'use strict';

// Queue tuần tự hoá thao tác Puppeteer — tránh race condition trong 1 browser slot
class AsyncQueue {
  constructor(name = 'default') {
    this._name    = name;
    this._running = false;
    this._queue   = [];
  }

  add(fn, label = 'task') {
    return new Promise((resolve, reject) => {
      this._queue.push({ fn, resolve, reject, label });
      this._next();
    });
  }

  async _next() {
    if (this._running || this._queue.length === 0) return;
    this._running = true;

    const { fn, resolve, reject, label } = this._queue.shift();
    try {
      console.log(`[queue:${this._name}] → ${label}`);
      resolve(await fn());
    } catch (err) {
      console.error(`[queue:${this._name}] ✗ ${label}:`, err.message);
      reject(err);
    } finally {
      this._running = false;
      this._next();
    }
  }

  get size() { return this._queue.length; }
  get busy() { return this._running; }
}

module.exports = new AsyncQueue('global');
module.exports.AsyncQueue = AsyncQueue;