Reactor Android

Reactor.kt

abstract class Reactor<in Action, Mutation, State, Navigation>(state: State) {
    private val actionSubject: Subject<Action> = PublishSubject.create()
    private val initialViewState = state
    var currentViewState = initialViewState
        private set

    val stateStream: Observable<State>

    init {
        val mutationsStream = actionSubject.flatMap { mutate(it) }.replay().refCount()
        stateStream = mutationsStream
                .scan(initialViewState) { state, mutation -> reduce(state, mutation) }
                .startWith(initialViewState)
                .doOnNext { currentViewState = it }
    }

    fun onAction(action: Action) = actionSubject.onNext(action)

    abstract fun mutate(action: Action): Observable<Mutation>
    abstract fun reduce(state: State, mutation: Mutation): State
}