BluetoothGatt — cos'è, metodi e protocollo GATT BLE in Android

// Creazione connessione BluetoothGatt
import android.bluetooth.*

class GattConnector(private val context: Context) {

    private var bluetoothGatt: BluetoothGatt? = null

    fun connect(device: BluetoothDevice): BluetoothGatt? {
        // Chiudi connessione precedente se esiste
        close()

        bluetoothGatt = device.connectGatt(
            context,
            false,  // autoConnect = false ( )
            object : BluetoothGattCallback() {
                override fun onConnectionStateChange(
                    gatt: BluetoothGatt, status: Int, newState: Int
                ) {
                    when (newState) {
                        BluetoothProfile.STATE_CONNECTED -> {
                            // 2. Connessione stabilita → Scoperta
                            gatt.discoverServices()
                        }
                        BluetoothProfile.STATE_DISCONNECTED -> {
                            // 3. Connessione persa
                            close()
                        }
                    }
                }

                override fun onServicesDiscovered(
                    gatt: BluetoothGatt, status: Int
                ) {
                    if (status == BluetoothGatt.GATT_SUCCESS) {
                        // 4. Gerarchia GATT ricevuta
                        onGattReady(gatt)
                    }
                }
            },
            BluetoothDevice.TRANSPORT_LE
        )
        return bluetoothGatt
    }

    private fun onGattReady(gatt: BluetoothGatt) {
        // GATT pronto per operazioni di lettura/scrittura
    }

    fun close() {
        bluetoothGatt?.disconnect()
        bluetoothGatt?.close()
        bluetoothGatt = null
    }
}

// Scoperta servizi e ricerca caratteristiche
class GattServiceExplorer {

    // Trova servizio per UUID
    fun findService(gatt: BluetoothGatt, uuid: UUID): BluetoothGattService? {
        return gatt.services?.firstOrNull { it.uuid == uuid }
    }

    // Trova caratteristica nel servizio
    fun findCharacteristic(
        service: BluetoothGattService,
        uuid: UUID
    ): BluetoothGattCharacteristic? {
        return service.characteristics?.firstOrNull { it.uuid == uuid }
    }

    // Ottieni tutte le operazioni caratteristica supportate
    fun getCharacteristicProperties(chars: BluetoothGattCharacteristic): List<String> {
        val props = mutableListOf<String>()
        with(chars.properties) {
            if (and(BluetoothGattCharacteristic.PROPERTY_READ) != 0) props.add("READ")
            if (and(BluetoothGattCharacteristic.PROPERTY_WRITE) != 0) props.add("SCRIVI")
            if (and(BluetoothGattCharacteristic.PROPERTY_WRITE_NO_RESPONSE) != 0) props.add("SCRIVI_SENZA_RISPOSTA")
            if (and(BluetoothGattCharacteristic.PROPERTY_NOTIFY) != 0) props.add("NOTIFY")
            if (and(BluetoothGattCharacteristic.PROPERTY_INDICATE) != 0) props.add("INDICATE")
        }
        return props
    }

    // Registra l'intera gerarchia GATT
    fun dumpGattTree(gatt: BluetoothGatt) {
        gatt.services?.forEach { service ->
            print("Service: ${service.uuid}")
            service.characteristics?.forEach { char ->
                print("  Characteristic: ${char.uuid}, properties: ${char.properties}")
                char.descriptors?.forEach { desc ->
                    print("    Descriptor: ${desc.uuid}")
                }
            }
        }
    }
}

// Leggi caratteristica e descrittore tramite BluetoothGatt
class GattReader {

    fun readHeartRate(gatt: BluetoothGatt) {
        // UUID servizio frequenza cardiaca = 0x180D
        val service = gatt.getService(UUID.fromString("0000180D-0000-1000-8000-00805F9B34FB"))
            ?: return
        // UUID misurazione frequenza cardiaca = 0x2A37
        val characteristic = service.getCharacteristic(
            UUID.fromString("00002A37-0000-1000-8000-00805F9B34FB")
        ) ?: return

        if (hasProperty(characteristic, BluetoothGattCharacteristic.PROPERTY_READ)) {
            gatt.readCharacteristic(characteristic)
        }
    }

    fun readDescriptor(gatt: BluetoothGatt, characteristic: BluetoothGattCharacteristic) {
        // CCCD (0x2902)
        val cccd = characteristic.getDescriptor(
            UUID.fromString("00002902-0000-1000-8000-00805F9B34FB")
        )
        cccd?.let { gatt.readDescriptor(it) }
    }

    // Elabora dati nel callback onCharacteristicRead:
    fun parseHeartRate(value: ByteArray): Int {
        // Frequenza cardiaca BLE: bytes = flags, second = bpm
        return if (value.isNotEmpty()) value[1].toInt() and 0xFF else 0
    }

    private fun hasProperty(char: BluetoothGattCharacteristic, prop: Int): Boolean {
        return char.properties and prop != 0
    }
}

