/*
    CrossFire, A Multiplayer game for X-windows

    Copyright (C) 2002 Mark Wedel & Crossfire Development Team
    Copyright (C) 1992 Frank Tore Johansen

    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., 675 Mass Ave, Cambridge, MA 02139, USA.

    The authors can be reached via e-mail at <crossfire@schmorp.de>
*/

#include <global.h>
#include <funcpoint.h>

/*
 * This code is no longer highly inefficient 8)
 */

/*
 * elmex:
 * This function takes a objectlink list with all the objects are going to be activated.
 * state is a true/false flag that will actiavte objects that have FLAG_ACTIVATE_ON_PUSH/RELEASE set.
 * The source argument can be 0 or the source object for this activation.
 */
void
activate_connection_link (objectlink * ol, bool state, object *source = 0)
{
  for (; ol; ol = ol->next)
    {
      if (!ol->ob)
        {
          LOG (llevError, "Internal error in activate_connection_link.\n");
          continue;
        }

      /* a button link object can become freed when the map is saving.  As
       * a map is saved, objects are removed and freed, and if an object is
       * on top of a button, this function is eventually called.  If a map
       * is getting moved out of memory, the status of buttons and levers
       * probably isn't important - it will get sorted out when the map is
       * re-loaded.  As such, just exit this function if that is the case.
       */

      if (QUERY_FLAG (ol->ob, FLAG_FREED))
        return;

      object *tmp = ol->ob;

      /* if the criteria isn't appropriate, don't do anything */
      if (state && !QUERY_FLAG (tmp, FLAG_ACTIVATE_ON_PUSH))
        continue;
      if (!state && !QUERY_FLAG (tmp, FLAG_ACTIVATE_ON_RELEASE))
        continue;

      switch (tmp->type)
        {
          case GATE:
          case HOLE:
            tmp->value = tmp->stats.maxsp ? !state : state;
            tmp->set_speed (0.5);
            break;

          case CF_HANDLE:
            SET_ANIMATION (tmp, (tmp->value = tmp->stats.maxsp ? !state : state));
            update_object (tmp, UP_OBJ_FACE);
            break;

          case SIGN:
            if (!tmp->stats.food || tmp->last_eat < tmp->stats.food)
              {
                new_info_map (NDI_UNIQUE | NDI_NAVY, tmp->map, tmp->msg);
                if (tmp->stats.food)
                  tmp->last_eat++;
              }
            break;

          case ALTAR:
            tmp->value = 1;
            SET_ANIMATION (tmp, tmp->value);
            update_object (tmp, UP_OBJ_FACE);
            break;

          case BUTTON:
          case PEDESTAL:
            tmp->value = state;
            SET_ANIMATION (tmp, tmp->value);
            update_object (tmp, UP_OBJ_FACE);
            break;

          case MOOD_FLOOR:
            do_mood_floor (tmp, source);
            break;

          case TIMED_GATE:
            tmp->set_speed (tmp->arch->clone.speed);
            tmp->value = tmp->arch->clone.value;
            tmp->stats.sp = 1;
            tmp->stats.hp = tmp->stats.maxhp;
            /* Handle multipart gates.  We copy the value for the other parts
             * from the head - this ensures that the data will consistent
             */
            for (tmp = tmp->more; tmp; tmp = tmp->more)
              {
                tmp->value = tmp->head->value;
                tmp->stats.sp = tmp->head->stats.sp;
                tmp->stats.hp = tmp->head->stats.hp;
                tmp->set_speed (tmp->head->speed);
              }
            break;

          case DIRECTOR:
          case FIREWALL:
            if (!QUERY_FLAG (tmp, FLAG_ANIMATE) && tmp->type == FIREWALL)
              move_firewall (tmp);
            else
              {
                if ((tmp->stats.sp += tmp->stats.maxsp) > 8)  /* next direction */
                  tmp->stats.sp = ((tmp->stats.sp - 1) % 8) + 1;
                animate_turning (tmp);
              }
            break;

          case TELEPORTER:
            move_teleporter (tmp);
            break;

          case CREATOR:
            move_creator (tmp);
            break;

          case TRIGGER_MARKER:
            move_marker (tmp);
            break;

          case DUPLICATOR:
            move_duplicator (tmp);
            break;
        }
    }
}

