/**
 * System takes care of updating all the entities (based on their component data)
 * @param apiSystem GameLib.API.System
 * @param domElement
 * @param domStats
 * @constructor
 */
GameLib.System = function(
    apiSystem,
	domElement,
	domStats
) {

	GameLib.API.System.call(
		this,
		apiSystem.id,
		apiSystem.name,
		apiSystem.systemType,
		apiSystem.entityManager,
		apiSystem.parentEntity
	);

	if (GameLib.Utils.UndefinedOrNull(domElement)){
		domElement = null;
	}
	this.domElement = domElement;

	if (GameLib.Utils.UndefinedOrNull(domStats)){
		domStats = null;
	}
	this.domStats = domStats;

};

GameLib.System.prototype = Object.create(GameLib.API.System.prototype);
GameLib.System.prototype.constructor = GameLib.System;

GameLib.System.SYSTEM_TYPE_RENDER       = 0x1;
GameLib.System.SYSTEM_TYPE_ANIMATION    = 0x2;
GameLib.System.SYSTEM_TYPE_INPUT        = 0x4;
GameLib.System.SYSTEM_TYPE_ALL          = 0x7;

/**
 * @callback
 * @override
 */
GameLib.System.prototype.start = function() {

	if (this.systemType == GameLib.System.SYSTEM_TYPE_INPUT) {
		this.driveInputObjects = this.entityManager.query([GameLib.D3.Input.Drive]);
	}

	if (this.systemType == GameLib.System.SYSTEM_TYPE_RENDER) {

		if (GameLib.Utils.UndefinedOrNull(this.domElement)) {
			console.warn('Cannot start a rendering system without a valid DOM element');
			throw new Error('Cannot start a rendering system without a valid DOM element');
		}

		this.domElement.innerHTML = '';

		if (GameLib.Utils.UndefinedOrNull(this.domStats)) {
			console.warn('No stats DOM - will run the render process without statistics information');
		} else {
			this.domElement.appendChild(this.domStats);
		}

		this.renderers = this.entityManager.query([GameLib.D3.Renderer]);
		this.renderers.forEach(
			function (renderer) {
				this.domElement.appendChild(renderer.instance.domElement);
			}.bind(this)
		);

		this.viewports = this.entityManager.query([GameLib.D3.Viewport]);
	}
	
	if (this.systemType == GameLib.System.SYSTEM_TYPE_ANIMATION) {
		this.pathFollowingObjects 	= this.entityManager.query([GameLib.D3.PathFollowing]);
		this.followObjects 			= this.entityManager.query([GameLib.D3.Follow]);
		this.meshObjects 			= this.entityManager.query([GameLib.D3.Mesh]);
		this.lookAtObjects 			= this.entityManager.query([GameLib.D3.LookAt]);
		this.cameraObjects 			= this.entityManager.query([GameLib.D3.Camera]);
		this.lightObjects 			= this.entityManager.query([GameLib.D3.Light]);
	}

};

/**
 * @callback
 * @override
 */
GameLib.System.prototype.update = function() {

	if (this.systemType == GameLib.System.SYSTEM_TYPE_INPUT) {
		this.driveInputObjects.forEach(
			function(object) {
				object.update(deltaTime);
			}
		);
	}

	if (this.systemType == GameLib.System.SYSTEM_TYPE_RENDER) {
		this.viewports.forEach(
			function (viewport) {
				viewport.update(deltaTime);
			}
		);
	}

	if (this.systemType == GameLib.System.SYSTEM_TYPE_ANIMATION) {
		this.pathFollowingObjects.forEach(
			function(object) {
				object.update(deltaTime);
			}
		);

		this.followObjects.forEach(
			function(object) {
				object.update(deltaTime);
			}
		);

		this.lookAtObjects.forEach(
			function(object) {
				object.update(deltaTime);
			}
		);

		this.meshObjects.forEach(
			function(object) {
				object.updateInstance();
			}
		);

		this.cameraObjects.forEach(
			function(object) {
				object.updateInstance();
			}
		);

		this.lightObjects.forEach(
			function(object) {
				object.updateInstance();
			}
		);
	}

};

/**
 * @callback
 * @override
 */
GameLib.System.prototype.stop = function() {

	if (this.systemType == GameLib.System.SYSTEM_TYPE_INPUT) {
		this.driveInputObjects = [];
	}

	if (this.systemType == GameLib.System.SYSTEM_TYPE_RENDER) {
		this.domElement.innerHTML = 'Rendering System Stopped';
		this.renderers = [];
		this.viewports = [];
	}

	if (this.systemType == GameLib.System.SYSTEM_TYPE_ANIMATION) {
		this.pathFollowingObjects 	= [];
		this.followObjects 			= [];
		this.meshObjects 			= [];
		this.lookAtObjects 			= [];
		this.cameraObjects 			= [];
		this.lightObjects 			= [];
	}

};