sealed class State {
    object Resting : State()
    object Working : State()
}


fun main() = runBlocking {

    backgroundStartsFirst()

}

@OptIn(ExperimentalCoroutinesApi::class)
suspend fun backgroundStartsFirst() {

    val backgroundFlow = flow {
        emit(State.Resting)
        delay(1000)

        emit(State.Working)
        delay(10000)

        emit(State.Resting)
    }


    val foregroundFlow = flow {
        emit(State.Resting)
        delay(2000)

        emit(State.Working)
        delay(1000)

        emit(State.Resting)
    }

    val workingCount = AtomicInteger(0)

    merge(backgroundFlow, foregroundFlow)
        .collect {

            when (it) {
                State.Working -> {
                    println("SOME ARE WORKING")
                    workingCount.incrementAndGet()
                }
                State.Resting -> {
                    println("SOME ARE RESTING")
                    if (workingCount.get() > 0) workingCount.decrementAndGet()
                }
            }
            if (workingCount.get() == 0) println("\tWE ARE ALL RESTING")
        }
}

Resting

Working

Working

Working

Resting

Resting

Working