// Emacs style mode select   -*- C++ -*-
//-----------------------------------------------------------------------------
//
// $Id:$
//
// Copyright (C) 1993-1996 by id Software, Inc.
//
// This source is available for distribution and/or modification
// only under the terms of the DOOM Source Code License as
// published by id Software. All rights reserved.
//
// The source is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// FITNESS FOR A PARTICULAR PURPOSE. See the DOOM Source Code License
// for more details.
//
// $Log:$
//
// 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.
//
//-----------------------------------------------------------------------------


static const char
rcsid[] = "$Id: r_plane.c,v 1.4 1997/02/03 16:47:55 b1 Exp $";

#include <stdlib.h>

#include "i_system.h"
#include "z_zone.h"
#include "w_wad.h"

#include "doomdef.h"
#include "doomstat.h"

#include "r_local.h"
#include "r_sky.h"



planefunction_t         floorfunc;
planefunction_t         ceilingfunc;

//
// opening
//

// Here comes the obnoxious "visplane".
#define MAXVISPLANES    256
visplane_t              visplanes[MAXVISPLANES];
visplane_t*             lastvisplane;
visplane_t*             floorplane;
visplane_t*             ceilingplane;

// ?
#define MAXOPENINGS     MAXSCREENWIDTH*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[MAXSCREENWIDTH];
short                   ceilingclip[MAXSCREENWIDTH];

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

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

fixed_t                 yslope[MAXSCREENHEIGHT];
fixed_t                 distscale[MAXSCREENWIDTH];
fixed_t                 basexscale;
fixed_t                 baseyscale;

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



//
// 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
        || (unsigned)y>viewheight)
    {
        I_Error ("R_MapPlane: %i, %i at %i, viewheight = %i",x1,x2,y, viewheight);
    }
#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;

#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
        ds_source = W_CacheLumpNum(firstflat +
                                   flattranslation[pl->picnum],
                                   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] = 0xffff;
        pl->top[pl->minx-1] = 0xffff;

        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]);
        }

        Z_ChangeTag (ds_source, PU_CACHE);
    }
}
