/*
 ** License Applicability. Except to the extent portions of this file are
 ** made subject to an alternative license as permitted in the SGI Free
 ** Software License B, Version 1.1 (the "License"), the contents of this
 ** file are subject only to the provisions of the License. You may not use
 ** this file except in compliance with the License. You may obtain a copy
 ** of the License at Silicon Graphics, Inc., attn: Legal Services, 1600
 ** Amphitheatre Parkway, Mountain View, CA 94043-1351, or at:
 ** 
 ** http://oss.sgi.com/projects/FreeB
 ** 
 ** Note that, as provided in the License, the Software is distributed on an
 ** "AS IS" basis, with ALL EXPRESS AND IMPLIED WARRANTIES AND CONDITIONS
 ** DISCLAIMED, INCLUDING, WITHOUT LIMITATION, ANY IMPLIED WARRANTIES AND
 ** CONDITIONS OF MERCHANTABILITY, SATISFACTORY QUALITY, FITNESS FOR A
 ** PARTICULAR PURPOSE, AND NON-INFRINGEMENT.
 ** 
 ** Original Code. The Original Code is: OpenGL Sample Implementation,
 ** Version 1.2.1, released January 26, 2000, developed by Silicon Graphics,
 ** Inc. The Original Code is Copyright (c) 1991-2000 Silicon Graphics, Inc.
 ** Copyright in any portions created by third parties is as indicated
 ** elsewhere herein. All Rights Reserved.
 ** 
 ** Additional Notice Provisions: The application programming interfaces
 ** established by SGI in conjunction with the Original Code are The
 ** OpenGL(R) Graphics System: A Specification (Version 1.2.1), released
 ** April 1, 1999; The OpenGL(R) Graphics System Utility Library (Version
 ** 1.3), released November 4, 1998; and OpenGL(R) Graphics with the X
 ** Window System(R) (Version 1.3), released October 19, 1998. This software
 ** was created using the OpenGL(R) version 1.2.1 Sample Implementation
 ** published by SGI, but has not been independently verified as being
 ** compliant with the OpenGL(R) version 1.2.1 Specification.
 **
 */
/*
 ** Author: Eric Veach, July 1994.
 **
 ** $Date: 2001/03/17 00:25:41 $ $Revision: 1.1 $
 ** $Header: /home/krh/git/sync/mesa-cvs-repo/Mesa/src/glu/sgi/libtess/geom.c,v 1.1 2001/03/17 00:25:41 brianp Exp $
 */

#include "gluos.h"
#include <assert.h>
#include "mesh.h"
#include "geom.h"

int __gl_vertLeq( GLUvertex *u, GLUvertex *v )
{
	/* Returns TRUE if u is lexicographically <= v. */

	return VertLeq( u, v );
}

GLdouble __gl_edgeEval( GLUvertex *u, GLUvertex *v, GLUvertex *w )
{
	/* Given three vertices u,v,w such that VertLeq(u,v) && VertLeq(v,w),
	 * evaluates the t-coord of the edge uw at the s-coord of the vertex v.
	 * Returns v->t - (uw)(v->s), ie. the signed distance from uw to v.
	 * If uw is vertical (and thus passes thru v), the result is zero.
	 *
	 * The calculation is extremely accurate and stable, even when v
	 * is very close to u or w.  In particular if we set v->t = 0 and
	 * let r be the negated result (this evaluates (uw)(v->s)), then
	 * r is guaranteed to satisfy MIN(u->t,w->t) <= r <= MAX(u->t,w->t).
	 */
	GLdouble gapL, gapR;

	assert( VertLeq( u, v ) && VertLeq( v, w ));

	gapL = v->s - u->s;
	gapR = w->s - v->s;

	if( gapL + gapR > 0 ) {
		if( gapL < gapR ) {
			return (v->t - u->t) + (u->t - w->t) * (gapL / (gapL + gapR));
		} else {
			return (v->t - w->t) + (w->t - u->t) * (gapR / (gapL + gapR));
		}
	}
	/* vertical line */
	return 0;
}

