class ChatRoomsViewModel(
    private val repository: ChatRoomsRepository,
    private val mapper: RoomMapper
) : ViewModel() {
    private val ordering: MutableLiveData<ChatRoomsRepository.Order> = MutableLiveData()
    private val runContext = newSingleThreadContext("chat-rooms-view-model")

    init {
        ordering.value = ChatRoomsRepository.Order.ACTIVITY
    }

    fun getChatRooms(): LiveData<List<ItemHolder<*>>> {
        return Transformations.switchMap(ordering) { order ->
            repository.getChatRooms(order)
                    .nonNull()
                    .distinct()
                    .transform(runContext) { rooms ->
                        rooms?.let {
                            mapper.map(rooms, order.isGrouped())
                        }
                    }
        }
    }

    fun setOrdering(order: ChatRoomsRepository.Order) {
        ordering.value = order
    }
}