/*
 * WebAudioSoundInstance
 * Visit http://createjs.com/ for documentation, updates and examples.
 *
 *
 * Copyright (c) 2012 gskinner.com, inc.
 *
 * Permission is hereby granted, free of charge, to any person
 * obtaining a copy of this software and associated documentation
 * files (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use,
 * copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following
 * conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 */

/**
 * @module SoundJS
 */

// namespace:
this.createjs = this.createjs || {};

/**
 * WebAudioSoundInstance extends the base api of {{#crossLink "AbstractSoundInstance"}}{{/crossLink}} and is used by
 * {{#crossLink "WebAudioPlugin"}}{{/crossLink}}.
 *
 * WebAudioSoundInstance exposes audioNodes for advanced users.
 *
 * @param {String} src The path to and file name of the sound.
 * @param {Number} startTime Audio sprite property used to apply an offset, in milliseconds.
 * @param {Number} duration Audio sprite property used to set the time the clip plays for, in milliseconds.
 * @param {Object} playbackResource Any resource needed by plugin to support audio playback.
 * @class WebAudioSoundInstance
 * @extends AbstractSoundInstance
 * @constructor
 */
(function () {
	"use strict";

	function WebAudioSoundInstance(src, startTime, duration, playbackResource) {
		this.AbstractSoundInstance_constructor(src, startTime, duration, playbackResource);


// public properties
		/**
		 * NOTE this is only intended for use by advanced users.
		 * <br />GainNode for controlling <code>WebAudioSoundInstance</code> volume. Connected to the {{#crossLink "WebAudioSoundInstance/destinationNode:property"}}{{/crossLink}}.
		 * @property gainNode
		 * @type {AudioGainNode}
		 * @since 0.4.0
		 *
		 */
		this.gainNode = s.context.createGain();

		/**
		 * NOTE this is only intended for use by advanced users.
		 * <br />A panNode allowing left and right audio channel panning only. Connected to WebAudioSoundInstance {{#crossLink "WebAudioSoundInstance/gainNode:property"}}{{/crossLink}}.
		 * @property panNode
		 * @type {AudioPannerNode}
		 * @since 0.4.0
		 */
		this.panNode = s.context.createPanner();
		this.panNode.panningModel = s._panningModel;
		this.panNode.connect(this.gainNode);
		this._updatePan();

		/**
		 * NOTE this is only intended for use by advanced users.
		 * <br />sourceNode is the audio source. Connected to WebAudioSoundInstance {{#crossLink "WebAudioSoundInstance/panNode:property"}}{{/crossLink}}.
		 * @property sourceNode
		 * @type {AudioNode}
		 * @since 0.4.0
		 *
		 */
		this.sourceNode = null;


// private properties
		/**
		 * Timeout that is created internally to handle sound playing to completion.
		 * Stored so we can remove it when stop, pause, or cleanup are called
		 * @property _soundCompleteTimeout
		 * @type {timeoutVariable}
		 * @default null
		 * @protected
		 * @since 0.4.0
		 */
		this._soundCompleteTimeout = null;

		/**
		 * NOTE this is only intended for use by very advanced users.
		 * _sourceNodeNext is the audio source for the next loop, inserted in a look ahead approach to allow for smooth
		 * looping. Connected to {{#crossLink "WebAudioSoundInstance/gainNode:property"}}{{/crossLink}}.
		 * @property _sourceNodeNext
		 * @type {AudioNode}
		 * @default null
		 * @protected
		 * @since 0.4.1
		 *
		 */
		this._sourceNodeNext = null;

		/**
		 * Time audio started playback, in seconds. Used to handle set position, get position, and resuming from paused.
		 * @property _playbackStartTime
		 * @type {Number}
		 * @default 0
		 * @protected
		 * @since 0.4.0
		 */
		this._playbackStartTime = 0;

