//
// Copyright(C) 1993-1996 Id Software, Inc.
// Copyright(C) 2005-2014 Simon Howard
//
// 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.
//
// DESCRIPTION:
//	Here is a core component: drawing the floors and ceilings,
//	 while maintaining a per column clipping list only.
//	Moreover, the sky areas have to be determined.
//

#include "doomdef.h"
#include "doomstat.h"
#include "i_system.h"
#include "r_local.h"
#include "r_sky.h"
#include "w_wad.h"
#include "z_zone.h"

#include <stdio.h>
#include <stdlib.h>

planefunction_t floorfunc;
planefunction_t ceilingfunc;

//
// opening
//

// Here comes the obnoxious "visplane".
#define MAXVISPLANES 128
visplane_t visplanes[MAXVISPLANES];
visplane_t* lastvisplane;
visplane_t* floorplane;
visplane_t* ceilingplane;

// ?
#define MAXOPENINGS SCREENWIDTH * 64
short openings[MAXOPENINGS];
short* lastopening;

//
// Clip values are the solid pixel bounding the range.
//  floorclip starts out SCREENHEIGHT
//  ceilingclip starts out -1
//
short floorclip[SCREENWIDTH];
short ceilingclip[SCREENWIDTH];

//
// spanstart holds the start of a plane span
// initialized to 0 at start
//
int spanstart[SCREENHEIGHT];
int spanstop[SCREENHEIGHT];

//
// texture mapping
//
lighttable_t** planezlight;
fixed_t planeheight;

fixed_t yslope[SCREENHEIGHT];
fixed_t distscale[SCREENWIDTH];
fixed_t basexscale;
fixed_t baseyscale;

fixed_t cachedheight[SCREENHEIGHT];
fixed_t cacheddistance[SCREENHEIGHT];
fixed_t cachedxstep[SCREENHEIGHT];
fixed_t cachedystep[SCREENHEIGHT];

//
// R_InitPlanes
// Only at game startup.
//
void R_InitPlanes(void) {
    // Doh!
}

//
// R_MapPlane
//
// Uses global vars:
//  planeheight
//  ds_source
//  basexscale
//  baseyscale
//  viewx
//  viewy
//
// BASIC PRIMITIVE
//
void R_MapPlane(int y, int x1, int x2) {
    angle_t angle;
    fixed_t distance;
    fixed_t length;
    unsigned index;

#ifdef RANGECHECK
    if (x2 < x1 || x1 < 0 || x2 >= viewwidth || y > viewheight) {
        I_Error("R_MapPlane: %i, %i at %i", x1, x2, y);
    }
#endif

    if (planeheight != cachedheight[y]) {
        cachedheight[y] = planeheight;
        distance = cacheddistance[y] = FixedMul(planeheight, yslope[y]);
        ds_xstep = cachedxstep[y] = FixedMul(distance, basexscale);
        ds_ystep = cachedystep[y] = FixedMul(distance, baseyscale);
    } else {
        distance = cacheddistance[y];
        ds_xstep = cachedxstep[y];
        ds_ystep = cachedystep[y];
    }

    length = FixedMul(distance, distscale[x1]);
    angle = (viewangle + xtoviewangle[x1]) >> ANGLETOFINESHIFT;
    ds_xfrac = viewx + FixedMul(finecosine[angle], length);
    ds_yfrac = -viewy - FixedMul(finesine[angle], length);

    if (fixedcolormap)
        ds_colormap = fixedcolormap;
    else {
        index = distance >> LIGHTZSHIFT;

        if (index >= MAXLIGHTZ)
            index = MAXLIGHTZ - 1;

        ds_colormap = planezlight[index];
    }

    ds_y = y;
    ds_x1 = x1;
    ds_x2 = x2;

    // high or low detail
    spanfunc();
}

//
// R_ClearPlanes
// At begining of frame.
//
void R_ClearPlanes(void) {
    int i;
    angle_t angle;

    // opening / clipping determination
    for (i = 0; i < viewwidth; i++) {
        floorclip[i] = viewheight;
        ceilingclip[i] = -1;
    }

    lastvisplane = visplanes;
    lastopening = openings;

    // texture calculation
    memset(cachedheight, 0, sizeof(cachedheight));

    // left to right mapping
    angle = (viewangle - ANG90) >> ANGLETOFINESHIFT;

    // scale will be unit scale at SCREENWIDTH/2 distance
    basexscale = FixedDiv(finecosine[angle], centerxfrac);
    baseyscale = -FixedDiv(finesine[angle], centerxfrac);
}

