// Emacs style mode select   -*- C++ -*- 
//-----------------------------------------------------------------------------
//
// Copyright(C) 1993-1996 Id Software, Inc.
// Copyright(C) 2005 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.
//
// 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.
//
// DESCRIPTION:
//	Rendering main loop and setup functions,
//	 utility functions (BSP, geometry, trigonometry).
//	See tables.c, too.
//
//-----------------------------------------------------------------------------

#include "vpo_local.h"

// #include "r_sky.h"

namespace vpo
{


// Fineangles in the SCREENWIDTH wide window.
#define FIELDOFVIEW		2048	

int			viewangleoffset;

// increment every time a check is made
int			validcount = 1;		


int			centerx;
int			centery;

fixed_t			centerxfrac;
fixed_t			centeryfrac;
fixed_t			projection;

// just for profiling purposes
int			framecount;	

int			sscount;
int			linecount;
int			loopcount;

fixed_t			viewx;
fixed_t			viewy;
fixed_t			viewz;

angle_t			viewangle;

fixed_t			viewcos;
fixed_t			viewsin;


//
// precalculated math tables
//
angle_t			clipangle;

// The viewangletox[viewangle + FINEANGLES/4] lookup
// maps the visible view angles to screen X coordinates,
// flattening the arc to a flat projection plane.
// There will be many angles mapped to the same X. 
int			viewangletox[FINEANGLES/2];

// The xtoviewangleangle[] table maps a screen pixel
// to the lowest viewangle that maps back to x ranges
// from clipangle to -clipangle.
angle_t			xtoviewangle[SCREENWIDTH+1];


// UNUSED.
// The finetangentgent[angle+FINEANGLES/4] table
// holds the fixed_t tangent values for view angles,
// ranging from INT_MIN to 0 to INT_MAX.
// fixed_t		finetangent[FINEANGLES/2];

// fixed_t		finesine[5*FINEANGLES/4];
const fixed_t*		finecosine = &finesine[FINEANGLES/4];


// bumped light from gun blasts
int			extralight;			


// from R_DRAW
int		viewwidth;
int		scaledviewwidth;
int		viewheight;
int		viewwindowx;
int		viewwindowy; 


// from R_THINGS
fixed_t  pspritescale;
fixed_t  pspriteiscale;

short  screenheightarray[SCREENWIDTH];
short  negonearray[SCREENWIDTH];


//
// R_AddPointToBox
// Expand a given bbox
// so that it encloses a given point.
//
void R_AddPointToBox ( int  x, int  y, fixed_t* box )
{
    if (x< box[BOXLEFT])
	box[BOXLEFT] = x;
    if (x> box[BOXRIGHT])
	box[BOXRIGHT] = x;
    if (y< box[BOXBOTTOM])
	box[BOXBOTTOM] = y;
    if (y> box[BOXTOP])
	box[BOXTOP] = y;
}


//
// R_PointOnSide
// Traverse BSP (sub) tree,
//  check point against partition plane.
// Returns side 0 (front) or 1 (back).
//
int R_PointOnSide ( fixed_t	x, fixed_t	y, node_t*	node )
{
    fixed_t	dx;
    fixed_t	dy;
    fixed_t	left;
    fixed_t	right;
	
    if (!node->dx)
    {
	if (x <= node->x)
	    return node->dy > 0;
	
	return node->dy < 0;
    }
    if (!node->dy)
    {
	if (y <= node->y)
	    return node->dx < 0;
	
	return node->dx > 0;
    }
	
    dx = (x - node->x);
    dy = (y - node->y);
	
