class Semaphore {
  private _count: number;
  private _queue: Function[];

  constructor(count: number) {
    this._count = count;
    this._queue = [];
  }

  public tryAcquire(): boolean {
    if (this._count > 0) {
      this._count--;
      return true;
    }
    return false;
  }

  public acquire(): Promise<void> {
    return new Promise<void>((resolve, reject) => {
      if (this._count > 0) {
        this._count--;
        resolve();
      } else {
        this._queue.push(resolve);
      }
    });
  }

  public release(): void {
    if (this._queue.length > 0) {
      // @ts-ignore
      this._queue.shift()();
    } else {
      this._count++;
    }
  }
}

export default Semaphore;