/*
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_edge.c

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

#if 0
// FIXME
the complex cases add new polys on most lines, so dont optimize for keeping them the same
have multiple free span lists to try to get better coherence?
low depth complexity -- 1 to 3 or so

this breaks spans at every edge, even hidden ones (bad)

have a sentinal at both ends?
#endif


edge_t  *auxedges;
edge_t  *r_edges, *edge_p, *edge_max;

surf_t  *surfaces, *surface_p, *surf_max;

// surfaces are generated in back to front order by the bsp, so if a surf
// pointer is greater than another one, it should be drawn in front
// surfaces[1] is the background, and is used as the active surface stack

edge_t  *newedges[MAXHEIGHT];
edge_t  *removeedges[MAXHEIGHT];

espan_t *span_p, *max_span_p;

int   r_currentkey;

extern  int screenwidth;

int current_iv;

int edge_head_u_shift20, edge_tail_u_shift20;

static void (*pdrawfunc)(void);

edge_t  edge_head;
edge_t  edge_tail;
edge_t  edge_aftertail;
edge_t  edge_sentinel;

float fv;

void R_GenerateSpans (void);
void R_GenerateSpansBackward (void);

void R_LeadingEdge (edge_t *edge);
void R_LeadingEdgeBackwards (edge_t *edge);
void R_TrailingEdge (surf_t *surf, edge_t *edge);


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


/*
==============
R_DrawCulledPolys
==============
*/
void R_DrawCulledPolys (void)
{
  surf_t      *s;
  msurface_t    *pface;

  currententity = &cl_entities[0];

  if (r_worldpolysbacktofront)
  {
    for (s=surface_p-1 ; s>&surfaces[1] ; s--)
    {
      if (!s->spans)
        continue;

      if (!(s->flags & SURF_DRAWBACKGROUND))
      {
        pface = (msurface_t *)s->data;
        R_RenderPoly (pface, 15);
      }
    }
  }
  else
  {
    for (s = &surfaces[1] ; s<surface_p ; s++)
    {
      if (!s->spans)
        continue;

      if (!(s->flags & SURF_DRAWBACKGROUND))
      {
        pface = (msurface_t *)s->data;
        R_RenderPoly (pface, 15);
      }
    }
  }
}


/*
==============
R_BeginEdgeFrame
==============
*/
void R_BeginEdgeFrame (void)
{
  int   v;

  edge_p = r_edges;
  edge_max = &r_edges[r_numallocatededges];

  surface_p = &surfaces[2]; // background is surface 1,
                //  surface 0 is a dummy
  surfaces[1].spans = NULL; // no background spans yet
  surfaces[1].flags = SURF_DRAWBACKGROUND;

// put the background behind everything in the world
  if (r_draworder.value)
  {
    pdrawfunc = R_GenerateSpansBackward;
    surfaces[1].key = 0;
    r_currentkey = 1;
  }
  else
  {
    pdrawfunc = R_GenerateSpans;
    surfaces[1].key = 0x7FFFFFFF;
    r_currentkey = 0;
  }

// FIXME: set with memset
  for (v=r_refdef.vrect.y ; v<r_refdef.vrectbottom ; v++)
  {
    newedges[v] = removeedges[v] = NULL;
  }
}


#if !id386

/*
==============
R_InsertNewEdges

Adds the edges in the linked list edgestoadd, adding them to the edges in the
linked list edgelist.  edgestoadd is assumed to be sorted on u, and non-empty (this is actually newedges[v]).  edgelist is assumed to be sorted on u, with a
sentinel at the end (actually, this is the active edge table starting at
edge_head.next).
==============
*/
void R_InsertNewEdges (edge_t *edgestoadd, edge_t *edgelist)
{
  edge_t  *next_edge;

  do
  {
    next_edge = edgestoadd->next;
edgesearch:
    if (edgelist->u >= edgestoadd->u)
      goto addedge;
    edgelist=edgelist->next;
    if (edgelist->u >= edgestoadd->u)
      goto addedge;
    edgelist=edgelist->next;
    if (edgelist->u >= edgestoadd->u)
      goto addedge;
    edgelist=edgelist->next;
    if (edgelist->u >= edgestoadd->u)
      goto addedge;
    edgelist=edgelist->next;
    goto edgesearch;

  // insert edgestoadd before edgelist
addedge:
    edgestoadd->next = edgelist;
    edgestoadd->prev = edgelist->prev;
    edgelist->prev->next = edgestoadd;
    edgelist->prev = edgestoadd;
  } while ((edgestoadd = next_edge) != NULL);
}

