//Create aggregator which will concat scan records with a device
    val aggregator = BleScanResultAggregator()
    BleScanner(context).scan()
        .map { aggregator.aggregateDevices(it) } //Add new device and return an aggregated list
        .onEach { _devices.value = it } //Propagated state to UI
        .launchIn(viewModelScope) //Scanning will stop after we leave the screen

viewModelScope.launch {
    //Connect a Bluetooth LE device. This is a suspend function which waits until device is in conncted state.
    val connection = blinkyDevice.connect(context) //blinkyDevice from scanner

    //Discover services on the Bluetooth LE Device. This is a suspend function which waits until device discovery is finished.
    val services = connection.discoverServices()

    //Remember needed service and characteristics which are used to communicate with the DK.
    val service = services.findService(BlinkySpecifications.UUID_SERVICE_DEVICE)!!
    ledCharacteristic = service.findCharacteristic(BlinkySpecifications.UUID_LED_CHAR)!!
    buttonCharacteristic = service.findCharacteristic(BlinkySpecifications.UUID_BUTTON_CHAR)!!

    //Observe button characteristic which detects when a button is pressed
    //getNotifications() is a suspend function which waits until notification is enabled.
    buttonCharacteristic.getNotifications().onEach {
        //_state is a MutableStateFlow which propagates data to UI.
        _state.value = _state.value.copy(isButtonPressed = BlinkyButtonParser.isButtonPressed(it))
    }.launchIn(viewModelScope)
    
    //Check the initial state of the Led. Read() is a suspend function which waits until the value is read from the DK.
    val isLedOn = BlinkyLedParser.isLedOn(ledCharacteristic.read())
    _state.value = _state.value.copy(isLedOn = isLedOn)
}

viewModelScope.launch {
    if (state.value.isLedOn) {
        //Write is a suspend function which waits for the operation to finish.
        ledCharacteristic.write(DataByteArray.from(0x00))
        //No exception means that writing was a success. We can update the UI.
        _state.value = _state.value.copy(isLedOn = false)
    } else {
        //Write is a suspend function which waits for the operation to finish.
        ledCharacteristic.write(DataByteArray.from(0x01))
        //No exception means that writing was a success. We can update the UI.
        _state.value = _state.value.copy(isLedOn = true)
    }
}

    val advertiser = BleAdvertiser.create(context)
    val advertiserConfig = BleAdvertisingConfig(
        settings = BleAdvertisingSettings(
            deviceName = "My Server" // Advertise a device name
        ),
        advertiseData = BleAdvertisingData(
            ParcelUuid(BlinkySpecifications.UUID_SERVICE_DEVICE) //Advertise main service uuid.
        )
    )

    viewModelScope.launch {
        advertiser.advertise(advertiserConfig) //Start advertising
            .cancellable()
            .catch { it.printStackTrace() }
            .collect { //Observe advertiser lifecycle events
                if (it is OnAdvertisingSetStarted) { //Handle advertising start event
                    _state.value = _state.value.copy(isAdvertising = true)
                }
                if (it is OnAdvertisingSetStopped) { //Handle advertising stop event
                    _state.value = _state.value.copy(isAdvertising = false)
                }
            }
    }

    viewModelScope.launch {
        //Define led characteristic
        val ledCharacteristic = BleServerGattCharacteristicConfig(
            BlinkySpecifications.UUID_LED_CHAR,
            listOf(BleGattProperty.PROPERTY_READ, BleGattProperty.PROPERTY_WRITE),
            listOf(BleGattPermission.PERMISSION_READ, BleGattPermission.PERMISSION_WRITE)
        )

        //Define button characteristic
        val buttonCharacteristic = BleServerGattCharacteristicConfig(
            BlinkySpecifications.UUID_BUTTON_CHAR,
            listOf(BleGattProperty.PROPERTY_READ, BleGattProperty.PROPERTY_NOTIFY),
            listOf(BleGattPermission.PERMISSION_READ, BleGattPermission.PERMISSION_WRITE)
        )

        //Put led and button characteristics inside a service
        val serviceConfig = BleServerGattServiceConfig(
            BlinkySpecifications.UUID_SERVICE_DEVICE,
            BleGattServerServiceType.SERVICE_TYPE_PRIMARY,
            listOf(ledCharacteristic, buttonCharacteristic)
        )

        val server = BleGattServer.create(context, viewModelScope, serviceConfig)
    }

    server.connectionEvents
        .mapNotNull { it as? ServerConnectionEvent.DeviceConnected }
        .map { it.connection }
        .onEach {
            it.services.findService(BlinkySpecifications.UUID_SERVICE_DEVICE)?.let {
                setUpServices(it)
            }
        }
        .launchIn(viewModelScope)

    private fun setUpServices(services: BleGattServerService) {
        val ledCharacteristic = services.findCharacteristic(BlinkySpecifications.UUID_LED_CHAR)!!
        val buttonCharacteristic = services.findCharacteristic(BlinkySpecifications.UUID_BUTTON_CHAR)!!

        ledCharacteristic.value.onEach {
            _state.value = _state.value.copy(isLedOn = it != DataByteArray.from(0x00))
        }.launchIn(viewModelScope)

        buttonCharacteristic.value.onEach {
            _state.value = _state.value.copy(isButtonPressed = it != DataByteArray.from(0x00))
        }.launchIn(viewModelScope)

        this.ledCharacteristic = ledCharacteristic
        this.buttonCharacteristic = buttonCharacteristic
    }

    fun onButtonPressedChanged(isButtonPressed: Boolean) = viewModelScope.launch {
        val value = if (isButtonPressed) {
            DataByteArray.from(0x01)
        } else {
            DataByteArray.from(0x00)
        }
        buttonCharacteristic.setValueAndNotifyClient(value)
    }