countDownLatch.ts

export interface CountDownLatchOptions
{
    timeout ?: number;
}

export type CountDownLatchCallback = (isTimeout ?:boolean)=>void;

/**
 * Count down to zero or timeout and invoke cb finally.
 */
export class CountDownLatch
{
    count: number;
    cb: CountDownLatchCallback;
    timerId: any;
    constructor(count : number, opts : CountDownLatchOptions, cb : CountDownLatchCallback)
    {
        this.count = count;
        this.cb = cb;
        let self = this;
        if (opts.timeout)
        {
            this.timerId = setTimeout(function ()
            {
                self.cb(true);
            }, opts.timeout);
        }
    };

    /**
     * Call when a task finish to count down.
     *
     * @api public
     */
    done()
    {
        if (this.count <= 0)
        {
            throw new Error('illegal state.');
        }

        this.count--;
        if (this.count === 0)
        {
            if (this.timerId)
            {
                clearTimeout(this.timerId);
            }
            this.cb();
        }
    };
}

/**
 * Create a count down latch
 *
 * @param {Integer} count
 * @param {Object} opts, opts.timeout indicates timeout, optional param
 * @param {Function} cb, cb(isTimeout)
 *
 * @api public
 */
export function createCountDownLatch(count : number, cb ?: CountDownLatchCallback):CountDownLatch;
export function createCountDownLatch(count : number, opts :  CountDownLatchOptions, cb ?: CountDownLatchCallback):CountDownLatch;
export function createCountDownLatch(count : number, opts ?: CountDownLatchCallback | CountDownLatchOptions, cb ?: CountDownLatchCallback)
 {
  if(!count || count <= 0) {
    throw new Error('count should be positive.');
  }

  if (!cb && typeof opts === 'function') {
    cb = opts;
    opts = {};
  }

  if(typeof cb !== 'function') {
    throw new Error('cb should be a function.');
  }

  return new CountDownLatch(count, opts as CountDownLatchOptions, cb);
};