fun interface Reducer<S : StoreState> {
    operator fun invoke(state: S, action: Action): S
}

fun interface ReducerType<S : StoreState, A : Action> {
    operator fun S.invoke(action: A): S
}

inline fun <S : StoreState, reified A : Action> Reducer(
    reducer: ReducerType<S, A>
): Reducer<S> =
    Reducer { state, action ->
        when (action) {
            is A -> reducer.run { state(action) }
            else -> state
        }
    }

val TodoReducer: Reducer<TodosState> =
    Reducer<TodosState, TodoListAction> { action ->
        when (action) {
            is LoadTodos -> this
        }
    }