package com.philperon.display {
	
	import flash.display.BitmapData;
	import flash.display.BlendMode;
	import flash.display.DisplayObject;
	import flash.geom.ColorTransform;
	import flash.geom.Matrix;
	import flash.geom.Rectangle;

    public class Collision {
    	
        public static function collisionTest(dispObj1:DisplayObject, dispObj2:DisplayObject, alphaTolerance:uint = 0):Rectangle {
			var rect1:Rectangle = dispObj1.getBounds(dispObj1.stage);
			var rect2:Rectangle = dispObj2.getBounds(dispObj2.stage);

			var objectIntersection:Rectangle = rect1.intersection(rect2);
			
			// don't bother with width or height values < 1.
			if((objectIntersection.width < 1) || (objectIntersection.height < 1)) return null;

			var bitmapData:BitmapData = new BitmapData(objectIntersection.width, objectIntersection.height, false);

			var mat:Matrix = dispObj1.transform.concatenatedMatrix;
			mat.tx -= objectIntersection.left;
			mat.ty -= objectIntersection.top;
			bitmapData.draw(dispObj1, mat, new ColorTransform(1, 1, 1, 1, 255, -255, -255, alphaTolerance));

			mat = dispObj2.transform.concatenatedMatrix;
			mat.tx -= objectIntersection.left;
			mat.ty -= objectIntersection.top;
			bitmapData.draw(dispObj2, mat, new ColorTransform(1, 1, 1, 1, 255, 255, 255, alphaTolerance), BlendMode.DIFFERENCE);

			var pixelIntersection:Rectangle = bitmapData.getColorBoundsRect(0xFFFFFFFF, 0xFF00FFFF);

			if(pixelIntersection.width == 0) return null;

			pixelIntersection.x += objectIntersection.left;
			pixelIntersection.y += objectIntersection.top;

			return pixelIntersection;
		}
    }
}