IntervalFlow.kt

import kotlinx.coroutines.*
import kotlinx.coroutines.flow.Flow
import kotlinx.coroutines.flow.channelFlow
import kotlinx.coroutines.flow.launchIn
import kotlinx.coroutines.flow.onEach

@FlowPreview
@ExperimentalCoroutinesApi
fun main() {
  runBlocking {
    intervalFlow(
      initialProgress = 0,
      maxProgress = 10,
      period = 300,
      loop = true
    )
      .onEach { println(it) }
      .launchIn(this)
  }
}

/**
 * @param initialProgress The initial value that is emitted.
 * @param maxProgress The max value that is emitted.
 * @param period The delay between each subsequent emission.
 * @param loop Whether or not the timer will restart or stop when the max progress is reached.
 * @param minimumProgress If [loop] is true, we return to this value after the [maxProgress] is reached.
 */
@ExperimentalCoroutinesApi
suspend fun intervalFlow(
  initialProgress: Long,
  maxProgress: Long,
  period: Long,
  loop: Boolean,
  minimumProgress: Long = 0L
): Flow<Long> {
  return channelFlow {
    var currentValue: Long = initialProgress
    while (isActive) {
      send(currentValue)
      currentValue++
      delay(period)

      if (currentValue == maxProgress + 1) {
        if (!loop) break
        currentValue = minimumProgress
      }
    }
  }
}