/*
Copyright (C) 1996-2001 Id Software, Inc.
Copyright (C) 2002-2009 John Fitzgibbons and others
Copyright (C) 2010-2014 QuakeSpasm developers

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.

*/
// gl_mesh.c: triangle model functions

#include "quakedef.hpp"


/*
=================================================================

ALIAS MODEL DISPLAY LIST GENERATION

=================================================================
*/

static unsigned char	used[MAXALIASTRIS];

// the command list holds counts and s/t values that are valid for
// every frame
static int		commands[MAXALIASTRIS*7 + 1];
static int		numcommands;

// all frames will have their vertexes rearranged and expanded
// so they are in the order expected by the command list
static int		vertexorder[MAXALIASTRIS * 3];
static int		numorder;

static int		stripverts[MAXALIASTRIS + 2];
static int		striptris[MAXALIASTRIS];
static int		stripcount;

/*
================
StripLength
================
*/
static int StripLength (int starttri, int startv)
{
	int			m1, m2;
	int			j;
	mtriangle_t	*last, *check;
	int			k;

	used[starttri] = 2;

	last = &triangles[starttri];

	stripverts[0] = last->vertindex[(startv)%3];
	stripverts[1] = last->vertindex[(startv+1)%3];
	stripverts[2] = last->vertindex[(startv+2)%3];

	striptris[0] = starttri;
	stripcount = 1;

	m1 = last->vertindex[(startv+2)%3];
	m2 = last->vertindex[(startv+1)%3];

	// look for a matching triangle
nexttri:
	for (j=starttri+1, check=&triangles[starttri+1] ; j<pheader->numtris ; j++, check++)
	{
		if (check->facesfront != last->facesfront)
			continue;
		for (k=0 ; k<3 ; k++)
		{
			if (check->vertindex[k] != m1)
				continue;
			if (check->vertindex[ (k+1)%3 ] != m2)
				continue;

			// this is the next part of the fan

			// if we can't use this triangle, this tristrip is done
			if (used[j])
				goto done;

			// the new edge
			if (stripcount & 1)
				m2 = check->vertindex[ (k+2)%3 ];
			else
				m1 = check->vertindex[ (k+2)%3 ];

			stripverts[stripcount+2] = check->vertindex[ (k+2)%3 ];
			striptris[stripcount] = j;
			stripcount++;

			used[j] = 2;
			goto nexttri;
		}
	}
done:

	// clear the temp used flags
	for (j=starttri+1 ; j<pheader->numtris ; j++)
		if (used[j] == 2)
			used[j] = 0;

	return stripcount;
}

/*
===========
FanLength
===========
*/
static int FanLength (int starttri, int startv)
{
	int		m1, m2;
	int		j;
	mtriangle_t	*last, *check;
	int		k;

	used[starttri] = 2;

	last = &triangles[starttri];

	stripverts[0] = last->vertindex[(startv)%3];
	stripverts[1] = last->vertindex[(startv+1)%3];
	stripverts[2] = last->vertindex[(startv+2)%3];

	striptris[0] = starttri;
	stripcount = 1;

	m1 = last->vertindex[(startv+0)%3];
	m2 = last->vertindex[(startv+2)%3];


	// look for a matching triangle
nexttri:
	for (j=starttri+1, check=&triangles[starttri+1] ; j<pheader->numtris ; j++, check++)
	{
		if (check->facesfront != last->facesfront)
			continue;
		for (k=0 ; k<3 ; k++)
		{
			if (check->vertindex[k] != m1)
				continue;
			if (check->vertindex[ (k+1)%3 ] != m2)
				continue;

			// this is the next part of the fan

			// if we can't use this triangle, this tristrip is done
			if (used[j])
				goto done;

			// the new edge
			m2 = check->vertindex[ (k+2)%3 ];

			stripverts[stripcount+2] = m2;
			striptris[stripcount] = j;
			stripcount++;

			used[j] = 2;
			goto nexttri;
		}
	}
done:

	// clear the temp used flags
	for (j=starttri+1 ; j<pheader->numtris ; j++)
		if (used[j] == 2)
			used[j] = 0;

	return stripcount;
}


/*
================
BuildTris

Generate a list of trifans or strips
for the model, which holds for all frames
================
*/
static void BuildTris (void)
{
	int		i, j, k;
	int		startv;
	float	s, t;
	int		len, bestlen, besttype;
	int		bestverts[MAXALIASTRIS + 2];
	int		besttris[MAXALIASTRIS];
	int		type;