// Scrittura caratteristica BLE su Android API 33+
class GattWriter {

    // Scrivi con risposta (withResponse)
    fun writeWithResponse(gatt: BluetoothGatt, characteristic: BluetoothGattCharacteristic, data: ByteArray) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
            // API 33+: writeCharacteristic
            val request = BluetoothGattCharacteristicWriteRequest(
                characteristic,
                data,
                BluetoothGattCharacteristicWriteRequest.WRITE_TYPE_DEFAULT,
                @android.annotation.RequiresPermission(android.Manifest.permission.BLUETOOTH_CONNECT)
            )
            gatt.writeCharacteristic(request)
        } else {
            // API < 33:   (deprecated)
            characteristic.setValue(data)
            gatt.writeCharacteristic(characteristic)
        }
    }

    // Scrivi senza risposta (velocità massima)
    fun writeWithoutResponse(gatt: BluetoothGatt, characteristic: BluetoothGattCharacteristic, data: ByteArray) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
            val request = BluetoothGattCharacteristicWriteRequest(
                characteristic,
                data,
                BluetoothGattCharacteristicWriteRequest.WRITE_TYPE_NO_RESPONSE,
                @android.annotation.RequiresPermission(android.Manifest.permission.BLUETOOTH_CONNECT)
            )
            gatt.writeCharacteristic(request)
        } else {
            characteristic.setValue(data)
            characteristic.writeType = BluetoothGattCharacteristic.WRITE_TYPE_NO_RESPONSE
            gatt.writeCharacteristic(characteristic)
        }
    }

    // Callback onCharacteristicWrite (API 33+)
    private val writeCallback = object : BluetoothGattCallback() {
        override fun onCharacteristicWrite(
            gatt: BluetoothGatt,
            characteristic: BluetoothGattCharacteristic,
            value: ByteArray,
            status: Int,
            callbackType: Int
        ) {
            if (status == BluetoothGatt.GATT_SUCCESS) {
                print("Write success: ${value.size} bytes")
            }
        }
    }
}

// Iscrizione corretta alle notifiche BLE
class GattNotificationManager {

    // 1. Abilita notifiche
    fun enableNotification(gatt: BluetoothGatt, characteristic: BluetoothGattCharacteristic) {
        // Passaggio 1: iscrizione locale Android
        val success = gatt.setCharacteristicNotification(characteristic, true)
        if (!success) {
            print("Iscrizione fallita")
            return
        }

        // Passaggio 2: scrivi CCCD (0x2902) sul dispositivo BLE
        val cccdDescriptor = characteristic.getDescriptor(
            UUID.fromString("00002902-0000-1000-8000-00805F9B34FB")
        ) ?: return

        // 0x0100 = notifica, 0x0200 = indicazione
        val cccdValue = if (characteristic.properties
            and BluetoothGattCharacteristic.PROPERTY_NOTIFY != 0) {
            BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE  // [0x01, 0x00]
        } else {
            BluetoothGattDescriptor.ENABLE_INDICATION_VALUE     // [0x02, 0x00]
        }

        cccdDescriptor.setValue(cccdValue)
        gatt.writeDescriptor(cccdDescriptor)
    }

    // 2. Scoperta caratteristiche
    fun disableNotification(gatt: BluetoothGatt, characteristic: BluetoothGattCharacteristic) {
        gatt.setCharacteristicNotification(characteristic, false)
        val cccdDescriptor = characteristic.getDescriptor(
            UUID.fromString("00002902-0000-1000-8000-00805F9B34FB")
        ) ?: return
        cccdDescriptor.setValue(BluetoothGattDescriptor.DISABLE_NOTIFICATION_VALUE)
        gatt.writeDescriptor(cccdDescriptor)
    }

    // 3. Callback notifica
    private val notificationCallback = object : BluetoothGattCallback() {
        override fun onCharacteristicChanged(
            gatt: BluetoothGatt,
            characteristic: BluetoothGattCharacteristic,
            value: ByteArray,
            callbackType: Int
        ) {
            // Nuovo valore dalla periferica BLE
            print("Notification: ${value.size} bytes")
        }
    }
}

// Client GATT completo con coroutine in Kotlin
class GattClient(context: Context) {

    private val context = context.applicationContext
    private var gatt: BluetoothGatt? = null

    // Connetti con coroutine
    suspend fun connect(device: BluetoothDevice): Boolean =
        suspendCoroutine { continuation ->
            gatt = device.connectGatt(
                context, false,
                object : BluetoothGattCallback() {
                    override fun onConnectionStateChange(
                        gatt: BluetoothGatt, status: Int, newState: Int
                    ) {
                        if (newState == BluetoothProfile.STATE_CONNECTED) {
                            gatt.discoverServices()
                        } else {
                            continuation.resume(false)
                        }
                    }

                    override fun onServicesDiscovered(gatt: BluetoothGatt, status: Int) {
                        continuation.resume(status == BluetoothGatt.GATT_SUCCESS)
                    }
                },
                BluetoothDevice.TRANSPORT_LE
            )
        }

    // Leggi caratteristica tramite coroutine
    suspend fun readCharacteristicValue(char: BluetoothGattCharacteristic): ByteArray? =
        suspendCoroutine { continuation ->
            gatt?.let { gatt ->
                // Salva tag caratteristica per identificazione callback
                gatt.setCharacteristic(char, null)  // per API < 33
                gatt.readCharacteristic(char)
            }
        }

    // Chiudi connessione
    fun release() {
        gatt?.disconnect()
        gatt?.close()
        gatt = null
    }
}