data class Album(
    val id: Int,
    val name: String
)

sealed class TaskState<out T> {
    object Initial : TaskState<Nothing>()
    object Progress : TaskState<Nothing>()
    class Failure(val error: Exception) : TaskState<Exception>()
    class Success<out T>(val result: T) : TaskState<T>()
}

class TaskViewModel : ViewModel() {

    sealed class AvailableTask<T>() {
        object Move : AvailableTask<Boolean>()
        object NewAlbum : AvailableTask<Album>()
    }

    private val moveStateFlow = MutableStateFlow<TaskState<Boolean>>(TaskState.Initial)
    private val newAlbumStateFlow = MutableStateFlow<TaskState<Album>>(TaskState.Initial)


    fun <T> observeTaskState(
        task: AvailableTask<T>,
        observer: Observer<TaskState<*>>
    ) {
        viewModelScope.launch(viewModelScope.coroutineContext + Job()) {
            val stateFlow = when (task) {
                is AvailableTask.Move -> moveStateFlow
                is AvailableTask.NewAlbum -> newAlbumStateFlow
            }

            stateFlow.collect {
                observer.onChanged(it)
            }
        }
    }
}

fun foo() {
    val v = TaskViewModel()
    v.observeTaskState(TaskViewModel.AvailableTask.Move) { taskState: TaskState<*> ->
        when (taskState) {
            TaskState.Initial -> {}
            TaskState.Progress -> {}
            is TaskState.Failure -> {}
            is TaskState.Success -> {
                val result = taskState.result as Boolean
                // ...
            }
        }
    }
}