function drawWorld(world, context) {
	for (var j = world.m_jointList; j; j = j.m_next) {
		drawJoint(j, context);
	}
	for (var b = world.m_bodyList; b; b = b.m_next) {
		for (var s = b.GetShapeList(); s != null; s = s.GetNext()) {
			drawShape(s, context);
		}
	}
}
function drawJoint(joint, context) {
	var b1 = joint.m_body1;
	var b2 = joint.m_body2;
	var x1 = b1.m_position;
	var x2 = b2.m_position;
	var p1 = joint.GetAnchor1();
	var p2 = joint.GetAnchor2();
	context.strokeStyle = '#00eeee';
	context.beginPath();
	switch (joint.m_type) {
	case b2Joint.e_distanceJoint:
		context.moveTo(p1.x, p1.y);
		context.lineTo(p2.x, p2.y);
		break;

	case b2Joint.e_pulleyJoint:
		// TODO
		break;

	default:
		if (b1 == world.m_groundBody) {
			context.moveTo(p1.x, p1.y);
			context.lineTo(x2.x, x2.y);
		}
		else if (b2 == world.m_groundBody) {
			context.moveTo(p1.x, p1.y);
			context.lineTo(x1.x, x1.y);
		}
		else {
			context.moveTo(x1.x, x1.y);
			context.lineTo(p1.x, p1.y);
			context.lineTo(x2.x, x2.y);
			context.lineTo(p2.x, p2.y);
		}
		break;
	}
	context.stroke();
}
function drawShape(shape, context) {
	context.strokeStyle = '#000000';
	context.beginPath();
	switch (shape.m_type) {
	case b2Shape.e_circleShape:
		{
			var circle = shape;
			var pos = circle.m_position;
			var r = circle.m_radius;
			var segments = 16.0;
			var theta = 0.0;
			var dtheta = 2.0 * Math.PI / segments;
			// draw circle
			context.moveTo(pos.x + r, pos.y);
			for (var i = 0; i < segments; i++) {
				var d = new b2Vec2(r * Math.cos(theta), r * Math.sin(theta));
				var v = b2Math.AddVV(pos, d);
				context.lineTo(v.x, v.y);
				theta += dtheta;
			}
			context.lineTo(pos.x + r, pos.y);
	
			// draw radius
			context.moveTo(pos.x, pos.y);
			var ax = circle.m_R.col1;
			var pos2 = new b2Vec2(pos.x + r * ax.x, pos.y + r * ax.y);
			context.lineTo(pos2.x, pos2.y);
		}
		break;
	case b2Shape.e_polyShape:
		{
			var poly = shape;
			var tV = b2Math.AddVV(poly.m_position, b2Math.b2MulMV(poly.m_R, poly.m_vertices[0]));
			context.moveTo(tV.x, tV.y);
			for (var i = 0; i < poly.m_vertexCount; i++) {
				var v = b2Math.AddVV(poly.m_position, b2Math.b2MulMV(poly.m_R, poly.m_vertices[i]));
				context.lineTo(v.x, v.y);
			}
			context.lineTo(tV.x, tV.y);
		}
		break;
	}
	context.stroke();
}


function createWorld() {
	var worldAABB = new b2AABB();
	worldAABB.minVertex.Set(-1000, -1000);
	worldAABB.maxVertex.Set(1000, 1000);
	var gravity = new b2Vec2(0, 300);
	var doSleep = true;
	var world = new b2World(worldAABB, gravity, doSleep);
	return world;
}

function createGround(world) {
	var groundSd = new b2BoxDef();
	groundSd.extents.Set(1000, 50);
	groundSd.restitution = 0.2;
	var groundBd = new b2BodyDef();
	groundBd.AddShape(groundSd);
	groundBd.position.Set(-500, 340);
	return world.CreateBody(groundBd)
}

function createBall(world, x, y) {
	var ballSd = new b2CircleDef();
	ballSd.density = 1.0;
	ballSd.radius = 20;
	ballSd.restitution = 1.0;
	ballSd.friction = 0;
	var ballBd = new b2BodyDef();
	ballBd.AddShape(ballSd);
	ballBd.position.Set(x,y);
	return world.CreateBody(ballBd);
}

function createBox(world, x, y, width, height, fixed, userData) {
	if (typeof(fixed) == 'undefined') fixed = true;
	var boxSd = new b2BoxDef();
	if (!fixed) boxSd.density = 1.0;
	
	boxSd.userData = userData;
	
	boxSd.extents.Set(width, height);
	var boxBd = new b2BodyDef();
	boxBd.AddShape(boxSd);
	boxBd.position.Set(x,y);
	return world.CreateBody(boxBd)
}