TapTempo.kt

package Bouh

import java.util.concurrent.TimeUnit

class TapTempo
{
    private val sample = 5
    private val resetTime = TimeUnit.NANOSECONDS.convert(5, TimeUnit.SECONDS)
    private val taps = ArrayList<Long>()

    fun run() {
        while (true) {
            readLine()
            tap()
            displayBPM()
        }
    }

    private fun tap() {
        val currentTap = System.nanoTime()
        checkResetTime()

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

        taps.add(currentTap)
    }

    private fun displayBPM()
    {
        if (taps.size == 1) {
            println("[Hit a key one more time to start bpm computation...]")
            return
        }

        println("Tempo: ${String.format("%.2f", getBPM())} bpm")
    }

    private fun getBPM(): Float {
        return (taps.size - 1) / (taps.last() - taps[0].toFloat()) * TimeUnit.NANOSECONDS.convert(60, TimeUnit.SECONDS)
    }

    private fun checkResetTime() {
        if (taps.isEmpty()) {
            return
        }

        if (System.nanoTime() - taps.last() > resetTime) {
            taps.clear()
        }
    }
}