#import "doombsp.h"

// I assume that a grid 8 is used for the maps, so a point will be considered
// on a line if it is within 8 pixels of it.  The accounts for floating error.

int		cuts;			// number of new lines generated by BSP process

/*
==================
=
= DivlineFromWorldline
=
==================
*/

void	DivlineFromWorldline (divline_t *d, line_t *w)
{
	d->pt = w->p1;
	d->dx = w->p2.x - w->p1.x;
	d->dy = w->p2.y - w->p1.y;
}

/*
==================
=
= PointOnSide
=
= Returns side 0 (front), 1 (back), or -1 (colinear)
==================
*/

int	PointOnSide (NXPoint *p, divline_t *l)
{
	float	dx,dy;
	float	left, right;
	float	a,b,c,d;
	
	if (!l->dx)
	{
		if (p->x > l->pt.x-2 && p->x < l->pt.x+2)
			return -1;
		if (p->x < l->pt.x)
			return l->dy > 0;
		return l->dy < 0;
	}
	if (!l->dy)
	{
		if (p->y > l->pt.y-2 && p->y < l->pt.y+2)
			return -1;
		if (p->y < l->pt.y)
			return l->dx < 0;
		return l->dx > 0;
	}

	dx = l->pt.x - p->x;
	dy = l->pt.y - p->y;
	a = l->dx*l->dx + l->dy*l->dy;
	b = 2*(l->dx*dx + l->dy*dy);
	c = dx*dx+dy*dy - 2*2;		// 2 unit radius
	d = b*b - 4*a*c;
	if (d>0)
		return -1;		// within four pixels of line
	
	
	dx = p->x - l->pt.x;
	dy = p->y - l->pt.y;
	
	left = l->dy * dx;
	right = dy * l->dx;
	
	if ( fabs (left-right) < 0.5 )	// allow slop
		return -1;		// on line
	if (right < left)
		return 0;		// front side
	return 1;			// back side
}

/*
=============
=
= sign
=
= Returns -1, 0, or 1, based on the input sign
=
==============
*/

int sign (float i)
{
	if (i<0)
		return -1;
	else if (i>0)
		return 1;
	return 0;
}

/*
==================
=
= LineOnSide
=
= Returns side 0 / 1, or -2 if line must be split
= If the line is colinear, it will be placed on the front side if
= it is going the same direction as the dividing line
==================
*/

boolean	LineOnSide (line_t *wl, divline_t *bl)
{
	int		s1,s2;
	float	dx, dy;
	
	s1 = PointOnSide (&wl->p1, bl);
	s2 = PointOnSide (&wl->p2, bl);

	if (s1 == s2)
	{
		if (s1 == -1)
		{	// colinear, so see if the directions are the same
			dx = wl->p2.x - wl->p1.x;
			dy = wl->p2.y - wl->p1.y;
			if (sign(dx) == sign (bl->dx) && sign(dy) == sign(bl->dy) )
				return 0;
			return 1;
		}
		return s1;
	}
	if (s1 == -1)
		return s2;
	if (s2 == -1)
		return s1;
		
	return -2;
}

/*
===============
=
= InterceptVector
=
= Returns the fractional intercept point along first vector
===============
*/

float InterceptVector (divline_t *v2, divline_t *v1)
{
#if 0

v1.x + f1*v1.xs = v2.x + f2*v2.xs	(parametric x coordinates)
f1*v1.xs = v2.x - v1.x + f2*v2.xs
f1 = (v2.x - v1.x +f2*v2.xs) / v1.xs

v1.y + f1*v1.ys = v2.y + f2*v2.ys	(parametric y coordinates)
f1 = (v2.y - v1.y + f2*v2.ys) / v1.ys

f1 = (v2.x - v1.x +f2*v2.xs) / v1.xs = (v2.y - v1.y + f2*v2.ys) / v1.ys
v1.ys*v2.x - v1.ys*v1.x + v1.ys*v2.xs*f2 = v1.xs*v2.y - v1.xs*v1.y + v1.xs*v2.ys*f2
(v1.ys*v2.xs - v1.xs*v2.ys)*f2 = -v1.ys*v2.x + v1.ys*v1.x + v1.xs*v2.y - v1.xs*v1.y
							= v1.ys*(v1.x-v2.x) + v1.xs*(v2.y-v1.y)
							