/*
 * elmex:
 * This is the new push_button function, it got split up so that
 * you can activate connections without a button now!
 * old but still valid comment:
 *
 * Push the specified object.  This can affect other buttons/gates/handles
 * altars/pedestals/holes in the whole map.
 * Changed the routine to loop through _all_ objects.
 * Better hurry with that linked list...
 *
 */
void
push_button (object *op)
{
  oblinkpt *obp = get_button_links (op);

  if (!obp)
    return;

  if (INVOKE_MAP (TRIGGER, op->map, ARG_INT64 (obp->value), ARG_INT (op->value)))
    return;

  activate_connection_link (obp->link, op->value, op);
}

/*
 * elmex:
 * This activates a connection, similar to push_button (object *op) but it takes
 * only a map, a connection value and a true or false flag that indicated whether
 * the connection was 'state' or 'released'. So that you can activate objects
 * who have FLAG_ACTIVATE_ON_PUSH/RELEASE set properly.
 *
 */
void
activate_connection (maptile *map, long connection, bool state)
{
  if (INVOKE_MAP (TRIGGER, map, ARG_INT64 (connection), ARG_INT (state)))
    return;

  oblinkpt *obp = get_connection_links (map, connection);

  if (obp)
    activate_connection_link (obp->link, state);
}

/*
 * Updates everything connected with the button op.
 * After changing the state of a button, this function must be called
 * to make sure that all gates and other buttons connected to the
 * button reacts to the (eventual) change of state.
 */
void
update_button (object *op)
{
  object *ab, *tmp, *head;
  int tot, any_down = 0, old_value = op->value;
  oblinkpt *obp = 0;
  objectlink *ol;

  obp = get_button_links (op);
  /* LOG(llevDebug, "update_button: %s (%d)\n", op->name, op->count); */
  if (obp)
    for (ol = obp->link; ol; ol = ol->next)
      {
        if (!ol->ob)
          {
            LOG (llevDebug, "Internal error in update_button (%s).\n", &op->name);
            continue;
          }

        tmp = ol->ob;
        if (tmp->type == BUTTON)
          {
            for (ab = tmp->above, tot = 0; ab != NULL; ab = ab->above)
              /* Bug? The pedestal code below looks for the head of
               * the object, this bit doesn't.  I'd think we should check
               * for head here also.  Maybe it also makese sense to 
               * make the for ab=tmp->above loop common, and alter
               * behaviour based on object within that loop?
               */

              /* Basically, if the move_type matches that on what the
               * button wants, we count it.  The second check is so that
               * objects don't move (swords, etc) will count.  Note that
               * this means that more work is needed to make buttons
               * that are only triggered by flying objects.
               */
              if ((ab->move_type & tmp->move_on) || ab->move_type == 0)
                tot += ab->weight * (ab->nrof ? ab->nrof : 1) + ab->carrying;

            tmp->value = (tot >= tmp->weight) ? 1 : 0;
            if (tmp->value)
              any_down = 1;
          }
        else if (tmp->type == PEDESTAL)
          {
            tmp->value = 0;
            for (ab = tmp->above; ab != NULL; ab = ab->above)
              {
                head = ab->head ? ab->head : ab;
                /* Same note regarding move_type for buttons above apply here. */
                if (((head->move_type & tmp->move_on) || ab->move_type == 0) &&
                    (head->race == tmp->slaying ||
                     ((head->type == SPECIAL_KEY) && (head->slaying == tmp->slaying)) ||
                     (!strcmp (tmp->slaying, "player") && head->type == PLAYER)))
                  tmp->value = 1;
              }
            if (tmp->value)
              any_down = 1;
          }
      }
  if (any_down)                 /* If any other buttons were down, force this to remain down */
    op->value = 1;

  /* If this button hasn't changed, don't do anything */
  if (op->value != old_value)
    {
      SET_ANIMATION (op, op->value);
      update_object (op, UP_OBJ_FACE);
      push_button (op);         /* Make all other buttons the same */
    }
}