#endif  // !id386
  

#if !id386

/*
==============
R_RemoveEdges
==============
*/
void R_RemoveEdges (edge_t *pedge)
{

  do
  {
    pedge->next->prev = pedge->prev;
    pedge->prev->next = pedge->next;
  } while ((pedge = pedge->nextremove) != NULL);
}

#endif  // !id386


#if !id386

/*
==============
R_StepActiveU
==============
*/
void R_StepActiveU (edge_t *pedge)
{
  edge_t    *pnext_edge, *pwedge;

  while (1)
  {
nextedge:
    pedge->u += pedge->u_step;
    if (pedge->u < pedge->prev->u)
      goto pushback;
    pedge = pedge->next;
      
    pedge->u += pedge->u_step;
    if (pedge->u < pedge->prev->u)
      goto pushback;
    pedge = pedge->next;
      
    pedge->u += pedge->u_step;
    if (pedge->u < pedge->prev->u)
      goto pushback;
    pedge = pedge->next;
      
    pedge->u += pedge->u_step;
    if (pedge->u < pedge->prev->u)
      goto pushback;
    pedge = pedge->next;
      
    goto nextedge;    
    
pushback:
    if (pedge == &edge_aftertail)
      return;
      
  // push it back to keep it sorted   
    pnext_edge = pedge->next;

  // pull the edge out of the edge list
    pedge->next->prev = pedge->prev;
    pedge->prev->next = pedge->next;

  // find out where the edge goes in the edge list
    pwedge = pedge->prev->prev;

    while (pwedge->u > pedge->u)
    {
      pwedge = pwedge->prev;
    }

  // put the edge back into the edge list
    pedge->next = pwedge->next;
    pedge->prev = pwedge;
    pedge->next->prev = pedge;
    pwedge->next = pedge;

    pedge = pnext_edge;
    if (pedge == &edge_tail)
      return;
  }
}

#endif  // !id386


/*
==============
R_CleanupSpan
==============
*/
void R_CleanupSpan ()
{
  surf_t  *surf;
  int   iu;
  espan_t *span;

// now that we've reached the right edge of the screen, we're done with any
// unfinished surfaces, so emit a span for whatever's on top
  surf = surfaces[1].next;
  iu = edge_tail_u_shift20;
  if (iu > surf->last_u)
  {
    span = span_p++;
    span->u = surf->last_u;
    span->count = iu - span->u;
    span->v = current_iv;
    span->pnext = surf->spans;
    surf->spans = span;
  }

// reset spanstate for all surfaces in the surface stack
  do
  {
    surf->spanstate = 0;
    surf = surf->next;
  } while (surf != &surfaces[1]);
}


/*
==============
R_LeadingEdgeBackwards
==============
*/
void R_LeadingEdgeBackwards (edge_t *edge)
{
  espan_t     *span;
  surf_t      *surf, *surf2;
  int       iu;

// it's adding a new surface in, so find the correct place
  surf = &surfaces[edge->surfs[1]];

// don't start a span if this is an inverted span, with the end
// edge preceding the start edge (that is, we've already seen the
// end edge)
  if (++surf->spanstate == 1)
  {
    surf2 = surfaces[1].next;

    if (surf->key > surf2->key)
      goto newtop;

  // if it's two surfaces on the same plane, the one that's already
  // active is in front, so keep going unless it's a bmodel
    if (surf->insubmodel && (surf->key == surf2->key))
    {
    // must be two bmodels in the same leaf; don't care, because they'll
    // never be farthest anyway
      goto newtop;
    }

continue_search:

    do
    {
      surf2 = surf2->next;
    } while (surf->key < surf2->key);

    if (surf->key == surf2->key)
    {
    // if it's two surfaces on the same plane, the one that's already
    // active is in front, so keep going unless it's a bmodel
      if (!surf->insubmodel)
        goto continue_search;

    // must be two bmodels in the same leaf; don't care which is really
    // in front, because they'll never be farthest anyway
    }

    goto gotposition;

newtop:
  // emit a span (obscures current top)
    iu = edge->u >> 20;

    if (iu > surf2->last_u)
    {
      span = span_p++;
      span->u = surf2->last_u;
      span->count = iu - span->u;
      span->v = current_iv;
      span->pnext = surf2->spans;
      surf2->spans = span;
    }

    // set last_u on the new span
    surf->last_u = iu;
        
gotposition:
  // insert before surf2
    surf->next = surf2;
    surf->prev = surf2->prev;
    surf2->prev->next = surf;
    surf2->prev = surf;
  }
}


