/*
Copyright (C) 1997-2001 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.

*/
// g_phys.c

#include "g_local.h"

/*


pushmove objects do not obey gravity, and do not interact with each other or trigger fields, but block normal movement and push normal objects when they move.

onground is set for toss objects when they come to a complete rest.  it is set for steping or walking objects 

doors, plats, etc are SOLID_BSP, and MOVETYPE_PUSH
bonus items are SOLID_TRIGGER touch, and MOVETYPE_TOSS
corpses are SOLID_NOT and MOVETYPE_TOSS
crates are SOLID_BBOX and MOVETYPE_TOSS
walking monsters are SOLID_SLIDEBOX and MOVETYPE_STEP
flying/floating monsters are SOLID_SLIDEBOX and MOVETYPE_FLY

solid_edge items only clip against bsp models.

*/


/*
============
SV_TestEntityPosition

============
*/
edict_t	*SV_TestEntityPosition (edict_t *ent)
{
	trace_t	trace;
	int		mask;

	if (ent->clipmask)
		mask = ent->clipmask;
	else
		mask = MASK_SOLID;
	trace = gi.trace (ent->s.origin, ent->mins, ent->maxs, ent->s.origin, ent, mask);
	
	if (trace.startsolid)
		return g_edicts;
		
	return NULL;
}


/*
================
SV_CheckVelocity
================
*/
void SV_CheckVelocity (edict_t *ent)
{
	int		i;

//
// bound velocity
//
	for (i=0 ; i<3 ; i++)
	{
		if (ent->velocity[i] > sv_maxvelocity->value)
			ent->velocity[i] = sv_maxvelocity->value;
		else if (ent->velocity[i] < -sv_maxvelocity->value)
			ent->velocity[i] = -sv_maxvelocity->value;
	}
}

/*
=============
SV_RunThink

Runs thinking code for this frame if necessary
=============
*/
qboolean SV_RunThink (edict_t *ent)
{
	float	thinktime;

	thinktime = ent->nextthink;
	if (thinktime <= 0)
		return true;
	if (thinktime > level.time+0.001)
		return true;
	
	ent->nextthink = 0;
	if (!ent->think)
		gi.error ("NULL ent->think");
	ent->think (ent);

	return false;
}

/*
==================
SV_Impact

Two entities have touched, so run their touch functions
==================
*/
void SV_Impact (edict_t *e1, trace_t *trace)
{
	edict_t		*e2;
//	cplane_t	backplane;

	e2 = trace->ent;

	if (e1->touch && e1->solid != SOLID_NOT)
		e1->touch (e1, e2, &trace->plane, trace->surface);
	
	if (e2->touch && e2->solid != SOLID_NOT)
		e2->touch (e2, e1, NULL, NULL);
}


/*
==================
ClipVelocity

Slide off of the impacting object
returns the blocked flags (1 = floor, 2 = step / wall)
==================
*/
#define	STOP_EPSILON	0.1

int ClipVelocity (vec3_t in, vec3_t normal, vec3_t out, float overbounce)
{
	float	backoff;
	float	change;
	int		i, blocked;
	
	blocked = 0;
	if (normal[2] > 0)
		blocked |= 1;		// floor
	if (!normal[2])
		blocked |= 2;		// step
	
	backoff = DotProduct (in, normal) * overbounce;

	for (i=0 ; i<3 ; i++)
	{
		change = normal[i]*backoff;
		out[i] = in[i] - change;
		if (out[i] > -STOP_EPSILON && out[i] < STOP_EPSILON)
			out[i] = 0;
	}

	return blocked;
}


/*
============
SV_FlyMove

The basic solid body movement clip that slides along multiple planes
Returns the clipflags if the velocity was modified (hit something solid)
1 = floor
2 = wall / step
4 = dead stop
============
*/
#define	MAX_CLIP_PLANES	5
int SV_FlyMove (edict_t *ent, float time, int mask)
{
	edict_t		*hit;
	int			bumpcount, numbumps;
	vec3_t		dir;
	float		d;
	int			numplanes;
	vec3_t		planes[MAX_CLIP_PLANES];
	vec3_t		primal_velocity, original_velocity, new_velocity;
	int			i, j;
	trace_t		trace;
	vec3_t		end;
	float		time_left;
	int			blocked;
	