/*
 * Updates every button on the map (by calling update_button() for them).
 */

void
update_buttons (maptile *m)
{
  objectlink *ol;
  oblinkpt *obp;

  for (obp = m->buttons; obp; obp = obp->next)
    for (ol = obp->link; ol; ol = ol->next)
      {
        if (!ol->ob)
          {
            LOG (llevError, "Internal error in update_button (%s (%dx%d), connected %ld).\n",
                 ol->ob ? (const char *) ol->ob->name : "null", ol->ob ? ol->ob->x : -1, ol->ob ? ol->ob->y : -1, obp->value);
            continue;
          }

        if (ol->ob->type == BUTTON || ol->ob->type == PEDESTAL)
          {
            update_button (ol->ob);
            break;
          }
      }
}

void
use_trigger (object *op)
{

  /* Toggle value */
  op->value = !op->value;
  push_button (op);
}

/*
 * Note: animate_object should be used instead of this,
 * but it can't handle animations in the 8 directions
 */

void
animate_turning (object *op)    /* only one part objects */
{
  if (++op->state >= NUM_ANIMATIONS (op) / 8)
    op->state = 0;
  SET_ANIMATION (op, (op->stats.sp - 1) * NUM_ANIMATIONS (op) / 8 + op->state);
  update_object (op, UP_OBJ_FACE);
}

#define ARCH_SACRIFICE(xyz) ((xyz)->slaying)
#define NROF_SACRIFICE(xyz) ((uint32)(xyz)->stats.food)

/* Returns true if the sacrifice meets the needs of the altar.
 *
 * Function put in (0.92.1) so that identify altars won't grab money
 * unnecessarily - we can see if there is sufficient money, see if something
 * needs to be identified, and then remove money if needed.
 *
 * 0.93.4: Linked objects (ie, objects that are connected) can not be
 * sacrificed.  This fixes a bug of trying to put multiple altars/related
 * objects on the same space that take the same sacrifice.
 */

int
check_altar_sacrifice (const object *altar, const object *sacrifice)
{
  if (!QUERY_FLAG (sacrifice, FLAG_ALIVE) && !QUERY_FLAG (sacrifice, FLAG_IS_LINKED) && sacrifice->type != PLAYER)
    {
      if ((ARCH_SACRIFICE (altar) == sacrifice->arch->name ||
           ARCH_SACRIFICE (altar) == sacrifice->name ||
           ARCH_SACRIFICE (altar) == sacrifice->slaying ||
           (!strcmp (ARCH_SACRIFICE (altar), query_base_name (sacrifice, 0))))
          && NROF_SACRIFICE (altar) <= (sacrifice->nrof ? sacrifice->nrof : 1))
        return 1;

      if (strcmp (ARCH_SACRIFICE (altar), "money") == 0
          && sacrifice->type == MONEY && sacrifice->nrof * sacrifice->value >= NROF_SACRIFICE (altar))
        return 1;
    }

  return 0;
}

/*
 * operate_altar checks if sacrifice was accepted and removes sacrificed
 * objects.  If sacrifice was succeed return 1 else 0.  Might be better to
 * call check_altar_sacrifice (above) than depend on the return value,
 * since operate_altar will remove the sacrifice also.
 *
 * If this function returns 1, '*sacrifice' is modified to point to the
 * remaining sacrifice, or is set to NULL if the sacrifice was used up.
 */
int
operate_altar (object *altar, object **sacrifice)
{
  if (!altar->map)
    {
      LOG (llevError, "BUG: operate_altar(): altar has no map\n");
      return 0;
    }

  if (!altar->slaying || altar->value)
    return 0;

  if (!check_altar_sacrifice (altar, *sacrifice))
    return 0;

  /* check_altar_sacrifice should have already verified that enough money
   * has been dropped.
   */
  if (!strcmp (ARCH_SACRIFICE (altar), "money"))
    {
      int number = NROF_SACRIFICE (altar) / (*sacrifice)->value;

      /* Round up any sacrifices.  Altars don't make change either */
      if (NROF_SACRIFICE (altar) % (*sacrifice)->value)
        number++;

      *sacrifice = decrease_ob_nr (*sacrifice, number);
    }
  else
    *sacrifice = decrease_ob_nr (*sacrifice, NROF_SACRIFICE (altar));

  if (altar->msg)
    new_info_map (NDI_BLACK, altar->map, altar->msg);

  return 1;
}

void
trigger_move (object *op, int state)    /* 1 down and 0 up */
{
  op->stats.wc = state;
  if (state)
    {
      use_trigger (op);
      op->set_speed (op->stats.exp > 0 ? 1. / op->stats.exp : 1.);
      op->speed_left = -1;
    }
  else
    {
      use_trigger (op);
      op->set_speed (0);
    }
}