/*
==============
R_TrailingEdge
==============
*/
void R_TrailingEdge (surf_t *surf, edge_t *edge)
{
  espan_t     *span;
  int       iu;

// don't generate a span if this is an inverted span, with the end
// edge preceding the start edge (that is, we haven't seen the
// start edge yet)
  if (--surf->spanstate == 0)
  {
    if (surf->insubmodel)
      r_bmodelactive--;

    if (surf == surfaces[1].next)
    {
    // emit a span (current top going away)
      iu = edge->u >> 20;
      if (iu > surf->last_u)
      {
        span = span_p++;
        span->u = surf->last_u;
        span->count = iu - span->u;
        span->v = current_iv;
        span->pnext = surf->spans;
        surf->spans = span;
      }

    // set last_u on the surface below
      surf->next->last_u = iu;
    }

    surf->prev->next = surf->next;
    surf->next->prev = surf->prev;
  }
}


#if !id386

/*
==============
R_LeadingEdge
==============
*/
void R_LeadingEdge (edge_t *edge)
{
  espan_t     *span;
  surf_t      *surf, *surf2;
  int       iu;
  double      fu, newzi, testzi, newzitop, newzibottom;

  if (edge->surfs[1])
  {
  // it's adding a new surface in, so find the correct place
    surf = &surfaces[edge->surfs[1]];

  // don't start a span if this is an inverted span, with the end
  // edge preceding the start edge (that is, we've already seen the
  // end edge)
    if (++surf->spanstate == 1)
    {
      if (surf->insubmodel)
        r_bmodelactive++;

      surf2 = surfaces[1].next;

      if (surf->key < surf2->key)
        goto newtop;

    // if it's two surfaces on the same plane, the one that's already
    // active is in front, so keep going unless it's a bmodel
      if (surf->insubmodel && (surf->key == surf2->key))
      {
      // must be two bmodels in the same leaf; sort on 1/z
        fu = (float)(edge->u - 0xFFFFF) * (1.0 / 0x100000);
        newzi = surf->d_ziorigin + fv*surf->d_zistepv +
            fu*surf->d_zistepu;
        newzibottom = newzi * 0.99;

        testzi = surf2->d_ziorigin + fv*surf2->d_zistepv +
            fu*surf2->d_zistepu;

        if (newzibottom >= testzi)
        {
          goto newtop;
        }

        newzitop = newzi * 1.01;
        if (newzitop >= testzi)
        {
          if (surf->d_zistepu >= surf2->d_zistepu)
          {
            goto newtop;
          }
        }
      }

continue_search:

      do
      {
        surf2 = surf2->next;
      } while (surf->key > surf2->key);

      if (surf->key == surf2->key)
      {
      // if it's two surfaces on the same plane, the one that's already
      // active is in front, so keep going unless it's a bmodel
        if (!surf->insubmodel)
          goto continue_search;

      // must be two bmodels in the same leaf; sort on 1/z
        fu = (float)(edge->u - 0xFFFFF) * (1.0 / 0x100000);
        newzi = surf->d_ziorigin + fv*surf->d_zistepv +
            fu*surf->d_zistepu;
        newzibottom = newzi * 0.99;

        testzi = surf2->d_ziorigin + fv*surf2->d_zistepv +
            fu*surf2->d_zistepu;

        if (newzibottom >= testzi)
        {
          goto gotposition;
        }

        newzitop = newzi * 1.01;
        if (newzitop >= testzi)
        {
          if (surf->d_zistepu >= surf2->d_zistepu)
          {
            goto gotposition;
          }
        }

        goto continue_search;
      }

      goto gotposition;

newtop:
    // emit a span (obscures current top)
      iu = edge->u >> 20;

      if (iu > surf2->last_u)
      {
        span = span_p++;
        span->u = surf2->last_u;
        span->count = iu - span->u;
        span->v = current_iv;
        span->pnext = surf2->spans;
        surf2->spans = span;
      }

      // set last_u on the new span
      surf->last_u = iu;
        
gotposition:
    // insert before surf2
      surf->next = surf2;
      surf->prev = surf2->prev;
      surf2->prev->next = surf;
      surf2->prev = surf;
    }
  }
}


/*
==============
R_GenerateSpans
==============
*/
void R_GenerateSpans (void)
{
  edge_t      *edge;
  surf_t      *surf;

  r_bmodelactive = 0;

// clear active surfaces to just the background surface
  surfaces[1].next = surfaces[1].prev = &surfaces[1];
  surfaces[1].last_u = edge_head_u_shift20;

