import videojs from 'video.js';
import QualityLevel from './quality-level.js';

/**
 * A list of QualityLevels.
 *
 * interface QualityLevelList : EventTarget {
 *   getter QualityLevel (unsigned long index);
 *   readonly attribute unsigned long length;
 *   readonly attribute long selectedIndex;
 *
 *   void addQualityLevel(QualityLevel qualityLevel)
 *   void removeQualityLevel(QualityLevel remove)
 *   QualityLevel? getQualityLevelById(DOMString id);
 *
 *   attribute EventHandler onchange;
 *   attribute EventHandler onaddqualitylevel;
 *   attribute EventHandler onremovequalitylevel;
 * };
 *
 * @extends videojs.EventTarget
 * @class QualityLevelList
 */
class QualityLevelList extends videojs.EventTarget {
  /**
   * Creates a QualityLevelList.
   */
  constructor() {
    super();

    let list = this; // eslint-disable-line

    list.levels_ = [];
    list.selectedIndex_ = -1;

    /**
     * Get the index of the currently selected QualityLevel.
     *
     * @returns {number} The index of the selected QualityLevel. -1 if none selected.
     * @readonly
     */
    Object.defineProperty(list, 'selectedIndex', {
      get() {
        return list.selectedIndex_;
      }
    });

    /**
     * Get the length of the list of QualityLevels.
     *
     * @returns {number} The length of the list.
     * @readonly
     */
    Object.defineProperty(list, 'length', {
      get() {
        return list.levels_.length;
      }
    });

    list[Symbol.iterator] = () => list.levels_.values();

    return list;
  }

  /**
   * Adds a quality level to the list.
   *
   * @param {Representation|Object} representation The representation of the quality level
   * @param {string}   representation.id        Unique id of the QualityLevel
   * @param {number=}  representation.width     Resolution width of the QualityLevel
   * @param {number=}  representation.height    Resolution height of the QualityLevel
   * @param {number}   representation.bandwidth Bitrate of the QualityLevel
   * @param {number=}  representation.frameRate Frame-rate of the QualityLevel
   * @param {Function} representation.enabled   Callback to enable/disable QualityLevel
   * @return {QualityLevel} the QualityLevel added to the list
   * @method addQualityLevel
   */
  addQualityLevel(representation) {
    let qualityLevel = this.getQualityLevelById(representation.id);

    // Do not add duplicate quality levels
    if (qualityLevel) {
      return qualityLevel;
    }

    const index = this.levels_.length;

    qualityLevel = new QualityLevel(representation);

    if (!('' + index in this)) {
      Object.defineProperty(this, index, {
        get() {
          return this.levels_[index];
        }
      });
    }

    this.levels_.push(qualityLevel);

    this.trigger({
      qualityLevel,
      type: 'addqualitylevel'
    });

    return qualityLevel;
  }

  /**
   * Removes a quality level from the list.
   *
   * @param {QualityLevel} qualityLevel The QualityLevel to remove from the list.
   * @return {QualityLevel|null} the QualityLevel removed or null if nothing removed
   * @method removeQualityLevel
   */
  removeQualityLevel(qualityLevel) {
    let removed = null;

    for (let i = 0, l = this.length; i < l; i++) {
      if (this[i] === qualityLevel) {
        removed = this.levels_.splice(i, 1)[0];

        if (this.selectedIndex_ === i) {
          this.selectedIndex_ = -1;
        } else if (this.selectedIndex_ > i) {
          this.selectedIndex_--;
        }
        break;
      }
    }

    if (removed) {
      this.trigger({
        qualityLevel,
        type: 'removequalitylevel'
      });
    }

    return removed;
  }

  /**
   * Searches for a QualityLevel with the given id.
   *
   * @param {string} id The id of the QualityLevel to find.
   * @return {QualityLevel|null} The QualityLevel with id, or null if not found.
   * @method getQualityLevelById
   */
  getQualityLevelById(id) {
    for (let i = 0, l = this.length; i < l; i++) {
      const level = this[i];

      if (level.id === id) {
        return level;
      }
    }
    return null;
  }

  /**
   * Resets the list of QualityLevels to empty
   *
   * @method dispose
   */
  dispose() {
    this.selectedIndex_ = -1;
    this.levels_.length = 0;
  }
}

/**
 * change - The selected QualityLevel has changed.
 * addqualitylevel - A QualityLevel has been added to the QualityLevelList.
 * removequalitylevel - A QualityLevel has been removed from the QualityLevelList.
 */
QualityLevelList.prototype.allowedEvents_ = {
  change: 'change',
  addqualitylevel: 'addqualitylevel',
  removequalitylevel: 'removequalitylevel'
};

// emulate attribute EventHandler support to allow for feature detection
for (const event in QualityLevelList.prototype.allowedEvents_) {
  QualityLevelList.prototype['on' + event] = null;
}

export default QualityLevelList;