#include "polygon.h"
#include <math.h>

#include <gl/glut.h>

long triangle_area(long V[6])
{
	int i;
	long mostleft=V[0],mostright=V[0],mosthigh=V[1],mostlow=V[1];

	// Pick Left

	for(i=1;i<3;i++)
	{
		if(V[i*2] < mostleft)
			mostleft=V[i*2];
	}

	// Pick Right

	for(i=1;i<3;i++)
	{
		if(V[i*2] > mostright)
			mostright=V[i*2];
	}

	// Pick High

	for(i=1;i<3;i++)
	{
		if(V[(i*2)+1] < mosthigh)
			mosthigh=V[(i*2)+1];
	}

	// Pick Low

	for(i=1;i<3;i++)
	{
		if(V[(i*2)+1] > mostlow)
			mostlow=V[(i*2)+1];
	}

	return ((mostright-mostleft)*(mostlow-mosthigh))/2;
}

long polygon_area(int nvert,in_vertex *V)
{
	// Add the area of a triangle fan around point 0

	int i;
	long list[6];
	long area=0;

	if(nvert<3)
		return 0;

	list[0]=V[0].X;
	list[1]=V[0].Y;

	for(i=2;i<nvert;i++)
	{
		list[2]=V[i-1].X;
		list[3]=V[i-1].Y;
		list[4]=V[i].X;
		list[5]=V[i].Y;
		area+=triangle_area(list);
	}

	return area;
}

bool isInPolygon(in_poly *polygon,long offx,long offy,long X,long Y)
{
	// Add the area of a triangle fan around the point

	long cur_area=0;
	int i,l=0,c=0;
	long list[6];
	if(!polygon)
		return 0;
	if(polygon->numVertices < 3)
		return 0;
	if(!polygon->vertices)
		return 0;

	list[0]=X-offx;
	list[1]=Y-offy;
	for(i=1;i<=polygon->numVertices;i++)
	{
		glColor3f(0.6f,0.5f+(0.25f/polygon->numVertices)*(i-1),0.5f);
		l=c;
		c=i;
		if(c==(polygon->numVertices))
			c=0;

		// Triangle is from p to current to last

		list[2]=polygon->vertices[c].X;
		list[3]=polygon->vertices[c].Y;
		list[4]=polygon->vertices[l].X;
		list[5]=polygon->vertices[1].Y;

		glBegin(GL_TRIANGLES);
		
		glVertex2i(list[0],list[1]);
		glVertex2i(list[2],list[3]);
		glVertex2i(list[4],list[5]);
		glEnd();
		cur_area+=triangle_area(list);
	}
	printf("%i,%i\r\n",cur_area,polygon_area(polygon->numVertices,polygon->vertices));
	return cur_area==polygon_area(polygon->numVertices,polygon->vertices);
}