terraform/website/source/assets/javascripts/app/Puller.js

(function(
	Engine,
	Vector
){

var Puller = function(x, y){
	this.pos.x = x;
	this.pos.y = y;
	this.pos = Vector.coerce(this.pos);
	this.home = this.pos.clone();
	this.accel = Vector.coerce(this.accel);
	this.vel = Vector.coerce(this.vel);
};

Puller.prototype = {

	fillStyle: '#ffffff',
	radius: 5,

	maxSpeed: 160,
	maxForce: 50,

	pos: {
		x: 0,
		y: 0
	},

	accel: {
		x: 0,
		y: 0
	},

	vel: {
		x: 0,
		y: 0
	},

	aRad: 200,

	safety: 0.25,

	update: function(engine){
		var distanceToMouse = this.distanceTo(engine.mouse),
			toHome, mag, safety;
			// distanceToHome = this.distanceTo(this.home);

		this.accel.mult(0);

		if (distanceToMouse < this.aRad) {
			this.toChase(engine.mouse);
		}

		this.toChase(this.home, this.maxForce / 2);

		this.vel.add(this.accel);
		this.pos.add(
			Vector.mult(this.vel, engine.tick)
		);

		toHome = Vector.sub(this.home, this.pos);
		mag = toHome.mag();
		safety = this.aRad * (this.safety * 3);
		if (mag > this.aRad - safety) {
			toHome.normalize();
			toHome.mult(this.aRad - safety);
			this.pos = Vector.sub(this.home, toHome);
		}
	},

	toChase: function(target, maxForce){
		var desired, steer, distance, mult, safety;

		maxForce = maxForce || this.maxForce;

		target = Vector.coerce(target);
		desired = Vector.sub(target, this.pos);
		distance = desired.mag();
		desired.normalize();

		safety = this.aRad * this.safety;

		if (distance < safety) {
			mult = Engine.map(distance, 0, safety, 0, this.maxSpeed);
		} else if (distance > this.aRad - safety){
			mult = Engine.map(this.aRad - distance, 0, safety, 0, this.maxSpeed);
		} else {
			mult = this.maxSpeed;
		}

		desired.mult(mult);

		steer = Vector.sub(desired, this.vel);
		steer.limit(maxForce);
		this.accel.add(steer);
	},

	draw: function(ctx, scale){
		// ctx.beginPath();
		// ctx.arc(
		//     this.home.x * scale,
		//     this.home.y * scale,
		//     this.aRad * scale,
		//     0,
		//     Math.PI * 2,
		//     false
		// );
		// ctx.fillStyle = 'rgba(255,255,255,0.1)';
		// ctx.fill();

		ctx.beginPath();
		ctx.arc(
			this.pos.x * scale,
			this.pos.y * scale,
			this.radius * scale,
			0,
			Math.PI * 2,
			false
		);
		ctx.fillStyle = this.fillStyle;
		ctx.fill();

	},

	distanceTo: function(target) {
		var xd = this.home.x - target.x;
		var yd = this.home.y - target.y;
		return Math.sqrt(xd * xd + yd * yd );
	}
};

window.Puller = Puller;

})(
	window.Engine,
	window.Vector
);