var Stats = function () {
	var mode = 0;
	var container = document.createElement( 'div' );
	container.style.cssText = 'position:fixed;top:0;left:0;cursor:pointer;opacity:0.9;z-index:10000';
	container.addEventListener( 'click', function ( event ) {
		event.preventDefault();
		showPanel( ++ mode % container.children.length );
	}, false );
	function addPanel( panel ) {
		container.appendChild( panel.dom );
		return panel;
	}
	function showPanel( id ) {
		for ( var i = 0; i < container.children.length; i ++ ) {
			container.children[ i ].style.display = i === id ? 'block' : 'none';
		}
		mode = id;
	}
	var beginTime = ( performance || Date ).now(), prevTime = beginTime, frames = 0;
	var fpsPanel = addPanel( new Stats.Panel( 'FPS', '#0ff', '#002' ) );
	var msPanel = addPanel( new Stats.Panel( 'MS', '#0f0', '#020' ) );
	if ( self.performance && self.performance.memory ) {
		var memPanel = addPanel( new Stats.Panel( 'MB', '#f08', '#201' ) );
	}
	showPanel( 0 );
	return {
		REVISION: 16,
		dom: container,
		addPanel: addPanel,
		showPanel: showPanel,
		begin: function () {
			beginTime = ( performance || Date ).now();
		},
		end: function () {
			frames ++;
			var time = ( performance || Date ).now();
			msPanel.update( time - beginTime, 200 );
			if ( time >= prevTime + 1000 ) {
				fpsPanel.update( ( frames * 1000 ) / ( time - prevTime ), 100 );
				prevTime = time;
				frames = 0;
				if ( memPanel ) {
					var memory = performance.memory;
					memPanel.update( memory.usedJSHeapSize / 1048576, memory.jsHeapSizeLimit / 1048576 );
				}
			}
			return time;
		},
		update: function () {
			beginTime = this.end();
		},
		domElement: container,
		setMode: showPanel
	};
};
Stats.Panel = function ( name, fg, bg ) {
	var min = Infinity, max = 0, round = Math.round;
	var PR = round( window.devicePixelRatio || 1 );
	var WIDTH = 80 * PR, HEIGHT = 48 * PR,
		TEXT_X = 3 * PR, TEXT_Y = 2 * PR,
		GRAPH_X = 3 * PR, GRAPH_Y = 15 * PR,
		GRAPH_WIDTH = 74 * PR, GRAPH_HEIGHT = 30 * PR;
	var canvas = document.createElement( 'canvas' );
	canvas.width = WIDTH;
	canvas.height = HEIGHT;
	canvas.style.cssText = 'width:80px;height:48px';
	var context = canvas.getContext( '2d' );
	context.font = 'bold ' + ( 9 * PR ) + 'px Helvetica,Arial,sans-serif';
	context.textBaseline = 'top';
	context.fillStyle = bg;
	context.fillRect( 0, 0, WIDTH, HEIGHT );
	context.fillStyle = fg;
	context.fillText( name, TEXT_X, TEXT_Y );
	context.fillRect( GRAPH_X, GRAPH_Y, GRAPH_WIDTH, GRAPH_HEIGHT );
	context.fillStyle = bg;
	context.globalAlpha = 0.9;
	context.fillRect( GRAPH_X, GRAPH_Y, GRAPH_WIDTH, GRAPH_HEIGHT );
	return {
		dom: canvas,
		update: function ( value, maxValue ) {
			min = Math.min( min, value );
			max = Math.max( max, value );
			context.fillStyle = bg;
			context.globalAlpha = 1;
			context.fillRect( 0, 0, WIDTH, GRAPH_Y );
			context.fillStyle = fg;
			context.fillText( round( value ) + ' ' + name + ' (' + round( min ) + '-' + round( max ) + ')', TEXT_X, TEXT_Y );
			context.drawImage( canvas, GRAPH_X + PR, GRAPH_Y, GRAPH_WIDTH - PR, GRAPH_HEIGHT, GRAPH_X, GRAPH_Y, GRAPH_WIDTH - PR, GRAPH_HEIGHT );
			context.fillRect( GRAPH_X + GRAPH_WIDTH - PR, GRAPH_Y, PR, GRAPH_HEIGHT );
			context.fillStyle = bg;
			context.globalAlpha = 0.9;
			context.fillRect( GRAPH_X + GRAPH_WIDTH - PR, GRAPH_Y, PR, round( ( 1 - ( value / maxValue ) ) * GRAPH_HEIGHT ) );
		}
	};
};

export { Stats as default };
