Implement syntax highlighting

- Create a generic incremental syntax highlighting system.
- Implement a ruby syntax highlighter for it.

src/internal/buffer/buffer.cc

@@ -1,12 +1,18 @@
 #include "internal/buffer/buffer.h"
+#include "bed.h"
 
 namespace bed::internal::buffer {
-Buffer::Buffer() : vase("/tmp") {
+Buffer::Buffer()
+    : vase("/tmp"), lang(syntax::ruby::lang_ruby()),
+      parser(vase, vase.lines(), lang) {
   line = vase.lines();
   modified = false;
 }
 
-Buffer::Buffer(std::string command) : vase(command, "/tmp") {
+Buffer::Buffer(std::string command)
+    : vase(command, "/tmp"),
+      lang(syntax::ruby::lang_ruby()),
+      parser(vase, vase.lines(), lang) {
   line = vase.lines();
   if (!line)
     return;
@@ -15,7 +21,10 @@ Buffer::Buffer(std::string command) : vase(command, "/tmp") {
   modified = false;
 }
 
-Buffer::Buffer(std::filesystem::path path) : vase(path, "/tmp") {
+Buffer::Buffer(std::filesystem::path path)
+    : vase(path, "/tmp"),
+      lang(syntax::ruby::lang_ruby()),
+      parser(vase, vase.lines(), lang) {
   line = vase.lines();
   if (!line)
     return;
@@ -28,6 +37,7 @@ Buffer::Buffer(std::filesystem::path path) : vase(path, "/tmp") {
 void Buffer::load(std::string command) {
   vase::Vase new_vase = vase::Vase(command, "/tmp");
   vase = std::move(new_vase);
+  parser.reset(vase, vase.lines(), lang);
   line = vase.lines();
   if (!line) {
     prev_range.start = 0;
@@ -42,6 +52,7 @@ void Buffer::load(std::string command) {
 void Buffer::load(std::filesystem::path path) {
   vase::Vase new_vase = vase::Vase(path, "/tmp");
   vase = std::move(new_vase);
+  parser.reset(vase, vase.lines(), lang);
   line = vase.lines();
   if (!line) {
     prev_range.start = 0;
@@ -93,10 +104,72 @@ void Buffer::join(uint64_t start_line, uint64_t end_line) {
   modified = true;
 }
 
-void Buffer::print(uint64_t start_line, uint64_t end_line) {
-  vase::Iterator it = vase.iterate(start_line - 1, Direction::Forward);
-  while (it.next() && start_line++ <= end_line)
-    std::cout << it.line << std::endl;
+inline void apply(std::ostream &out, const theme::Highlight &hl) {
+  out << "\x1b[0m";
+  const uint8_t r = (hl.fg >> 16) & 0xff;
+  const uint8_t g = (hl.fg >> 8) & 0xff;
+  const uint8_t b = hl.fg & 0xff;
+  out << "\x1b[38;2;"
+      << static_cast<unsigned>(r) << ';'
+      << static_cast<unsigned>(g) << ';'
+      << static_cast<unsigned>(b) << 'm';
+  if (hl.bg != 0) {
+    const uint8_t br = (hl.bg >> 16) & 0xff;
+    const uint8_t bg = (hl.bg >> 8) & 0xff;
+    const uint8_t bb = hl.bg & 0xff;
+    out << "\x1b[48;2;"
+        << static_cast<unsigned>(br) << ';'
+        << static_cast<unsigned>(bg) << ';'
+        << static_cast<unsigned>(bb) << 'm';
+  }
+  if (hl.flags & theme::Highlight::Bold)
+    out << "\x1b[1m";
+  if (hl.flags & theme::Highlight::Italic)
+    out << "\x1b[3m";
+  if (hl.flags & theme::Highlight::Underline)
+    out << "\x1b[4m";
+  if (hl.flags & theme::Highlight::Strikethrough)
+    out << "\x1b[9m";
+}
+
+inline void reset(std::ostream &out) {
+  out << "\x1b[0m";
+}
+
+void Buffer::print(BEd &ctx, uint64_t start_line, uint64_t end_line) {
+  std::optional<syntax::Parser::Iterator> it_o = parser.get_hl(vase, start_line - 1);
+  if (!it_o)
+    throw ed_error("shouldn't be possible if line existed, which is checked by print's callers.");
+  auto &it = *it_o;
+  while (start_line <= end_line) {
+    it.next();
+    const std::string &line = it.it->line;
+    const auto &tokens = it.tokens;
+    uint32_t cursor = 0;
+    for (const auto &token : tokens) {
+      const uint32_t start = token.start;
+      const uint32_t end = token.end;
+      if (start > line.size())
+        break;
+      if (end > line.size())
+        break;
+      if (cursor < start) {
+        std::cout.write(
+          line.data() + cursor,
+          start - cursor
+        );
+      }
+      const auto highlight = ctx.theme.get(token);
+      apply(std::cout, highlight);
+      std::cout.write(line.data() + start, end - start);
+      reset(std::cout);
+      cursor = end;
+    }
+    if (cursor < line.size())
+      std::cout.write(line.data() + cursor, line.size() - cursor);
+    std::cout << '\n';
+    ++start_line;
+  }
   prev_range.start = start_line;
   prev_range.end = end_line;
 }