/*
 * cause != NULL: something has moved on top of op
 *
 * cause == NULL: nothing has moved, we have been called from
 * animate_trigger().
 *
 * TRIGGER_ALTAR: Returns 1 if 'cause' was destroyed, 0 if not.
 *
 * TRIGGER: Returns 1 if handle could be moved, 0 if not.
 *
 * TRIGGER_BUTTON, TRIGGER_PEDESTAL: Returns 0.
 */
int
check_trigger (object *op, object *cause)
{
  object *tmp;
  int push = 0, tot = 0;
  int in_movement = op->stats.wc || op->speed;

  switch (op->type)
    {
        case TRIGGER_BUTTON:
          if (op->weight > 0)
            {
              if (cause)
                {
                  for (tmp = op->above; tmp; tmp = tmp->above)
                    /* Comment reproduced from update_buttons(): */
                    /* Basically, if the move_type matches that on what the
                     * button wants, we count it.  The second check is so that
                     * objects that don't move (swords, etc) will count.  Note that
                     * this means that more work is needed to make buttons
                     * that are only triggered by flying objects.
                     */

                    if ((tmp->move_type & op->move_on) || tmp->move_type == 0)
                      {
                        tot += tmp->weight * (tmp->nrof ? tmp->nrof : 1) + tmp->carrying;
                      }
                  if (tot >= op->weight)
                    push = 1;
                  if (op->stats.ac == push)
                    return 0;
                  op->stats.ac = push;
                  if (NUM_ANIMATIONS (op) > 1)
                    {
                      SET_ANIMATION (op, push);
                      update_object (op, UP_OBJ_FACE);
                    }
                  if (in_movement || !push)
                    return 0;
                }
              trigger_move (op, push);
            }
          return 0;

        case TRIGGER_PEDESTAL:
          if (cause)
            {
              for (tmp = op->above; tmp; tmp = tmp->above)
                {
                  object *head = tmp->head ? tmp->head : tmp;

                  /* See comment in TRIGGER_BUTTON about move_types */
                  if (((head->move_type & op->move_on) || head->move_type == 0)
                      && (head->race == op->slaying || (!strcmp (op->slaying, "player") && head->type == PLAYER)))
                    {
                      push = 1;
                      break;
                    }
                }
              if (op->stats.ac == push)
                return 0;
              op->stats.ac = push;
              if (NUM_ANIMATIONS (op) > 1)
                {
                  SET_ANIMATION (op, push);
                  update_object (op, UP_OBJ_FACE);
                }
              update_object (op, UP_OBJ_FACE);
              if (in_movement || !push)
                return 0;
            }
          trigger_move (op, push);
          return 0;

        case TRIGGER_ALTAR:
          if (cause)
            {
              if (in_movement)
                return 0;
              if (operate_altar (op, &cause))
                {
                  if (NUM_ANIMATIONS (op) > 1)
                    {
                      SET_ANIMATION (op, 1);
                      update_object (op, UP_OBJ_FACE);
                    }
                  if (op->last_sp >= 0)
                    {
                      trigger_move (op, 1);
                      if (op->last_sp > 0)
                        op->last_sp = -op->last_sp;
                    }
                  else
                    {
                      /* for trigger altar with last_sp, the ON/OFF
                       * status (-> +/- value) is "simulated": 
                       */
                      op->value = !op->value;
                      trigger_move (op, 1);
                      op->last_sp = -op->last_sp;
                      op->value = !op->value;
                    }
                  return cause == NULL;
                }
              else
                {
                  return 0;
                }
            }
          else
            {
              if (NUM_ANIMATIONS (op) > 1)
                {
                  SET_ANIMATION (op, 0);
                  update_object (op, UP_OBJ_FACE);
                }

