 1ull << 30;
+  if (ftruncate(fd, allocated_capacity) == -1)
+    throw std::runtime_error("ftruncate failed");
+  buf = (char *)mmap(nullptr, allocated_capacity, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
+  if (buf == MAP_FAILED)
+    throw std::runtime_error("mmap failed");
+}
+
+AppendStorage::~AppendStorage() {
+  if (buf && buf != MAP_FAILED)
+    munmap(buf, allocated_capacity);
+  if (fd != -1)
+    close(fd);
+}
+
+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)
+      new_capacity = current_size + len + (1ull << 30);
+    if (ftruncate(fd, new_capacity) == -1)
+      throw std::runtime_error("ftruncate failed");
+#if defined(__linux__)
+    void *new_buf = mremap(buf, allocated_capacity, new_capacity, MREMAP_MAYMOVE);
+    if (new_buf == MAP_FAILED)
+      throw std::runtime_error("mremap failed");
+#else
+    munmap(buf, allocated_capacity);
+    void *new_buf = mmap(nullptr, new_capacity, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
+    if (new_buf == MAP_FAILED)
+      throw std::runtime_error("mmap failed");
+#endif
+    allocated_capacity = new_capacity;
+    buf = (char *)new_buf;
+  }
+}
+
+uint64_t AppendStorage::append(const char c) {
+  grow(1);
+  buf[current_size++] = c;
+  return current_size - 1;
+}
+
+uint64_t AppendStorage::append(const char *text, uint64_t len) {
+  grow(len);
+  memcpy(buf + current_size, text, len);
+  uint64_t old_pos = current_size;
+  current_size += len;
+  return old_pos;
+}
+
+const char *AppendStorage::read(uint64_t pos) {
+  if (pos >= current_size)
+    return nullptr;
+  return buf + pos;
+}
+
+uint64_t AppendStorage::length() {
+  return current_size;
+}
+} // namespace bed::internal::vase

src/internal/vase/storage/original.cc

@@ -0,0 +1,47 @@
+#include "internal/vase/vase.h"
+
+namespace bed::internal::vase {
+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";
+  char *s = strdup(base_dir.c_str());
+  fd = mkstemp(s);
+  if (fd == -1)
+    throw std::runtime_error("mkstemp failed");
+  unlink(s);
+  free(s);
+}
+
+OriginalStorage::~OriginalStorage() {
+  if (buf)
+    munmap((char *)buf, len);
+  if (fd != -1)
+    close(fd);
+}
+
+void OriginalStorage::initialize() {
+  struct stat st;
+  if (fstat(fd, &st) == -1)
+    throw std::runtime_error("fstat failed");
+  len = (uint64_t)st.st_size;
+  buf = (const char *)mmap(nullptr, len, PROT_READ, MAP_PRIVATE, fd, 0);
+  if (buf == MAP_FAILED) {
+    buf = nullptr;
+    throw std::runtime_error("mmap failed");
+  }
+  madvise((void *)buf, len, MADV_RANDOM);
+  close(fd);
+  fd = -1;
+}
+
+const char *OriginalStorage::read(uint64_t pos) {
+  if (pos >= len)
+    return nullptr;
+  return buf + pos;
+}
+
+uint64_t OriginalStorage::length() {
+  return len;
+}
+} // namespace bed::internal::vase

src/internal/vase/vase.cc

@@ -0,0 +1,327 @@
+#include "internal/vase/vase.h"
+#include "internal/io/io.h"
+
+namespace bed::internal::vase {
+std::string to_string(Shard *root) {
+  std::string out;
+  if (!root)
+    return out;
+  PetalIterator it(root, Direction::Forward);
+  it.seek_offset(0);
+  const char *data;
+  uint64_t len;
+  while (it.next(&data, &len))
+    out.append(data, len);
+  return out;
+}
+
+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(root, range.start);
+  it.seek_offset(start);
+  const char *data;
+  uint64_t len;
+  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);
+    remaining -= n;
+  }
+  return out;
+}
+
+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);
+  Shard *new_root = Shard::concat(left2, right);
+  Shard::release(left2);
+  Shard::release(right);
+  Shard::release(root);
+  if (key == '\n')
+    *point = {point->row + 1, 0};
+  else
+    point->col++;
+  return new_root;
+}
+
+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(ap, &root, point, data, chunk_size);
+    len -= chunk_size;
+    data += chunk_size;
+  }
+  return root;
+}
+
+void _insert(AppendStorage *ap, Shard **root, Point *point, const char *data, uint64_t len) {
+  if (len == 0)
+    return;
+  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;
+  const char *end = start + len;
+  while ((data = (const char *)memchr(data, '\n', end - data))) {
+    ++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;
+  }
+  if (lines) {
+    point->row += lines;
+    point->col = col;
+  } else {
+    point->col += col;
+  }
+  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 *erase(Shard *root, Range range) {
+  Point start = range.start;
+  Point end = range.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);
+  Shard *new_root = Shard::concat(a, c);
+  Shard::release(a);
+  Shard::release(b);
+  Shard::release(c);
+  Shard::release(d);
+  Shard::release(root);
+  return new_root;
+}
+
+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);
+}
+
+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;
+  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;
+    }
+  }
+  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;
+}
+
+static Shard *newline(AppendStorage *ap) {
+  uint64_t pos = ap->append('\n');
+  return new Petal(1, true, ap, pos);
+}
+
+Shard *insert(AppendStorage *ap, Shard *root, Shard *text, uint64_t line) {
+  if (!root) {
+    if (line != 0)
+      throw ed_error("line out of range");
+    Shard::retain(text);
+    return text;
+  }
+  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;
+  }
+  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;
+}
+
+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;
+  }
+  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

