//
// Copyright(C) 1993-1996 Id Software, Inc.
// Copyright(C) 1993-2008 Raven Software
// 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.
//
// R_bsp.c

#include "doomdef.h"
#include "i_system.h"
#include "m_bbox.h"
#include "i_system.h"
#include "r_local.h"

seg_t *curline;
side_t *sidedef;
line_t *linedef;
sector_t *frontsector, *backsector;

drawseg_t drawsegs[MAXDRAWSEGS], *ds_p;

void R_StoreWallRange(int start, int stop);

/*
====================
=
= R_ClearDrawSegs
=
====================
*/

void R_ClearDrawSegs(void)
{
    ds_p = drawsegs;
}

//=============================================================================


/*
===============================================================================
=
= ClipWallSegment
=
= Clips the given range of columns and includes it in the new clip list
===============================================================================
*/

typedef struct
{
    int first, last;
} cliprange_t;

// We must expand MAXSEGS to the theoretical limit of the number of solidsegs
// that can be generated in a scene by the DOOM engine. This was determined by
// Lee Killough during BOOM development to be a function of the screensize.
// The simplest thing we can do, other than fix this bug, is to let the game
// render overage and then bomb out by detecting the overflow after the 
// fact. -haleyjd
//#define MAXSEGS 32
#define MAXSEGS (SCREENWIDTH / 2 + 1)

cliprange_t solidsegs[MAXSEGS], *newend;        // newend is one past the last valid seg


void R_ClipSolidWallSegment(int first, int last)
{
    cliprange_t *next, *start;

// find the first range that touches the range (adjacent pixels are touching)
    start = solidsegs;
    while (start->last < first - 1)
        start++;

    if (first < start->first)
    {
        if (last < start->first - 1)
        {                       // post is entirely visible (above start), so insert a new clippost
            R_StoreWallRange(first, last);
            next = newend;
            newend++;
            while (next != start)
            {
                *next = *(next - 1);
                next--;
            }
            next->first = first;
            next->last = last;
            return;
        }

        // there is a fragment above *start
        R_StoreWallRange(first, start->first - 1);
        start->first = first;   // adjust the clip size
    }

    if (last <= start->last)
        return;                 // bottom contained in start

    next = start;
    while (last >= (next + 1)->first - 1)
    {
        // there is a fragment between two posts
        R_StoreWallRange(next->last + 1, (next + 1)->first - 1);
        next++;
        if (last <= next->last)
        {                       // bottom is contained in next
            start->last = next->last;   // adjust the clip size
            goto crunch;
        }
    }

    // there is a fragment after *next
    R_StoreWallRange(next->last + 1, last);
    start->last = last;         // adjust the clip size


// remove start+1 to next from the clip list,
// because start now covers their area
  crunch:
    if (next == start)
        return;                 // post just extended past the bottom of one post

    while (next++ != newend)    // remove a post
        *++start = *next;
    newend = start + 1;
}

/*
===============================================================================
=
= R_ClipPassWallSegment
=
= Clips the given range of columns, but does not includes it in the clip list
===============================================================================
*/

void R_ClipPassWallSegment(int first, int last)
{
    cliprange_t *start;

// find the first range that touches the range (adjacent pixels are touching)
    start = solidsegs;
    while (start->last < first - 1)
        start++;

    if (first < start->first)
    {
        if (last < start->first - 1)
        {                       // post is entirely visible (above start)
            R_StoreWallRange(first, last);
            return;
        }

        // there is a fragment above *start
        R_StoreWallRange(first, start->first - 1);
    }

    if (last <= start->last)
        return;                 // bottom contained in start

    while (last >= (start + 1)->first - 1)
    {
        // there is a fragment between two posts
        R_StoreWallRange(start->last + 1, (start + 1)->first - 1);
        start++;
        if (last <= start->last)
            return;
    }

    // there is a fragment after *next
    R_StoreWallRange(start->last + 1, last);
}