	//
	// build tristrips
	//
	numorder = 0;
	numcommands = 0;
	memset (used, 0, sizeof(used));
	for (i = 0; i < pheader->numtris; i++)
	{
		// pick an unused triangle and start the trifan
		if (used[i])
			continue;

		bestlen = 0;
		besttype = 0;
		for (type = 0 ; type < 2 ; type++)
//	type = 1;
		{
			for (startv = 0; startv < 3; startv++)
			{
				if (type == 1)
					len = StripLength (i, startv);
				else
					len = FanLength (i, startv);
				if (len > bestlen)
				{
					besttype = type;
					bestlen = len;
					for (j = 0; j < bestlen+2; j++)
						bestverts[j] = stripverts[j];
					for (j = 0; j < bestlen; j++)
						besttris[j] = striptris[j];
				}
			}
		}

		// mark the tris on the best strip as used
		for (j = 0; j < bestlen; j++)
			used[besttris[j]] = 1;

		if (besttype == 1)
			commands[numcommands++] = (bestlen+2);
		else
			commands[numcommands++] = -(bestlen+2);

		for (j = 0; j < bestlen+2; j++)
		{
			int		tmp;

			// emit a vertex into the reorder buffer
			k = bestverts[j];
			vertexorder[numorder++] = k;

			// emit s/t coords into the commands stream
			s = stverts[k].s;
			t = stverts[k].t;
			if (!triangles[besttris[0]].facesfront && stverts[k].onseam)
				s += pheader->skinwidth / 2;	// on back side
			s = (s + 0.5) / pheader->skinwidth;
			t = (t + 0.5) / pheader->skinheight;

		//	*(float *)&commands[numcommands++] = s;
		//	*(float *)&commands[numcommands++] = t;
			// NOTE: 4 == sizeof(int)
			//	   == sizeof(float)
			memcpy (&tmp, &s, 4);
			commands[numcommands++] = tmp;
			memcpy (&tmp, &t, 4);
			commands[numcommands++] = tmp;
		}
	}

	commands[numcommands++] = 0;		// end of list marker

	console::trace ("%3i tri %3i vert %3i cmd\n", pheader->numtris, numorder, numcommands);
}

static void GL_MakeAliasModelDisplayLists_VBO (qmodel_t *, aliashdr_t *);
static void GLMesh_LoadVertexBuffer (qmodel_t *m, const aliashdr_t *hdr);

/*
================
GL_MakeAliasModelDisplayLists
================
*/
void GL_MakeAliasModelDisplayLists (qmodel_t *m, aliashdr_t *hdr)
{
	int		i, j;
	int			*cmds;
	trivertx_t	*verts;
	float	hscale, vscale; //johnfitz -- padded skins
	int		count; //johnfitz -- precompute texcoords for padded skins
	int		*loadcmds; //johnfitz
	aliashdr_t	*paliashdr = hdr;	// (aliashdr_t *)Mod_Extradata (m);

	//johnfitz -- padded skins
	hscale = (float)hdr->skinwidth/(float)TexMgr_PadConditional(hdr->skinwidth);
	vscale = (float)hdr->skinheight/(float)TexMgr_PadConditional(hdr->skinheight);
	//johnfitz

//johnfitz -- generate meshes
	console::trace ("meshing %s...\n",m->name);
	BuildTris ();

	// save the data out

	paliashdr->poseverts = numorder;

	cmds = (int *) Hunk_Alloc (numcommands * 4);
	paliashdr->commands = (byte *)cmds - (byte *)paliashdr;

	//johnfitz -- precompute texcoords for padded skins
	loadcmds = commands;
	while(1)
	{
		*cmds++ = count = *loadcmds++;

		if (!count)
			break;

		if (count < 0)
			count = -count;

		do
		{
			*(float *)cmds++ = hscale * (*(float *)loadcmds++);
			*(float *)cmds++ = vscale * (*(float *)loadcmds++);
		} while (--count);
	}
	//johnfitz

	verts = (trivertx_t *) Hunk_Alloc (paliashdr->numposes * paliashdr->poseverts * sizeof(trivertx_t));
	paliashdr->posedata = (byte *)verts - (byte *)paliashdr;
	for (i=0 ; i<paliashdr->numposes ; i++)
		for (j=0 ; j<numorder ; j++)
			*verts++ = poseverts[i][vertexorder[j]];

	// ericw
	GL_MakeAliasModelDisplayLists_VBO (m, paliashdr);
}

/*
================
GL_MakeAliasModelDisplayLists_VBO

Saves data needed to build the VBO for this model on the hunk. Afterwards this
is copied to Mod_Extradata.

