package {
	import Box2D.Dynamics.*;
	import Box2D.Collision.*;
	import Box2D.Collision.Shapes.*;
	import Box2D.Common.Math.*;
	import flash.display.Sprite;
	import flash.events.MouseEvent;
	import flash.events.Event;
	public class Main extends Sprite {
		private var world:b2World=new b2World(new b2Vec2(0,10),true);
		private var worldScale:int=30;
		private var debris:Sprite;
		private var canvas:Sprite;
		private var laserSegment:b2Segment;
		private var drawing:Boolean=false;
		private var affectedByLaser:Vector.<b2Body>;
		private var entryPoint:Vector.<b2Vec2>;
		public function Main() {
			debugDraw();
			addStuff();
			debris = new Sprite();
			addChild(debris);
			canvas = new Sprite();
			addChild(canvas);
			addEventListener(Event.ENTER_FRAME, updateWorld);
			stage.addEventListener(MouseEvent.MOUSE_DOWN,mousePressed);
			stage.addEventListener(MouseEvent.MOUSE_MOVE,mouseMoved);
			stage.addEventListener(MouseEvent.MOUSE_UP,mouseReleased);
		}
		private function mousePressed(e:MouseEvent):void {
			drawing=true;
			laserSegment=new b2Segment();
			laserSegment.p1=new b2Vec2(mouseX/worldScale,mouseY/worldScale);
		}
		private function mouseMoved(e:MouseEvent):void {
			if (drawing) {
				canvas.graphics.clear();
				canvas.graphics.lineStyle(1,0xff0000);
				canvas.graphics.moveTo(laserSegment.p1.x*worldScale,laserSegment.p1.y*worldScale);
				canvas.graphics.lineTo(mouseX,mouseY);
			}
		}
		private function mouseReleased(e:MouseEvent):void {
			drawing=false;
			laserSegment.p2=new b2Vec2(mouseX/worldScale,mouseY/worldScale);
		}
		private function debugDraw():void {
			var debugDraw:b2DebugDraw = new b2DebugDraw();
			var debugSprite:Sprite = new Sprite();
			addChild(debugSprite);
			debugDraw.SetSprite(debugSprite);
			debugDraw.SetDrawScale(worldScale);
			debugDraw.SetFlags(b2DebugDraw.e_shapeBit|b2DebugDraw.e_jointBit);
			debugDraw.SetFillAlpha(0.5);
			world.SetDebugDraw(debugDraw);
		}
		private function addStuff():void {
			var floorBody:b2BodyDef= new b2BodyDef();
			floorBody.position.Set(11,29);
			floorBody.userData=new Object();
			var floorShape:b2PolygonShape = new b2PolygonShape();
			floorShape.SetAsBox(40,15);
			var floorFixture:b2FixtureDef = new b2FixtureDef();
			floorFixture.shape=floorShape;
			var worldFloor:b2Body=world.CreateBody(floorBody);
			worldFloor.CreateFixture(floorFixture);
			//
			var squareBody:b2BodyDef= new b2BodyDef();
			squareBody.position.Set(16,5);
			var squareShape:b2PolygonShape = new b2PolygonShape();
			squareShape.SetAsBox(2.5,2.5);
			var squareFixture:b2FixtureDef = new b2FixtureDef();
			squareFixture.shape=squareShape;
			var worldSquare:b2Body=world.CreateBody(squareBody);
			worldSquare.CreateFixture(squareFixture);
			//
			var circleVector:Vector.<b2Vec2>=new Vector.<b2Vec2>();
			var circleSteps:int=12;
			var circleRadius:Number=3;
			for (var i:int=0; i<circleSteps; i++) {
				circleVector.push(new b2Vec2(circleRadius*Math.cos(2*Math.PI/circleSteps*i),circleRadius*Math.sin(2*Math.PI/circleSteps*i)));
			}
			var circleBody:b2BodyDef= new b2BodyDef();
			circleBody.position.Set(5,5);
			var circleShape:b2PolygonShape = new b2PolygonShape();
			circleShape.SetAsVector(circleVector,circleSteps);
			var circleFixture:b2FixtureDef = new b2FixtureDef();
			circleFixture.shape=circleShape;
			var worldCircle:b2Body=world.CreateBody(circleBody);
			worldCircle.CreateFixture(circleFixture);
		}
		private function updateWorld(e:Event):void {
			world.Step(1/30,10,10);
			world.ClearForces();
			if (laserSegment&&! drawing) {
				affectedByLaser=new Vector.<b2Body>();
				entryPoint=new Vector.<b2Vec2>();
				world.RayCast(laserFired,laserSegment.p1,laserSegment.p2);
				world.RayCast(laserFired,laserSegment.p2,laserSegment.p1);
				laserSegment=null;
			}
			for (var currentBody:b2Body=world.GetBodyList(); currentBody; currentBody=currentBody.GetNext()) {
				if (currentBody.GetUserData()!=null) {
					currentBody.GetUserData().x=currentBody.GetPosition().x*worldScale;
					currentBody.GetUserData().y=currentBody.GetPosition().y*worldScale;
					currentBody.GetUserData().rotation=currentBody.GetAngle()*180/Math.PI;
				}
			}
			world.DrawDebugData();
		}
