class_name NonReentrantCoroutineMutex extends RefCounted

signal relinquished

var _thread_mutex: Mutex
var _busy := false

func _init() -> void:
	_thread_mutex = Mutex.new()

func acquire() -> void:
	_thread_mutex.lock()
	while _busy:
		await relinquished
	_busy = true

func relinquish() -> void:
	if _busy:
		_busy = false
		relinquished.emit()
	_thread_mutex.unlock()

func guard(thunk: Callable) -> Variant:
	await acquire()
	var result: Variant = await thunk.call()
	relinquish()
	return result