/*
Copyright (C) 1996-1997 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.

*/
// sv_phys.c

#include "quakedef.h"
#include "host.h"
#include "progs.h"
#include "server.h"
#include "world.h"
#include "console.h"
#include "sys.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.

*/

cvar_t sv_friction = { "sv_friction", "4", false, true };
cvar_t sv_stopspeed = { "sv_stopspeed", "100" };
cvar_t sv_gravity = { "sv_gravity", "800", false, true };
cvar_t sv_maxvelocity = { "sv_maxvelocity", "2000" };
cvar_t sv_nostep = { "sv_nostep", "0" };

#define	MOVE_EPSILON	0.01

void SV_Physics_Toss(edict_t *ent);

/*
================
SV_CheckAllEnts
================
*/
void
SV_CheckAllEnts(void)
{
    int e;
    edict_t *check;

// see if any solid entities are inside the final position
    check = NEXT_EDICT(sv.edicts);
    for (e = 1; e < sv.num_edicts; e++, check = NEXT_EDICT(check)) {
	if (check->free)
	    continue;
	if (check->v.movetype == MOVETYPE_PUSH
	    || check->v.movetype == MOVETYPE_NONE
	    || check->v.movetype == MOVETYPE_NOCLIP)
	    continue;

	if (SV_TestEntityPosition(check))
	    Con_Printf("entity in invalid position\n");
    }
}

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

//
// bound velocity
//
    for (i = 0; i < 3; i++) {
	if (IS_NAN(ent->v.velocity[i])) {
	    Con_Printf("Got a NaN velocity on %s\n",
		       PR_GetString(ent->v.classname));
	    ent->v.velocity[i] = 0;
	}
	if (IS_NAN(ent->v.origin[i])) {
	    Con_Printf("Got a NaN origin on %s\n",
		       PR_GetString(ent->v.classname));
	    ent->v.origin[i] = 0;
	}
	if (ent->v.velocity[i] > sv_maxvelocity.value)
	    ent->v.velocity[i] = sv_maxvelocity.value;
	else if (ent->v.velocity[i] < -sv_maxvelocity.value)
	    ent->v.velocity[i] = -sv_maxvelocity.value;
    }
}

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

Runs thinking code if time.  There is some play in the exact time the think
function will be called, because it is called before any movement is done
in a frame.  Not used for pushmove objects, because they must be exact.
Returns false if the entity removed itself.
=============
*/
qboolean
SV_RunThink(edict_t *ent)
{
    float thinktime;

    thinktime = ent->v.nextthink;
    if (thinktime <= 0 || thinktime > sv.time + host_frametime)
	return true;

    if (thinktime < sv.time)
	thinktime = sv.time;	// don't let things stay in the past.
    // it is possible to start that way
    // by a trigger with a local time.
    ent->v.nextthink = 0;
    pr_global_struct->time = thinktime;
    pr_global_struct->self = EDICT_TO_PROG(ent);
    pr_global_struct->other = EDICT_TO_PROG(sv.edicts);
    PR_ExecuteProgram(ent->v.think);

    return !ent->free;
}

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

Two entities have touched, so run their touch functions
==================
*/
void
SV_Impact(edict_t *e1, edict_t *e2)
{
    int old_self, old_other;

    old_self = pr_global_struct->self;
    old_other = pr_global_struct->other;

    pr_global_struct->time = sv.time;
    if (e1->v.touch && e1->v.solid != SOLID_NOT) {
	pr_global_struct->self = EDICT_TO_PROG(e1);
	pr_global_struct->other = EDICT_TO_PROG(e2);
	PR_ExecuteProgram(e1->v.touch);
    }

    if (e2->v.touch && e2->v.solid != SOLID_NOT) {
	pr_global_struct->self = EDICT_TO_PROG(e2);
	pr_global_struct->other = EDICT_TO_PROG(e1);
	PR_ExecuteProgram(e2->v.touch);
    }