	numbumps = 4;
	
	blocked = 0;
	VectorCopy (ent->velocity, original_velocity);
	VectorCopy (ent->velocity, primal_velocity);
	numplanes = 0;
	
	time_left = time;

	ent->groundentity = NULL;
	for (bumpcount=0 ; bumpcount<numbumps ; bumpcount++)
	{
		for (i=0 ; i<3 ; i++)
			end[i] = ent->s.origin[i] + time_left * ent->velocity[i];

		trace = gi.trace (ent->s.origin, ent->mins, ent->maxs, end, ent, mask);

		if (trace.allsolid)
		{	// entity is trapped in another solid
			VectorCopy (vec3_origin, ent->velocity);
			return 3;
		}

		if (trace.fraction > 0)
		{	// actually covered some distance
			VectorCopy (trace.endpos, ent->s.origin);
			VectorCopy (ent->velocity, original_velocity);
			numplanes = 0;
		}

		if (trace.fraction == 1)
			 break;		// moved the entire distance

		hit = trace.ent;

		if (trace.plane.normal[2] > 0.7)
		{
			blocked |= 1;		// floor
			if ( hit->solid == SOLID_BSP)
			{
				ent->groundentity = hit;
				ent->groundentity_linkcount = hit->linkcount;
			}
		}
		if (!trace.plane.normal[2])
		{
			blocked |= 2;		// step
		}

//
// run the impact function
//
		SV_Impact (ent, &trace);
		if (!ent->inuse)
			break;		// removed by the impact function

		
		time_left -= time_left * trace.fraction;
		
	// cliped to another plane
		if (numplanes >= MAX_CLIP_PLANES)
		{	// this shouldn't really happen
			VectorCopy (vec3_origin, ent->velocity);
			return 3;
		}

		VectorCopy (trace.plane.normal, planes[numplanes]);
		numplanes++;

//
// modify original_velocity so it parallels all of the clip planes
//
		for (i=0 ; i<numplanes ; i++)
		{
			ClipVelocity (original_velocity, planes[i], new_velocity, 1);

			for (j=0 ; j<numplanes ; j++)
				if ((j != i) && !VectorCompare (planes[i], planes[j]))
				{
					if (DotProduct (new_velocity, planes[j]) < 0)
						break;	// not ok
				}
			if (j == numplanes)
				break;
		}
		
		if (i != numplanes)
		{	// go along this plane
			VectorCopy (new_velocity, ent->velocity);
		}
		else
		{	// go along the crease
			if (numplanes != 2)
			{
//				gi.dprintf ("clip velocity, numplanes == %i\n",numplanes);
				VectorCopy (vec3_origin, ent->velocity);
				return 7;
			}
			CrossProduct (planes[0], planes[1], dir);
			d = DotProduct (dir, ent->velocity);
			VectorScale (dir, d, ent->velocity);
		}

//
// if original velocity is against the original velocity, stop dead
// to avoid tiny occilations in sloping corners
//
		if (DotProduct (ent->velocity, primal_velocity) <= 0)
		{
			VectorCopy (vec3_origin, ent->velocity);
			return blocked;
		}
	}

	return blocked;
}


/*
============
SV_AddGravity

============
*/
void SV_AddGravity (edict_t *ent)
{
	ent->velocity[2] -= ent->gravity * sv_gravity->value * FRAMETIME;
}

/*
===============================================================================

PUSHMOVE

===============================================================================
*/

/*
============
SV_PushEntity

Does not change the entities velocity at all
============
*/
trace_t SV_PushEntity (edict_t *ent, vec3_t push)
{
	trace_t	trace;
	vec3_t	start;
	vec3_t	end;
	int		mask;