f2 = (v1.ys*(v1.x-v2.x) + v1.xs*(v2.y-v1.y)) / (v1.ys*v2.xs - v1.xs*v2.ys)
#endif

	float	frac, num, den;
	
	den = v1->dy*v2->dx - v1->dx*v2->dy;
	if (den == 0)
		Error ("InterceptVector: parallel");
	num = (v1->pt.x - v2->pt.x)*v1->dy + (v2->pt.y - v1->pt.y)*v1->dx;
	frac = num / den;

	if (frac <= 0.0 || frac >= 1.0)
		Error ("InterceptVector: intersection outside line");
		
	return frac;
}


/*
==================
=
= CutLine
=
= Truncates the given worldline to the front side of the divline
= and returns the cut off back side in a newly allocated worldline
==================
*/

float round (float x)
{
	if (x>0)
	{
		if (x - (int)x < 0.1)
			return (int)x;
		else if (x - (int)x > 0.9)
			return (int)x+1;
		else
			return x;
	}
	
	if ((int)x - x < 0.1)
		return (int)x;
	else if ((int)x - x > 0.9)
		return  (int)x - 1;
	return x;
}

line_t	*CutLine (line_t *wl, divline_t *bl)
{
	int			side;
	line_t		*new_p;
	divline_t	wld;
	float		frac;
	NXPoint		intr;
	int			offset;
	
	cuts++;
	DivlineFromWorldline (&wld, wl);
	new_p = malloc (sizeof(line_t));
	memset (new_p,0,sizeof(*new_p));
	*new_p = *wl; 
	
	frac = InterceptVector (&wld, bl);
	intr.x = wld.pt.x + round(wld.dx*frac);
	intr.y = wld.pt.y + round(wld.dy*frac);
	offset = wl->offset + round(frac*sqrt(wld.dx*wld.dx+wld.dy*wld.dy));
	side = PointOnSide (&wl->p1, bl);
	if (side == 0)
	{	// line starts on front side
		wl->p2 = intr;
		new_p->p1 = intr;
		new_p->offset = offset;
	}
	else
	{	// line starts on back side
		wl->p1 = intr;
		wl->offset = offset;
		new_p->p2 = intr;
	}
	
	return new_p;
}


/*
================
=
= EvaluateSplit
=
= Returns a number grading the quality of a split along the givent line
= for the current list of lines.  Evaluation is halted as soon as it is
= determined that a better split already exists
= 
= A split is good if it divides the lines evenly without cutting many lines
= A horizontal or vertical split is better than a sloping split
=
= The LOWER the returned value, the better.  If the split line does not divide
= any of the lines at all, MAXINT will be returned
================
*/

int EvaluateSplit (id lines_i, line_t *spliton, int bestgrade)
{
	int				i,c,side;
	line_t			*line_p;
	divline_t		divline;
	int				frontcount, backcount, max, new;
	int				grade;
	worldline_t		*wl;
	
	wl = [linestore_i elementAt: spliton->linedef];
#if 0
	if (wl->special == BSPSLIDEENDSPECIAL)
		return MAXINT;	// NEVER split on this, because it moves
#endif
	DivlineFromWorldline (&divline, spliton);
	
	frontcount = backcount = 0;
	c = [lines_i count];
	grade = 0;
		
	for (i=0 ; i<c ; i++)
	{
		line_p = [lines_i elementAt:i];
		if (line_p == spliton)
			side = 0;
		else
			side = LineOnSide (line_p, &divline);
		switch (side)
		{
		case 0:
			frontcount++;
			break;
		case 1:
			backcount++;
			break;
		case -2:
			wl = [linestore_i elementAt: line_p->linedef];
#if 0
			if (wl->special == BSPSLIDESIDESPECIAL)
				return MAXINT;	// NEVER split this line, because it slides
#endif
			frontcount++;
			backcount++;
			break;
		}
		
		max = MAX(frontcount,backcount);
		new = (frontcount+backcount) - c;
		grade = max+new*8;
		if (grade > bestgrade)
			return grade;		// might as well stop now
	}
	
	if (frontcount == 0 || backcount == 0)
		return MAXINT;			// line does not partition at all
		
	return grade;
}


/*
================
=
= ExecuteSplit
=
= Actually splits the line list as EvaluateLines predicted
================
*/

void ExecuteSplit (id lines_i, line_t *spliton
	, id frontlist_i, id backlist_i)
{
	int				i,c,side;
	line_t			*line_p, *newline_p;
	divline_t		divline;
	
