/**
 * Trigger System
 * 
 * Enables entities to act as trigger area.
 * 
 * @class trigger
 * @namespace zerk.game.engine.system
 * @extends zerk.game.engine.system
 * @module zerk
 **/
zerk.define({
	
	name: 'zerk.game.engine.system.trigger',
	extend: 'zerk.game.engine.system'
	
},{
	
	/**
	 * Name of the system
	 * 
	 * @property _name
	 * @type String
	 * @protected
	 **/
	_name: 'trigger',
	
	/**
	 * 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.trigger').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=='trigger');
		
	},
	
	/**
	 * Starts the system
	 * 
	 * @method start
	 **/
	start: function() {
		
		zerk.parent('zerk.game.engine.system.trigger').start.apply(
			this,
			arguments
		);
		
		this._physics.on(
			'contactbegin',
			this._onContactBegin,
			this
		);
		
	},
	
	/**
	 * Fires when two fixtures start colliding
	 * 
	 * @method _onContactBegin
	 * @param {Object} sourceInfo Contact source information
	 * @param {Object} targetInfo Contact target information
	 * @protected
	 **/
	_onContactBegin: function(sourceInfo,targetInfo) {
		
		if (typeof targetInfo.entity.components.trigger=='undefined') {
			return true;
		}
		
		var componentTrigger=targetInfo.entity.components.trigger;
		
		if (!componentTrigger.targetEntityTag) {
			console.log('No target entity specified');
			return;
		}
		
		if (!componentTrigger.targetSystem) {
			console.log('No target system specified');
			return;
		}
		
		if (!componentTrigger.targetMethod) {
			console.log('No target method specified');
			return;
		}
		
		var system=this._engine.getSystem(
			componentTrigger.targetSystem
		);
		
		var entities=this._engine.getEntitiesByTags(
			componentTrigger.targetEntityTag
		);
		
		for (var i=0;i<entities.length;i++) {
			
			system[componentTrigger.targetMethod](entities[i]);
			
		}
		
	}
	
});