//Adapted from Frequent Time Update for HTML5 Video
//https://github.com/nathancahill/video-freqtimeupdate

// Polyfill from MDN for the CustomEvent constructor in IE9+
// https://developer.mozilla.org/en-US/docs/Web/API/CustomEvent/CustomEvent
(function() {
  function CustomEvent(event, params) {
    params = params || { bubbles: false, cancelable: false, detail: undefined };
    var evt = document.createEvent('CustomEvent');
    evt.initCustomEvent(
      event,
      params.bubbles,
      params.cancelable,
      params.detail,
    );
    return evt;
  }

  CustomEvent.prototype = window.Event.prototype;

  window.CustomEvent = CustomEvent;
})();

(function(global) {
  'use strict';

  // Create the new `freqtimeupdate` event
  var freqtimeupdate = global.CustomEvent('freqtimeupdate'),
    // The event frequency in milliseconds
    frequency = 100,
    // Wrappers around setInterval and clearInterval to ensure one interval per audio
    setInterval = function() {
      if (!this.hasOwnProperty('_interval')) {
        this._interval = global.setInterval(intervalFunc.bind(this), frequency);
      }
    },
    clearInterval = function() {
      global.clearInterval(this._interval);
      delete this._interval;
    },
    // The actual interval function that dispatches the event
    intervalFunc = function() {
      this.dispatchEvent(freqtimeupdate);
    },
    // Get all audios from the page to add the event to
    audios = global.document.getElementsByTagName('audio');

  // Add listeners to the audios for adding and removing the interval
  for (var i = 0; i < audios.length; i++) {
    if (!audios[i].paused) {
      setInterval.call(audios[i]);
    }

    audios[i].addEventListener('play', setInterval);
    audios[i].addEventListener('playing', setInterval);
    audios[i].addEventListener('seeked', setInterval);

    audios[i].addEventListener('abort', clearInterval);
    audios[i].addEventListener('emptied', clearInterval);
    audios[i].addEventListener('ended', clearInterval);
    audios[i].addEventListener('pause', clearInterval);
  }
})(window);