		private function laserFired(fixture:b2Fixture,point:b2Vec2,normal:b2Vec2,fraction:Number):Number {
			var affectedBody:b2Body=fixture.GetBody();
			var affectedPolygon:b2PolygonShape=fixture.GetShape() as b2PolygonShape;
			var fixtureIndex:int=affectedByLaser.indexOf(affectedBody);
			if (fixtureIndex==-1) {
				affectedByLaser.push(affectedBody);
				entryPoint.push(point);
			} else {
				var rayCenter:b2Vec2=new b2Vec2((point.x+entryPoint[fixtureIndex].x)/2,(point.y+entryPoint[fixtureIndex].y)/2);
				var rayAngle:Number=Math.atan2(entryPoint[fixtureIndex].y-point.y,entryPoint[fixtureIndex].x-point.x);
				var polyVertices:Vector.<b2Vec2>=affectedPolygon.GetVertices();
				var newPolyVertices1:Vector.<b2Vec2>=new Vector.<b2Vec2>();
				var newPolyVertices2:Vector.<b2Vec2>=new Vector.<b2Vec2>();
				var currentPoly:int=0;
				var cutPlaced1:Boolean=false;
				var cutPlaced2:Boolean=false;
				for (var i:int=0; i<polyVertices.length; i++) {
					var worldPoint:b2Vec2=affectedBody.GetWorldPoint(polyVertices[i]);
					var cutAngle:Number=Math.atan2(worldPoint.y-rayCenter.y,worldPoint.x-rayCenter.x)-rayAngle;
					if (cutAngle<Math.PI*-1) {
						cutAngle+=2*Math.PI;
					}
					if (cutAngle>0&&cutAngle<=Math.PI) {
						if (currentPoly==2) {
							cutPlaced1=true;
							newPolyVertices1.push(point);
							newPolyVertices1.push(entryPoint[fixtureIndex]);
						}
						newPolyVertices1.push(worldPoint);
						currentPoly=1;
					} else {
						if (currentPoly==1) {
							cutPlaced2=true;
							newPolyVertices2.push(entryPoint[fixtureIndex]);
							newPolyVertices2.push(point);
						}
						newPolyVertices2.push(worldPoint);
						currentPoly=2;
 
					}
				}
				if (! cutPlaced1) {
					newPolyVertices1.push(point);
					newPolyVertices1.push(entryPoint[fixtureIndex]);
				}
				if (! cutPlaced2) {
					newPolyVertices2.push(entryPoint[fixtureIndex]);
					newPolyVertices2.push(point);
				}
				createSlice(newPolyVertices1,newPolyVertices1.length);
				createSlice(newPolyVertices2,newPolyVertices2.length);
				if (affectedBody.GetUserData()!=null) {
					debris.removeChild(affectedBody.GetUserData());
				}
				world.DestroyBody(affectedBody);
			}
			return 1;
		}
		private function findCentroid(vs:Vector.<b2Vec2>, count:uint):b2Vec2 {
			var c:b2Vec2 = new b2Vec2();
			var area:Number=0.0;
			var p1X:Number=0.0;
			var p1Y:Number=0.0;
			var inv3:Number=1.0/3.0;
			for (var i:int = 0; i < count; ++i) {
				var p2:b2Vec2=vs[i];
				var p3:b2Vec2=i+1<count?vs[int(i+1)]:vs[0];
				var e1X:Number=p2.x-p1X;
				var e1Y:Number=p2.y-p1Y;
				var e2X:Number=p3.x-p1X;
				var e2Y:Number=p3.y-p1Y;
				var D:Number = (e1X * e2Y - e1Y * e2X);
				var triangleArea:Number=0.5*D;
				area+=triangleArea;
				c.x += triangleArea * inv3 * (p1X + p2.x + p3.x);
				c.y += triangleArea * inv3 * (p1Y + p2.y + p3.y);
			}
			c.x*=1.0/area;
			c.y*=1.0/area;
			return c;
		}
		private function createSlice(vertices:Vector.<b2Vec2>,numVertices:int):void {
			var centre:b2Vec2=findCentroid(vertices,vertices.length);
			var sliceBody:b2BodyDef=new b2BodyDef  ;
			sliceBody.position.Set(centre.x,centre.y);
			sliceBody.type=b2Body.b2_dynamicBody;
			sliceBody.userData=new Sprite  ;
			debris.addChild(sliceBody.userData);
			sliceBody.userData.graphics.lineStyle(2,Math.random()*0xFFFFFF);
			sliceBody.userData.graphics.beginFill(Math.random()*0xFFFFFF);
			for (var i:int=0; i<numVertices; i++) {
				vertices[i].Subtract(centre);
				if (i==0) {
					sliceBody.userData.graphics.moveTo(vertices[i].x*worldScale,vertices[i].y*worldScale);
				} else {
					sliceBody.userData.graphics.lineTo(vertices[i].x*worldScale,vertices[i].y*worldScale);
				}
			}
			sliceBody.userData.graphics.lineTo(vertices[0].x*worldScale,vertices[0].y*worldScale);
			sliceBody.userData.graphics.endFill();
			var slicePoly:b2PolygonShape=new b2PolygonShape  ;
			slicePoly.SetAsVector(vertices,numVertices);
			var sliceFixture:b2FixtureDef=new b2FixtureDef  ;
			sliceFixture.shape=slicePoly;
			sliceFixture.density=1;
			var worldSlice:b2Body=world.CreateBody(sliceBody);
			worldSlice.CreateFixture(sliceFixture);
			for (i=0; i<numVertices; i++) {
				vertices[i].Add(centre);
			}
		}
	}
}