class Actor {
    private static final ArrayList<ItemSlot> BOTH_HANDS = [MAIN_HAND, OFF_HAND]
    private static final ArrayList<ItemSlot> BOTH_RINGS = [RING_RIGHT, RING_LEFT]
    // items
    Collection<Item> inventory = []
    Map<ItemSlot, Item> equipment = [:]



    void useOrEquip(int itemId, ItemSlot targetSlot) {
        Item item = inventory.find { it.id == itemId }
        if (item) {
            switch (item.type) {
                case ItemType.EQUIPABLE:
                    List<ItemSlot> slotsToEmpty
                    ItemSlot destination = item.slot
                    if (item.isTwoHanded) {
                        slotsToEmpty = BOTH_HANDS
                        destination = MAIN_HAND
                    } else if (equipment.get(MAIN_HAND).isTwoHanded && targetSlot in BOTH_HANDS) {
                        slotsToEmpty = [MAIN_HAND]
                        destination
                    } else if ((equipment.keySet().containsAll(BOTH_HANDS) && targetSlot in BOTH_HANDS)
                            || (equipment.keySet().containsAll(BOTH_RINGS) && targetSlot in BOTH_RINGS)) {
                        slotsToEmpty = [targetSlot]
                        destination = targetSlot
                    } else {
                        slotsToEmpty = [item.slot]
                    }
                    slotsToEmpty.each { inventory.add(equipment.remove(it)) }
                    inventory.remove item
                    equipment.put destination, item
                    break
                case ItemType.USABLE:
                    break
            }
        }
    }
}