(function(global) {
    /**
* Creates a new YoutubePlayer object
*
* @constructor
* @param {String} HTML id of the element containing the Youtube flash player
* @param {String} Youtube video id
*
* @returns {YoutubePlayer} An object of YoutubePlayer
*/
    function YoutubePlayer(elementId, videoId) {
        this.id = elementId;
        this.videoId = videoId;
        this.handlers = {};

        this.embed();

        YoutubePlayer.register(this);
    }

    /**
* Embeds the Youtube video on the page replacing the placeholder
* element whose id was passed in the constructor.
*
* The <object> element that replaces the placeholder gets the same
* id as that of the placeholder
*
* This relies on the SWFObject library.
* @requires swfobject See http://code.google.com/p/swfobject/wiki/hosted_library
*
* @private
*
*/
    YoutubePlayer.prototype.embed = function() {
        var params = { allowScriptAccess: 'always' };
        var attrs = { id: this.id };

        var videoUrl = 'http://www.youtube.com/watch?v={videoId}';
        videoUrl = videoUrl.replace('{videoId}', this.videoId);
        videoUrl = videoUrl.replace('{playerId}', this.id);

        if(!swfobject) {
            throw new ReferenceError('YoutubePlayer depends on the SWFObject library but it is missing.');
        }

        swfobject.embedSWF(videoUrl, this.id, '300', '225', '8', null, null, params, attrs);
    };

    /**
* Add the given handler as a listener for the given event
*
* @param eventName {String} name of the event
* @param handler {Function} callback for the event
*/
    YoutubePlayer.prototype.on = function(eventName, handler) {
        this.handlers[eventName] = this.handlers[eventName] || [];
        this.handlers[eventName].push(handler);
    };

    /**
* Sets up event handlers for player state
* changes once it's available.
*
* @private
*
*/
    YoutubePlayer.prototype.onReady = function() {
        var player = document.getElementById(this.id);
        var callbackStr = 'YoutubePlayer.dispatchEvent("{id}")';
        var callback = callbackStr.replace("{id}", this.id);

        player.addEventListener('onStateChange', callback);
    };

    /**
* Receives notification of player state changes
*
* @private
* @param eventId {String} Youtube player event id
*
*/
    YoutubePlayer.prototype.notifyEvent = function(eventId) {
        var states = YoutubePlayer.STATES;

        for(var eventName in states) {
            if(states[eventName] == eventId) {
                this.fireEvent(eventName);
            }
        }
    };

    /**
* Notify each registered subscriber of this event
*
* @param eventName {String} Name of the player event
*/
    YoutubePlayer.prototype.fireEvent = function(eventName) {
        var handlers = this.handlers[eventName];
        if(!handlers) {
            return;
        }

        for(var i = 0; i < handlers.length; i++) {
            handlers[i](eventName);
        }
    };

    /**
* Holds instances of player objects to be able to
* dispatch events to them globally
*
* @private
*/
    YoutubePlayer.instances = [];

    /**
* @private
*/
    YoutubePlayer.register = function(player) {
        this.instances.push(player);
    };

    /**
* Search the player object by its HTML id.
* Useful when dispatching events to the player object
* sent from the Youtube flash player

* @param playerId {String} HTML id of the player object
* @returns {YoutubePlayer} The object of YoutubePlayer that wraps this player
*
* @private
*/
    YoutubePlayer.findById = function(playerId) {
        var player = null;

        for(var i = 0; i < this.instances.length; i++) {
            if(this.instances[i].id == playerId) {
                player = this.instances[i];
            }
        }

        return player;
    };

    /**
* Central event dispatcher which receives all player
* events directly from the flash player and dispatches
* them to the player object for which the event occurred.
*
* @param playerId
*
* @private
*/
    YoutubePlayer.dispatchEvent = function(playerId) {
        var player = YoutubePlayer.findById(playerId);
        return function(eventId) {
            player.notifyEvent(eventId);
        };
    };

    /**
* Various state change events that the Youtube flash player triggers
*
* @private
*/
    YoutubePlayer.STATES = {
        unstarted: -1,
        ended: 0,
        playing: 1,
        paused: 2,
        buffering: 3,
        cued: 5
    };

    /**
* Make the YoutubePlayer available globally
*/
    global.YoutubePlayer = YoutubePlayer;

    /**
* Create a global handler that receives notification of when
* the Youtube flash player has been initialized
* on the page
*
* @param playerId {String}
*/
    global.onYouTubePlayerReady = function(playerId) {
        YoutubePlayer.findById(playerId).onReady();
    };

})(window);