/**************************************************************************
 Calculates the turns which are needed to build the requested
 type in the city. GUI Independend
**************************************************************************/
int city_turns_to_build(struct city *pcity, int id, int id_is_unit)
{
  if (pcity->shield_surplus > 0)
  {
    int rounds, cost;
    int shield_stock = pcity->shield_stock;

    if (id_is_unit)
    {
      if (!pcity->is_building_unit)
	shield_stock /= 2;
      cost = get_unit_type(id)->build_cost;
    }
    else
    {
      if (pcity->is_building_unit || (is_wonder(pcity->currently_building) != is_wonder(id)))
	shield_stock /= 2;
      cost = get_improvement_type(id)->build_cost;
    }

    rounds = (cost - shield_stock + pcity->shield_surplus - 1) / pcity->shield_surplus;

    return (rounds > 0) ? rounds : 0;
  }
  return 999;
}