    // Try to quickly decide by looking at sign bits.
    if ( (node->dy ^ node->dx ^ dx ^ dy)&0x80000000 )
    {
	if  ( (node->dy ^ dx) & 0x80000000 )
	{
	    // (left is negative)
	    return 1;
	}
	return 0;
    }

    left = FixedMul ( node->dy>>FRACBITS , dx );
    right = FixedMul ( dy , node->dx>>FRACBITS );
	
    if (right < left)
    {
	// front side
	return 0;
    }
    // back side
    return 1;			
}


int R_PointOnSegSide ( fixed_t	x, fixed_t	y, seg_t*	line )
{
    fixed_t	lx;
    fixed_t	ly;
    fixed_t	ldx;
    fixed_t	ldy;
    fixed_t	dx;
    fixed_t	dy;
    fixed_t	left;
    fixed_t	right;
	
    lx = line->v1->x;
    ly = line->v1->y;
	
    ldx = line->v2->x - lx;
    ldy = line->v2->y - ly;
	
    if (!ldx)
    {
	if (x <= lx)
	    return ldy > 0;
	
	return ldy < 0;
    }
    if (!ldy)
    {
	if (y <= ly)
	    return ldx < 0;
	
	return ldx > 0;
    }
	
    dx = (x - lx);
    dy = (y - ly);
	
    // Try to quickly decide by looking at sign bits.
    if ( (ldy ^ ldx ^ dx ^ dy)&0x80000000 )
    {
	if  ( (ldy ^ dx) & 0x80000000 )
	{
	    // (left is negative)
	    return 1;
	}
	return 0;
    }

    left = FixedMul ( ldy>>FRACBITS , dx );
    right = FixedMul ( dy , ldx>>FRACBITS );
	
    if (right < left)
    {
	// front side
	return 0;
    }
    // back side
    return 1;			
}


//
// R_PointToAngle
// To get a global angle from cartesian coordinates,
//  the coordinates are flipped until they are in
//  the first octant of the coordinate system, then
//  the y (<=x) is scaled and divided by x to get a
//  tangent (slope) value which is looked up in the
//  tantoangle[] table.

angle_t R_PointToAngle ( fixed_t	x, fixed_t	y )
{	
    x -= viewx;
    y -= viewy;
    
    if ( (!x) && (!y) )
	return 0;

    if (x>= 0)
    {
	// x >=0
	if (y>= 0)
	{
	    // y>= 0

	    if (x>y)
	    {
		// octant 0
		return tantoangle[ SlopeDiv(y,x)];
	    }
	    else
	    {
		// octant 1
		return ANG90-1-tantoangle[ SlopeDiv(x,y)];
	    }
	}
	else
	{
	    // y<0
	    y = -y;

	    if (x>y)
	    {
		// octant 8
		return -tantoangle[SlopeDiv(y,x)];
	    }
	    else
	    {
		// octant 7
		return ANG270+tantoangle[ SlopeDiv(x,y)];
	    }
	}
    }
    else
    {
	// x<0
	x = -x;

	if (y>= 0)
	{
	    // y>= 0
	    if (x>y)
	    {
		// octant 3
		return ANG180-1-tantoangle[ SlopeDiv(y,x)];
	    }
	    else
	    {
		// octant 2
		return ANG90+ tantoangle[ SlopeDiv(x,y)];
	    }
	}
	else
	{
	    // y<0
	    y = -y;

	    if (x>y)
	    {
		// octant 4
		return ANG180+tantoangle[ SlopeDiv(y,x)];
	    }
	    else
	    {
		 // octant 5
		return ANG270-1-tantoangle[ SlopeDiv(x,y)];
	    }
	}
    }
    return 0;
}


angle_t R_PointToAngle2 ( fixed_t	x1, fixed_t	y1, fixed_t	x2, fixed_t	y2 )
{	
    viewx = x1;
    viewy = y1;
    
    return R_PointToAngle (x2, y2);
}


fixed_t R_PointToDist ( fixed_t	x, fixed_t	y )
{
    int		angle;
    fixed_t	dx;
    fixed_t	dy;
    fixed_t	temp;
    fixed_t	dist;
    fixed_t     frac;
	
    dx = abs(x - viewx);
    dy = abs(y - viewy);
	
    if (dy>dx)
    {
	temp = dx;
	dx = dy;
	dy = temp;
    }

    // Fix crashes in udm1.wad

    if (dx != 0)
    {
        frac = FixedDiv(dy, dx);
    }
    else
    {
	frac = 0;
    }
	
    angle = (tantoangle[frac>>DBITS]+ANG90) >> ANGLETOFINESHIFT;