Original code by MH from RMQEngine
================
*/
static void GL_MakeAliasModelDisplayLists_VBO (qmodel_t *aliasmodel, aliashdr_t *paliashdr)
{
	int i, j;
	int mark;
	trivertx_t *verts;
	unsigned short *indexes;
	unsigned short *remap;
	aliasmesh_t *desc;

	if (!gl_glsl_alias_able)
		return;

	// first, copy the verts onto the hunk
	verts = (trivertx_t *) Hunk_Alloc (paliashdr->numposes * paliashdr->numverts * sizeof(trivertx_t));
	paliashdr->vertexes = (byte *)verts - (byte *)paliashdr;
	for (i=0 ; i<paliashdr->numposes ; i++)
		for (j=0 ; j<paliashdr->numverts ; j++)
			verts[i*paliashdr->numverts + j] = poseverts[i][j];

	// there can never be more than this number of verts and we just put them all on the hunk
	// (each vertex can be used twice, once with the original UVs and once with the seam adjustment)
	desc = (aliasmesh_t *) Hunk_Alloc (sizeof (aliasmesh_t) * pheader->numverts * 2);

	// there will always be this number of indexes
	indexes = (unsigned short *) Hunk_Alloc (sizeof (unsigned short) * pheader->numtris * 3);

	pheader->indexes = (intptr_t) indexes - (intptr_t) pheader;
	pheader->meshdesc = (intptr_t) desc - (intptr_t) pheader;
	pheader->numindexes = 0;
	pheader->numverts_vbo = 0;

	mark = Hunk_LowMark ();

	// each pair of elements in the remap array corresponds to one source vertex
	// each value is the final index + 1, or 0 if the corresponding vertex hasn't been emitted yet
	remap = (unsigned short *) Hunk_Alloc (paliashdr->numverts * 2 * sizeof (remap[0]));

	for (i = 0; i < pheader->numtris; i++)
	{
		for (j = 0; j < 3; j++)
		{
			// index into hdr->vertexes
			unsigned short vertindex = triangles[i].vertindex[j];

			// index into remap table
			int v = vertindex * 2;

			// check for back side
			if (!triangles[i].facesfront && stverts[vertindex].onseam)
				v++;

			// emit new vertex if it doesn't already exist
			if (!remap[v])
			{
				// basic s/t coords
				int s = stverts[vertindex].s;
				int t = stverts[vertindex].t;

				// check for back side and adjust texcoord s
				if (v & 1)
					s += paliashdr->skinwidth / 2;

				desc[pheader->numverts_vbo].vertindex = vertindex;
				desc[pheader->numverts_vbo].st[0] = s;
				desc[pheader->numverts_vbo].st[1] = t;

				remap[v] = ++pheader->numverts_vbo;
			}

			// emit index
			indexes[pheader->numindexes++] = remap[v] - 1;
		}
	}

	// free temporary data
	Hunk_FreeToLowMark (mark);

	// upload immediately
	GLMesh_LoadVertexBuffer (aliasmodel, pheader);
}

/*
================
GLMesh_LoadVertexBuffer

Upload the given alias model's mesh to a VBO

Original code by MH from RMQEngine
================
*/
static void GLMesh_LoadVertexBuffer (qmodel_t *m, const aliashdr_t *hdr)
{
	int totalvbosize = 0;
	const aliasmesh_t *desc;
	const short *indexes;
	const trivertx_t *trivertexes;
	byte *vbodata;
	int f;

	if (!gl_glsl_alias_able)
		return;

// count the sizes we need
	
	// ericw -- RMQEngine stored these vbo*ofs values in aliashdr_t, but we must not
	// mutate Mod_Extradata since it might be reloaded from disk, so I moved them to qmodel_t
	// (test case: roman1.bsp from arwop, 64mb heap)
	m->vboindexofs = 0;

	m->vboxyzofs = 0;
	totalvbosize += (hdr->numposes * hdr->numverts_vbo * sizeof (meshxyz_t)); // ericw -- what RMQEngine called nummeshframes is called numposes in QuakeSpasm

	m->vbostofs = totalvbosize;
	totalvbosize += (hdr->numverts_vbo * sizeof (meshst_t));

	if (!hdr->numindexes) return;
	if (!totalvbosize) return;

// grab the pointers to data in the extradata

	desc = (aliasmesh_t *) ((byte *) hdr + hdr->meshdesc);
	indexes = (short *) ((byte *) hdr + hdr->indexes);
	trivertexes = (trivertx_t *) ((byte *)hdr + hdr->vertexes);

