var Stats = function () {
	var startTime = Date.now(), prevTime = startTime;
	var ms = 0, msMin = Infinity, msMax = 0;
	var fps = 0, fpsMin = Infinity, fpsMax = 0;
	var frames = 0, mode = 0;

	var container = document.createElement('div');
	container.id = 'stats';
	container.addEventListener('mousedown', function (event) {
		event.preventDefault();
		setMode(++mode % 2)
	}, false);
	container.style.cssText = 'width:80px;opacity:0.9;cursor:pointer';

	var fpsDiv = document.createElement('div');
	fpsDiv.id = 'fps';
	fpsDiv.style.cssText = 'padding:0 0 3px 3px;text-align:left;background-color:#002';
	container.appendChild(fpsDiv);

	var fpsText = document.createElement('div');
	fpsText.id = 'fpsText';
	fpsText.style.cssText = 'color:#0ff;font-family:Helvetica,Arial,sans-serif;font-size:9px;font-weight:bold;line-height:15px';
	fpsText.innerHTML = 'FPS';
	fpsDiv.appendChild(fpsText);

	var fpsGraph = document.createElement('div');
	fpsGraph.id = 'fpsGraph';
	fpsGraph.style.cssText = 'position:relative;width:74px;height:30px;background-color:#0ff';
	fpsDiv.appendChild(fpsGraph);

	while (fpsGraph.children.length < 74) {

		var bar = document.createElement('span');
		bar.style.cssText = 'width:1px;height:30px;float:left;background-color:#113';
		fpsGraph.appendChild(bar);

	}

	var msDiv = document.createElement('div');
	msDiv.id = 'ms';
	msDiv.style.cssText = 'padding:0 0 3px 3px;text-align:left;background-color:#020;display:none';
	container.appendChild(msDiv);

	var msText = document.createElement('div');
	msText.id = 'msText';
	msText.style.cssText = 'color:#0f0;font-family:Helvetica,Arial,sans-serif;font-size:9px;font-weight:bold;line-height:15px';
	msText.innerHTML = 'MS';
	msDiv.appendChild(msText);

	var msGraph = document.createElement('div');
	msGraph.id = 'msGraph';
	msGraph.style.cssText = 'position:relative;width:74px;height:30px;background-color:#0f0';
	msDiv.appendChild(msGraph);

	while (msGraph.children.length < 74) {

		var bar = document.createElement('span');
		bar.style.cssText = 'width:1px;height:30px;float:left;background-color:#131';
		msGraph.appendChild(bar);

	}

	var setMode = function (value) {

		mode = value;

		switch (mode) {

			case 0:
				fpsDiv.style.display = 'block';
				msDiv.style.display = 'none';
				break;
			case 1:
				fpsDiv.style.display = 'none';
				msDiv.style.display = 'block';
				break;
		}

	}

	var updateGraph = function (dom, value) {

		var child = dom.appendChild(dom.firstChild);
		child.style.height = value + 'px';

	}

	return {

		REVISION: 11,

		domElement: container,

		setMode: setMode,

		begin: function () {

			startTime = Date.now();

		},

		end: function () {

			var time = Date.now();

			ms = time - startTime;
			msMin = Math.min(msMin, ms);
			msMax = Math.max(msMax, ms);

			msText.textContent = ms + ' MS (' + msMin + '-' + msMax + ')';
			updateGraph(msGraph, Math.min(30, 30 - (ms / 200) * 30));

			frames++;

			if (time > prevTime + 1000) {

				fps = Math.round((frames * 1000) / (time - prevTime));
				fpsMin = Math.min(fpsMin, fps);
				fpsMax = Math.max(fpsMax, fps);

				fpsText.textContent = fps + ' FPS (' + fpsMin + '-' + fpsMax + ')';
				updateGraph(fpsGraph, Math.min(30, 30 - (fps / 100) * 30));

				prevTime = time;
				frames = 0;

			}

			return time;

		},

		update: function () {

			startTime = this.end();

		}

	}

};

//执行
var stats = new Stats();
stats.domElement.style.position = 'absolute';
stats.domElement.style.top = '0px';
document.body.appendChild(stats.domElement);
aa();

function aa() {
	stats.update();
	requestAnimationFrame(aa)
}