    // use as cosine
    dist = FixedDiv (dx, finesine[angle] );	
	
    return dist;
}


//
// R_ScaleFromGlobalAngle
// Returns the texture mapping scale
//  for the current line (horizontal span)
//  at the given angle.
// rw_distance must be calculated first.
//
fixed_t R_ScaleFromGlobalAngle (angle_t visangle)
{
    fixed_t		scale;
    angle_t		anglea;
    angle_t		angleb;
    int			sinea;
    int			sineb;
    fixed_t		num;
    int			den;

    // UNUSED
#if 0
{
    fixed_t		dist;
    fixed_t		z;
    fixed_t		sinv;
    fixed_t		cosv;
	
    sinv = finesine[(visangle-rw_normalangle)>>ANGLETOFINESHIFT];	
    dist = FixedDiv (rw_distance, sinv);
    cosv = finecosine[(viewangle-visangle)>>ANGLETOFINESHIFT];
    z = abs(FixedMul (dist, cosv));
    scale = FixedDiv(projection, z);
    return scale;
}
#endif

    anglea = ANG90 + (visangle-viewangle);
    angleb = ANG90 + (visangle-rw_normalangle);

    // both sines are allways positive
    sinea = finesine[anglea>>ANGLETOFINESHIFT];	
    sineb = finesine[angleb>>ANGLETOFINESHIFT];
    num = FixedMul(projection,sineb)<<0;
    den = FixedMul(rw_distance,sinea);

    if (den > num>>16)
    {
	scale = FixedDiv (num, den);

	if (scale > 64*FRACUNIT)
	    scale = 64*FRACUNIT;
	else if (scale < 256)
	    scale = 256;
    }
    else
	scale = 64*FRACUNIT;
	
    return scale;
}


void R_InitBuffer ( int		width, int		height ) 
{ 
    int		i;
	
    // Handle resize,
    //  e.g. smaller view windows
    //  with border and/or status bar.
    viewwindowx = (SCREENWIDTH-width) >> 1; 
    viewwindowy = 0; 

    // this was from R_InitSprites
    for (i=0 ; i<SCREENWIDTH ; i++)
    {
      negonearray[i] = -1;
    }

#if 0
    // Column offset. For windows.
    for (i=0 ; i<width ; i++) 
	columnofs[i] = viewwindowx + i;

    // Samw with base row offset.
    if (width == SCREENWIDTH) 
	viewwindowy = 0; 
    else 
	viewwindowy = (SCREENHEIGHT-SBARHEIGHT-height) >> 1; 

    // Preclaculate all row offsets.
    for (i=0 ; i<height ; i++) 
	ylookup[i] = screens[0] + (i+viewwindowy)*SCREENWIDTH; 
#endif
} 


//
// R_InitTextureMapping
//
void R_InitTextureMapping (void)
{
    int			i;
    int			x;
    int			t;
    fixed_t		focallength;
    
    // Use tangent table to generate viewangletox:
    //  viewangletox will give the next greatest x
    //  after the view angle.
    //
    // Calc focallength
    //  so FIELDOFVIEW angles covers SCREENWIDTH.
    focallength = FixedDiv (centerxfrac,
			    finetangent[FINEANGLES/4+FIELDOFVIEW/2] );
	
    for (i=0 ; i<FINEANGLES/2 ; i++)
    {
	if (finetangent[i] > FRACUNIT*2)
	    t = -1;
	else if (finetangent[i] < -FRACUNIT*2)
	    t = viewwidth+1;
	else
	{
	    t = FixedMul (finetangent[i], focallength);
	    t = (centerxfrac - t+FRACUNIT-1)>>FRACBITS;

	    if (t < -1)
		t = -1;
	    else if (t>viewwidth+1)
		t = viewwidth+1;
	}
	viewangletox[i] = t;
    }
    
