NodeJS | Module: Repeat | Offers an abstraction for a repeatable task execution, wrapping it up in a startable and stoppable object.

repeat.js

/**
 * @module  Repeat
 * @desc    Offers an abstraction for a repeatable task execution, wrapping it up in a startable and stoppable object.
 * @see     {@link https://gist.github.com/andresmatasuarez/34ff17f63affe05e77a3| GitHub gist}
 * @author  Andrés Mata Suárez <amatasuarez@gmail>
 * @license {@link http://www.opensource.org/licenses/mit-license.php| MIT License}
 *
 * @requires {@link https://github.com/petkaantonov/bluebird| bluebird}
 * @requires {@link https://gist.github.com/andresmatasuarez/66edcd9710986cca4c59| Log}
 *
 * @example
 * var Repeat = require('./repeat');
 *
 * var task = function(){
 *   return promiseAction(...);
 * };
 *
 * var repeatable = new Repeat('My task', task, 5000);
 *
 * // Start task
 * repeatable.start();
 *
 * // Stop task
 * repeatable.stop();
 */

'use strict';

var CancellationError = require('bluebird').CancellationError;
var Log               = require('./log');

function _repeat(taskName, task, delay){
  return task()
  .cancellable()
  .then(function(){
    Log.Repeat.waiting(delay, taskName);
  })
  .delay(delay)
  .then(function(){
    Log.Repeat.repeat(taskName);
    return _repeat(taskName, task, delay);
  })
  .catch(CancellationError, function(){
    Log.Repeat.stop(taskName);
  });
}

/**
 * @constructor
 *
 * @param {string}   taskName  - Name that identifies this task.
 * @param {function} task      - Task to be repeated (as a function returning a Bluebird promise).
 * @param {number}   delay     - Delay before repetition after task completion.
 *
 */
function Repeat(taskName, task, delay){
  this.taskName       = taskName;
  this.task           = task;
  this.delay          = delay;
  this.firstExecution = true;
}

/**
 * Starts execution of task.
 */
Repeat.prototype.start = function(){
  if (this.runningTask){
    Log.Repeat.alreadyStarted(this.taskName);
    return;
  }

  Log.Repeat.start(this.taskName);

  this.firstExecution = false;
  this.runningTask    = _repeat(this.taskName, this.task, this.delay);
};

/**
 * Stops execution of task.
 */
Repeat.prototype.stop = function(){
  if (!this.runningTask){
    Log.Repeat.alreadyStopped(this.taskName);
    return;
  }
  Log.Repeat.stop(this.taskName);
  this.runningTask.cancel();
  this.firstExecution = true;
  delete this.runningTask;
};

/**
 * Static method to fire a repeatable task and forget about it, leaving it running indefinitely.
 */
Repeat.fireAndForget = function(taskName, task, delay){
  new Repeat(taskName, task, delay).start();
};

module.exports = Repeat;