              /* If trigger_altar has "last_sp > 0" set on the map,
               * it will push the connected value only once per sacrifice.
               * Otherwise (default), the connected value will be
               * pushed twice: First by sacrifice, second by reset! -AV 
               */
              if (!op->last_sp)
                trigger_move (op, 0);
              else
                {
                  op->stats.wc = 0;
                  op->value = !op->value;
                  op->set_speed (0);
                }
            }
          return 0;

        case TRIGGER:
          if (cause)
            {
              if (in_movement)
                return 0;

              push = 1;
            }

          if (NUM_ANIMATIONS (op) > 1)
            {
              SET_ANIMATION (op, push);
              update_object (op, UP_OBJ_FACE);
            }

          trigger_move (op, push);
          return 1;

        default:
          LOG (llevDebug, "Unknown trigger type: %s (%d)\n", &op->name, op->type);
          return 0;
    }
}

void
add_button_link (object *button, maptile *map, int connected)
{
  oblinkpt *obp;
  objectlink *ol = get_objectlink ();

  if (!map)
    {
      LOG (llevError, "Tried to add button-link without map.\n");
      return;
    }

  button->path_attuned = connected;   /* peterm:  I need this so I can rebuild 
                                         a connected map from a template map. */

  SET_FLAG (button, FLAG_IS_LINKED);

  ol->ob = button;

  for (obp = map->buttons; obp && obp->value != connected; obp = obp->next)
    ;

  if (obp)
    {
      ol->next = obp->link;
      obp->link = ol;
    }
  else
    {
      obp = get_objectlinkpt ();
      obp->value = connected;

      obp->next = map->buttons;
      map->buttons = obp;
      obp->link = ol;
    }
}

/*
 * Remove the object from the linked lists of buttons in the map.
 * This is only needed by editors.
 */

void
remove_button_link (object *op)
{
  oblinkpt *obp;
  objectlink **olp, *ol;

  if (op->map == NULL)
    {
      LOG (llevError, "remove_button_link() in object without map.\n");
      return;
    }

  if (!QUERY_FLAG (op, FLAG_IS_LINKED))
    {
      LOG (llevError, "remove_button_linked() in unlinked object.\n");
      return;
    }

  for (obp = op->map->buttons; obp; obp = obp->next)
    for (olp = &obp->link; (ol = *olp); olp = &ol->next)
      if (ol->ob == op)
        {

/*        LOG(llevDebug, "Removed link %d in button %s and map %s.\n",
           obp->value, op->name, op->map->path);
*/
          *olp = ol->next;
          delete ol;
          return;
        }

  LOG (llevError, "remove_button_linked(): couldn't find object.\n");
  CLEAR_FLAG (op, FLAG_IS_LINKED);
}

/*
 * Gets the objectlink for this connection from the map.
 */
oblinkpt *
get_connection_links (maptile *map, long connection)
{
  for (oblinkpt * obp = map->buttons; obp; obp = obp->next)
    if (obp->value == connection)
      return obp;

  return 0;
}

/*
 * Return the first objectlink in the objects linked to this one
 */

oblinkpt *
get_button_links (const object *button)
{
  oblinkpt *obp;
  objectlink *ol;

  if (!button->map)
    return NULL;

  for (obp = button->map->buttons; obp; obp = obp->next)
    for (ol = obp->link; ol; ol = ol->next)
      if (ol->ob == button)
        return obp;

  return NULL;
}

/*
 * Made as a separate function to increase efficiency
 */

int
get_button_value (const object *button)
{
  oblinkpt *obp;
  objectlink *ol;

  if (!button->map)
    return 0;
  for (obp = button->map->buttons; obp; obp = obp->next)
    for (ol = obp->link; ol; ol = ol->next)
      if (ol->ob == button)
        return obp->value;
  return 0;
}

/* This routine makes monsters who are  
 * standing on the 'mood floor' change their
 * disposition if it is different.  
 * If floor is to be triggered must have
 * a speed of zero (default is 1 for all
 * but the charm floor type).
 * by b.t. thomas@nomad.astro.psu.edu
 */

void
do_mood_floor (object *op, object *source)
{
  object *tmp;
  object *tmp2;

  if (!source)
    source = op;

  for (tmp = GET_MAP_OB (op->map, op->x, op->y); tmp; tmp = tmp->above)
    if (QUERY_FLAG (tmp, FLAG_MONSTER))
      break;