//
// R_FindPlane
//
visplane_t* R_FindPlane(fixed_t height, int picnum, int lightlevel) {
    visplane_t* check;

    if (picnum == skyflatnum) {
        height = 0; // all skys map together
        lightlevel = 0;
    }

    for (check = visplanes; check < lastvisplane; check++) {
        if (height == check->height && picnum == check->picnum && lightlevel == check->lightlevel) {
            break;
        }
    }

    if (check < lastvisplane)
        return check;

    if (lastvisplane - visplanes == MAXVISPLANES)
        I_Error("R_FindPlane: no more visplanes");

    lastvisplane++;

    check->height = height;
    check->picnum = picnum;
    check->lightlevel = lightlevel;
    check->minx = SCREENWIDTH;
    check->maxx = -1;

    memset(check->top, 0xff, sizeof(check->top));

    return check;
}

//
// R_CheckPlane
//
visplane_t* R_CheckPlane(visplane_t* pl, int start, int stop) {
    int intrl;
    int intrh;
    int unionl;
    int unionh;
    int x;

    if (start < pl->minx) {
        intrl = pl->minx;
        unionl = start;
    } else {
        unionl = pl->minx;
        intrl = start;
    }

    if (stop > pl->maxx) {
        intrh = pl->maxx;
        unionh = stop;
    } else {
        unionh = pl->maxx;
        intrh = stop;
    }

    for (x = intrl; x <= intrh; x++)
        if (pl->top[x] != 0xff)
            break;

    if (x > intrh) {
        pl->minx = unionl;
        pl->maxx = unionh;

        // use the same one
        return pl;
    }

    // make a new visplane
    lastvisplane->height = pl->height;
    lastvisplane->picnum = pl->picnum;
    lastvisplane->lightlevel = pl->lightlevel;

    pl = lastvisplane++;
    pl->minx = start;
    pl->maxx = stop;

    memset(pl->top, 0xff, sizeof(pl->top));

    return pl;
}

//
// R_MakeSpans
//
void R_MakeSpans(int x, int t1, int b1, int t2, int b2) {
    while (t1 < t2 && t1 <= b1) {
        R_MapPlane(t1, spanstart[t1], x - 1);
        t1++;
    }
    while (b1 > b2 && b1 >= t1) {
        R_MapPlane(b1, spanstart[b1], x - 1);
        b1--;
    }

    while (t2 < t1 && t2 <= b2) {
        spanstart[t2] = x;
        t2++;
    }
    while (b2 > b1 && b2 >= t2) {
        spanstart[b2] = x;
        b2--;
    }
}

//
// R_DrawPlanes
// At the end of each frame.
//
void R_DrawPlanes(void) {
    visplane_t* pl;
    int light;
    int x;
    int stop;
    int angle;
    int lumpnum;

#ifdef RANGECHECK
    if (ds_p - drawsegs > MAXDRAWSEGS)
        I_Error("R_DrawPlanes: drawsegs overflow (%i)", ds_p - drawsegs);

    if (lastvisplane - visplanes > MAXVISPLANES)
        I_Error("R_DrawPlanes: visplane overflow (%i)", lastvisplane - visplanes);

    if (lastopening - openings > MAXOPENINGS)
        I_Error("R_DrawPlanes: opening overflow (%i)", lastopening - openings);
#endif

    for (pl = visplanes; pl < lastvisplane; pl++) {
        if (pl->minx > pl->maxx)
            continue;

        // sky flat
        if (pl->picnum == skyflatnum) {
            dc_iscale = pspriteiscale >> detailshift;

            // Sky is allways drawn full bright,
            //  i.e. colormaps[0] is used.
            // Because of this hack, sky is not affected
            //  by INVUL inverse mapping.
            dc_colormap = colormaps;
            dc_texturemid = skytexturemid;
            for (x = pl->minx; x <= pl->maxx; x++) {
                dc_yl = pl->top[x];
                dc_yh = pl->bottom[x];

                if (dc_yl <= dc_yh) {
                    angle = (viewangle + xtoviewangle[x]) >> ANGLETOSKYSHIFT;
                    dc_x = x;
                    dc_source = R_GetColumn(skytexture, angle);
                    colfunc();
                }
            }
            continue;
        }

        // regular flat
        lumpnum = firstflat + flattranslation[pl->picnum];
        ds_source = W_CacheLumpNum(lumpnum, PU_STATIC);

        planeheight = abs(pl->height - viewz);
        light = (pl->lightlevel >> LIGHTSEGSHIFT) + extralight;

        if (light >= LIGHTLEVELS)
            light = LIGHTLEVELS - 1;

        if (light < 0)
            light = 0;

        planezlight = zlight[light];

        pl->top[pl->maxx + 1] = 0xff;
        pl->top[pl->minx - 1] = 0xff;

        stop = pl->maxx + 1;

        for (x = pl->minx; x <= stop; x++) {
            R_MakeSpans(x, pl->top[x - 1], pl->bottom[x - 1], pl->top[x], pl->bottom[x]);
        }

        W_ReleaseLumpNum(lumpnum);
    }
}