GLdouble __gl_edgeSign( GLUvertex *u, GLUvertex *v, GLUvertex *w )
{
	/* Returns a number whose sign matches EdgeEval(u,v,w) but which
	 * is cheaper to evaluate.  Returns > 0, == 0 , or < 0
	 * as v is above, on, or below the edge uw.
	 */
	GLdouble gapL, gapR;

	assert( VertLeq( u, v ) && VertLeq( v, w ));

	gapL = v->s - u->s;
	gapR = w->s - v->s;

	if( gapL + gapR > 0 ) {
		return (v->t - w->t) * gapL + (v->t - u->t) * gapR;
	}
	/* vertical line */
	return 0;
}


/***********************************************************************
 * Define versions of EdgeSign, EdgeEval with s and t transposed.
 */

GLdouble __gl_transEval( GLUvertex *u, GLUvertex *v, GLUvertex *w )
{
	/* Given three vertices u,v,w such that TransLeq(u,v) && TransLeq(v,w),
	 * evaluates the t-coord of the edge uw at the s-coord of the vertex v.
	 * Returns v->s - (uw)(v->t), ie. the signed distance from uw to v.
	 * If uw is vertical (and thus passes thru v), the result is zero.
	 *
	 * The calculation is extremely accurate and stable, even when v
	 * is very close to u or w.  In particular if we set v->s = 0 and
	 * let r be the negated result (this evaluates (uw)(v->t)), then
	 * r is guaranteed to satisfy MIN(u->s,w->s) <= r <= MAX(u->s,w->s).
	 */
	GLdouble gapL, gapR;

	assert( TransLeq( u, v ) && TransLeq( v, w ));

	gapL = v->t - u->t;
	gapR = w->t - v->t;

	if( gapL + gapR > 0 ) {
		if( gapL < gapR ) {
			return (v->s - u->s) + (u->s - w->s) * (gapL / (gapL + gapR));
		} else {
			return (v->s - w->s) + (w->s - u->s) * (gapR / (gapL + gapR));
		}
	}
	/* vertical line */
	return 0;
}

GLdouble __gl_transSign( GLUvertex *u, GLUvertex *v, GLUvertex *w )
{
	/* Returns a number whose sign matches TransEval(u,v,w) but which
	 * is cheaper to evaluate.  Returns > 0, == 0 , or < 0
	 * as v is above, on, or below the edge uw.
	 */
	GLdouble gapL, gapR;

	assert( TransLeq( u, v ) && TransLeq( v, w ));

	gapL = v->t - u->t;
	gapR = w->t - v->t;

	if( gapL + gapR > 0 ) {
		return (v->s - w->s) * gapL + (v->s - u->s) * gapR;
	}
	/* vertical line */
	return 0;
}


int __gl_vertCCW( GLUvertex *u, GLUvertex *v, GLUvertex *w )
{
	/* For almost-degenerate situations, the results are not reliable.
	 * Unless the floating-point arithmetic can be performed without
	 * rounding errors, *any* implementation will give incorrect results
	 * on some degenerate inputs, so the client must have some way to
	 * handle this situation.
	 */
	return (u->s*(v->t - w->t) + v->s*(w->t - u->t) + w->s*(u->t - v->t)) >= 0;
}

/* Given parameters a,x,b,y returns the value (b*x+a*y)/(a+b),
 * or (x+y)/2 if a==b==0.  It requires that a,b >= 0, and enforces
 * this in the rare case that one argument is slightly negative.
 * The implementation is extremely stable numerically.
 * In particular it guarantees that the result r satisfies
 * MIN(x,y) <= r <= MAX(x,y), and the results are very accurate
 * even when a and b differ greatly in magnitude.
 */
#define RealInterpolate(a,x,b,y)			\
	(a = (a < 0) ? 0 : a, b = (b < 0) ? 0 : b,		\
			((a <= b) ? ((b == 0) ? ((x+y) / 2)			\
					: (x + (y-x) * (a/(a+b))))	\
					: (y + (x-y) * (b/(a+b)))))