		// Proxies, make removing listeners easier.
		this._endedHandler = createjs.proxy(this._handleSoundComplete, this);
	};
	var p = createjs.extend(WebAudioSoundInstance, createjs.AbstractSoundInstance);
	var s = WebAudioSoundInstance;

	/**
	 * Note this is only intended for use by advanced users.
	 * <br />Audio context used to create nodes.  This is and needs to be the same context used by {{#crossLink "WebAudioPlugin"}}{{/crossLink}}.
  	 * @property context
	 * @type {AudioContext}
	 * @static
	 * @since 0.6.0
	 */
	s.context = null;

	/**
	 * Note this is only intended for use by advanced users.
	 * <br />The scratch buffer that will be assigned to the buffer property of a source node on close.  
	 * This is and should be the same scratch buffer referenced by {{#crossLink "WebAudioPlugin"}}{{/crossLink}}.
  	 * @property _scratchBuffer
	 * @type {AudioBufferSourceNode}
	 * @static
	 */
	s._scratchBuffer = null;

	/**
	 * Note this is only intended for use by advanced users.
	 * <br /> Audio node from WebAudioPlugin that sequences to <code>context.destination</code>
	 * @property destinationNode
	 * @type {AudioNode}
	 * @static
	 * @since 0.6.0
	 */
	s.destinationNode = null;

	/**
	 * Value to set panning model to equal power for WebAudioSoundInstance.  Can be "equalpower" or 0 depending on browser implementation.
	 * @property _panningModel
	 * @type {Number / String}
	 * @protected
	 * @static
	 * @since 0.6.0
	 */
	s._panningModel = "equalpower";


// Public methods
	p.destroy = function() {
		this.AbstractSoundInstance_destroy();

		this.panNode.disconnect(0);
		this.panNode = null;
		this.gainNode.disconnect(0);
		this.gainNode = null;
	};

	p.toString = function () {
		return "[WebAudioSoundInstance]";
	};


// Private Methods
	p._updatePan = function() {
		this.panNode.setPosition(this._pan, 0, -0.5);
		// z need to be -0.5 otherwise the sound only plays in left, right, or center
	};

	p._removeLooping = function(value) {
		this._sourceNodeNext = this._cleanUpAudioNode(this._sourceNodeNext);
	};

	p._addLooping = function(value) {
		if (this.playState != createjs.Sound.PLAY_SUCCEEDED) { return; }
		this._sourceNodeNext = this._createAndPlayAudioNode(this._playbackStartTime, 0);
	};

	p._setDurationFromSource = function () {
		this._duration = this.playbackResource.duration * 1000;
	};

	p._handleCleanUp = function () {
		if (this.sourceNode && this.playState == createjs.Sound.PLAY_SUCCEEDED) {
			this.sourceNode = this._cleanUpAudioNode(this.sourceNode);
			this._sourceNodeNext = this._cleanUpAudioNode(this._sourceNodeNext);
		}

		if (this.gainNode.numberOfOutputs != 0) {this.gainNode.disconnect(0);}
		// OJR there appears to be a bug that this doesn't always work in webkit (Chrome and Safari). According to the documentation, this should work.

		clearTimeout(this._soundCompleteTimeout);

		this._playbackStartTime = 0;	// This is used by _getPosition
	};

	/**
	 * Turn off and disconnect an audioNode, then set reference to null to release it for garbage collection
	 * @method _cleanUpAudioNode
	 * @param audioNode
	 * @return {audioNode}
	 * @protected
	 * @since 0.4.1
	 */
	p._cleanUpAudioNode = function(audioNode) {
		if(audioNode) {
			audioNode.stop(0);
			audioNode.disconnect(0);
			// necessary to prevent leak on iOS Safari 7-9. will throw in almost all other
			// browser implementations.
			if ( createjs.BrowserDetect.isIOS ) {
				try { audioNode.buffer = s._scratchBuffer; } catch(e) {}
			}
			audioNode = null;
		}
		return audioNode;
	};

	p._handleSoundReady = function (event) {
		this.gainNode.connect(s.destinationNode);  // this line can cause a memory leak.  Nodes need to be disconnected from the audioDestination or any sequence that leads to it.

