/**
 * Fall System
 * 
 * Enabled entities to fall suddenly.
 * 
 * @class fall
 * @namespace zerk.game.engine.system
 * @extends zerk.game.engine.system
 * @module zerk
 **/
zerk.define({
	
	name: 'zerk.game.engine.system.fall',
	extend: 'zerk.game.engine.system'
	
},{
	
	/**
	 * Name of the system
	 * 
	 * @property _name
	 * @type String
	 * @protected
	 **/
	_name: 'fall',
	
	/**
	 * Thread that runs this system
	 * 
	 * @property _thread
	 * @type String
	 * @protected
	 **/
	_thread: 'simulation',
	
	/**
	 * Physics system instance
	 * 
	 * @property _physics
	 * @type zerk.game.engine.system.physics
	 * @protected
	 **/
	_physics: null,
	
	/**
	 * Class constructor
	 * 
	 * @method init
	 * @param {zerk.game.engine} engine Game engine
	 * @param {Object} config System configuration
	 **/
	init: function(engine,config) {
		
		zerk.parent('zerk.game.engine.system.fall').init.apply(
			this,
			arguments
		);
		
		this._physics=this._getSystem('physics');
		
	},
	
	/**
	 * Returns true when the system is interested in given component
	 * 
	 * @method useComponent
	 * @param {String} name Component name
	 * @return {Boolean} True when the system is intereseted in given component
	 **/
	useComponent: function(name) {
		
		return (name=='fall');
		
	},
	
	/**
	 * Starts the system
	 * 
	 * @method start
	 **/
	start: function() {
		
		zerk.parent('zerk.game.engine.system.fall').start.apply(
			this,
			arguments
		);
		
		this._physics.on(
			'contactbegin',
			this._onContactBegin,
			this
		);
		
	},
	
	
	/**
	 * Stops the system
	 * 
	 * @method stop
	 **/
	stop: function() {
		
		zerk.parent('zerk.game.engine.system.fall').stop.apply(
			this,
			arguments
		);
		
		this._physics.un(
			'contactbegin',
			this._onContactBegin
		);
		
	},
	
	/**
	 * Fires when two fixtures collide
	 * 
	 * @method _onContactBegin
	 * @param {Object} sourceInfo Contact source information
	 * @param {Object} targetInfo Contact target information
	 * @protected
	 **/
	_onContactBegin: function(source,target) {
		
		if (!zerk.isDefined(target.entity.components.fall)) {
			return true;
		}
		
		var self=this;
		
		window.setTimeout(
			function() {
				
				self._physics.setBodyMoveable(target.entity,'main',true);
				
			},
			target.entity.components.fall.releaseDelay
		);
		
	}
	
});