Debounce

Debounce.kt

import kotlinx.coroutines.experimental.DefaultDispatcher
import kotlinx.coroutines.experimental.channels.ReceiveChannel
import kotlinx.coroutines.experimental.channels.consumeEach
import kotlinx.coroutines.experimental.channels.produce
import kotlinx.coroutines.experimental.delay
import kotlinx.coroutines.experimental.runBlocking
import kotlin.coroutines.experimental.CoroutineContext

fun <T> ReceiveChannel<T>.debounce(
    wait: Long = 300,
    context: CoroutineContext = DefaultDispatcher
): ReceiveChannel<T> = produce(context) {
    var nextTime = 0L
    consumeEach {
        val curTime = System.currentTimeMillis()
        if (curTime < nextTime) {
            // not enough time passed from last send
            delay(nextTime - curTime)
            var mostRecent = it
            while (!isEmpty) { mostRecent = receive() } // take the most recently sent without waiting
            nextTime += wait // maintain strict time interval between sends
            send(mostRecent)
        } else {
            // big pause between original events
            nextTime = curTime + wait // start tracking time interval from scratch
            send(it)
        }
    }
}

fun main(args: Array<String>) = runBlocking {
    val channel = produce<Int> {
        (0..100).forEach {
            println("send")
            send(it)
            delay(100)
        }
    }
    channel.debounce().consumeEach { println("Yay!")  }
}