TapTempo.fan

class TapTempo
{
  Int sample := 5
  Duration[] taps := Duration[,]
  Duration resetTime := 60sec
  Int precision := 2

  public Void main()
  {
    while (true) {
      Env.cur.in.readLine()
      tap
      displayBPM
    }
  }

  private Void tap()
  {
      currentTap := Duration.now
      checkResetTime

      if (taps.size == sample)
        taps.removeAt(0)

      taps.add(currentTap)
  }

  private Void displayBPM()
  {
    if (taps.size == 1) {
      Env.cur.out.printLine("[Hit a key one more time to start bpm computation...]")
      return
    }

    Env.cur.out.printLine("Tempo: " + getBPM.toLocale("0." + "0" * precision) + " bpm")
  }

  private Float getBPM()
  {
    (taps.size - 1f) / (taps[-1] - taps[0]).toMillis * 60000
  }

  private Void checkResetTime()
  {
    if (taps.isEmpty)
      return

    if (Duration.now - taps[-1] > resetTime)
      taps.clear
  }
}