(function ($) {
  AblePlayer.prototype.initDescription = function() {

    // set default mode for delivering description (open vs closed)
    // based on availability and user preference

    // called when player is being built, or when a user
    // toggles the Description button or changes a description-related preference
    // In the latter two scendarios, this.refreshingDesc == true via control.js > handleDescriptionToggle()

    // The following variables are applicable to delivery of description:
    // prefDesc == 1 if user wants description (i.e., Description button is on); else 0
    // prefDescFormat == either 'video' or 'text'
    // prefDescPause == 1 to pause video when description starts; else 0
    // prefVisibleDesc == 1 to visibly show text-based description area; else 0
    // hasOpenDesc == true if a described version of video is available via data-desc-src attribute
    // hasClosedDesc == true if a description text track is available
    // this.useDescFormat == either 'video' or 'text'; the format ultimately delivered
    // descOn == true if description of either type is on
    if (!this.refreshingDesc) {
      // this is the initial build
      // first, check to see if there's an open-described version of this video
      // checks only the first source since if a described version is provided,
      // it must be provided for all sources
      this.descFile = this.$sources.first().attr('data-desc-src');
      if (typeof this.descFile !== 'undefined') {
        this.hasOpenDesc = true;
      }
      else {
        // there's no open-described version via data-desc-src, but what about data-youtube-desc-src?
        if (this.youTubeDescId) {
          this.hasOpenDesc = true;
        }
        else { // there are no open-described versions from any source
          this.hasOpenDesc = false;
        }
      }
    }
    // update this.useDescFormat based on media availability & user preferences
    if (this.prefDesc) {
      if (this.hasOpenDesc && this.hasClosedDesc) {
        // both formats are available. Use whichever one user prefers
        this.useDescFormat = this.prefDescFormat;
        this.descOn = true;
      }
      else if (this.hasOpenDesc) {
        this.useDescFormat = 'video';
        this.descOn = true;
      }
      else if (this.hasClosedDesc) {
        this.useDescFormat = 'text';
        this.descOn = true;
      }
    }
    else { // description button is off
      if (this.refreshingDesc) { // user just now toggled it off
        this.prevDescFormat = this.useDescFormat;
        this.useDescFormat = false;
        this.descOn = false;
      }
      else { // desc has always been off
        this.useDescFormat = false;
      }
    }

    if (this.descOn) {

      if (this.useDescFormat === 'video') {

        if (!this.usingAudioDescription()) {
          // switched from non-described to described version
          this.swapDescription();
        }
        // hide description div
        this.$descDiv.hide();
        this.$descDiv.removeClass('able-clipped');
      }
      else if (this.useDescFormat === 'text') {
        this.$descDiv.show();
        if (this.prefVisibleDesc) { // make it visible to everyone
          this.$descDiv.removeClass('able-clipped');
        }
        else { // keep it visible to screen readers, but hide from everyone else
          this.$descDiv.addClass('able-clipped');
        }
        if (!this.swappingSrc) {
          this.showDescription(this.getElapsed());
        }
      }
    }
    else { // description is off.

      if (this.prevDescFormat === 'video') { // user was previously using description via video
        if (this.usingAudioDescription()) {
          this.swapDescription();
        }
      }
      else if (this.prevDescFormat === 'text') { // user was previously using text description
        // hide description div from everyone, including screen reader users
        this.$descDiv.hide();
        this.$descDiv.removeClass('able-clipped');
      }
    }
    this.refreshingDesc = false;
  };

  // Returns true if currently using audio description, false otherwise.
  AblePlayer.prototype.usingAudioDescription = function () {

    if (this.player === 'youtube') {
      return (this.activeYouTubeId === this.youTubeDescId);
    }
    else {
      return (this.$sources.first().attr('data-desc-src') === this.$sources.first().attr('src'));
    }
  };

  AblePlayer.prototype.swapDescription = function() {
    // swap described and non-described source media, depending on which is playing
    // this function is only called in two circumstances:
    // 1. Swapping to described version when initializing player (based on user prefs & availability)
    // 2. User is toggling description
    var thisObj, i, origSrc, descSrc, srcType, jwSourceIndex, newSource;

    thisObj = this;

