bt-sensors-plugin-sk/Queue.js

Bluetooth Sensors for Signalk - see https://www.npmjs.com/package/bt-sensors-plugin-sk#supported-sensors for a list of supported sensors

/*
see: https://stackoverflow.com/questions/53540348/js-async-await-tasks-queue 
*/
 class Queue {
    constructor() { this._items = []; }
    enqueue(item) { this._items.push(item); }
    dequeue()     { return this._items.shift(); }
    get size()    { return this._items.length; }
  }
  
   class AutoQueue extends Queue {
    constructor() {
      super();
      this._pendingPromise = false;
    }
  
    enqueue(action) {
      return new Promise((resolve, reject) => {
        super.enqueue({ action, resolve, reject });
        this.dequeue();
      });
    }
  
    async dequeue() {
      if (this._pendingPromise) return false;
  
      let item = super.dequeue();
  
      if (!item) return false;
  
      try {
        this._pendingPromise = true;
  
        let payload = await item.action(this);
  
        this._pendingPromise = false;
        item.resolve(payload);
      } catch (e) {
        this._pendingPromise = false;
        item.reject(e);
      } finally {
        this.dequeue();
      }
  
      return true;
    }
  }
  module.exports = AutoQueue