/**
 *  StartAudioContext.js
 *  @author Yotam Mann
 *  @license http://opensource.org/licenses/MIT MIT License
 *  @copyright 2016 Yotam Mann
 */
(function (root, factory) {
  if (typeof define === "function" && define.amd) {
    define([], factory);
  } else if (typeof module === "object" && module.exports) {
    module.exports = factory();
  } else {
    root.StartAudioContext = factory();
  }
})(this, function () {
  /**
   * The StartAudioContext object
   */
  var StartAudioContext = {
    /**
     * The audio context passed in by the user
     * @type {AudioContext}
     */
    context: null,
    /**
     * The TapListeners bound to the elements
     * @type {Array}
     * @private
     */
    _tapListeners: [],
    /**
     * Callbacks to invoke when the audio context is started
     * @type {Array}
     * @private
     */
    _onStarted: [],
  };

  /**
   * Set the context
   * @param {AudioContext} ctx
   * @returns {StartAudioContext}
   */
  StartAudioContext.setContext = function (ctx) {
    StartAudioContext.context = ctx;
    return StartAudioContext;
  };

  /**
   * Add a tap listener to the audio context
   * @param  {Array|Element|String|jQuery} element
   * @returns {StartAudioContext}
   */
  StartAudioContext.on = function (element) {
    if (Array.isArray(element) || (NodeList && element instanceof NodeList)) {
      for (var i = 0; i < element.length; i++) {
        StartAudioContext.on(element[i]);
      }
    } else if (typeof element === "string") {
      StartAudioContext.on(document.querySelectorAll(element));
    } else if (element.jquery && typeof element.toArray === "function") {
      StartAudioContext.on(element.toArray());
    } else if (Element && element instanceof Element) {
      //if it's an element, create a TapListener
      var tap = new TapListener(element, onTap);
      StartAudioContext._tapListeners.push(tap);
    }
    return StartAudioContext;
  };

  /**
   * Bind a callback to when the audio context is started.
   * @param {Function} cb
   * @return {StartAudioContext}
   */
  StartAudioContext.onStarted = function (cb) {
    //if it's already started, invoke the callback
    if (StartAudioContext.isStarted()) {
      cb();
    } else {
      StartAudioContext._onStarted.push(cb);
    }
    return StartAudioContext;
  };

  /**
   * returns true if the context is started
   * @return {Boolean}
   */
  StartAudioContext.isStarted = function () {
    return (
      StartAudioContext.context !== null &&
      StartAudioContext.context.state === "running"
    );
  };

  /**
   * @class  Listens for non-dragging tap ends on the given element
   * @param {Element} element
   * @internal
   */
  var TapListener = function (element) {
    this._dragged = false;

    this._element = element;

    this._bindedMove = this._moved.bind(this);
    this._bindedEnd = this._ended.bind(this);

    element.addEventListener("touchmove", this._bindedMove);
    element.addEventListener("touchend", this._bindedEnd);
    element.addEventListener("mouseup", this._bindedEnd);
  };

  /**
   * drag move event
   */
  TapListener.prototype._moved = function (e) {
    this._dragged = true;
  };

  /**
   * tap ended listener
   */
  TapListener.prototype._ended = function (e) {
    if (!this._dragged) {
      onTap();
    }
    this._dragged = false;
  };

  /**
   * remove all the bound events
   */
  TapListener.prototype.dispose = function () {
    this._element.removeEventListener("touchmove", this._bindedMove);
    this._element.removeEventListener("touchend", this._bindedEnd);
    this._element.removeEventListener("mouseup", this._bindedEnd);
    this._bindedMove = null;
    this._bindedEnd = null;
    this._element = null;
  };

  /**
   * Invoked the first time of the elements is tapped.
   * Creates a silent oscillator when a non-dragging touchend
   * event has been triggered.
   */
  function onTap() {
    //start the audio context with a silent oscillator
    if (StartAudioContext.context && !StartAudioContext.isStarted()) {
      var osc = StartAudioContext.context.createOscillator();
      var silent = StartAudioContext.context.createGain();
      silent.gain.value = 0;
      osc.connect(silent);
      silent.connect(StartAudioContext.context.destination);
      var now = StartAudioContext.context.currentTime;
      osc.start(now);
      osc.stop(now + 0.5);
    }

    //dispose all the tap listeners
    if (StartAudioContext._tapListeners) {
      for (var i = 0; i < StartAudioContext._tapListeners.length; i++) {
        StartAudioContext._tapListeners[i].dispose();
      }
      StartAudioContext._tapListeners = null;
    }
    //the onstarted callbacks
    if (StartAudioContext._onStarted) {
      for (var j = 0; j < StartAudioContext._onStarted.length; j++) {
        StartAudioContext._onStarted[j]();
      }
      StartAudioContext._onStarted = null;
    }
  }

  return StartAudioContext;
});