(function () {
	var ns = $.namespace("pskl.rendering");

	ns.DrawingLoop = function () {
		this.requestAnimationFrame = this.getRequestAnimationFrameShim_();
		this.isRunning = false;
		this.previousTime = 0;
		this.callbacks = [];
	};

	ns.DrawingLoop.prototype.addCallback = function (callback, scope, args) {
		var callbackObj = {
			fn : callback, 
			scope : scope, 
			args : args
		};
		this.callbacks.push(callbackObj);
		return callbackObj;
	};

	ns.DrawingLoop.prototype.removeCallback = function (callbackObj) {
		var index = this.callbacks.indexOf(callbackObj);
		if (index != -1) {
			this.callbacks.splice(index, 1);
		}
	};

	ns.DrawingLoop.prototype.start = function () {
		this.isRunning = true;
		this.loop_();
	};

	ns.DrawingLoop.prototype.loop_ = function () {
		var currentTime = Date.now();
		var delta = currentTime - this.previousTime;
		this.executeCallbacks_(delta);
		this.previousTime = currentTime;
		this.requestAnimationFrame.call(window, this.loop_.bind(this));
	};

	ns.DrawingLoop.prototype.executeCallbacks_ = function (deltaTime) {
		for (var i = 0 ; i < this.callbacks.length ; i++) {
			var cb = this.callbacks[i];
			cb.fn.call(cb.scope, deltaTime, cb.args);
		}
	};

	ns.DrawingLoop.prototype.stop = function () {
		this.isRunning = false;
	};

	ns.DrawingLoop.prototype.getRequestAnimationFrameShim_ = function () {
		var requestAnimationFrame = window.requestAnimationFrame || window.mozRequestAnimationFrame ||  
		window.webkitRequestAnimationFrame || window.msRequestAnimationFrame || function (callback) {window.setTimeout(callback, 1000/60)};

		return requestAnimationFrame;
	}
})()