function _WebGLComm() {

	this.gameInstance;
	this.callbacks = {};


	/*
	 * Invokes the function registered as 'functionId', used by the
	 * WebGLComm plugin as enter point to Unity WebGL.
	 *
	 * Captures any exception and logs it to the console.
	 *
	 * If a 'callback' parameters is defined in teh parameters, its
	 * value is used as the function id of a function in Unity WebGL
	 * that will be invoked passing the returned values as parameters.
	 * This callback receives the returned parameters in the key
	 * 'returned' if an object, that also includes the key 'isCallback'
	 * to indicate to WebGLComm that this is a callback and has to be
	 * managed so.
	 *
	 * @param functionId Key of the function.
	 * @objParams One object with the parameters passed to the
	 * function.
	 */
	this.call = function(functionId, objParams){

		try {
			var returned = this.callbacks[functionId](objParams);

			if ('undefined' !== objParams['callback']) {

				this.callToUnity(objParams['callback'], { returned : returned, isCallback: true });
			}
		} catch (e) {
			console.log(e + ', ' + functionId + ',' + objParams);
		}
	}

	/*
	 * Associates a key to a function.
	 *
	 * @param functionId Key of of the function.
	 * @param callback The function to be invoked (receives one 
	 * object as paramters)
	 */
	this.addListener = function(functionId, callback) {

		this.callbacks[functionId] = callback;
	}


	/*
	 * Entry point to invoke a function in Unity WebGL.
	 *
	 * tgis.gameInstance must have been initialized with an instance 
	 * returned by UnityLoader.instantiate.
	 *
	 * The game object in the scene that will receive the message
	 * must be named 'WebGLComm' and must contain the component 
	 * WebGLComm.
	 *
	 * @functionId Key of the function to be invoked in Unity 
	 * WebGL (must be previously registered as listener in Unity 
	 * WebGL)
	 * @params One object that contains the parameters for the 
	 * function invoked in Unity WebGL.
	 */
	this.callToUnity = function(functionId, params) {

		if ('undefined' === this.gameInstance) {
			console.log('Undefined this.gameInstance; must be an instance returned by UnityLoader.instantiate');
			return;
		}

		if ('object' !== typeof params) {
			console.log('Object expected, received ' + (typeof params));
			return;
		}

		params['functionId'] = functionId;
		this.gameInstance.SendMessage('WebGLComm', 'MessageFromWeb', JSON.stringify(params));
	}
}


var WebGLComm = new _WebGLComm();