/*
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"

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 ();
}


