/*
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"

/*


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_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] > 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;
   float oldframe; //johnfitz
   int      i; //johnfitz

   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.

   oldframe = ent->v.frame; //johnfitz

   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);

//johnfitz -- PROTOCOL_FITZQUAKE
//capture interval to nextthink here and send it to client for better
//lerp timing, but only if interval is not 0.1 (which client assumes)
   ent->sendinterval = false;
   if (!ent->free && ent->v.nextthink && (ent->v.movetype == MOVETYPE_STEP || ent->v.frame != oldframe))
   {
      i = Q_rint((ent->v.nextthink-thinktime)*255);
      if (i >= 0 && i < 256 && i != 25 && i != 26) //25 and 26 are close enough to 0.1 to not send
         ent->sendinterval = true;
   }
//johnfitz

   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 * 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;
}              

trace_t SV_TraceBox(vec3_t start, vec3_t mins, vec3_t maxs, vec3_t end, int type, edict_t *passedict, int hitsupercontentsmask) /* FS: Needed for Nehahra, from DarkPlaces, tweaked for QDOS */
{
	trace_t trace;
//	vec3_t temp;
	trace = SV_Move(start, mins, maxs, end, type, passedict);
	if (passedict)
	{
//		VectorCopy(trace.endpos, temp);
	}
	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; //johnfitz -- dynamically allocate
   vec3_t      *moved_from; //johnfitz -- dynamically allocate
   int         mark; //johnfitz

   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);

   //johnfitz -- dynamically allocate
   mark = Hunk_LowMark ();
   moved_edict = Hunk_Alloc (sv.num_edicts*sizeof(edict_t *));
   moved_from = Hunk_Alloc (sv.num_edicts*sizeof(vec3_t));
   //johnfitz

// 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);
         }
         Hunk_FreeToLowMark (mark); //johnfitz
         return;
      }  
   }

   Hunk_FreeToLowMark (mark); //johnfitz

}

/*
================
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)
   {
         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(DEVELOPER_MSG_SERVER, "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(DEVELOPER_MSG_SERVER, "Unstuck.\n");
               SV_LinkEdict (ent, true);
               return;
            }
         }
         
   VectorCopy (org, ent->v.origin);
   Con_DPrintf(DEVELOPER_MSG_SERVER, "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(DEVELOPER_MSG_SERVER, "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 ("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_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);
      }
   }

// 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_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 ("SV_Physics: bad movetype %i", (int)ent->v.movetype);        
   }
   
   if (pr_global_struct->force_retouch)
      pr_global_struct->force_retouch--;  

   sv.time += host_frametime;
}