		var dur = this._duration * 0.001,
			pos = Math.min(Math.max(0, this._position) * 0.001, dur);
		this.sourceNode = this._createAndPlayAudioNode((s.context.currentTime - dur), pos);
		this._playbackStartTime = this.sourceNode.startTime - pos;

		this._soundCompleteTimeout = setTimeout(this._endedHandler, (dur - pos) * 1000);

		if(this._loop != 0) {
			this._sourceNodeNext = this._createAndPlayAudioNode(this._playbackStartTime, 0);
		}
	};

	/**
	 * Creates an audio node using the current src and context, connects it to the gain node, and starts playback.
	 * @method _createAndPlayAudioNode
	 * @param {Number} startTime The time to add this to the web audio context, in seconds.
	 * @param {Number} offset The amount of time into the src audio to start playback, in seconds.
	 * @return {audioNode}
	 * @protected
	 * @since 0.4.1
	 */
	p._createAndPlayAudioNode = function(startTime, offset) {
		var audioNode = s.context.createBufferSource();
		audioNode.buffer = this.playbackResource;
		audioNode.connect(this.panNode);
		var dur = this._duration * 0.001;
		audioNode.startTime = startTime + dur;
		audioNode.start(audioNode.startTime, offset+(this._startTime*0.001), dur - offset);
		return audioNode;
	};

	p._pause = function () {
		this._position = (s.context.currentTime - this._playbackStartTime) * 1000;  // * 1000 to give milliseconds, lets us restart at same point
		this.sourceNode = this._cleanUpAudioNode(this.sourceNode);
		this._sourceNodeNext = this._cleanUpAudioNode(this._sourceNodeNext);

		if (this.gainNode.numberOfOutputs != 0) {this.gainNode.disconnect(0);}

		clearTimeout(this._soundCompleteTimeout);
	};

	p._resume = function () {
		this._handleSoundReady();
	};

	/*
	p._handleStop = function () {
		// web audio does not need to do anything extra
	};
	*/

	p._updateVolume = function () {
		var newVolume = this._muted ? 0 : this._volume;
	  	if (newVolume != this.gainNode.gain.value) {
		  this.gainNode.gain.value = newVolume;
  		}
	};

	p._calculateCurrentPosition = function () {
		return ((s.context.currentTime - this._playbackStartTime) * 1000); // pos in seconds * 1000 to give milliseconds
	};

	p._updatePosition = function () {
		this.sourceNode = this._cleanUpAudioNode(this.sourceNode);
		this._sourceNodeNext = this._cleanUpAudioNode(this._sourceNodeNext);
		clearTimeout(this._soundCompleteTimeout);

		if (!this._paused) {this._handleSoundReady();}
	};

	// OJR we are using a look ahead approach to ensure smooth looping.
	// We add _sourceNodeNext to the audio context so that it starts playing even if this callback is delayed.
	// This technique is described here:  http://www.html5rocks.com/en/tutorials/audio/scheduling/
	// NOTE the cost of this is that our audio loop may not always match the loop event timing precisely.
	p._handleLoop = function () {
		this._cleanUpAudioNode(this.sourceNode);
		this.sourceNode = this._sourceNodeNext;
		this._playbackStartTime = this.sourceNode.startTime;
		this._sourceNodeNext = this._createAndPlayAudioNode(this._playbackStartTime, 0);
		this._soundCompleteTimeout = setTimeout(this._endedHandler, this._duration);
	};

	p._updateDuration = function () {
		if(this.playState == createjs.Sound.PLAY_SUCCEEDED) {
			this._pause();
			this._resume();
		}
	};

	createjs.WebAudioSoundInstance = createjs.promote(WebAudioSoundInstance, "AbstractSoundInstance");
}());