/*
	sw_redge.c

	(description)

	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:

		Free Software Foundation, Inc.
		59 Temple Place - Suite 330
		Boston, MA  02111-1307, USA

*/
#ifdef HAVE_CONFIG_H
# include "config.h"
#endif

#include "d_ifacea.h"
#include "r_internal.h"
#include "vid_internal.h"

/*
  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?
*/

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;
static espan_t *max_span_p;

int         r_currentkey;


int         current_iv;

int         edge_head_u_shift20, edge_tail_u_shift20;

static void (*pdrawfunc) (void);

// FIXME: make stack vars when debugging done
edge_t      edge_head;
edge_t      edge_tail;
edge_t      edge_aftertail;
static edge_t      edge_sentinel;

float       fv;

static void
R_DrawCulledPolys (void)
{
	surf_t     *s;
	msurface_t *pface;

	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 (s->entity, 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 (s->entity, pface, 15);
			}
		}
	}
}

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
	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;
	}
}

#ifdef PIC
# undef USE_INTEL_ASM //XXX asm pic hack
#endif

#ifndef USE_INTEL_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);
}

void
R_RemoveEdges (edge_t *pedge)
{

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

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_INTEL_ASM

#ifndef USE_INTEL_ASM

static 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 already active
				// one 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;
		}
	}
}

static 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;
	}
}

static void
R_CleanupSpan (void)
{
	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]);
}

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_INTEL_ASM

/*
	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 *)
		((intptr_t) (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 needs to be set up only 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 = 32767 << 16;		// 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) {
			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 ();
}