class NumberRepo(
    scope: CoroutineScope,
    private val loadInitialValueFromDisk: suspend () -> Int
) : CoroutineScope by scope {

    private val intentions = Channel<Intention>()

    private val reduce: (State, Intention) -> State = { state: State, intention: Intention ->
        when (intention) {
            Intention.Increment -> State(state.value + 1)
            Intention.Decrement -> State(state.value - 1)
        }
    }

    private val sharedStateFlow: SharedFlow<State> = intentions.receiveAsFlow()
        .scan(
            runBlocking { // how can I avoid a runBlocking here?
                State(loadInitialValueFromDisk())
            }
        ) { state: State, intention: Intention ->
            reduce(state, intention)
        }
        .shareIn(
            this,
            SharingStarted.Eagerly, // begin observing immediately!
            replay = 1 // so each subscriber gets the current state
        )

    val states: Flow<State> = sharedStateFlow

    suspend fun increment() {
        intentions.send(Intention.Increment)
    }

    suspend fun decrement() {
        intentions.send(Intention.Decrement)
    }

    private sealed class Intention {
        object Increment : Intention()
        object Decrement : Intention()
    }

    data class State(val value: Int)
}