@@ -1,25 +1,22 @@
-#include "io/file.h"
+#include "bed.h"
 #include "pch.h"
-#include "vase/shard.h"
-#include "vase/vase.h"
 
-int main() {
-  char *text;
-  uint32_t len;
-
-  int s = read_file("./flake.nix", &text, &len);
-  if (!s)
+int main(int argc, char *argv[]) {
+  std::vector<std::string> args(argv, argv + argc);
+  try {
+    bed::internal::io::IO io = bed::internal::io::IO();
+    bed::BEd ed(args, io);
+    ed.run();
+  } catch (bed::fatal_error &e) {
+    if (e.code)
+      printf("Fatal error: %s\n", e.what());
+    return e.code;
+  }
+#ifndef DEBUG
+  catch (...) {
+    printf("Unexpected error.\n");
     return 1;
-
-  Vase vase = Vase(text, len);
-
-  print_shard(vase.root.ptr);
-
-  std::cout << "\n->\n\n";
-
-  vase.insert(14, "gr\ntt", 5);
-
-  print_shard(vase.root.ptr);
-
+  }
+#endif
   return 0;
 }

src/vase/buffer/append.cc

@@ -1,155 +0,0 @@
-#include "vase/buffer/append.h"
-
-AppendBuffer::AppendBuffer() {
-  new_text_chunk();
-  new_line_chunk();
-}
-
-AppendBuffer::~AppendBuffer() {
-  for (auto p : buf)
-    free(p);
-  for (auto p : newlines)
-    free(p);
-}
-
-inline uint32_t AppendBuffer::key(char c) {
-  if (t_offset == CHUNK_SIZE)
-    new_text_chunk();
-
-  (*t_current)[t_offset++] = c;
-
-  if (c == '\n') {
-    if (l_offset == CHUNK_SIZE)
-      new_line_chunk();
-    (*l_current)[l_offset++] = current_offset;
-  }
-  ++current_offset;
-
-  return current_offset - 1;
-}
-
-uint32_t AppendBuffer::append(const char *text, uint32_t length, uint32_t *line_count) {
-  uint32_t start = current_offset;
-
-  while (length) {
-    uint32_t space = CHUNK_SIZE - t_offset;
-
-    if (space == 0) {
-      new_text_chunk();
-      space = CHUNK_SIZE;
-    }
-
-    uint32_t copy = length < space ? length : space;
-    *line_count += _append(text, copy);
-
-    text += copy;
-    length -= copy;
-  }
-
-  return start;
-}
-
-const char *AppendBuffer::read(uint32_t pos, uint32_t *out_len) {
-  if (pos >= current_offset)
-    return nullptr;
-
-  uint32_t local_offset = pos % CHUNK_SIZE;
-
-  if (out_len) {
-    uint32_t remaining = current_offset - pos;
-    uint32_t until_chunk_end = CHUNK_SIZE - local_offset;
-    *out_len = std::min(remaining, until_chunk_end);
-  }
-
-  return &(*buf[pos / CHUNK_SIZE])[local_offset];
-}
-
-uint32_t AppendBuffer::find_newline(uint32_t target, uint32_t low, uint32_t high) {
-  if (low >= high)
-    return low;
-
-  uint32_t first_chunk = low / CHUNK_SIZE;
-  uint32_t last_chunk = (high - 1) / CHUNK_SIZE;
-  uint32_t left = first_chunk;
-  uint32_t right = last_chunk;
-
-  while (left < right) {
-    uint32_t mid = left + (right - left) / 2;
-    uint32_t first_value = (*newlines[mid])[0];
-    if (first_value < target)
-      left = mid + 1;
-    else
-      right = mid;
-  }
-
-  uint32_t chunk = left;
-  if (chunk > first_chunk) {
-    LChunk &prev = *newlines[chunk - 1];
-    uint32_t prev_size =
-      (chunk - 1 == newlines.size() - 1) ? l_offset : CHUNK_SIZE;
-    if (prev[prev_size - 1] >= target)
-      chunk--;
-  }
-
-  LChunk &c = *newlines[chunk];
-  uint32_t chunk_size =
-    (chunk == newlines.size() - 1) ? l_offset : CHUNK_SIZE;
-  uint32_t l = 0;
-  uint32_t r = chunk_size;
-
-  while (l < r) {
-    uint32_t m = l + (r - l) / 2;
-    if (c[m] < target)
-      l = m + 1;
-    else
-      r = m;
-  }
-
-  return chunk * CHUNK_SIZE + l;
-}
-
-uint32_t AppendBuffer::count_lines(uint32_t pos, uint32_t length) {
-  if (newlines.empty())
-    return 0;
-
-  uint32_t total_newlines = CHUNK_SIZE * (newlines.size() - 1) + l_offset;
-  uint32_t pos_index = find_newline(pos, 0, total_newlines);
-  uint32_t end_index = find_newline(pos + length, pos_index, total_newlines);
-
-  return end_index - pos_index;
-}
-
-inline void AppendBuffer::new_text_chunk() {
-  t_current = (TChunk *)malloc(sizeof(TChunk));
-  buf.push_back(t_current);
-  t_offset = 0;
-}
-
-inline void AppendBuffer::new_line_chunk() {
-  l_current = (LChunk *)malloc(sizeof(LChunk));
-  newlines.push_back(l_current);
-  l_offset = 0;
-}
-
-inline uint32_t AppendBuffer::_append(const char *text, uint32_t length) {
-  memcpy((*t_current) + t_offset, text, length);
-
-  const char *p = text;
-  const char *end = text + length;
-
-  uint32_t start_index = l_offset;
-  while (p < end) {
-    p = (const char *)memchr(p, '\n', end - p);
-    if (!p)
-      break;
-    if (l_offset == CHUNK_SIZE)
-      new_line_chunk();
-    (*l_current)[l_offset++] = current_offset + uint32_t(p - text);
-    p++;
-  }
-
-  t_offset += length;
-  current_offset += length;
-
-  return l_offset - start_index;
-}