#ifndef FOR_TRITE_TEST_PROGRAM
#define Interpolate(a,x,b,y)	RealInterpolate(a,x,b,y)
#else

/* Claim: the ONLY property the sweep algorithm relies on is that
 * MIN(x,y) <= r <= MAX(x,y).  This is a nasty way to test that.
 */
#include <stdlib.h>
extern int RandomInterpolate;

GLdouble Interpolate( GLdouble a, GLdouble x, GLdouble b, GLdouble y)
{
	printf("*********************%d\n",RandomInterpolate);
	if( RandomInterpolate ) {
		a = 1.2 * drand48() - 0.1;
		a = (a < 0) ? 0 : ((a > 1) ? 1 : a);
		b = 1.0 - a;
	}
	return RealInterpolate(a,x,b,y);
}

#endif

#define Swap(a,b)	if (1) { GLUvertex *t = a; a = b; b = t; } else

void __gl_edgeIntersect( GLUvertex *o1, GLUvertex *d1,
		GLUvertex *o2, GLUvertex *d2,
		GLUvertex *v )
/* Given edges (o1,d1) and (o2,d2), compute their point of intersection.
 * The computed point is guaranteed to lie in the intersection of the
 * bounding rectangles defined by each edge.
 */
{
	GLdouble z1, z2;

	/* This is certainly not the most efficient way to find the intersection
	 * of two line segments, but it is very numerically stable.
	 *
	 * Strategy: find the two middle vertices in the VertLeq ordering,
	 * and interpolate the intersection s-value from these.  Then repeat
	 * using the TransLeq ordering to find the intersection t-value.
	 */

	if( ! VertLeq( o1, d1 )) { Swap( o1, d1 ); }
	if( ! VertLeq( o2, d2 )) { Swap( o2, d2 ); }
	if( ! VertLeq( o1, o2 )) { Swap( o1, o2 ); Swap( d1, d2 ); }

	if( ! VertLeq( o2, d1 )) {
		/* Technically, no intersection -- do our best */
		v->s = (o2->s + d1->s) / 2;
	} else if( VertLeq( d1, d2 )) {
		/* Interpolate between o2 and d1 */
		z1 = EdgeEval( o1, o2, d1 );
		z2 = EdgeEval( o2, d1, d2 );
		if( z1+z2 < 0 ) { z1 = -z1; z2 = -z2; }
		v->s = Interpolate( z1, o2->s, z2, d1->s );
	} else {
		/* Interpolate between o2 and d2 */
		z1 = EdgeSign( o1, o2, d1 );
		z2 = -EdgeSign( o1, d2, d1 );
		if( z1+z2 < 0 ) { z1 = -z1; z2 = -z2; }
		v->s = Interpolate( z1, o2->s, z2, d2->s );
	}

	/* Now repeat the process for t */

	if( ! TransLeq( o1, d1 )) { Swap( o1, d1 ); }
	if( ! TransLeq( o2, d2 )) { Swap( o2, d2 ); }
	if( ! TransLeq( o1, o2 )) { Swap( o1, o2 ); Swap( d1, d2 ); }

	if( ! TransLeq( o2, d1 )) {
		/* Technically, no intersection -- do our best */
		v->t = (o2->t + d1->t) / 2;
	} else if( TransLeq( d1, d2 )) {
		/* Interpolate between o2 and d1 */
		z1 = TransEval( o1, o2, d1 );
		z2 = TransEval( o2, d1, d2 );
		if( z1+z2 < 0 ) { z1 = -z1; z2 = -z2; }
		v->t = Interpolate( z1, o2->t, z2, d1->t );
	} else {
		/* Interpolate between o2 and d2 */
		z1 = TransSign( o1, o2, d1 );
		z2 = -TransSign( o1, d2, d1 );
		if( z1+z2 < 0 ) { z1 = -z1; z2 = -z2; }
		v->t = Interpolate( z1, o2->t, z2, d2->t );
	}
}