#include "QF/sys.h"
#include "world.h"

static int
HullPointContents (hull_t *hull, int num, const vec3_t p)
{
	float		d;
	dclipnode_t	*node;
	mplane_t	*plane;

	while (num >= 0)
	{
		if (num < hull->firstclipnode || num > hull->lastclipnode)
			Sys_Error ("HullPointContents: bad node number");

		node = hull->clipnodes + num;
		plane = hull->planes + node->planenum;

		if (plane->type < 3)
			d = p[plane->type] - plane->dist;
		else
			d = DotProduct (plane->normal, p) - plane->dist;
		if (d < 0)
			num = node->children[1];
		else
			num = node->children[0];
	}

	return num;
}

// 1/32 epsilon to keep floating point happy
#ifndef DIST_EPSILON
#define	DIST_EPSILON	(0.03125)
#endif

static qboolean
SV_RecursiveHullCheck (hull_t *hull, int num, float p1f, float p2f, const vec3_t p1, const vec3_t p2, trace_t *trace)
{
	dclipnode_t	*node;
	mplane_t	*plane;
	float		t1, t2;
	float		frac;
	int			i;
	vec3_t		mid;
	int			side;
	float		midf;

// check for empty
	if (num < 0)
	{
		if (num != CONTENTS_SOLID)
		{
			trace->allsolid = false;
			if (num == CONTENTS_EMPTY)
				trace->inopen = true;
			else
				trace->inwater = true;
		}
		else
			trace->startsolid = true;
		return true;		// empty
	}

	if (num < hull->firstclipnode || num > hull->lastclipnode)
		Sys_Error ("SV_RecursiveHullCheck: bad node number");

//
// find the point distances
//
	node = hull->clipnodes + num;
	plane = hull->planes + node->planenum;

	if (plane->type < 3)
	{
		t1 = p1[plane->type] - plane->dist;
		t2 = p2[plane->type] - plane->dist;
	}
	else
	{
		t1 = DotProduct (plane->normal, p1) - plane->dist;
		t2 = DotProduct (plane->normal, p2) - plane->dist;
	}

	if (t1 >= 0 && t2 >= 0)
		return SV_RecursiveHullCheck (hull, node->children[0], p1f, p2f, p1, p2, trace);
	if (t1 < 0 && t2 < 0)
		return SV_RecursiveHullCheck (hull, node->children[1], p1f, p2f, p1, p2, trace);

// put the crosspoint DIST_EPSILON pixels on the near side
	if (t1 < 0)
		frac = (t1 + DIST_EPSILON)/(t1-t2);
	else
		frac = (t1 - DIST_EPSILON)/(t1-t2);
	if (frac < 0)
		frac = 0;
	if (frac > 1)
		frac = 1;

	midf = p1f + (p2f - p1f)*frac;
	for (i=0 ; i<3 ; i++)
		mid[i] = p1[i] + frac*(p2[i] - p1[i]);

	side = (t1 < 0);

// move up to the node
	if (!SV_RecursiveHullCheck (hull, node->children[side], p1f, midf, p1, mid, trace) )
		return false;

	if (HullPointContents (hull, node->children[side^1], mid)
	!= CONTENTS_SOLID)
// go past the node
		return SV_RecursiveHullCheck (hull, node->children[side^1], midf, p2f, mid, p2, trace);

	if (trace->allsolid)
		return false;		// never got out of the solid area

//==================
// the other side of the node is solid, this is the impact point
//==================
	if (!side)
	{
		VectorCopy (plane->normal, trace->plane.normal);
		trace->plane.dist = plane->dist;
	}
	else
	{
		VectorSubtract (vec3_origin, plane->normal, trace->plane.normal);
		trace->plane.dist = -plane->dist;
	}
#if 0
	while (HullPointContents (hull, hull->firstclipnode, mid)
	== CONTENTS_SOLID)
	{ // shouldn't really happen, but does occasionally
		frac -= 0.1;
		if (frac < 0)
		{
			trace->fraction = midf;
			VectorCopy (mid, trace->endpos);
			//Con_DPrintf ("backup past 0\n");
			return false;
		}
		midf = p1f + (p2f - p1f)*frac;
		for (i=0 ; i<3 ; i++)
			mid[i] = p1[i] + frac*(p2[i] - p1[i]);
	}
#endif
	trace->fraction = midf;
	VectorCopy (mid, trace->endpos);

	return false;
}

void
MOD_TraceLine (hull_t *hull, int num,
			   const vec3_t start_point, const vec3_t end_point,
			   trace_t *trace)
{
	trace->fraction = 1;
	trace->allsolid = true;
	SV_RecursiveHullCheck (hull, num, 0, 1, start_point, end_point, trace);
}