// upload indices buffer

	GL_DeleteBuffersFunc (1, &m->meshindexesvbo);
	GL_GenBuffersFunc (1, &m->meshindexesvbo);
	GL_BindBufferFunc (GL_ELEMENT_ARRAY_BUFFER, m->meshindexesvbo);
	GL_BufferDataFunc (GL_ELEMENT_ARRAY_BUFFER, hdr->numindexes * sizeof (unsigned short), indexes, GL_STATIC_DRAW);

// create the vertex buffer (empty)

	vbodata = (byte *) malloc(totalvbosize);
	memset(vbodata, 0, totalvbosize);

// fill in the vertices at the start of the buffer
	for (f = 0; f < hdr->numposes; f++) // ericw -- what RMQEngine called nummeshframes is called numposes in QuakeSpasm
	{
		int v;
		meshxyz_t *xyz = (meshxyz_t *) (vbodata + (f * hdr->numverts_vbo * sizeof (meshxyz_t)));
		const trivertx_t *tv = trivertexes + (hdr->numverts * f);

		for (v = 0; v < hdr->numverts_vbo; v++)
		{
			trivertx_t trivert = tv[desc[v].vertindex];

			xyz[v].xyz[0] = trivert.v[0];
			xyz[v].xyz[1] = trivert.v[1];
			xyz[v].xyz[2] = trivert.v[2];
			xyz[v].xyz[3] = 1;	// need w 1 for 4 byte vertex compression

			// map the normal coordinates in [-1..1] to [-127..127] and store in an unsigned char.
			// this introduces some error (less than 0.004), but the normals were very coarse
			// to begin with
			xyz[v].normal[0] = 127 * r_avertexnormals[trivert.lightnormalindex][0];
			xyz[v].normal[1] = 127 * r_avertexnormals[trivert.lightnormalindex][1];
			xyz[v].normal[2] = 127 * r_avertexnormals[trivert.lightnormalindex][2];
			xyz[v].normal[3] = 0;	// unused; for 4-byte alignment
		}
	}

// fill in the ST coords at the end of the buffer
	{
		meshst_t *st;
		float hscale, vscale;

		//johnfitz -- padded skins
		hscale = 1.0f / (float)TexMgr_PadConditional(hdr->skinwidth);
		vscale = 1.0f / (float)TexMgr_PadConditional(hdr->skinheight);
		//johnfitz

		st = (meshst_t *) (vbodata + m->vbostofs);
		for (f = 0; f < hdr->numverts_vbo; f++)
		{
			st[f].st[0] = hscale * ((float) desc[f].st[0] + 0.5f);
			st[f].st[1] = vscale * ((float) desc[f].st[1] + 0.5f);
		}
	}

// upload vertexes buffer
	GL_DeleteBuffersFunc (1, &m->meshvbo);
	GL_GenBuffersFunc (1, &m->meshvbo);
	GL_BindBufferFunc (GL_ARRAY_BUFFER, m->meshvbo);
	GL_BufferDataFunc (GL_ARRAY_BUFFER, totalvbosize, vbodata, GL_STATIC_DRAW);

	free (vbodata);

// invalidate the cached bindings
	GL_ClearBufferBindings ();
}

/*
================
GLMesh_LoadVertexBuffers

Loop over all precached alias models, and upload each one to a VBO.
================
*/
void GLMesh_LoadVertexBuffers (void)
{
	int j;
	qmodel_t *m;
	const aliashdr_t *hdr;

	if (!gl_glsl_alias_able)
		return;

	for (j = 1; j < MAX_MODELS; j++)
	{
		if (!(m = cl.model_precache[j])) break;
		if (m->type != mod_alias) continue;

		hdr = (const aliashdr_t *) Mod_Extradata (m);
		
		GLMesh_LoadVertexBuffer (m, hdr);
	}
}

/*
================
GLMesh_DeleteVertexBuffers

Delete VBOs for all loaded alias models
================
*/
void GLMesh_DeleteVertexBuffers (void)
{
	int j;
	qmodel_t *m;
	
	if (!gl_glsl_alias_able)
		return;

	for (j = 1; j < MAX_MODELS; j++)
	{
		if (!(m = cl.model_precache[j])) break;
		if (m->type != mod_alias) continue;
		
		GL_DeleteBuffersFunc (1, &m->meshvbo);
		m->meshvbo = 0;

		GL_DeleteBuffersFunc (1, &m->meshindexesvbo);
		m->meshindexesvbo = 0;
	}

	GL_ClearBufferBindings ();
}
