import {VideoTrackKind} from './track-enums';
import Track from './track';
import merge from '../utils/merge-options';
import * as browser from '../utils/browser.js';

/**
 * A representation of a single `VideoTrack`.
 *
 * @see [Spec]{@link https://html.spec.whatwg.org/multipage/embedded-content.html#videotrack}
 * @extends Track
 */
class VideoTrack extends Track {

  /**
   * Create an instance of this class.
   *
   * @param {Object} [options={}]
   *        Object of option names and values
   *
   * @param {string} [options.kind='']
   *        A valid {@link VideoTrack~Kind}
   *
   * @param {string} [options.id='vjs_track_' + Guid.newGUID()]
   *        A unique id for this AudioTrack.
   *
   * @param {string} [options.label='']
   *        The menu label for this track.
   *
   * @param {string} [options.language='']
   *        A valid two character language code.
   *
   * @param {boolean} [options.selected]
   *        If this track is the one that is currently playing.
   */
  constructor(options = {}) {
    const settings = merge(options, {
      kind: VideoTrackKind[options.kind] || ''
    });

    // on IE8 this will be a document element
    // for every other browser this will be a normal object
    const track = super(settings);
    let selected = false;

    if (browser.IS_IE8) {
      for (const prop in VideoTrack.prototype) {
        if (prop !== 'constructor') {
          track[prop] = VideoTrack.prototype[prop];
        }
      }
    }

    /**
     * @member {boolean} selected
     *         If this `VideoTrack` is selected or not. When setting this will
     *         fire {@link VideoTrack#selectedchange} if the state of selected changed.
     *
     * @fires VideoTrack#selectedchange
     */
    Object.defineProperty(track, 'selected', {
      get() {
        return selected;
      },
      set(newSelected) {
        // an invalid or unchanged value
        if (typeof newSelected !== 'boolean' || newSelected === selected) {
          return;
        }
        selected = newSelected;

        /**
         * An event that fires when selected changes on this track. This allows
         * the VideoTrackList that holds this track to act accordingly.
         *
         * > Note: This is not part of the spec! Native tracks will do
         *         this internally without an event.
         *
         * @event VideoTrack#selectedchange
         * @type {EventTarget~Event}
         */
        this.trigger('selectedchange');
      }
    });

    // if the user sets this track to selected then
    // set selected to that true value otherwise
    // we keep it false
    if (settings.selected) {
      track.selected = settings.selected;
    }

    return track;
  }
}

export default VideoTrack;