Implement syntax highlighting

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

include/internal/syntax/ruby/parser.h

@@ -0,0 +1,103 @@
+#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;
+
+  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(uint32_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 = 0,
+      .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> *);
+} // namespace bed::internal::syntax::ruby