#include <ruby/ruby.h>
#include <ruby/debug.h>

static VALUE rb_mPlainApm = Qnil;
static VALUE rb_mObjTracing = Qnil;

static __thread uint64_t allocated_objects = 0;

#ifdef OBJECT_TRACING_ENABLED
static int object_tracing_active = 0;

static void track_thread_allocated_objects(VALUE tpval, void *data) {
  allocated_objects++;
}
#endif

static VALUE total_thread_allocated_objects(VALUE self) {
  return ULL2NUM(allocated_objects);
}

void Init_object_tracing(void) {
  rb_mPlainApm = rb_define_module("PlainApm");
  rb_gc_register_address(&rb_mPlainApm);

  rb_mObjTracing = rb_define_module_under(rb_mPlainApm, "ObjectTracing");
  rb_gc_register_address(&rb_mObjTracing);

  rb_define_singleton_method(rb_mObjTracing, "total_thread_allocated_objects", total_thread_allocated_objects, 0);

#ifdef OBJECT_TRACING_ENABLED
  /* Ensure the tracepoint is attached only once. */
  if (object_tracing_active) { return; }

  object_tracing_active = 1;

  /* Object allocation tracing is impacted by these bugs:
   *
   * https://bugs.ruby-lang.org/issues/19112 in Rubies 3.x.x
   * https://bugs.ruby-lang.org/issues/18464 in Rubies 3.0, 3.1, and 3.2
   *
   * According to
   *
   * https://www.ruby-lang.org/en/downloads/branches/
   *
   * 3.0 goes out of maintenance mid 2024. The latter bug was backported to the
   * other branches.
   *
   * For the former, there's https://github.com/ruby/ruby/pull/7184 open,
   * unmerged as of Dec 2023.
   *
   */

  VALUE tpval = rb_tracepoint_new(0, RUBY_INTERNAL_EVENT_NEWOBJ, track_thread_allocated_objects, NULL);
  rb_tracepoint_enable(tpval);
#endif
}