/*
  Copyright (C) 2010-2011  Charles Pence <charles@charlespence.net>
  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 3 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, see <http://www.gnu.org/licenses/>.
*/
#include "pch.h"
#include "quakedef.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.

*/

#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_FOLLOW
        || 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;
    float max = Cvar_VariableValue("sv_maxvelocity");

//
// 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_strings + 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_strings + ent->v.classname);
            ent->v.origin[i] = 0;
        }
        if (ent->v.velocity[i] > max)
            ent->v.velocity[i] = max;
        else if (ent->v.velocity[i] < -max)
            ent->v.velocity[i] = -max;
    }
}

/*
=============
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 ("SV_FlyMove: !trace.ent");

        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 * Cvar_VariableValue("sv_gravity") * 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_FOLLOW
        || 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_PushRotate

============
*/
void SV_PushRotate (edict_t *pusher, float movetime)
{
    int            i, e;
    edict_t        *check, *block;
    vec3_t        move, a, amove;
    vec3_t        entorig, pushorig;
    int            num_moved;
    edict_t        *moved_edict[MAX_EDICTS];
    vec3_t        moved_from[MAX_EDICTS];
    vec3_t        org, org2;
    vec3_t        forward, right, up;

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

    for (i=0 ; i<3 ; i++)
        amove[i] = pusher->v.avelocity[i] * movetime;

    VectorSubtract (vec3_origin, amove, a);
    AngleVectors (a, forward, right, up);

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

// move the pusher to it's final position

    VectorAdd (pusher->v.angles, amove, pusher->v.angles);
    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_FOLLOW
        || 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] >= pusher->v.absmax[0]
            || check->v.absmin[1] >= pusher->v.absmax[1]
            || check->v.absmin[2] >= pusher->v.absmax[2]
            || check->v.absmax[0] <= pusher->v.absmin[0]
            || check->v.absmax[1] <= pusher->v.absmin[1]
            || check->v.absmax[2] <= pusher->v.absmin[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++;

        // calculate destination position
        VectorSubtract (check->v.origin, pusher->v.origin, org);
        org2[0] = DotProduct (org, forward);
        org2[1] = -DotProduct (org, right);
        org2[2] = DotProduct (org, up);
        VectorSubtract (org2, org, move);

        // 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.angles);
            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);
                VectorSubtract (moved_edict[i]->v.angles, amove, moved_edict[i]->v.angles);
                SV_LinkEdict (moved_edict[i], false);
            }
            return;
        }
        else
        {
            VectorAdd (check->v.angles, amove, check->v.angles);
        }
    }
}

/*
================
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)
    {
        if (ent->v.solid == SOLID_BSP && (ent->v.avelocity[0] || ent->v.avelocity[1] || ent->v.avelocity[2]))
            SV_PushRotate (ent, movetime);
        else
            SV_PushMove (ent, movetime);    // advances ent->v.ltime if not blocked
    }

    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 (Cvar_VariableValue("sv_nostep"))
        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 ("SV_Physics_client: bad movetype %i", (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_Follow

Entities that are "stuck" to another entity
=============
*/
void SV_Physics_Follow (edict_t *ent)
{
// regular thinking
    SV_RunThink (ent);
    VectorAdd (PROG_TO_EDICT(ent->v.aiment)->v.origin, ent->v.v_angle, ent->v.origin);
    SV_LinkEdict (ent, true);
}

/*
=============
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;
    vec3_t    point;

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

    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 if (ent->v.movetype == MOVETYPE_BOUNCEMISSILE)
        backoff = 2.0;
    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.movetype != MOVETYPE_BOUNCEMISSILE))
        {
            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] < Cvar_VariableValue("sv_gravity") * -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);
        }
    }

// regular thinking
    SV_RunThink (ent);

    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_FOLLOW)
            SV_Physics_Follow (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_BOUNCEMISSILE
        || ent->v.movetype == MOVETYPE_FLY
        || ent->v.movetype == MOVETYPE_FLYMISSILE)
            SV_Physics_Toss (ent);
        else
            Sys_Error ("SV_Physics: bad movetype %i", (int)ent->v.movetype);
    }

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

    sv.time += host_frametime;
}
