/*
		PolyK library
		url: http://polyk.ivank.net
		Released under MIT licence.
		
		Copyright (c) 2012 Ivan Kuckir

		Permission is hereby granted, free of charge, to any person
		obtaining a copy of this software and associated documentation
		files (the "Software"), to deal in the Software without
		restriction, including without limitation the rights to use,
		copy, modify, merge, publish, distribute, sublicense, and/or sell
		copies of the Software, and to permit persons to whom the
		Software is furnished to do so, subject to the following
		conditions:

		The above copyright notice and this permission notice shall be
		included in all copies or substantial portions of the Software.

		THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
		EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
		OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
		NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
		HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
		WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
		FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
		OTHER DEALINGS IN THE SOFTWARE.
	
		This is an amazing lib! 
		
		slightly modified by mat groves (matgroves.com);
	* */
	
	PIXI.PolyK = {};
	
	PIXI.PolyK.Triangulate = function(p)
	{
		var sign = true;
		
		var n = p.length>>1;
		if(n<3) return [];
		var tgs = [];
		var avl = [];
		for(var i=0; i<n; i++) avl.push(i);
		
		var i = 0;
		var al = n;
		while(al > 3)
		{
			var i0 = avl[(i+0)%al];
			var i1 = avl[(i+1)%al];
			var i2 = avl[(i+2)%al];
			
			var ax = p[2*i0],  ay = p[2*i0+1];
			var bx = p[2*i1],  by = p[2*i1+1];
			var cx = p[2*i2],  cy = p[2*i2+1];
			
			var earFound = false;
			if(PIXI.PolyK._convex(ax, ay, bx, by, cx, cy, sign))
			{
				earFound = true;
				for(var j=0; j<al; j++)
				{
					var vi = avl[j];
					if(vi==i0 || vi==i1 || vi==i2) continue;
					if(PIXI.PolyK._PointInTriangle(p[2*vi], p[2*vi+1], ax, ay, bx, by, cx, cy)) {earFound = false; break;}
				}
			}
			if(earFound)
			{
				tgs.push(i0, i1, i2);
				avl.splice((i+1)%al, 1);
				al--;
				i = 0;
			}
			else if(i++ > 3*al) 
			{
				// need to flip flip reverse it!
				// reset!
				if(sign)
				{
					var tgs = [];
					avl = [];
					for(var i=0; i<n; i++) avl.push(i);
					
					i = 0;
					al = n;
					
					sign = false;
				}
				else
				{
					return [];
				}				
			}
		}
		tgs.push(avl[0], avl[1], avl[2]);
		return tgs;
	}
	
	PIXI.PolyK._PointInTriangle = function(px, py, ax, ay, bx, by, cx, cy)
	{
		var v0x = cx-ax;
		var v0y = cy-ay;
		var v1x = bx-ax;
		var v1y = by-ay;
		var v2x = px-ax;
		var v2y = py-ay;
		
		var dot00 = v0x*v0x+v0y*v0y;
		var dot01 = v0x*v1x+v0y*v1y;
		var dot02 = v0x*v2x+v0y*v2y;
		var dot11 = v1x*v1x+v1y*v1y;
		var dot12 = v1x*v2x+v1y*v2y;
		
		var invDenom = 1 / (dot00 * dot11 - dot01 * dot01);
		var u = (dot11 * dot02 - dot01 * dot12) * invDenom;
		var v = (dot00 * dot12 - dot01 * dot02) * invDenom;

		// Check if point is in triangle
		return (u >= 0) && (v >= 0) && (u + v < 1);
	}
	

	PIXI.PolyK._convex = function(ax, ay, bx, by, cx, cy, sign)
	{
		return ((ay-by)*(cx-bx) + (bx-ax)*(cy-by) >= 0) == sign;
	}