FriendsViewModel.kt

class FriendsViewModel @Inject constructor(
    private val getFriendsUseCase: GetFriendsUseCase
) : BaseViewModel() {

    sealed class FriendsState {
        object Loading : FriendsState()
        object Empty : FriendsState()
        data class Success(val users: List<UserUiModel>) : FriendsState()
    }

    val state = MutableLiveData<FriendsState>().apply {
        this.value = FriendsState.Loading
    }

    fun loadData() {
        val params = GetFriendsUseCase.Params(50)
        getFriendsUseCase.invoke(viewModelScope, params) { it.either(::handleFailure, ::handleSuccess) }
    }

    private fun handleSuccess(list: List<User>) {
        when {
            list.isEmpty() -> state.value = FriendsState.Empty
            list.isNotEmpty() -> state.value = FriendsState.Success(mapToPresentation(list))
        }
    }

    private fun mapToPresentation(friends: List<User>): List<UserUiModel> {
        return friends.map { UserUiModel(it.name, it.pictureUrl) }
    }
}