    pr_global_struct->self = old_self;
    pr_global_struct->other = old_other;
}


/*
==================
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
If steptrace is not NULL, the trace of any vertical wall hit will be stored
============
*/
#define	MAX_CLIP_PLANES	5
int
SV_FlyMove(edict_t *ent, float time, trace_t *steptrace)
{
    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->v.velocity, original_velocity);
    VectorCopy(ent->v.velocity, primal_velocity);
    numplanes = 0;

    time_left = time;

    for (bumpcount = 0; bumpcount < numbumps; bumpcount++) {
	if (!ent->v.velocity[0] && !ent->v.velocity[1] && !ent->v.velocity[2])
	    break;

	for (i = 0; i < 3; i++)
	    end[i] = ent->v.origin[i] + time_left * ent->v.velocity[i];

	trace =
	    SV_Move(ent->v.origin, ent->v.mins, ent->v.maxs, end, false, ent);

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

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

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

	if (!trace.ent)
	    Sys_Error("%s: !trace.ent", __func__);

	if (trace.plane.normal[2] > 0.7) {
	    blocked |= 1;	// floor
	    if (trace.ent->v.solid == SOLID_BSP) {
		ent->v.flags = (int)ent->v.flags | FL_ONGROUND;
		ent->v.groundentity = EDICT_TO_PROG(trace.ent);
	    }
	}
	if (!trace.plane.normal[2]) {
	    blocked |= 2;	// step
	    if (steptrace)
		*steptrace = trace;	// save for player extrafriction
	}
//
// run the impact function
//
	SV_Impact(ent, trace.ent);
	if (ent->free)
	    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->v.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) {
		    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->v.velocity);
	} else {		// go along the crease
	    if (numplanes != 2) {
//                              Con_Printf ("clip velocity, numplanes == %i\n",numplanes);
		VectorCopy(vec3_origin, ent->v.velocity);
		return 7;
	    }
	    CrossProduct(planes[0], planes[1], dir);
	    d = DotProduct(dir, ent->v.velocity);
	    VectorScale(dir, d, ent->v.velocity);
	}

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

    return blocked;
}


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

============
*/
void
SV_AddGravity(edict_t *ent)
{
    float ent_gravity;
    eval_t *val;

    val = GetEdictFieldValue(ent, "gravity");
    if (val && val->_float)
	ent_gravity = val->_float;
    else
	ent_gravity = 1.0;

    ent->v.velocity[2] -= ent_gravity * sv_gravity.value * host_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 end;

    VectorAdd(ent->v.origin, push, end);

    if (ent->v.movetype == MOVETYPE_FLYMISSILE)
	trace =
	    SV_Move(ent->v.origin, ent->v.mins, ent->v.maxs, end,
		    MOVE_MISSILE, ent);
    else if (ent->v.solid == SOLID_TRIGGER || ent->v.solid == SOLID_NOT)
	// only clip against bmodels
	trace =
	    SV_Move(ent->v.origin, ent->v.mins, ent->v.maxs, end,
		    MOVE_NOMONSTERS, ent);
    else
	trace =
	    SV_Move(ent->v.origin, ent->v.mins, ent->v.maxs, end,
		    MOVE_NORMAL, ent);

    VectorCopy(trace.endpos, ent->v.origin);
    SV_LinkEdict(ent, true);

    if (trace.ent)
	SV_Impact(ent, trace.ent);

    return trace;
}


/*
============
SV_PushMove

============
*/
void
SV_PushMove(edict_t *pusher, float movetime)
{
    int i, e;
    edict_t *check, *block;
    vec3_t mins, maxs, move;
    vec3_t entorig, pushorig;
    int num_moved;
    edict_t *moved_edict[MAX_EDICTS];
    vec3_t moved_from[MAX_EDICTS];

    if (!pusher->v.velocity[0] && !pusher->v.velocity[1]
	&& !pusher->v.velocity[2]) {
	pusher->v.ltime += movetime;
	return;
    }

    for (i = 0; i < 3; i++) {
	move[i] = pusher->v.velocity[i] * movetime;
	mins[i] = pusher->v.absmin[i] + move[i];
	maxs[i] = pusher->v.absmax[i] + move[i];
    }

    VectorCopy(pusher->v.origin, pushorig);