	VectorCopy (ent->s.origin, start);
	VectorAdd (start, push, end);

retry:
	if (ent->clipmask)
		mask = ent->clipmask;
	else
		mask = MASK_SOLID;

	trace = gi.trace (start, ent->mins, ent->maxs, end, ent, mask);
	
	VectorCopy (trace.endpos, ent->s.origin);
	gi.linkentity (ent);

	if (trace.fraction != 1.0)
	{
		SV_Impact (ent, &trace);

		// if the pushed entity went away and the pusher is still there
		if (!trace.ent->inuse && ent->inuse)
		{
			// move the pusher back and try again
			VectorCopy (start, ent->s.origin);
			gi.linkentity (ent);
			goto retry;
		}
	}

	if (ent->inuse)
		G_TouchTriggers (ent);

	return trace;
}					


typedef struct
{
	edict_t	*ent;
	vec3_t	origin;
	vec3_t	angles;
	float	deltayaw;
} pushed_t;
pushed_t	pushed[MAX_EDICTS], *pushed_p;

edict_t	*obstacle;

/*
============
SV_Push

Objects need to be moved back on a failed push,
otherwise riders would continue to slide.
============
*/
qboolean SV_Push (edict_t *pusher, vec3_t move, vec3_t amove)
{
	int			i, e;
	edict_t		*check, *block;
	vec3_t		mins, maxs;
	pushed_t	*p;
	vec3_t		org, org2, move2, forward, right, up;

	// clamp the move to 1/8 units, so the position will
	// be accurate for client side prediction
	for (i=0 ; i<3 ; i++)
	{
		float	temp;
		temp = move[i]*8.0;
		if (temp > 0.0)
			temp += 0.5;
		else
			temp -= 0.5;
		move[i] = 0.125 * (int)temp;
	}

	// find the bounding box
	for (i=0 ; i<3 ; i++)
	{
		mins[i] = pusher->absmin[i] + move[i];
		maxs[i] = pusher->absmax[i] + move[i];
	}

// we need this for pushing things later
	VectorSubtract (vec3_origin, amove, org);
	AngleVectors (org, forward, right, up);

// save the pusher's original position
	pushed_p->ent = pusher;
	VectorCopy (pusher->s.origin, pushed_p->origin);
	VectorCopy (pusher->s.angles, pushed_p->angles);
	if (pusher->client)
		pushed_p->deltayaw = pusher->client->ps.pmove.delta_angles[YAW];
	pushed_p++;

// move the pusher to it's final position
	VectorAdd (pusher->s.origin, move, pusher->s.origin);
	VectorAdd (pusher->s.angles, amove, pusher->s.angles);
	gi.linkentity (pusher);

// see if any solid entities are inside the final position
	check = g_edicts+1;
	for (e = 1; e < globals.num_edicts; e++, check++)
	{
		if (!check->inuse)
			continue;
		if (check->movetype == MOVETYPE_PUSH
		|| check->movetype == MOVETYPE_STOP
		|| check->movetype == MOVETYPE_NONE
		|| check->movetype == MOVETYPE_NOCLIP)
			continue;

		if (!check->area.prev)
			continue;		// not linked in anywhere

	// if the entity is standing on the pusher, it will definitely be moved
		if (check->groundentity != pusher)
		{
			// see if the ent needs to be tested
			if ( check->absmin[0] >= maxs[0]
			|| check->absmin[1] >= maxs[1]
			|| check->absmin[2] >= maxs[2]
			|| check->absmax[0] <= mins[0]
			|| check->absmax[1] <= mins[1]
			|| check->absmax[2] <= mins[2] )
				continue;

			// see if the ent's bbox is inside the pusher's final position
			if (!SV_TestEntityPosition (check))
				continue;
		}

		if ((pusher->movetype == MOVETYPE_PUSH) || (check->groundentity == pusher))
		{