custom-idle-queue/dist/es/index.js

Optimize the speed of important tasks on limited ressources

/**
 * Creates a new Idle-Queue
 * @constructor
 * @param {number} [parallels=1] amount of parrallel runs of the limited-ressource
 */
export var IdleQueue = function IdleQueue() {
  var parallels = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : 1;
  this._parallels = parallels || 1;
  /**
   * _queueCounter
   * each lock() increased this number
   * each unlock() decreases this number
   * If _qC==0, the state is in idle
   * @type {Number}
   */

  this._qC = 0;
  /**
   * _idleCalls
   * contains all promises that where added via requestIdlePromise()
   * and not have been resolved
   * @type {Set<Promise>} _iC with oldest promise first
   */

  this._iC = new Set();
  /**
   * _lastHandleNumber
   * @type {Number}
   */

  this._lHN = 0;
  /**
   * _handlePromiseMap
   * Contains the handleNumber on the left
   * And the assigned promise on the right.
   * This is stored so you can use cancelIdleCallback(handleNumber)
   * to stop executing the callback.
   * @type {Map<Number><Promise>}
   */

  this._hPM = new Map();
  this._pHM = new Map(); // _promiseHandleMap
};
IdleQueue.prototype = {
  isIdle: function isIdle() {
    return this._qC < this._parallels;
  },

  /**
   * creates a lock in the queue
   * and returns an unlock-function to remove the lock from the queue
   * @return {function} unlock function than must be called afterwards
   */
  lock: function lock() {
    this._qC++;
  },
  unlock: function unlock() {
    this._qC--;

    _tryIdleCall(this);
  },

  /**
   * wraps a function with lock/unlock and runs it
   * @param  {function}  fun
   * @return {Promise<any>}
   */
  wrapCall: function wrapCall(fun) {
    var _this = this;

    this.lock();
    var maybePromise;

    try {
      maybePromise = fun();
    } catch (err) {
      this.unlock();
      throw err;
    }

    if (!maybePromise.then || typeof maybePromise.then !== 'function') {
      // no promise
      this.unlock();
      return maybePromise;
    } else {
      // promise
      return maybePromise.then(function (ret) {
        // sucessfull -> unlock before return
        _this.unlock();

        return ret;
      })["catch"](function (err) {
        // not sucessfull -> unlock before throwing
        _this.unlock();

        throw err;
      });
    }
  },

  /**
   * does the same as requestIdleCallback() but uses promises instead of the callback
   * @param {{timeout?: number}} options like timeout
   * @return {Promise<void>} promise that resolves when the database is in idle-mode
   */
  requestIdlePromise: function requestIdlePromise(options) {
    var _this2 = this;

    options = options || {};
    var resolve;
    var prom = new Promise(function (res) {
      return resolve = res;
    });

    var resolveFromOutside = function resolveFromOutside() {
      _removeIdlePromise(_this2, prom);

      resolve();
    };

    prom._manRes = resolveFromOutside;

    if (options.timeout) {
      // if timeout has passed, resolve promise even if not idle
      var timeoutObj = setTimeout(function () {
        prom._manRes();
      }, options.timeout);
      prom._timeoutObj = timeoutObj;
    }

    this._iC.add(prom);

    _tryIdleCall(this);

    return prom;
  },

  /**
   * remove the promise so it will never be resolved
   * @param  {Promise} promise from requestIdlePromise()
   * @return {void}
   */
  cancelIdlePromise: function cancelIdlePromise(promise) {
    _removeIdlePromise(this, promise);
  },

  /**
   * api equal to
   * @link https://developer.mozilla.org/en-US/docs/Web/API/Window/requestIdleCallback
   * @param  {Function} callback
   * @param  {options}   options  [description]
   * @return {number} handle which can be used with cancelIdleCallback()
   */
  requestIdleCallback: function requestIdleCallback(callback, options) {
    var handle = this._lHN++;
    var promise = this.requestIdlePromise(options);

    this._hPM.set(handle, promise);

    this._pHM.set(promise, handle);

    promise.then(function () {
      return callback();
    });
    return handle;
  },

  /**
   * API equal to
   * @link https://developer.mozilla.org/en-US/docs/Web/API/Window/cancelIdleCallback
   * @param  {number} handle returned from requestIdleCallback()
   * @return {void}
   */
  cancelIdleCallback: function cancelIdleCallback(handle) {
    var promise = this._hPM.get(handle);

    this.cancelIdlePromise(promise);
  },

  /**
   * clears and resets everything
   * @return {void}
   */
  clear: function clear() {
    var _this3 = this;

    // remove all non-cleared
    this._iC.forEach(function (promise) {
      return _removeIdlePromise(_this3, promise);
    });

    this._qC = 0;

    this._iC.clear();

    this._hPM = new Map();
    this._pHM = new Map();
  }
};
/**
 * processes the oldest call of the idleCalls-queue
 * @return {Promise<void>}
 */

function _resolveOneIdleCall(idleQueue) {
  if (idleQueue._iC.size === 0) return;

  var iterator = idleQueue._iC.values();

  var oldestPromise = iterator.next().value;

  oldestPromise._manRes(); // try to call the next tick


  setTimeout(function () {
    return _tryIdleCall(idleQueue);
  }, 0);
}
/**
 * removes the promise from the queue and maps and also its corresponding handle-number
 * @param  {Promise} promise from requestIdlePromise()
 * @return {void}
 */


function _removeIdlePromise(idleQueue, promise) {
  if (!promise) return; // remove timeout if exists

  if (promise._timeoutObj) clearTimeout(promise._timeoutObj); // remove handle-nr if exists

  if (idleQueue._pHM.has(promise)) {
    var handle = idleQueue._pHM.get(promise);

    idleQueue._hPM["delete"](handle);

    idleQueue._pHM["delete"](promise);
  } // remove from queue


  idleQueue._iC["delete"](promise);
}
/**
 * resolves the last entry of this._iC
 * but only if the queue is empty
 * @return {Promise}
 */


function _tryIdleCall(idleQueue) {
  // ensure this does not run in parallel
  if (idleQueue._tryIR || idleQueue._iC.size === 0) return;
  idleQueue._tryIR = true; // w8 one tick

  setTimeout(function () {
    // check if queue empty
    if (!idleQueue.isIdle()) {
      idleQueue._tryIR = false;
      return;
    }
    /**
     * wait 1 tick here
     * because many functions do IO->CPU->IO
     * which means the queue is empty for a short time
     * but the ressource is not idle
     */


    setTimeout(function () {
      // check if queue still empty
      if (!idleQueue.isIdle()) {
        idleQueue._tryIR = false;
        return;
      } // ressource is idle


      _resolveOneIdleCall(idleQueue);

      idleQueue._tryIR = false;
    }, 0);
  }, 0);
}