class Pool {

    constructor (queues, options) {
        options = options || {};
        this._polling = options.polling || 100;
        this._qq = [];
        for (let i = 0; i < queues; i++) {
            this._qq.push(new Queue(i + 1));
        }
    }

    addTask (weight, task) {
        if (typeof(weight) === "function") {
            task = weight;
            weight = 1;
        }

        let queue = this._qq[0];
        if (this._qq.length > 1) {
            for (const q of this._qq) {
                if (queue.weight === 0) break;
                if (q.weight < queue.weight) queue = q;
            };
        };
        queue.add(weight, task);
    }

    addBatch (tasks) {
        for (const task of tasks) {
            this.addTask(task);
        }
    }

    wait (timeout = null) {
        const start = new Date();

        return new Promise((resolve, reject) => {
            const timerId = setInterval(() => {

                let q, isFinished = true;
                for (q of this._qq) {
                    if (q.weight > 0) {
                        isFinished = false;
                        break;
                    }
                }

                if (isFinished) {
                    clearInterval(timerId);
                    resolve();
                    return;
                }

                if (timeout != null && (new Date() - start > timeout)) {
                    clearInterval(timerId);
                    for (q of this._qq) {
                        q.close();
                    }
                    reject(Error(`Timeout ${timeout} ms has expired`));
                    return;
                }
            }, this._polling);
        })
    }
}