// move the pusher to it's final position

    VectorAdd(pusher->v.origin, move, pusher->v.origin);
    pusher->v.ltime += movetime;
    SV_LinkEdict(pusher, false);


// see if any solid entities are inside the final position
    num_moved = 0;
    check = NEXT_EDICT(sv.edicts);
    for (e = 1; e < sv.num_edicts; e++, check = NEXT_EDICT(check)) {
	if (check->free)
	    continue;
	if (check->v.movetype == MOVETYPE_PUSH
	    || check->v.movetype == MOVETYPE_NONE
	    || check->v.movetype == MOVETYPE_NOCLIP)
	    continue;

	// if the entity is standing on the pusher, it will definately be moved
	if (!(((int)check->v.flags & FL_ONGROUND)
	      && PROG_TO_EDICT(check->v.groundentity) == pusher)) {
	    if (check->v.absmin[0] >= maxs[0]
		|| check->v.absmin[1] >= maxs[1]
		|| check->v.absmin[2] >= maxs[2]
		|| check->v.absmax[0] <= mins[0]
		|| check->v.absmax[1] <= mins[1]
		|| check->v.absmax[2] <= mins[2])
		continue;

	    // see if the ent's bbox is inside the pusher's final position
	    if (!SV_TestEntityPosition(check))
		continue;
	}
	// remove the onground flag for non-players
	if (check->v.movetype != MOVETYPE_WALK)
	    check->v.flags = (int)check->v.flags & ~FL_ONGROUND;

	VectorCopy(check->v.origin, entorig);
	VectorCopy(check->v.origin, moved_from[num_moved]);
	moved_edict[num_moved] = check;
	num_moved++;

	// try moving the contacted entity
	pusher->v.solid = SOLID_NOT;
	SV_PushEntity(check, move);
	pusher->v.solid = SOLID_BSP;

	// if it is still inside the pusher, block
	block = SV_TestEntityPosition(check);
	if (block) {		// fail the move
	    if (check->v.mins[0] == check->v.maxs[0])
		continue;
	    if (check->v.solid == SOLID_NOT || check->v.solid == SOLID_TRIGGER) {	// corpse
		check->v.mins[0] = check->v.mins[1] = 0;
		VectorCopy(check->v.mins, check->v.maxs);
		continue;
	    }

	    VectorCopy(entorig, check->v.origin);
	    SV_LinkEdict(check, true);

	    VectorCopy(pushorig, pusher->v.origin);
	    SV_LinkEdict(pusher, false);
	    pusher->v.ltime -= movetime;

	    // if the pusher has a "blocked" function, call it
	    // otherwise, just stay in place until the obstacle is gone
	    if (pusher->v.blocked) {
		pr_global_struct->self = EDICT_TO_PROG(pusher);
		pr_global_struct->other = EDICT_TO_PROG(check);
		PR_ExecuteProgram(pusher->v.blocked);
	    }
	    // move back any entities we already moved
	    for (i = 0; i < num_moved; i++) {
		VectorCopy(moved_from[i], moved_edict[i]->v.origin);
		SV_LinkEdict(moved_edict[i], false);
	    }
	    return;
	}
    }


}

/*
================
SV_Physics_Pusher

================
*/
void
SV_Physics_Pusher(edict_t *ent)
{
    float thinktime;
    float oldltime;
    float movetime;

    oldltime = ent->v.ltime;

    thinktime = ent->v.nextthink;
    if (thinktime < ent->v.ltime + host_frametime) {
	movetime = thinktime - ent->v.ltime;
	if (movetime < 0)
	    movetime = 0;
    } else
	movetime = host_frametime;

    if (movetime) {
	// advances ent->v.ltime if not blocked
	SV_PushMove(ent, movetime);
    }

    if (thinktime > oldltime && thinktime <= ent->v.ltime) {
	ent->v.nextthink = 0;
	pr_global_struct->time = sv.time;
	pr_global_struct->self = EDICT_TO_PROG(ent);
	pr_global_struct->other = EDICT_TO_PROG(sv.edicts);
	PR_ExecuteProgram(ent->v.think);
	if (ent->free)
	    return;
    }

