/*
	Copyright (C) 1996-1997  Id Software, Inc.

	This program is free software; you can redistribute it and/or modify
	it under the terms of the GNU General Public License as published by
	the Free Software Foundation; either version 2 of the License, or
	(at your option) any later version.

	This program is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
	GNU General Public License for more details.

	You should have received a copy of the GNU General Public License
	along with this program; if not, write to the Free Software
	Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA

	See file, 'COPYING', for details.
*/
#ifdef HAVE_CONFIG_H
# include "config.h"
#endif

static __attribute__ ((unused)) const char rcsid[] =
	"$Id$";

#include "QF/sys.h"

#include "bsp5.h"

#define CONTINUOUS_EPSILON	0.001


/*
	TryMerge

	If two polygons share a common edge and the edges that meet at the common
	points are both inside the other polygons, merge them

	Returns NULL if the faces couldn't be merged, or the new face.
	The originals will NOT be freed.
*/
static face_t     *
TryMerge (face_t *f1, face_t *f2)
{
	face_t     *newf;
	int         i, j, k, l;
	plane_t    *plane;
	qboolean    keep1, keep2;
	vec3_t      normal, delta, planenormal;
	vec_t       dot;
	vec_t      *p1, *p2, *p3, *p4, *back;

	if (f1->numpoints == -1 || f2->numpoints == -1)
		return NULL;
	if (f1->planeside != f2->planeside)
		return NULL;
	if (f1->texturenum != f2->texturenum)
		return NULL;
	if (f1->contents[0] != f2->contents[0])
		return NULL;
	if (f1->contents[1] != f2->contents[1])
		return NULL;

	// find a common edge
	p1 = p2 = NULL;						// stop compiler warning
	j = 0;

	for (i = 0; i < f1->numpoints; i++) {
		p1 = f1->pts[i];
		p2 = f1->pts[(i + 1) % f1->numpoints];
		for (j = 0; j < f2->numpoints; j++) {
			p3 = f2->pts[j];
			p4 = f2->pts[(j + 1) % f2->numpoints];
			for (k = 0; k < 3; k++) {
				if (fabs (p1[k] - p4[k]) > EQUAL_EPSILON)
					break;
				if (fabs (p2[k] - p3[k]) > EQUAL_EPSILON)
					break;
			}
			if (k == 3)
				break;
		}
		if (j < f2->numpoints)
			break;
	}

	if (i == f1->numpoints)
		return NULL;					// no matching edges

	// check slope of connected lines
	// if the slopes are colinear, the point can be removed
	plane = &planes[f1->planenum];
	VectorCopy (plane->normal, planenormal);
	if (f1->planeside)
		VectorNegate (planenormal, planenormal);

	back = f1->pts[(i + f1->numpoints - 1) % f1->numpoints];
	VectorSubtract (p1, back, delta);
	CrossProduct (planenormal, delta, normal);
	_VectorNormalize (normal);

	back = f2->pts[(j + 2) % f2->numpoints];
	VectorSubtract (back, p1, delta);
	dot = DotProduct (delta, normal);
	if (dot > CONTINUOUS_EPSILON)
		return NULL;					// not a convex polygon
	keep1 = dot < -CONTINUOUS_EPSILON;

	back = f1->pts[(i + 2) % f1->numpoints];
	VectorSubtract (back, p2, delta);
	CrossProduct (planenormal, delta, normal);
	_VectorNormalize (normal);

	back = f2->pts[(j + f2->numpoints - 1) % f2->numpoints];
	VectorSubtract (back, p2, delta);
	dot = DotProduct (delta, normal);
	if (dot > CONTINUOUS_EPSILON)
		return NULL;					// not a convex polygon
	keep2 = dot < -CONTINUOUS_EPSILON;

	// build the new polygon
	if (f1->numpoints + f2->numpoints > MAXEDGES) {
//		Sys_Error ("TryMerge: too many edges!");
		return NULL;
	}

	newf = NewFaceFromFace (f1);

	// copy first polygon
	for (k = (i + 1) % f1->numpoints; k != i; k = (k + 1) % f1->numpoints) {
		if (k == (i + 1) % f1->numpoints && !keep2)
			continue;

		VectorCopy (f1->pts[k], newf->pts[newf->numpoints]);
		newf->numpoints++;
	}

	// copy second polygon
	for (l = (j + 1) % f2->numpoints; l != j; l = (l + 1) % f2->numpoints) {
		if (l == (j + 1) % f2->numpoints && !keep1)
			continue;
		VectorCopy (f2->pts[l], newf->pts[newf->numpoints]);
		newf->numpoints++;
	}

	return newf;
}

qboolean    mergedebug;
face_t     *
MergeFaceToList (face_t *face, face_t *list)
{
	face_t     *newf, *f;

	for (f = list; f; f = f->next) {
//		CheckColinear (f);        
		if (mergedebug) {
			Draw_ClearWindow ();
			Draw_DrawFace (face);
			Draw_DrawFace (f);
			Draw_SetBlack ();
		}
		newf = TryMerge (face, f);
		if (!newf)
			continue;
		FreeFace (face);
		f->numpoints = -1;				// merged out
		return MergeFaceToList (newf, list);
	}

	// didn't merge, so add at start
	face->next = list;
	return face;
}

face_t     *
FreeMergeListScraps (face_t *merged)
{
	face_t     *head, *next;

	head = NULL;
	for (; merged; merged = next) {
		next = merged->next;
		if (merged->numpoints == -1)
			FreeFace (merged);
		else {
			merged->next = head;
			head = merged;
		}
	}

	return head;
}

void
MergePlaneFaces (surface_t *plane)
{
	face_t     *merged, *next, *f1;

	merged = NULL;

	for (f1 = plane->faces; f1; f1 = next) {
		next = f1->next;
		merged = MergeFaceToList (f1, merged);
	}

	// chain all of the non-empty faces to the plane
	plane->faces = FreeMergeListScraps (merged);
}

void
MergeAll (surface_t * surfhead)
{
	face_t     *f;
	int         mergefaces;
	surface_t  *surf;

	printf ("---- MergeAll ----\n");

	mergefaces = 0;
	for (surf = surfhead; surf; surf = surf->next) {
		MergePlaneFaces (surf);
		Draw_ClearWindow ();
		for (f = surf->faces; f; f = f->next) {
			Draw_DrawFace (f);
			mergefaces++;
		}
	}

	printf ("%i mergefaces\n", mergefaces);
}