/*
Copyright (C) 1997-2001 Id Software, Inc.

This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.

*/
#include "../g_local.h"

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

PLAYER TRAIL

==============================================================================

This is a circular list containing the a list of points of where
the player has been recently.  It is used by monsters for pursuit.

.origin		the spot
.owner		forward link
.aiment		backward link
*/

#define TRAIL_LENGTH 8

edict_t *trail[TRAIL_LENGTH];
int trail_head;
bool trail_active = false;

#define NEXT(n) (((n) + 1) & (TRAIL_LENGTH - 1))
#define PREV(n) (((n)-1) & (TRAIL_LENGTH - 1))

void PlayerTrail_Init(void) {
  int n;

  if(deathmatch->value /* FIXME || coop */)
    return;

  for(n = 0; n < TRAIL_LENGTH; n++) {
    trail[n] = G_Spawn(0);
    trail[n]->classname = "player_trail";
  }

  trail_head = 0;
  trail_active = true;
}

void PlayerTrail_Add(vec3_t spot) {
  vec3_t temp;

  if(!trail_active)
    return;

  VectorCopy(spot, trail[trail_head]->s.origin);

  trail[trail_head]->timestamp = level.time;

  VectorSubtract(spot, trail[PREV(trail_head)]->s.origin, temp);
  trail[trail_head]->s.angles[1] = vectoyaw(temp);

  trail_head = NEXT(trail_head);
}

void PlayerTrail_New(vec3_t spot) {
  if(!trail_active)
    return;

  PlayerTrail_Init();
  PlayerTrail_Add(spot);
}

edict_t *PlayerTrail_PickFirst(edict_t *self) {
  int marker;
  int n;

  if(!trail_active)
    return NULL;

  for(marker = trail_head, n = TRAIL_LENGTH; n; n--) {
    if(trail[marker]->timestamp <= self->monsterinfo.trail_time)
      marker = NEXT(marker);
    else
      break;
  }

  if(visible(self, trail[marker])) {
    return trail[marker];
  }

  if(visible(self, trail[PREV(marker)])) {
    return trail[PREV(marker)];
  }

  return trail[marker];
}

edict_t *PlayerTrail_PickNext(edict_t *self) {
  int marker;
  int n;

  if(!trail_active)
    return NULL;

  for(marker = trail_head, n = TRAIL_LENGTH; n; n--) {
    if(trail[marker]->timestamp <= self->monsterinfo.trail_time)
      marker = NEXT(marker);
    else
      break;
  }

  return trail[marker];
}

edict_t *PlayerTrail_LastSpot(void) { return trail[PREV(trail_head)]; }