}


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

CLIENT MOVEMENT

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

/*
=============
SV_CheckStuck

This is a big hack to try and fix the rare case of getting stuck in the world
clipping hull.
=============
*/
void
SV_CheckStuck(edict_t *ent)
{
    int i, j;
    int z;
    vec3_t org;

    if (!SV_TestEntityPosition(ent)) {
	VectorCopy(ent->v.origin, ent->v.oldorigin);
	return;
    }

    VectorCopy(ent->v.origin, org);
    VectorCopy(ent->v.oldorigin, ent->v.origin);
    if (!SV_TestEntityPosition(ent)) {
	Con_DPrintf("Unstuck.\n");
	SV_LinkEdict(ent, true);
	return;
    }

    for (z = 0; z < 18; z++)
	for (i = -1; i <= 1; i++)
	    for (j = -1; j <= 1; j++) {
		ent->v.origin[0] = org[0] + i;
		ent->v.origin[1] = org[1] + j;
		ent->v.origin[2] = org[2] + z;
		if (!SV_TestEntityPosition(ent)) {
		    Con_DPrintf("Unstuck.\n");
		    SV_LinkEdict(ent, true);
		    return;
		}
	    }

    VectorCopy(org, ent->v.origin);
    Con_DPrintf("player is stuck.\n");
}


/*
=============
SV_CheckWater
=============
*/
qboolean
SV_CheckWater(edict_t *ent)
{
    vec3_t point;
    int cont;

    point[0] = ent->v.origin[0];
    point[1] = ent->v.origin[1];
    point[2] = ent->v.origin[2] + ent->v.mins[2] + 1;

    ent->v.waterlevel = 0;
    ent->v.watertype = CONTENTS_EMPTY;
    cont = SV_PointContents(point);
    if (cont <= CONTENTS_WATER) {
	ent->v.watertype = cont;
	ent->v.waterlevel = 1;
	point[2] = ent->v.origin[2] + (ent->v.mins[2] + ent->v.maxs[2]) * 0.5;
	cont = SV_PointContents(point);
	if (cont <= CONTENTS_WATER) {
	    ent->v.waterlevel = 2;
	    point[2] = ent->v.origin[2] + ent->v.view_ofs[2];
	    cont = SV_PointContents(point);
	    if (cont <= CONTENTS_WATER)
		ent->v.waterlevel = 3;
	}
    }

    return ent->v.waterlevel > 1;
}

/*
============
SV_WallFriction

============
*/
void
SV_WallFriction(edict_t *ent, trace_t *trace)
{
    vec3_t forward, right, up;
    float d, i;
    vec3_t into, side;

    AngleVectors(ent->v.v_angle, forward, right, up);
    d = DotProduct(trace->plane.normal, forward);

    d += 0.5;
    if (d >= 0)
	return;

// cut the tangential velocity
    i = DotProduct(trace->plane.normal, ent->v.velocity);
    VectorScale(trace->plane.normal, i, into);
    VectorSubtract(ent->v.velocity, into, side);

    ent->v.velocity[0] = side[0] * (1 + d);
    ent->v.velocity[1] = side[1] * (1 + d);
}

/*
=====================
SV_TryUnstick

Player has come to a dead stop, possibly due to the problem with limited
float precision at some angle joins in the BSP hull.

Try fixing by pushing one pixel in each direction.

This is a hack, but in the interest of good gameplay...
======================
*/
int
SV_TryUnstick(edict_t *ent, vec3_t oldvel)
{
    int i;
    vec3_t oldorg;
    vec3_t dir;
    int clip;
    trace_t steptrace;

    VectorCopy(ent->v.origin, oldorg);
    VectorCopy(vec3_origin, dir);

    for (i = 0; i < 8; i++) {
// try pushing a little in an axial direction
	switch (i) {
	case 0:
	    dir[0] = 2;
	    dir[1] = 0;
	    break;
	case 1:
	    dir[0] = 0;
	    dir[1] = 2;
	    break;
	case 2:
	    dir[0] = -2;
	    dir[1] = 0;
	    break;
	case 3:
	    dir[0] = 0;
	    dir[1] = -2;
	    break;
	case 4:
	    dir[0] = 2;
	    dir[1] = 2;
	    break;
	case 5:
	    dir[0] = -2;
	    dir[1] = 2;
	    break;
	case 6:
	    dir[0] = 2;
	    dir[1] = -2;
	    break;
	case 7:
	    dir[0] = -2;
	    dir[1] = -2;
	    break;
	}

