/*
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"
#include "sound.h"

// FIXME - header hacks
extern int screenwidth;

#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;

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 = &r_worldentity;
    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;
    }
}


#ifndef USE_X86_ASM

/*
==============
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 /* USE_X86_ASM */


#ifndef USE_X86_ASM

/*
==============
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 /* USE_X86_ASM */


#ifndef USE_X86_ASM

/*
==============
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 /* USE_X86_ASM */


/*
==============
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;
    }
}


#ifndef USE_X86_ASM

/*
==============
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 /* USE_X86_ASM */


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

	// FIXME - which is correct QW had >, NQ had >= (and QF has >)
	//if (span_p >= max_span_p) {
	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();
}