src/vase/buffer/original.cc

@@ -1,24 +0,0 @@
-#include "vase/buffer/original.h"
-
-const char *OriginalBuffer::read(uint32_t pos, uint32_t *out_len) {
-  if (pos >= length)
-    return nullptr;
-  *out_len = length - pos;
-  return buf + pos;
-}
-
-uint32_t OriginalBuffer::count_lines(uint32_t pos, uint32_t length) {
-  auto start = std::lower_bound(
-    newlines.begin(),
-    newlines.end(),
-    pos
-  );
-
-  auto end = std::lower_bound(
-    start,
-    newlines.end(),
-    pos + length
-  );
-
-  return (uint32_t)(end - start);
-}

src/vase/shard.cc

@@ -1,87 +0,0 @@
-#include "vase/shard.h"
-
-std::pair<ShardPtr, ShardPtr> split_shard(Shard *n, uint32_t offset) {
-  if (!n)
-    return {nullptr, nullptr};
-  if (offset == 0)
-    return {nullptr, ShardPtr(n)};
-  if (offset == n->length)
-    return {ShardPtr(n), nullptr};
-
-  if (n->kind == Shard::ShardKind::Branch) {
-    Branch *b = (Branch *)n;
-
-    if (offset < b->left.ptr->length) {
-      auto [a, b2] = split_shard(b->left.ptr, offset);
-      return {a, ShardPtr(new Branch(b2.ptr, b->right.ptr))};
-    } else {
-      auto [a, b2] = split_shard(b->right.ptr, offset - b->left.ptr->length);
-      return {ShardPtr(new Branch(b->left.ptr, a.ptr)), b2};
-    }
-  } else {
-    Petal *p = (Petal *)n;
-
-    auto left = new Petal(
-      offset,
-      p->source->count_lines(0, offset),
-      p->source,
-      p->pos
-    );
-    auto right = new Petal(
-      p->length - offset,
-      p->source->count_lines(offset, p->length),
-      p->source,
-      p->pos + offset
-    );
-
-    return {ShardPtr(left), ShardPtr(right)};
-  }
-}
-
-ShardPtr concat_shard(ShardPtr left, ShardPtr right) {
-  if (!left.ptr)
-    return right;
-  if (!right.ptr)
-    return left;
-  return new Branch(left.ptr, right.ptr);
-}
-
-void print_shard(const Shard *shard, int depth) {
-  if (!shard) {
-    std::cout << std::string(depth * 2, ' ') << "<null>\n";
-    return;
-  }
-
-  std::string indent(depth * 2, ' ');
-  std::cout << indent;
-
-  if (shard->kind == Shard::ShardKind::Branch) {
-    auto *branch = static_cast<const Branch *>(shard);
-
-    std::cout
-      << "Branch"
-      << " @" << shard
-      << " len=" << shard->length
-      << " lines=" << shard->lines
-      << " refs=" << shard->refs.load()
-      << "\n";
-
-    std::cout << indent << "├─ left:\n";
-    print_shard(branch->left.ptr, depth + 2);
-
-    std::cout << indent << "└─ right:\n";
-    print_shard(branch->right.ptr, depth + 2);
-  } else {
-    auto *petal = static_cast<const Petal *>(shard);
-
-    std::cout
-      << "Petal"
-      << " @" << shard
-      << " len=" << shard->length
-      << " lines=" << shard->lines
-      << " refs=" << shard->refs.load()
-      << " source=@" << petal->source
-      << " pos=" << petal->pos
-      << "\n";
-  }
-}