BlogSKMM1.RestaurantDetailViewModelImpl.kt

class RestaurantDetailViewModelImpl(api: Api, restaurantId: Int): RestaurantDetailViewModel {

    private val _restaurant = api.restaurant(restaurantId)
    private val _reservations = api.restaurantReservations(restaurantId)

    private val _output = combine(_restaurant, _reservations) { restaurantResponse, reservationsResponse ->
        // for simplicity we ignore error handling and exclude specific loading state for when the restaurant is loading
        RestaurantDetailViewModel.Output(
            name = (restaurantResponse as? Response.Success)?.data?.name ?: "Loading or error...",
            priceCategory = (restaurantResponse as? Response.Success)?.data?.priceCategory ?: "Loading or error...",
            reservations = when(reservationsResponse) {
                is Response.Loading -> RestaurantDetailViewModel.Output.Reservations.Loading
                is Response.Failed -> RestaurantDetailViewModel.Output.Reservations.NoReservations("Failed")
                is Response.Success -> {
                    val reservations = reservationsResponse.data
                    if (reservations.isEmpty()) {
                        RestaurantDetailViewModel.Output.Reservations.NoReservations("No reservations yet")
                    } else {
                        RestaurantDetailViewModel.Output.Reservations.ReservationList(reservations.map {
                            RestaurantDetailViewModel.Output.Reservations.ReservationList.Reservation(
                                id = it.id,
                                date = "epoch: ${it.date}", // normally would do some formatting
                                numberOfGuests = it.numberOfGuests
                            )
                        })
                    }
                }
            }
        )
    }

    override val output = _output.distinctUntilChanged().wrap()
}