// generate spans
  for (edge=edge_head.next ; edge != &edge_tail; edge=edge->next)
  {     
    if (edge->surfs[0])
    {
    // it has a left surface, so a surface is going away for this span
      surf = &surfaces[edge->surfs[0]];

      R_TrailingEdge (surf, edge);

      if (!edge->surfs[1])
        continue;
    }

    R_LeadingEdge (edge);
  }

  R_CleanupSpan ();
}

#endif  // !id386


/*
==============
R_GenerateSpansBackward
==============
*/
void R_GenerateSpansBackward (void)
{
  edge_t      *edge;

  r_bmodelactive = 0;

// clear active surfaces to just the background surface
  surfaces[1].next = surfaces[1].prev = &surfaces[1];
  surfaces[1].last_u = edge_head_u_shift20;

// generate spans
  for (edge=edge_head.next ; edge != &edge_tail; edge=edge->next)
  {     
    if (edge->surfs[0])
      R_TrailingEdge (&surfaces[edge->surfs[0]], edge);

    if (edge->surfs[1])
      R_LeadingEdgeBackwards (edge);
  }

  R_CleanupSpan ();
}


/*
==============
R_ScanEdges

Input: 
newedges[] array
  this has links to edges, which have links to surfaces

Output:
Each surface has a linked list of its visible spans
==============
*/
void R_ScanEdges (void)
{
  int   iv, bottom;
  byte  basespans[MAXSPANS*sizeof(espan_t)+CACHE_SIZE];
  espan_t *basespan_p;
  surf_t  *s;

  basespan_p = (espan_t *)
      ((long)(basespans + CACHE_SIZE - 1) & ~(CACHE_SIZE - 1));
  max_span_p = &basespan_p[MAXSPANS - r_refdef.vrect.width];

  span_p = basespan_p;

// clear active edges to just the background edges around the whole screen
// FIXME: most of this only needs to be set up once
  edge_head.u = r_refdef.vrect.x << 20;
  edge_head_u_shift20 = edge_head.u >> 20;
  edge_head.u_step = 0;
  edge_head.prev = NULL;
  edge_head.next = &edge_tail;
  edge_head.surfs[0] = 0;
  edge_head.surfs[1] = 1;
  
  edge_tail.u = (r_refdef.vrectright << 20) + 0xFFFFF;
  edge_tail_u_shift20 = edge_tail.u >> 20;
  edge_tail.u_step = 0;
  edge_tail.prev = &edge_head;
  edge_tail.next = &edge_aftertail;
  edge_tail.surfs[0] = 1;
  edge_tail.surfs[1] = 0;
  
  edge_aftertail.u = -1;    // force a move
  edge_aftertail.u_step = 0;
  edge_aftertail.next = &edge_sentinel;
  edge_aftertail.prev = &edge_tail;

// FIXME: do we need this now that we clamp x in r_draw.c?
  edge_sentinel.u = 2000 << 24;   // make sure nothing sorts past this
  edge_sentinel.prev = &edge_aftertail;

//  
// process all scan lines
//
  bottom = r_refdef.vrectbottom - 1;

  for (iv=r_refdef.vrect.y ; iv<bottom ; iv++)
  {
    current_iv = iv;
    fv = (float)iv;

  // mark that the head (background start) span is pre-included
    surfaces[1].spanstate = 1;

    if (newedges[iv])
    {
      R_InsertNewEdges (newedges[iv], edge_head.next);
    }

    (*pdrawfunc) ();

  // flush the span list if we can't be sure we have enough spans left for
  // the next scan
    if (span_p >= max_span_p)
    {
      VID_UnlockBuffer ();
      S_ExtraUpdate (); // don't let sound get messed up if going slow
      VID_LockBuffer ();
    
      if (r_drawculledpolys)
      {
        R_DrawCulledPolys ();
      }
      else
      {
        D_DrawSurfaces ();
      }

    // clear the surface span pointers
      for (s = &surfaces[1] ; s<surface_p ; s++)
        s->spans = NULL;

      span_p = basespan_p;
    }

    if (removeedges[iv])
      R_RemoveEdges (removeedges[iv]);

    if (edge_head.next != &edge_tail)
      R_StepActiveU (edge_head.next);
  }

// do the last scan (no need to step or sort or remove on the last scan)

  current_iv = iv;
  fv = (float)iv;

// mark that the head (background start) span is pre-included
  surfaces[1].spanstate = 1;

  if (newedges[iv])
    R_InsertNewEdges (newedges[iv], edge_head.next);

  (*pdrawfunc) ();

// draw whatever's left in the span list
  if (r_drawculledpolys)
    R_DrawCulledPolys ();
  else
    D_DrawSurfaces ();
}