/**
 * represents an acquired lock that can be released
 */
export interface Lock extends Disposable {
	dispose(): void;
}

/**
 * provides mutual exclusion for async operations
 */
class Mutex {
	#promise = Promise.resolve();

	/**
	 * acquires the mutex, blocking until available
	 * @returns a lock that must be disposed to release the mutex
	 */
	async acquire(): Promise<Lock> {
		const { promise, resolve } = Promise.withResolvers<void>();

		const previous = this.#promise;

		this.#promise = promise;
		await previous;

		return { [Symbol.dispose]: resolve, dispose: resolve };
	}
}

export default Mutex;