	DivlineFromWorldline (&divline, spliton);
	DrawDivLine (&divline);
	
	c = [lines_i count];
		
	for (i=0 ; i<c ; i++)
	{
		line_p = [lines_i elementAt:i];
		if (line_p == spliton)
			side = 0;
		else
			side = LineOnSide (line_p, &divline);
		switch (side)
		{
		case 0:
			[frontlist_i addElement: line_p];
			break;
		case 1:
			[backlist_i addElement: line_p];
			break;
		case -2:
			newline_p = CutLine (line_p, &divline);
			[frontlist_i addElement: line_p];
			[backlist_i addElement: newline_p];
			break;
		default:
			Error ("ExecuteSplit: bad side");
		}
	}
}


/*
================
=
= BSPList
=
= Takes a storage of lines and recursively partitions the list
= Returns a bspnode_t
================
*/

float	gray = NX_WHITE;

bspnode_t *BSPList (id lines_i)
{
	id				frontlist_i, backlist_i;
	int				i,c, step;
	line_t			*line_p, *bestline_p;
	int				v, bestv;
	bspnode_t		*node_p;
	
	if (draw)
		PSsetgray (gray);
	gray = 1.0 - gray;
	DrawLineStore (lines_i);
	
	node_p = malloc (sizeof(*node_p));
	memset (node_p, 0, sizeof(*node_p));

//
// find the best line to partition on 
//
	c = [lines_i count];
	bestv = MAXINT;	
	bestline_p = NULL;
	step = (c/40)+1;		// set this to 1 for an exhaustive search
research:
	for (i=0 ; i<c ; i+=step)
	{
		line_p = [lines_i elementAt:i];
		v = EvaluateSplit (lines_i, line_p, bestv);
		if (v<bestv)
		{
			bestv = v;
			bestline_p = line_p;
		}
	}
	
//
// if none of the lines should be split, the remaining lines
// are convex, and form a terminal node
//
//printf ("bestv:%i\n",bestv);

	if (bestv == MAXINT)
	{
		if (step > 1)
		{	// possible to get here with non convex area if BSPSLIDE specials
			// caused rejections
			step = 1;
			goto research;
		}
		node_p->lines_i = lines_i;
		return node_p;
	}
	
//
// divide the line list into two nodes along the best split line
//
	DivlineFromWorldline (&node_p->divline, bestline_p);

	frontlist_i =
	[[Storage alloc]
		initCount:		0
		elementSize:	sizeof(line_t)
		description:	NULL];
	backlist_i =
	[[Storage alloc]
		initCount:		0
		elementSize:	sizeof(line_t)
		description:	NULL];
		
	ExecuteSplit (lines_i, bestline_p, frontlist_i, backlist_i);

//
// recursively divide the lists
//
	node_p->side[0] = BSPList (frontlist_i);
	node_p->side[1] = BSPList (backlist_i);
	
	return node_p;
}



/*
=====================
=
= MakeSegs
=
=====================
*/

id segstore_i;

void MakeSegs (void)
{
	int				i, count;
	worldline_t		*wl;
	line_t			li;

	segstore_i =
	[[Storage alloc]
		initCount:		0
		elementSize:	sizeof(line_t)
		description:	NULL];
	
	count = [linestore_i count];
	wl = [linestore_i elementAt:0];
	for (i= 0 ; i<count ; i++, wl++)
	{
		li.p1 = wl->p1;
		li.p2 = wl->p2;
		li.linedef = i;
		li.side = 0;
		li.offset = 0;
		li.grouped = false;
		[segstore_i addElement: &li];
		
		if (wl->flags & ML_TWOSIDED)
		{
			li.p1 = wl->p2;
			li.p2 = wl->p1;
			li.linedef = i;
			li.side = 1;
			li.offset = 0;
			li.grouped = false;
			[segstore_i addElement: &li];
		}
	}		
}


/*
=====================
=
= BuildBSP
=
=====================
*/

bspnode_t	*startnode;

void BuildBSP (void)
{
	MakeSegs ();
	cuts = 0;
	startnode = BSPList (segstore_i);
}