    // get current time, and start new video at the same time
    // NOTE: There is some risk in resuming playback at the same start time
    // since the described version might include extended audio description (with pauses)
    // and might therefore be longer than the non-described version
    // The benefits though would seem to outweigh this risk
    this.swapTime = this.getElapsed(); // video will scrub to this time after loaded (see event.js)

    if (this.descOn) {
      // user has requested the described version
      this.showAlert(this.tt.alertDescribedVersion);
    }
    else {
      // user has requested the non-described version
      this.showAlert(this.tt.alertNonDescribedVersion);
    }

    if (this.player === 'html5') {

      if (this.usingAudioDescription()) {
        // the described version is currently playing. Swap to non-described
        for (i=0; i < this.$sources.length; i++) {
          // for all <source> elements, replace src with data-orig-src
          origSrc = this.$sources[i].getAttribute('data-orig-src');
          srcType = this.$sources[i].getAttribute('type');
          if (origSrc) {
            this.$sources[i].setAttribute('src',origSrc);
          }
          if (srcType === 'video/mp4') {
            jwSourceIndex = i;
          }
        }
        // No need to check for this.initializing
        // This function is only called during initialization
        // if swapping from non-described to described
        this.swappingSrc = true;
      }
      else {
        // the non-described version is currently playing. Swap to described.
        for (i=0; i < this.$sources.length; i++) {
          // for all <source> elements, replace src with data-desc-src (if one exists)
          // then store original source in a new data-orig-src attribute
          origSrc = this.$sources[i].getAttribute('src');
          descSrc = this.$sources[i].getAttribute('data-desc-src');
          srcType = this.$sources[i].getAttribute('type');
          if (descSrc) {
            this.$sources[i].setAttribute('src',descSrc);
            this.$sources[i].setAttribute('data-orig-src',origSrc);
          }
          if (srcType === 'video/mp4') {
            jwSourceIndex = i;
          }
        }
        this.swappingSrc = true;
      }

      // now reload the source file.
      if (this.player === 'html5') {
        this.media.load();
      }
      else if (this.player === 'youtube') {
        // TODO: Load new youTubeId
      }
      else if (this.player === 'jw' && this.jwPlayer) {
        newSource = this.$sources[jwSourceIndex].getAttribute('src');
        this.jwPlayer.load({file: newSource});
      }
    }
    else if (this.player === 'youtube') {

      if (this.usingAudioDescription()) {
        // the described version is currently playing. Swap to non-described
        this.activeYouTubeId = this.youTubeId;
        this.showAlert(this.tt.alertNonDescribedVersion);
      }
      else {
        // the non-described version is currently playing. Swap to described.
        this.activeYouTubeId = this.youTubeDescId;
        this.showAlert(this.tt.alertDescribedVersion);
      }
      if (typeof this.youTubePlayer !== 'undefined') {

        // retrieve/setup captions for the new video from YouTube
        this.setupAltCaptions().then(function() {

          if (thisObj.playing) {
            // loadVideoById() loads and immediately plays the new video at swapTime
            thisObj.youTubePlayer.loadVideoById(thisObj.activeYouTubeId,thisObj.swapTime);
          }
          else {
            // cueVideoById() loads the new video and seeks to swapTime, but does not play
            thisObj.youTubePlayer.cueVideoById(thisObj.activeYouTubeId,thisObj.swapTime);
          }
        });
      }
    }
  };

  AblePlayer.prototype.showDescription = function(now) {

    // there's a lot of redundancy between this function and showCaptions
    // Trying to combine them ended up in a mess though. Keeping as is for now.

    if (this.swappingSrc) {
      return;
    }

    var d, thisDescription;
    var flattenComponentForDescription = function (component) {
      var result = [];
      if (component.type === 'string') {
        result.push(component.value);
      }
      else {
        for (var ii = 0; ii < component.children.length; ii++) {
          result.push(flattenComponentForDescription(component.children[ii]));
        }
      }
      return result.join('');
    };

    var cues;
    if (this.selectedDescriptions) {
      cues = this.selectedDescriptions.cues;
    }
    else if (this.descriptions.length >= 1) {
      cues = this.descriptions[0].cues;
    }
    else {
      cues = [];
    }
    for (d = 0; d < cues.length; d++) {
      if ((cues[d].start <= now) && (cues[d].end > now)) {
        thisDescription = d;
        break;
      }
    }
    if (typeof thisDescription !== 'undefined') {
      if (this.currentDescription !== thisDescription) {
        // temporarily remove aria-live from $status in order to prevent description from being interrupted
        this.$status.removeAttr('aria-live');
        // load the new description into the container div
        this.$descDiv.html(flattenComponentForDescription(cues[thisDescription].components));
        if (this.prefDescPause) {
          this.pauseMedia();
        }
        this.currentDescription = thisDescription;
      }
    }
    else {
      this.$descDiv.html('');
      this.currentDescription = -1;
      // restore aria-live to $status
      this.$status.attr('aria-live','polite');
    }
  };

})(jQuery);