Debounce in Scala

debounce.scala

import scala.compat.Platform.{currentTime => now}
import scala.concurrent.duration.FiniteDuration

import java.util.concurrent.atomic.AtomicBoolean

/**
 * Debounce a function i.e. it can only be invoked iff it is not already running
 * and atleast wait duration has passed since it last stopped running
 * Usage:
 *    def test(i: Int) = println(i)
 *    val f = debounce(1.second)(test)
 *    (0 to 1e9.toInt).par.map(f)
 *
 * @return a function such that it returns Some(original output) if it was invoked
 *         or else if it failed to run because of above rules, None
 */
def debounce[A, B](wait: FiniteDuration)(f: A => B): A => Option[B] = {
  var (isRunning, lastStopTime) = (new AtomicBoolean(false), Long.MinValue)
  (input: A) => {
    val doneWaiting = lastStopTime + wait.toMillis <= now
    if (isRunning.compareAndSet(false, doneWaiting) && doneWaiting) {
      try {
        Some(f(input))
      } finally {
        lastStopTime = now
        isRunning.set(false)
      }
    } else {
      None
    }
  }
}