	SV_PushEntity(ent, dir);

// retry the original move
	ent->v.velocity[0] = oldvel[0];
	ent->v.velocity[1] = oldvel[1];
	ent->v.velocity[2] = 0;
	clip = SV_FlyMove(ent, 0.1, &steptrace);

	if (fabs(oldorg[1] - ent->v.origin[1]) > 4
	    || fabs(oldorg[0] - ent->v.origin[0]) > 4) {
//Con_DPrintf ("unstuck!\n");
	    return clip;
	}
// go back to the original pos and try again
	VectorCopy(oldorg, ent->v.origin);
    }

    VectorCopy(vec3_origin, ent->v.velocity);
    return 7;			// still not moving
}

/*
=====================
SV_WalkMove

Only used by players
======================
*/
#define	STEPSIZE	18
void
SV_WalkMove(edict_t *ent)
{
    vec3_t upmove, downmove;
    vec3_t oldorg, oldvel;
    vec3_t nosteporg, nostepvel;
    int clip;
    int oldonground;
    trace_t steptrace, downtrace;

//
// do a regular slide move unless it looks like you ran into a step
//
    oldonground = (int)ent->v.flags & FL_ONGROUND;
    ent->v.flags = (int)ent->v.flags & ~FL_ONGROUND;

    VectorCopy(ent->v.origin, oldorg);
    VectorCopy(ent->v.velocity, oldvel);

    clip = SV_FlyMove(ent, host_frametime, &steptrace);

    if (!(clip & 2))
	return;			// move didn't block on a step

    if (!oldonground && ent->v.waterlevel == 0)
	return;			// don't stair up while jumping

    if (ent->v.movetype != MOVETYPE_WALK)
	return;			// gibbed by a trigger

    if (sv_nostep.value)
	return;

    if ((int)sv_player->v.flags & FL_WATERJUMP)
	return;

    VectorCopy(ent->v.origin, nosteporg);
    VectorCopy(ent->v.velocity, nostepvel);

//
// try moving up and forward to go up a step
//
    VectorCopy(oldorg, ent->v.origin);	// back to start pos

    VectorCopy(vec3_origin, upmove);
    VectorCopy(vec3_origin, downmove);
    upmove[2] = STEPSIZE;
    downmove[2] = -STEPSIZE + oldvel[2] * host_frametime;

// move up
    SV_PushEntity(ent, upmove);	// FIXME: don't link?

// move forward
    ent->v.velocity[0] = oldvel[0];
    ent->v.velocity[1] = oldvel[1];
    ent->v.velocity[2] = 0;
    clip = SV_FlyMove(ent, host_frametime, &steptrace);

// check for stuckness, possibly due to the limited precision of floats
// in the clipping hulls
    if (clip) {
	if (fabs(oldorg[1] - ent->v.origin[1]) < 0.03125 && fabs(oldorg[0] - ent->v.origin[0]) < 0.03125) {	// stepping up didn't make any progress
	    clip = SV_TryUnstick(ent, oldvel);
	}
    }
// extra friction based on view angle
    if (clip & 2)
	SV_WallFriction(ent, &steptrace);

// move down
    downtrace = SV_PushEntity(ent, downmove);	// FIXME: don't link?

    if (downtrace.plane.normal[2] > 0.7) {
	if (ent->v.solid == SOLID_BSP) {
	    ent->v.flags = (int)ent->v.flags | FL_ONGROUND;
	    ent->v.groundentity = EDICT_TO_PROG(downtrace.ent);
	}
    } else {
// if the push down didn't end up on good ground, use the move without
// the step up.  This happens near wall / slope combinations, and can
// cause the player to hop up higher on a slope too steep to climb
	VectorCopy(nosteporg, ent->v.origin);
	VectorCopy(nostepvel, ent->v.velocity);
    }
}


