Countdown timer

SimpleTimer

import android.os.CountDownTimer
import java.util.concurrent.TimeUnit

/**
 * Countdown timer helper
 * @author Ivan V on 23.04.2020.
 * @version 1.0
 */
class SimpleTimer {

    private var inFuture: Long = 0
    private var interval: Long = 0
    private lateinit var observer: TimerObserver

    private var finished: Boolean = true
    private var currentMillis: Long = 0

    private lateinit var timer: CountDownTimer

    private constructor()
    constructor(millisInFuture: Long, countDownInterval: Long, observer: TimerObserver) {
        this.inFuture = millisInFuture
        this.interval = countDownInterval
        this.observer = observer
        initTimer()
    }

    private fun initTimer() {
        timer = object: CountDownTimer(inFuture, interval) {
            override fun onTick(millisUntilFinished: Long) {
                currentMillis = millisUntilFinished
                finished = false
                timeResolver(millisUntilFinished)
            }

            override fun onFinish() {
                finished = true
                observer.timerFinished()
            }
        }
    }

    fun start() {
        timer.start()
    }

    fun stop() {
        timer.cancel()
        finished = true
        observer.timerCanceled()
    }

    fun isFinished() = finished

    fun getCurrentMillis() = currentMillis

    private fun timeResolver(millisUntilFinished:Long) {
        var millis:Long = millisUntilFinished
        val days = TimeUnit.MILLISECONDS.toDays(millis)
        millis -= TimeUnit.DAYS.toMillis(days)

        val hours = TimeUnit.MILLISECONDS.toHours(millis)
        millis -= TimeUnit.HOURS.toMillis(hours)

        val minutes = TimeUnit.MILLISECONDS.toMinutes(millis)
        millis -= TimeUnit.MINUTES.toMillis(minutes)

        val seconds = TimeUnit.MILLISECONDS.toSeconds(millis)

        observer.timerResult(days, hours, minutes, seconds)
    }

    /**
     * Timer result observer
     */
    interface TimerObserver {
        fun timerResult(days: Long, hours: Long, minutes: Long, seconds: Long)
        fun timerFinished()
        fun timerCanceled()
    }

}