//class AnimLib inspired by bit101's js lib (write with es6)
class AnimLib {
  	constructor(renderCallback, fps = 60){
		this.renderCallback = renderCallback;
		this.fps = fps;
	}
 
 	start(){
		if (!this.running) {
			this.running = true;
			this.render();
		}
		this.shouldKill = false;
	}
  
	stop(){
		this.shouldKill = true;
	}
  
 	toggle(){
		if (this.running) {
			this.stop();
		}
		else {
			this.start();
		}
  	}
 	
	render(){
		if(this.shouldKill) {
			this.shouldKill = false;
			this.running = false;
		}  
		if (this.running) {
			this.renderCallback();
			setTimeout(() => requestAnimationFrame(() => this.render()), 1000 / this.fps);
		}
	}
}
const degreeToRadius = Math.PI / 180;

const canvas = document.getElementById("canvas");
const context = canvas.getContext("2d");

const canvasWidth = canvas.width;
const canvasHeight = canvas.height;

const rectWidth = 100;
const rectHeight = 10;
let rotation = 0;

let mouse = {x:0, y:0};
canvas.addEventListener("mousemove", (event) => {
	mouse.x = event.pageX - canvas.offsetLeft;
	mouse.y = event.pageY - canvas.offsetTop;
});

const canvasHalfHeight = canvasHeight * 0.5|0;
const canvasHalfWidth = canvasWidth * 0.5|0;

const rectHalfWidth = rectWidth * 0.5|0;
const rectHalfHeight = rectHeight * 0.5|0;

let render = () => {
	context.clearRect(0, 0, canvasWidth, canvasHeight);
	rotation = Math.atan2(mouse.y - canvasHalfHeight, mouse.x - canvasHalfWidth);
	context.save();
	context.translate(canvasHalfWidth, canvasHalfHeight);
	context.rotate(rotation);
	context.fillStyle = "yellow";
	context.fillRect(-rectHalfWidth, -rectHalfHeight, rectWidth, rectHeight);
	context.restore();
}

//this motion inspired by the html5 animation with javascript (by Billy Lamberta & Keith Peters)
let ns = new AnimLib(render, 60);
ns.start();