/*
================
SV_Physics_Client

Player character actions
================
*/
void
SV_Physics_Client(edict_t *ent, int num)
{
    if (!svs.clients[num - 1].active)
	return;			// unconnected slot

//
// call standard client pre-think
//
    pr_global_struct->time = sv.time;
    pr_global_struct->self = EDICT_TO_PROG(ent);
    PR_ExecuteProgram(pr_global_struct->PlayerPreThink);

//
// do a move
//
    SV_CheckVelocity(ent);

//
// decide which move function to call
//
    switch ((int)ent->v.movetype) {
    case MOVETYPE_NONE:
	if (!SV_RunThink(ent))
	    return;
	break;

    case MOVETYPE_WALK:
	if (!SV_RunThink(ent))
	    return;
	if (!SV_CheckWater(ent) && !((int)ent->v.flags & FL_WATERJUMP))
	    SV_AddGravity(ent);
	SV_CheckStuck(ent);
	SV_WalkMove(ent);
	break;

    case MOVETYPE_TOSS:
    case MOVETYPE_BOUNCE:
	SV_Physics_Toss(ent);
	break;

    case MOVETYPE_FLY:
	if (!SV_RunThink(ent))
	    return;
	SV_FlyMove(ent, host_frametime, NULL);
	break;

    case MOVETYPE_NOCLIP:
	if (!SV_RunThink(ent))
	    return;
	VectorMA(ent->v.origin, host_frametime, ent->v.velocity,
		 ent->v.origin);
	break;

    default:
	Sys_Error("%s: bad movetype %i", __func__, (int)ent->v.movetype);
    }

//
// call standard player post-think
//
    SV_LinkEdict(ent, true);

    pr_global_struct->time = sv.time;
    pr_global_struct->self = EDICT_TO_PROG(ent);
    PR_ExecuteProgram(pr_global_struct->PlayerPostThink);
}

//============================================================================

/*
=============
SV_Physics_None

Non moving objects can only think
=============
*/
void
SV_Physics_None(edict_t *ent)
{
// regular thinking
    SV_RunThink(ent);
}

/*
=============
SV_Physics_Noclip

A moving object that doesn't obey physics
=============
*/
void
SV_Physics_Noclip(edict_t *ent)
{
// regular thinking
    if (!SV_RunThink(ent))
	return;

    VectorMA(ent->v.angles, host_frametime, ent->v.avelocity, ent->v.angles);
    VectorMA(ent->v.origin, host_frametime, ent->v.velocity, ent->v.origin);

    SV_LinkEdict(ent, false);
}

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

TOSS / BOUNCE

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

/*
=============
SV_CheckWaterTransition

=============
*/
void
SV_CheckWaterTransition(edict_t *ent)
{
    int cont;

    cont = SV_PointContents(ent->v.origin);

    if (!ent->v.watertype) {	// just spawned here
	ent->v.watertype = cont;
	ent->v.waterlevel = 1;
	return;
    }

    if (cont <= CONTENTS_WATER) {
	if (ent->v.watertype == CONTENTS_EMPTY) {	// just crossed into water
	    SV_StartSound(ent, 0, "misc/h2ohit1.wav", 255, 1);
	}
	ent->v.watertype = cont;
	ent->v.waterlevel = 1;
    } else {
	if (ent->v.watertype != CONTENTS_EMPTY) {	// just crossed into water
	    SV_StartSound(ent, 0, "misc/h2ohit1.wav", 255, 1);
	}
	ent->v.watertype = CONTENTS_EMPTY;
	ent->v.waterlevel = cont;
    }
}

/*
=============
SV_Physics_Toss

Toss, bounce, and fly movement.  When onground, do nothing.
=============
*/
void
SV_Physics_Toss(edict_t *ent)
{
    trace_t trace;
    vec3_t move;
    float backoff;

    // regular thinking
    if (!SV_RunThink(ent))
	return;

// if onground, return without moving
    if (((int)ent->v.flags & FL_ONGROUND))
	return;

    SV_CheckVelocity(ent);

// add gravity
    if (ent->v.movetype != MOVETYPE_FLY
	&& ent->v.movetype != MOVETYPE_FLYMISSILE)
	SV_AddGravity(ent);