  /* doesn't effect players, and if there is a player on this space, won't also
   * be a monster here.
   */
  if (!tmp || tmp->type == PLAYER)
    return;

  switch (op->last_sp)
    {
      case 0:                /* furious--make all monsters mad */
        if (QUERY_FLAG (tmp, FLAG_UNAGGRESSIVE))
          CLEAR_FLAG (tmp, FLAG_UNAGGRESSIVE);
        if (QUERY_FLAG (tmp, FLAG_FRIENDLY))
          {
            CLEAR_FLAG (tmp, FLAG_FRIENDLY);
            remove_friendly_object (tmp);
            tmp->attack_movement = 0;
            /* lots of checks here, but want to make sure we don't
             * dereference a null value
             */
            if (tmp->type == GOLEM && tmp->owner && tmp->owner->type == PLAYER && tmp->owner->contr->ranges[range_golem] == tmp)
              tmp->owner->contr->ranges[range_golem] = 0;

            tmp->owner = 0;
          }
        break;
      case 1:                /* angry -- get neutral monsters mad */
        if (QUERY_FLAG (tmp, FLAG_UNAGGRESSIVE) && !QUERY_FLAG (tmp, FLAG_FRIENDLY))
          CLEAR_FLAG (tmp, FLAG_UNAGGRESSIVE);
        break;
      case 2:                /* calm -- pacify unfriendly monsters */
        if (!QUERY_FLAG (tmp, FLAG_UNAGGRESSIVE))
          SET_FLAG (tmp, FLAG_UNAGGRESSIVE);
        break;
      case 3:                /* make all monsters fall asleep */
        if (!QUERY_FLAG (tmp, FLAG_SLEEP))
          SET_FLAG (tmp, FLAG_SLEEP);
        break;
      case 4:                /* charm all monsters */
        if (op == source)
          break;              /* only if 'connected' */

        for (tmp2 = GET_MAP_OB (source->map, source->x, source->y);   /* finding an owner */
             tmp2->type != PLAYER; tmp2 = tmp2->above)
          if (tmp2->above == NULL)
            break;

        if (tmp2->type != PLAYER)
          break;

        tmp->set_owner (tmp2);
        SET_FLAG (tmp, FLAG_MONSTER);

        tmp->stats.exp = 0;
        SET_FLAG (tmp, FLAG_FRIENDLY);

        add_friendly_object (tmp);
        tmp->attack_movement = PETMOVE;
        break;

      default:
        break;
    }
}

/* this function returns the object it matches, or NULL if non.
 * It will descend through containers to find the object.
 *		slaying = match object slaying flag
 * 		race = match object archetype name flag
 *		hp = match object type (excpt type '0'== PLAYER)
 */
object *
check_inv_recursive (object *op, const object *trig)
{
  object *tmp, *ret = NULL;

  /* First check the object itself. */
  if ((trig->stats.hp && (op->type == trig->stats.hp))
      || (trig->slaying && (op->slaying == trig->slaying))
      || (trig->race && (op->arch->name == trig->race)))
    return op;

  for (tmp = op->inv; tmp; tmp = tmp->below)
    {
      if (tmp->inv)
        {
          ret = check_inv_recursive (tmp, trig);
          if (ret)
            return ret;
        }
      else if ((trig->stats.hp && (tmp->type == trig->stats.hp))
               || (trig->slaying && (tmp->slaying == trig->slaying))
               || (trig->race && (tmp->arch->name == trig->race)))
        return tmp;
    }
  return NULL;
}

/* check_inv(), a function to search the inventory, 
 * of a player and then based on a set of conditions,
 * the square will activate connected items. 
 * Monsters can't trigger this square (for now)
 * Values are:	last_sp = 1/0 obj/no obj triggers 
 * 		last_heal = 1/0  remove/dont remove obj if triggered
 * -b.t. (thomas@nomad.astro.psu.edu 
 *
 * Tue Dec 19 15:34:00 CET 2006 elmex: changed the function to ignore op
 * because the check-inventory semantic essentially only applies when
 * something is above the inventory checker.
 * The semantic prior this change was: trigger if something has moved on or off
 *    and has a matching item. Imagine what happens if someone steps on the inventory
 *    checker with a matching item, has it, activates the connection, throws the item
 *    away, and then leaves the inventory checker. That would've caused an always-enabled
 *    state in the inventory checker. This won't happen anymore now.
 *
 */
void
check_inv (object *op, object *trig)
{
  trig->value = 0; // deactivate if none of the following conditions apply

  if (object *pl = trig->ms ().player ())
    {
      object *match = check_inv_recursive (pl, trig);

      if (match && trig->last_sp) // match == having
        {
          if (trig->last_heal)
            decrease_ob (match);

          trig->value = 1;
        }
      else if (!match && !trig->last_sp) // match == not having
        trig->value = 1;
    }

  push_button (trig);
}