Add basic scripting support.

- Fix certain bugs in ruby parser
- And a lot more cleanup/minor fixes.

include/internal/scripting/ruby.h

@@ -0,0 +1,43 @@
+#pragma once
+
+#include "definitions.h"
+#include "pch.h"
+
+namespace bed::internal::scripting {
+struct Block {
+  mrb_value proc;
+  mrb_state *mrb;
+
+  Block(mrb_state *mrb, mrb_value proc)
+      : proc(proc), mrb(mrb) {
+    mrb_gc_register(mrb, proc);
+  }
+
+  Block() : proc(mrb_nil_value()) {}
+
+  ~Block() {
+    if (!mrb_nil_p(proc))
+      mrb_gc_unregister(mrb, proc);
+  }
+
+  void set_proc(mrb_value new_proc) {
+    if (!mrb_nil_p(proc))
+      mrb_gc_unregister(mrb, proc);
+    proc = new_proc;
+    mrb_gc_register(mrb, proc);
+  }
+
+  Block(const Block &) = delete;
+  Block &operator=(const Block &) = delete;
+
+  mrb_value call(int argc = 0, mrb_value *argv = nullptr) const {
+    if (mrb_nil_p(proc))
+      return mrb_nil_value();
+    mrb_value result = mrb_funcall_argv(mrb, proc, mrb_intern_cstr(mrb, "call"), argc, argv);
+    return result;
+  }
+};
+
+void register_basic(BEd &ctx);
+void run(BEd &ctx, const std::string &str);
+}; // namespace bed::internal::scripting