7_3_tamper_free_queue.js

const http = require('http');

class Queue {
  constructor(executor) {
    this._queue = [];
    this._commandQueue = [];

    const enqueue = (item) => {
      this._queue.push(item);

      this._commandQueue.forEach(command => command());
      this._commandQueue = [];
    };
    executor(enqueue);
  }

  dequeue() {
    if (this._queue.length === 0) {
      return new Promise((resolve, reject) => {
        const command = () => this.dequeue().then(resolve, reject);
        process.nextTick(() => this._commandQueue.push(command));
      });
    }

    return new Promise((resolve, reject) => {
      try {
        const item = this._queue.shift();
        resolve(item);
      } catch (err) {
        reject(err);
      }
    });
  }
}

const messagesQueue = new Queue((enqueue) => {
  http
    .createServer((req, res) => {
      let data = '';

      req.on('data', chunk => {
        data += chunk;
      });

      req.on('end', () => {
        enqueue(data);
        res.end();
      });
    })
    .listen(8080, async () => {
      console.log('Server listening on http://localhost:8080');
      console.log('Waiting for messages to be enqueued...');

      while (true) {
        const msg = await messagesQueue.dequeue();
        console.log(`Dequeued message "${msg}"`);
      }
    });
});