/*
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.

*/
// r_light.c

#include "quakedef.h"
#include "r_local.h"

int r_dlightframecount;


/*
==================
R_AnimateLight
==================
*/
void
R_AnimateLight(void)
{
    int i, j, k;

//
// light animations
// 'm' is normal light, 'a' is no light, 'z' is double bright
    i = (int)(cl.time * 10);
    for (j = 0; j < MAX_LIGHTSTYLES; j++) {
	if (!cl_lightstyle[j].length) {
	    d_lightstylevalue[j] = 256;
	    continue;
	}
	k = i % cl_lightstyle[j].length;
	k = cl_lightstyle[j].map[k] - 'a';
	k = k * 22;
	d_lightstylevalue[j] = k;
    }
}


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

DYNAMIC LIGHTS

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

/*
=============
R_MarkLights
=============
*/
void
R_MarkLights(dlight_t *light, int bit, mnode_t *node)
{
    mplane_t *splitplane;
    float dist;
    msurface_t *surf;
    int i;

    if (node->contents < 0)
	return;

    splitplane = node->plane;
    dist = DotProduct(light->origin, splitplane->normal) - splitplane->dist;

    if (dist > light->radius) {
	R_MarkLights(light, bit, node->children[0]);
	return;
    }
    if (dist < -light->radius) {
	R_MarkLights(light, bit, node->children[1]);
	return;
    }
// mark the polygons
    surf = cl.worldmodel->surfaces + node->firstsurface;
    for (i = 0; i < node->numsurfaces; i++, surf++) {
	if (surf->dlightframe != r_dlightframecount) {
	    surf->dlightbits = 0;
	    surf->dlightframe = r_dlightframecount;
	}
	surf->dlightbits |= bit;
    }

    R_MarkLights(light, bit, node->children[0]);
    R_MarkLights(light, bit, node->children[1]);
}


/*
=============
R_PushDlights
=============
*/
void
R_PushDlights(void)
{
    int i;
    dlight_t *l;

    r_dlightframecount = r_framecount + 1;	// because the count hasn't
    //  advanced yet for this frame
    l = cl_dlights;

    for (i = 0; i < MAX_DLIGHTS; i++, l++) {
	if (l->die < cl.time || !l->radius)
	    continue;
	R_MarkLights(l, 1 << i, cl.worldmodel->nodes);
    }
}


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

LIGHT SAMPLING

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

int
RecursiveLightPoint(mnode_t *node, vec3_t start, vec3_t end)
{
    int r;
    float front, back, frac;
    int side;
    mplane_t *plane;
    vec3_t mid;
    msurface_t *surf;
    int s, t, ds, dt;
    int i;
    mtexinfo_t *tex;
    byte *lightmap;
    unsigned scale;
    int maps;

    if (node->contents < 0)
	return -1;		// didn't hit anything

// calculate mid point

    plane = node->plane;
    switch (plane->type) {
    case PLANE_X:
    case PLANE_Y:
    case PLANE_Z:
	front = start[plane->type - PLANE_X] - plane->dist;
	back = end[plane->type - PLANE_X] - plane->dist;
	break;
    default:
	front = DotProduct(start, plane->normal) - plane->dist;
	back = DotProduct(end, plane->normal) - plane->dist;
	break;
    }
    side = front < 0;

    /* FIXME - tail recursion => optimize */
    if ((back < 0) == side)
	return RecursiveLightPoint(node->children[side], start, end);

    frac = front / (front - back);
    mid[0] = start[0] + (end[0] - start[0]) * frac;
    mid[1] = start[1] + (end[1] - start[1]) * frac;
    mid[2] = start[2] + (end[2] - start[2]) * frac;

// go down front side
    r = RecursiveLightPoint(node->children[side], start, mid);
    if (r >= 0)
	return r;		// hit something

    if ((back < 0) == side)
	return -1;		// didn't hit anuthing

// check for impact on this node

    surf = cl.worldmodel->surfaces + node->firstsurface;
    for (i = 0; i < node->numsurfaces; i++, surf++) {
	if (surf->flags & SURF_DRAWTILED)
	    continue;		// no lightmaps

	tex = surf->texinfo;

	s = DotProduct(mid, tex->vecs[0]) + tex->vecs[0][3];
	t = DotProduct(mid, tex->vecs[1]) + tex->vecs[1][3];;

	if (s < surf->texturemins[0] || t < surf->texturemins[1])
	    continue;

	ds = s - surf->texturemins[0];
	dt = t - surf->texturemins[1];

	if (ds > surf->extents[0] || dt > surf->extents[1])
	    continue;

	if (!surf->samples)
	    return 0;

	ds >>= 4;
	dt >>= 4;

	/* FIXME: does this account properly for dynamic lights? e.g. rocket */
	lightmap = surf->samples;
	r = 0;
	if (lightmap) {
	    lightmap += dt * ((surf->extents[0] >> 4) + 1) + ds;
	    for (maps = 0; maps < MAXLIGHTMAPS && surf->styles[maps] != 255;
		 maps++) {
		scale = d_lightstylevalue[surf->styles[maps]];
		r += *lightmap * scale;
		lightmap += ((surf->extents[0] >> 4) + 1) *
		    ((surf->extents[1] >> 4) + 1);
	    }
	    r >>= 8;
	}

	return r;
    }

    /* FIXME - tail recursion => optimize */
    /* go down back side */
    return RecursiveLightPoint(node->children[!side], mid, end);
}

/*
 * FIXME - check what the callers do, but I don't think this will check the
 * light value of a bmodel below the point. Models could easily be standing on
 * a func_plat or similar...
 */
int
R_LightPoint(vec3_t p)
{
    vec3_t end;
    int r;

    if (!cl.worldmodel->lightdata)
	return 255;

    end[0] = p[0];
    end[1] = p[1];
    end[2] = p[2] - (8192 + 2); /* Max distance + error margin */

    r = RecursiveLightPoint(cl.worldmodel->nodes, p, end);

    if (r == -1)
	r = 0;

    if (r < r_refdef.ambientlight)
	r = r_refdef.ambientlight;

    return r;
}
