static struct impr_type improvement_types[B_LAST];

/**********************************************************************//**
  Initialize building structures.
**************************************************************************/
void improvements_init(void)
{
  int i;

  /* Can't use improvement_iterate() or improvement_by_number() here
   * because num_impr_types isn't known yet. */
  for (i = 0; i < ARRAY_SIZE(improvement_types); i++) {
    struct impr_type *p = &improvement_types[i];

    p->item_number = i;
    requirement_vector_init(&p->reqs);
    requirement_vector_init(&p->obsolete_by);
    p->ruledit_disabled = FALSE;
    p->ruledit_dlg = NULL;
  }
  BV_CLR_ALL(obsoletion_checking);
}

bool improvement_obsolete(const struct player *pplayer,
                          const struct impr_type *pimprove,
                          const struct city *pcity)
{
  const struct req_context context = {
    .player = pplayer,
    .city = pcity,
    .tile = pcity ? city_tile(pcity) : NULL,
    .building = pimprove,
  };
  bool result = FALSE;

  requirement_vector_iterate(&pimprove->obsolete_by, preq) {
    int id = -1;

    if (VUT_IMPROVEMENT == preq->source.kind) {
      /* Avoid cyclical obsoletion */
      id = improvement_index(preq->source.value.building);
      if (BV_ISSET(obsoletion_checking, id)) {
        /* Building's obsoletion depends on itself. Resolve to present
         * (that may result in obsoletion on top level). */
        BV_CLR(obsoletion_checking, id);
        return preq->present;
      } else {
        BV_SET(obsoletion_checking, id);
      }
    }
    result = is_req_active(&context, NULL, preq, RPT_CERTAIN);
    if (id >= 0) {
      BV_CLR(obsoletion_checking, id);
    }
    if (result) {
      break;
    }
  } requirement_vector_iterate_end;

  return result;
}