#include <stdio.h>

#include "copyright.h"
#include "config.h"
#include "db.h"
#include "externs.h"
#include "params.h"
#include "lru.h"

#ifdef USE_DBP

static dbref head = NOTHING;
static dbref tail = NOTHING;
static int listlen = 0;

int lru_count(void)
{
   return listlen;
}

void lru_use(dbref key)
{
   dbref tmp, scout;

   if (head == NOTHING)
   {
      head = tail = key;
      listlen++;
      DBSTORE(key, lru_next, NOTHING);
      return;
   }

   if (head == key)
      return;

   for (tmp = head; tmp != NOTHING; tmp = DBFETCH(tmp)->lru_next)
   {
      scout = DBFETCH(tmp)->lru_next;
      if (scout == key)
      {
         DBSTORE(tmp, lru_next, DBFETCH(scout)->lru_next);
         DBSTORE(scout, lru_next, head);
         head = scout;
         if (tail == scout)
            tail = tmp;
      }
   }

   if (head != key)
   {
      DBSTORE(key, lru_next, head);
      head = key;
      listlen++;
   }
}

dbref lru_old(void)
{
   dbref ret, tmp, previous;

   if (tail == NOTHING)
      return NOTHING;

   ret = tail;

   if (tail == head)
   {
      tail = head = NOTHING;
   }
   else
   {
      for (tmp = head; tmp != tail; tmp = DBFETCH(tmp)->lru_next)
         previous = tmp;
      DBSTORE(previous, lru_next, NOTHING);
      tail = previous;
   }
      
   listlen--;

   return ret;
}

int lru_hasp(dbref key)
{
   dbref tmp;

   for (tmp = head; tmp != NOTHING; tmp = DBFETCH(tmp)->lru_next)
      if (tmp == key)
         return 1;

   return 0;
}

dbref lru_head(void)
{
   return(head);
}

#endif