/*
====================
=
= R_ClearClipSegs
=
====================
*/

void R_ClearClipSegs(void)
{
    solidsegs[0].first = -0x7fffffff;
    solidsegs[0].last = -1;
    solidsegs[1].first = viewwidth;
    solidsegs[1].last = 0x7fffffff;
    newend = solidsegs + 2;
}


//=============================================================================

/*
======================
=
= R_AddLine
=
= Clips the given segment and adds any visible pieces to the line list
=
======================
*/

void R_AddLine(seg_t * line)
{
    int x1, x2;
    angle_t angle1, angle2, span, tspan;

    curline = line;

// OPTIMIZE: quickly reject orthogonal back sides

    angle1 = R_PointToAngle(line->v1->x, line->v1->y);
    angle2 = R_PointToAngle(line->v2->x, line->v2->y);

//
// clip to view edges
// OPTIMIZE: make constant out of 2*clipangle (FIELDOFVIEW)
    span = angle1 - angle2;
    if (span >= ANG180)
        return;                 // back side

    rw_angle1 = angle1;         // global angle needed by segcalc
    angle1 -= viewangle;
    angle2 -= viewangle;

    tspan = angle1 + clipangle;
    if (tspan > 2 * clipangle)
    {
        tspan -= 2 * clipangle;
        if (tspan >= span)
            return;             // totally off the left edge
        angle1 = clipangle;
    }
    tspan = clipangle - angle2;
    if (tspan > 2 * clipangle)
    {
        tspan -= 2 * clipangle;
        if (tspan >= span)
            return;             // totally off the left edge
        angle2 = -clipangle;
    }

//
// the seg is in the view range, but not necessarily visible
//
    angle1 = (angle1 + ANG90) >> ANGLETOFINESHIFT;
    angle2 = (angle2 + ANG90) >> ANGLETOFINESHIFT;
    x1 = viewangletox[angle1];
    x2 = viewangletox[angle2];
    if (x1 == x2)
        return;                 // does not cross a pixel

    backsector = line->backsector;

    if (!backsector)
        goto clipsolid;         // single sided line

    if (backsector->ceilingheight <= frontsector->floorheight
        || backsector->floorheight >= frontsector->ceilingheight)
        goto clipsolid;         // closed door

    if (backsector->ceilingheight != frontsector->ceilingheight
        || backsector->floorheight != frontsector->floorheight)
        goto clippass;          // window

// reject empty lines used for triggers and special events
    if (backsector->ceilingpic == frontsector->ceilingpic
        && backsector->floorpic == frontsector->floorpic
        && backsector->lightlevel == frontsector->lightlevel
        && curline->sidedef->midtexture == 0)
        return;

  clippass:
    R_ClipPassWallSegment(x1, x2 - 1);
    return;

  clipsolid:
    R_ClipSolidWallSegment(x1, x2 - 1);
}

//============================================================================


/*
===============================================================================
=
= R_CheckBBox
=
= Returns true if some part of the bbox might be visible
=
===============================================================================
*/

int checkcoord[12][4] = {
    {3, 0, 2, 1},
    {3, 0, 2, 0},
    {3, 1, 2, 0},
    {0},
    {2, 0, 2, 1},
    {0, 0, 0, 0},
    {3, 1, 3, 0},
    {0},
    {2, 0, 3, 1},
    {2, 1, 3, 1},
    {2, 1, 3, 0}
};


boolean R_CheckBBox(fixed_t * bspcoord)
{
    int boxx, boxy, boxpos;
    fixed_t x1, y1, x2, y2;
    angle_t angle1, angle2, span, tspan;
    cliprange_t *start;
    int sx1, sx2;