    // Scan viewangletox[] to generate xtoviewangle[]:
    //  xtoviewangle will give the smallest view angle
    //  that maps to x.	
    for (x=0;x<=viewwidth;x++)
    {
	i = 0;
	while (viewangletox[i]>x)
	    i++;
	xtoviewangle[x] = (i<<ANGLETOFINESHIFT)-ANG90;
    }
    
    // Take out the fencepost cases from viewangletox.
    for (i=0 ; i<FINEANGLES/2 ; i++)
    {
	t = FixedMul (finetangent[i], focallength);
	t = centerx - t;
	
	if (viewangletox[i] == -1)
	    viewangletox[i] = 0;
	else if (viewangletox[i] == viewwidth+1)
	    viewangletox[i]  = viewwidth;
    }
	
    clipangle = xtoviewangle[0];
}



//
// R_SetViewSize
//
void R_SetViewSize ( int  blocks, int  detail )
{
    fixed_t	cosadj;
    fixed_t	dy;
    int		i;

    if (blocks == 11)
    {
	scaledviewwidth = SCREENWIDTH;
	viewheight = SCREENHEIGHT;
    }
    else
    {
	scaledviewwidth = blocks*32;
	viewheight = (blocks*168/10)&~7;
    }
    
    viewwidth = scaledviewwidth >> 0;
	
    centery = viewheight/2;
    centerx = viewwidth/2;
    centerxfrac = centerx<<FRACBITS;
    centeryfrac = centery<<FRACBITS;
    projection = centerxfrac;

    R_InitBuffer (scaledviewwidth, viewheight);
	
    R_InitTextureMapping ();

    // psprite scales
    pspritescale = FRACUNIT*viewwidth/SCREENWIDTH;
    pspriteiscale = FRACUNIT*SCREENWIDTH/viewwidth;
    
    // thing clipping
    for (i=0 ; i<viewwidth ; i++)
	screenheightarray[i] = viewheight;
    
    // planes
    for (i=0 ; i<viewheight ; i++)
    {
	dy = ((i-viewheight/2)<<FRACBITS)+FRACUNIT/2;
	dy = abs(dy);
	yslope[i] = FixedDiv ( (viewwidth<<0)/2*FRACUNIT, dy);
    }
	
    for (i=0 ; i<viewwidth ; i++)
    {
	cosadj = abs(finecosine[xtoviewangle[i]>>ANGLETOFINESHIFT]);
	distscale[i] = FixedDiv (FRACUNIT,cosadj);
    }
    
}



//
// R_Init
//
void R_Init (void)
{
    R_SetViewSize (11, 0);
	
    framecount = 0;
}


//
// R_PointInSubsector
//
subsector_t* R_PointInSubsector ( fixed_t	x, fixed_t	y )
{
    node_t*	node;
    int		side;
    int		nodenum;

    // single subsector is a special case
    if (!numnodes)				
	return subsectors;
		
    nodenum = numnodes-1;

    while (! (nodenum & NF_SUBSECTOR) )
    {
	node = &nodes[nodenum];
	side = R_PointOnSide (x, y, node);
	nodenum = node->children[side];
    }
	
    return &subsectors[nodenum & ~NF_SUBSECTOR];
}


//
// R_SetupFrame
//
void R_SetupFrame (fixed_t x, fixed_t y, fixed_t z, angle_t angle)
{		
    viewx = x;
    viewy = y;
    viewz = z;

    viewangle = angle;

    viewsin = finesine[viewangle>>ANGLETOFINESHIFT];
    viewcos = finecosine[viewangle>>ANGLETOFINESHIFT];
	
    sscount = 0;
	
    framecount++;
    validcount++;
}


//
// R_RenderView
//
void R_RenderView (fixed_t x, fixed_t y, fixed_t z, angle_t angle)
{	
    R_SetupFrame (x, y, z, angle);

    // Clear buffers.
    R_ClearClipSegs ();
    R_ClearDrawSegs ();
    R_ClearPlanes ();
///  R_ClearSprites ();
    
    // The head node is the last node output.
    R_RenderBSPNode (numnodes - 1);
}


} // namespace vpo