ObserveState.kt

    operator fun invoke(): Flow<State> = timeApi
        .ticker()
        .combine(transitionApi.observeTransitionLog()) { now, transition ->
            transition.toState(now)
        }
        .distinctUntilChanged()
        .onEach {
            try {
                if (it is State.Pomodoro) turnOnZenMode() else turnOffZenMode()
            } catch (e: Exception) {
                errorChannel.send(e)
            }
        }
        .onEach {
            if (it is State.Pomodoro || it is State.Break) it.doOnTimeUp {
                nextState(Action.COMPLETE)
            }
        }