// find the corners of the box that define the edges from current viewpoint
    if (viewx <= bspcoord[BOXLEFT])
        boxx = 0;
    else if (viewx < bspcoord[BOXRIGHT])
        boxx = 1;
    else
        boxx = 2;

    if (viewy >= bspcoord[BOXTOP])
        boxy = 0;
    else if (viewy > bspcoord[BOXBOTTOM])
        boxy = 1;
    else
        boxy = 2;

    boxpos = (boxy << 2) + boxx;
    if (boxpos == 5)
        return true;

    x1 = bspcoord[checkcoord[boxpos][0]];
    y1 = bspcoord[checkcoord[boxpos][1]];
    x2 = bspcoord[checkcoord[boxpos][2]];
    y2 = bspcoord[checkcoord[boxpos][3]];


//
// check clip list for an open space
//      
    angle1 = R_PointToAngle(x1, y1) - viewangle;
    angle2 = R_PointToAngle(x2, y2) - viewangle;

    span = angle1 - angle2;
    if (span >= ANG180)
        return true;            // sitting on a line
    tspan = angle1 + clipangle;
    if (tspan > 2 * clipangle)
    {
        tspan -= 2 * clipangle;
        if (tspan >= span)
            return false;       // totally off the left edge
        angle1 = clipangle;
    }
    tspan = clipangle - angle2;
    if (tspan > 2 * clipangle)
    {
        tspan -= 2 * clipangle;
        if (tspan >= span)
            return false;       // totally off the left edge
        angle2 = -clipangle;
    }


// find the first clippost that touches the source post (adjacent pixels are touching)
    angle1 = (angle1 + ANG90) >> ANGLETOFINESHIFT;
    angle2 = (angle2 + ANG90) >> ANGLETOFINESHIFT;
    sx1 = viewangletox[angle1];
    sx2 = viewangletox[angle2];
    if (sx1 == sx2)
        return false;           // does not cross a pixel
    sx2--;

    start = solidsegs;
    while (start->last < sx2)
        start++;
    if (sx1 >= start->first && sx2 <= start->last)
        return false;           // the clippost contains the new span

    return true;
}


/*
================
=
= R_Subsector
=
= Draw one or more segments
================
*/

void R_Subsector(int num)
{
    int count;
    seg_t *line;
    subsector_t *sub;

#ifdef RANGECHECK
    if (num >= numsubsectors)
        I_Error("R_Subsector: ss %i with numss = %i", num, numsubsectors);
#endif

    sscount++;
    sub = &subsectors[num];
    frontsector = sub->sector;
    count = sub->numlines;
    line = &segs[sub->firstline];

    if (frontsector->floorheight < viewz)
        floorplane = R_FindPlane(frontsector->floorheight,
                                 frontsector->floorpic,
                                 frontsector->lightlevel,
                                 frontsector->special);
    else
        floorplane = NULL;
    if (frontsector->ceilingheight > viewz
        || frontsector->ceilingpic == skyflatnum)
        ceilingplane = R_FindPlane(frontsector->ceilingheight,
                                   frontsector->ceilingpic,
                                   frontsector->lightlevel, 0);
    else
        ceilingplane = NULL;

    R_AddSprites(frontsector);

    while (count--)
    {
        R_AddLine(line);
        line++;
    }

    // check for solidsegs overflow - extremely unsatisfactory!
    if(newend > &solidsegs[32])
        I_Error("R_Subsector: solidsegs overflow (vanilla may crash here)\n");
}


/*
===============================================================================
=
= RenderBSPNode
=
===============================================================================
*/

void R_RenderBSPNode(int bspnum)
{
    node_t *bsp;
    int side;

    if (bspnum & NF_SUBSECTOR)
    {
        if (bspnum == -1)
            R_Subsector(0);
        else
            R_Subsector(bspnum & (~NF_SUBSECTOR));
        return;
    }

    bsp = &nodes[bspnum];

//
// decide which side the view point is on
//
    side = R_PointOnSide(viewx, viewy, bsp);

    R_RenderBSPNode(bsp->children[side]);       // recursively divide front space

    if (R_CheckBBox(bsp->bbox[side ^ 1]))       // possibly divide back space
        R_RenderBSPNode(bsp->children[side ^ 1]);
}
