Building an Android service that never stops running

class EndlessService : Service() {

    private var wakeLock: PowerManager.WakeLock? = null
    private var isServiceStarted = false

    override fun onBind(intent: Intent): IBinder? {
        log("Some component want to bind with the service")
        // We don't provide binding, so return null
        return null
    }

    override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {
        log("onStartCommand executed with startId: $startId")
        if (intent != null) {
            val action = intent.action
            log("using an intent with action $action")
            when (action) {
                Actions.START.name -> startService()
                Actions.STOP.name -> stopService()
                else -> log("This should never happen. No action in the received intent")
            }
        } else {
            log(
                "with a null intent. It has been probably restarted by the system."
            )
        }
        // by returning this we make sure the service is restarted if the system kills the service
        return START_STICKY
    }

    override fun onCreate() {
        super.onCreate()
        log("The service has been created".toUpperCase())
        var notification = createNotification()
        startForeground(1, notification)
    }

    override fun onDestroy() {
        super.onDestroy()
        log("The service has been destroyed".toUpperCase())
        Toast.makeText(this, "Service destroyed", Toast.LENGTH_SHORT).show()
    }

    private fun startService() {
        if (isServiceStarted) return
        log("Starting the foreground service task")
        Toast.makeText(this, "Service starting its task", Toast.LENGTH_SHORT).show()
        isServiceStarted = true
        setServiceState(this, ServiceState.STARTED)

        // we need this lock so our service gets not affected by Doze Mode
        wakeLock =
            (getSystemService(Context.POWER_SERVICE) as PowerManager).run {
                newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, "EndlessService::lock").apply {
                    acquire()
                }
            }

        // we're starting a loop in a coroutine
        GlobalScope.launch(Dispatchers.IO) {
            while (isServiceStarted) {
                launch(Dispatchers.IO) {
                    pingFakeServer()
                }
                delay(1 * 60 * 1000)
            }
            log("End of the loop for the service")
        }
    }

    private fun stopService() {
        log("Stopping the foreground service")
        Toast.makeText(this, "Service stopping", Toast.LENGTH_SHORT).show()
        try {
            wakeLock?.let {
                if (it.isHeld) {
                    it.release()
                }
            }
            stopForeground(true)
            stopSelf()
        } catch (e: Exception) {
            log("Service stopped without being started: ${e.message}")
        }
        isServiceStarted = false
        setServiceState(this, ServiceState.STOPPED)
    }

    private fun pingFakeServer() {
        val df = SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.mmmZ")
        val gmtTime = df.format(Date())

        val deviceId = Settings.Secure.getString(applicationContext.contentResolver, Settings.Secure.ANDROID_ID)

        val json =
            """
                {
                    "deviceId": "$deviceId",
                    "createdAt": "$gmtTime"
                }
            """
        try {
            Fuel.post("https://jsonplaceholder.typicode.com/posts")
                .jsonBody(json)
                .response { _, _, result ->
                    val (bytes, error) = result
                    if (bytes != null) {
                        log("[response bytes] ${String(bytes)}")
                    } else {
                        log("[response error] ${error?.message}")
                    }
                }
        } catch (e: Exception) {
            log("Error making the request: ${e.message}")
        }
    }

    private fun createNotification(): Notification {
        val notificationChannelId = "ENDLESS SERVICE CHANNEL"

        // depending on the Android API that we're dealing with we will have
        // to use a specific method to create the notification
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            val notificationManager = getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager;
            val channel = NotificationChannel(
                notificationChannelId,
                "Endless Service notifications channel",
                NotificationManager.IMPORTANCE_HIGH
            ).let {
                it.description = "Endless Service channel"
                it.enableLights(true)
                it.lightColor = Color.RED
                it.enableVibration(true)
                it.vibrationPattern = longArrayOf(100, 200, 300, 400, 500, 400, 300, 200, 400)
                it
            }
            notificationManager.createNotificationChannel(channel)
        }

        val pendingIntent: PendingIntent = Intent(this, MainActivity::class.java).let { notificationIntent ->
            PendingIntent.getActivity(this, 0, notificationIntent, 0)
        }

        val builder: Notification.Builder = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) Notification.Builder(
            this,
            notificationChannelId
        ) else Notification.Builder(this)

        return builder
            .setContentTitle("Endless Service")
            .setContentText("This is your favorite endless service working")
            .setContentIntent(pendingIntent)
            .setSmallIcon(R.mipmap.ic_launcher)
            .setTicker("Ticker text")
            .setPriority(Notification.PRIORITY_HIGH) // for under android 26 compatibility
            .build()
    }
}

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        title = "Endless Service"

        findViewById<Button>(R.id.btnStartService).let {
            it.setOnClickListener {
                log("START THE FOREGROUND SERVICE ON DEMAND")
                actionOnService(Actions.START)
            }
        }

        findViewById<Button>(R.id.btnStopService).let {
            it.setOnClickListener {
                log("STOP THE FOREGROUND SERVICE ON DEMAND")
                actionOnService(Actions.STOP)
            }
        }
    }

    private fun actionOnService(action: Actions) {
        if (getServiceState(this) == ServiceState.STOPPED && action == Actions.STOP) return
        Intent(this, EndlessService::class.java).also {
            it.action = action.name
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
                log("Starting the service in >=26 Mode")
                startForegroundService(it)
                return
            }
            log("Starting the service in < 26 Mode")
            startService(it)
        }
    }
}

class StartReceiver : BroadcastReceiver() {

    override fun onReceive(context: Context, intent: Intent) {
        if (intent.action == Intent.ACTION_BOOT_COMPLETED && getServiceState(context) == ServiceState.STARTED) {
            Intent(context, EndlessService::class.java).also {
                it.action = Actions.START.name
                if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
                    log("Starting the service in >=26 Mode from a BroadcastReceiver")
                    context.startForegroundService(it)
                    return
                }
                log("Starting the service in < 26 Mode from a BroadcastReceiver")
                context.startService(it)
            }
        }
    }
}

override fun onTaskRemoved(rootIntent: Intent) {
    val restartServiceIntent = Intent(applicationContext, EndlessService::class.java).also {
        it.setPackage(packageName)
    };
    val restartServicePendingIntent: PendingIntent = PendingIntent.getService(this, 1, restartServiceIntent, PendingIntent.FLAG_ONE_SHOT);
    applicationContext.getSystemService(Context.ALARM_SERVICE);
    val alarmService: AlarmManager = applicationContext.getSystemService(Context.ALARM_SERVICE) as AlarmManager;
    alarmService.set(AlarmManager.ELAPSED_REALTIME, SystemClock.elapsedRealtime() + 1000, restartServicePendingIntent);
}