// move angles
    VectorMA(ent->v.angles, host_frametime, ent->v.avelocity, ent->v.angles);

// move origin
    VectorScale(ent->v.velocity, host_frametime, move);
    trace = SV_PushEntity(ent, move);
    if (trace.fraction == 1)
	return;
    if (ent->free)
	return;

    if (ent->v.movetype == MOVETYPE_BOUNCE)
	backoff = 1.5;
    else
	backoff = 1;

    ClipVelocity(ent->v.velocity, trace.plane.normal, ent->v.velocity,
		 backoff);

// stop if on ground
    if (trace.plane.normal[2] > 0.7) {
	if (ent->v.velocity[2] < 60 || ent->v.movetype != MOVETYPE_BOUNCE) {
	    ent->v.flags = (int)ent->v.flags | FL_ONGROUND;
	    ent->v.groundentity = EDICT_TO_PROG(trace.ent);
	    VectorCopy(vec3_origin, ent->v.velocity);
	    VectorCopy(vec3_origin, ent->v.avelocity);
	}
    }
// check for in water
    SV_CheckWaterTransition(ent);
}

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

STEPPING MOVEMENT

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

/*
=============
SV_Physics_Step

Monsters freefall when they don't have a ground entity, otherwise
all movement is done with discrete steps.

This is also used for objects that have become still on the ground, but
will fall if the floor is pulled out from under them.
=============
*/
void
SV_Physics_Step(edict_t *ent)
{
    qboolean hitsound;

    // freefall if not onground
    if (!((int)ent->v.flags & (FL_ONGROUND | FL_FLY | FL_SWIM))) {
	if (ent->v.velocity[2] < sv_gravity.value * -0.1)
	    hitsound = true;
	else
	    hitsound = false;

	SV_AddGravity(ent);
	SV_CheckVelocity(ent);
	SV_FlyMove(ent, host_frametime, NULL);
	SV_LinkEdict(ent, true);

	if ((int)ent->v.flags & FL_ONGROUND) {
	    // just hit ground
	    if (hitsound)
		SV_StartSound(ent, 0, "demon/dland2.wav", 255, 1);
	}
    }

    SV_RunThink(ent); // regular thinking
    SV_CheckWaterTransition(ent);
}

//============================================================================

/*
================
SV_Physics

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

    // let the progs know that a new frame has started
    pr_global_struct->self = EDICT_TO_PROG(sv.edicts);
    pr_global_struct->other = EDICT_TO_PROG(sv.edicts);
    pr_global_struct->time = sv.time;
    PR_ExecuteProgram(pr_global_struct->StartFrame);

    //SV_CheckAllEnts ();

    //
    // treat each object in turn
    //
    ent = sv.edicts;
    for (i = 0; i < sv.num_edicts; i++, ent = NEXT_EDICT(ent)) {
	if (ent->free)
	    continue;

	if (pr_global_struct->force_retouch) {
	    SV_LinkEdict(ent, true);	// force retouch even for stationary
	}

	if (i > 0 && i <= svs.maxclients)
	    SV_Physics_Client(ent, i);
	else if (ent->v.movetype == MOVETYPE_PUSH)
	    SV_Physics_Pusher(ent);
	else if (ent->v.movetype == MOVETYPE_NONE)
	    SV_Physics_None(ent);
	else if (ent->v.movetype == MOVETYPE_NOCLIP)
	    SV_Physics_Noclip(ent);
	else if (ent->v.movetype == MOVETYPE_STEP)
	    SV_Physics_Step(ent);
	else if (ent->v.movetype == MOVETYPE_TOSS
		 || ent->v.movetype == MOVETYPE_BOUNCE
		 || ent->v.movetype == MOVETYPE_FLY
		 || ent->v.movetype == MOVETYPE_FLYMISSILE)
	    SV_Physics_Toss(ent);
	else
	    Sys_Error("%s: bad movetype %i", __func__, (int)ent->v.movetype);
    }

    if (pr_global_struct->force_retouch)
	pr_global_struct->force_retouch--;

    sv.time += host_frametime;
}
