#include "Face.h"
using namespace CCS;

Vector calcCcwNormal(EdgeUse &e1, EdgeUse &e2)
{
	if(e1.getUseEnd() != e2.getUseStart()) {
		__ERROR__("calcCcwNormal called with two edges that don't connect, or connect in t he wrong order");
		exit(1);
	}

	Point a = e1.getUseStart()->p;
	Point b = e1.getUseEnd()->p;
	Point c = e2.getUseEnd()->p;

	Vector d1 = b-a;
	d1[3] = 0.0;
	d1.Normalize();

	Vector d2 = c-b;
	d2[3] = 0.0;
	d2.Normalize();

	Vector n = d1 * d2;
	n[3] = 0.0;
	n.Normalize();

	return n;
}

Vector Face::calcNormalAt(Vertex* v)
{
	// Iterate through each edge use until we find
	// the one that starts at v
	list<EdgeUse>::iterator eu_iter;
	list<EdgeUse>::iterator endsV = this->edgeUses.end();
	for(eu_iter = this->edgeUses.begin(); eu_iter != this->edgeUses.end(); ++eu_iter) {
		EdgeUse eu = *eu_iter;
		if(eu.getUseEnd() == v) {
			// found it
			endsV = eu_iter;
			break;
		}
	}

	if(endsV == this->edgeUses.end()) {
		__ERROR__("getNormalAt called for a vertex that wasn't on this face!");
		exit(1);
	}

	// *endsV is the edge use that starts a v
	// find the next one, which starts at V
	// make sure to loop around if necessary
	list<EdgeUse>::iterator startsV = endsV;
	++startsV;
	if(startsV == this->edgeUses.end()) {
		startsV = this->edgeUses.begin();
	}

	// go!
	return calcCcwNormal(*endsV, *startsV);
}

TXS::NormRGB Face::getColorAt(Vertex *v)
{
	// iterate in parallel through edge use list and UV list

	list<EdgeUse>::iterator eu_iter = edgeUses.begin();
	list<TXS::UVs>::iterator uv_iter = uvs.begin();
	for(; eu_iter != edgeUses.end(); ++eu_iter, ++uv_iter) {
		EdgeUse eu = *eu_iter;
		if(eu.getUseStart() == v) {
			TXS::UVs uv = *uv_iter;
			// NOTE: We are using no wrap for this, because we assume all vertex UVs are in [0,1]
			return this->txtr->getRgbAtUVNoWrap(uv);
		}
	}

	__ERROR__("CCS::Face::getColorAt called with non-incident vertex!!");
	exit(1);

	return TXS::NormRGB();
}

list<TXS::UVs>::iterator Face::getUvIterAtVert(Vertex *v)
{
	// iterate in parallel through edge use list and UV list

	list<EdgeUse>::iterator eu_iter = edgeUses.begin();
	list<TXS::UVs>::iterator uv_iter = uvs.begin();
	for(; eu_iter != edgeUses.end(); ++eu_iter, ++uv_iter) {
		EdgeUse eu = *eu_iter;
		if(eu.getUseStart() == v) {
			// got it!
			return uv_iter;
		}
	}

	__ERROR__("CCS::Face::getUvIterAtVert called with non-incident vertex!!");
	exit(1);

	return uvs.end();
}

void Face::getItersForVert(Vertex *v, list<EdgeUse>::iterator &eu_out, list<TXS::UVs>::iterator &uv_out)
{
	eu_out = edgeUses.begin();
	uv_out = uvs.begin();

	for(; eu_out != edgeUses.end(); ++eu_out, ++uv_out) {
		EdgeUse eu = *eu_out;
		if(eu.getUseStart() == v) {
			// found it!
			// we're done.  leave the iters as is
			return;
		}
	}

	__ERROR__("CCS::Face::getItersForVert called with non-incident vertex!!");
	exit(1);
}