package com.example.medilightv2android.ble

import android.annotation.SuppressLint
import android.bluetooth.*
import android.bluetooth.le.*
import android.content.Context
import android.os.Build
import android.os.Handler
import android.os.Looper
import android.util.Log
import androidx.compose.runtime.mutableStateListOf
import androidx.compose.runtime.mutableStateOf
import java.util.UUID

data class BleDevice(
    val device: BluetoothDevice,
    var rssi: Int,
    var isConnecting: Boolean = false,
    var isConnected: Boolean = false
) {
    val name: String @SuppressLint("MissingPermission") get() = try { device.name ?: "Unknown" } catch (_: Exception) { "Unknown" }
    val address: String get() = device.address
}

@SuppressLint("MissingPermission")
class BleManager private constructor(private val context: Context) {

    companion object {
        private const val TAG = "BleManager"

        @Volatile
        private var instance: BleManager? = null
        fun getInstance(context: Context): BleManager =
            instance ?: synchronized(this) {
                instance ?: BleManager(context.applicationContext).also { instance = it }
            }

        val SERVICE_UUID: UUID = UUID.fromString("6E400001-B5A3-F393-E0A9-E50E24DCCA9E")
        val TX_CHAR_UUID: UUID = UUID.fromString("6E400002-B5A3-F393-E0A9-E50E24DCCA9E")
        val RX_CHAR_UUID: UUID = UUID.fromString("6E400003-B5A3-F393-E0A9-E50E24DCCA9E")
        val CCCD_UUID: UUID = UUID.fromString("00002902-0000-1000-8000-00805f9b34fb")
    }

    private val bluetoothManager = context.getSystemService(Context.BLUETOOTH_SERVICE) as BluetoothManager
    private val bluetoothAdapter: BluetoothAdapter? = bluetoothManager.adapter
    private var bluetoothLeScanner: BluetoothLeScanner? = null
    private var bluetoothGatt: BluetoothGatt? = null
    private var txCharacteristic: BluetoothGattCharacteristic? = null
    private var rxCharacteristic: BluetoothGattCharacteristic? = null
    private val handler = Handler(Looper.getMainLooper())
    private var scanTimer: Runnable? = null
    private var batteryTimer: Runnable? = null
    private var connectionTimer: Runnable? = null
    private var isUserDisconnect = false

    val discoveredDevices = mutableStateListOf<BleDevice>()
    val isScanning = mutableStateOf(false)
    val isConnected = mutableStateOf(false)
    val connectedDeviceName = mutableStateOf("")
    val batteryLevel = mutableStateOf(0)
    val bluetoothEnabled = mutableStateOf(bluetoothAdapter?.isEnabled == true)
    val isServiceReady = mutableStateOf(false)
    val isReconnecting = mutableStateOf(false)
    val connectionError = mutableStateOf<String?>(null)

    // Callbacks
    var onConnectionStateChanged: ((Boolean) -> Unit)? = null
    var onNirsPowerOnReceived: (() -> Unit)? = null
    var onNirsSensorActivated: (() -> Unit)? = null
    var onNirsMagReceived: ((ByteArray) -> Unit)? = null
    var onNirsMcjReceived: ((ByteArray) -> Unit)? = null
    var onPiezoDataReceived: ((ByteArray) -> Unit)? = null
    var onUnexpectedDisconnect: (() -> Unit)? = null
    var onReconnectionFailed: (() -> Unit)? = null

    val isBluetoothReady: Boolean get() = bluetoothAdapter?.isEnabled == true

    // Scanning
    fun startScan() {
        if (bluetoothAdapter?.isEnabled != true) {
            bluetoothEnabled.value = false
            return
        }
        bluetoothEnabled.value = true
        discoveredDevices.clear()
        isScanning.value = true
        bluetoothLeScanner = bluetoothAdapter.bluetoothLeScanner

        if (bluetoothLeScanner == null) {
            Log.e(TAG, "BluetoothLeScanner is null")
            isScanning.value = false
            return
        }

        val settings = ScanSettings.Builder()
            .setScanMode(ScanSettings.SCAN_MODE_LOW_LATENCY)
            .build()

        try {
            bluetoothLeScanner?.startScan(null, settings, scanCallback)
            Log.d(TAG, "BLE scan started")
        } catch (e: Exception) {
            Log.e(TAG, "Failed to start scan: ${e.message}")
            isScanning.value = false
            return
        }

        scanTimer?.let { handler.removeCallbacks(it) }
        val timeout = Runnable { stopScan() }
        scanTimer = timeout
        handler.postDelayed(timeout, 15000)
    }

    fun stopScan() {
        try {
            bluetoothLeScanner?.stopScan(scanCallback)
        } catch (e: Exception) {
            Log.w(TAG, "Failed to stop scan: ${e.message}")
        }
        isScanning.value = false
        scanTimer?.let { handler.removeCallbacks(it) }
        scanTimer = null
    }

    private val scanCallback = object : ScanCallback() {
        override fun onScanResult(callbackType: Int, result: ScanResult) {
            val device = result.device
            val name = try { device.name } catch (_: Exception) { null } ?: return
            if (name.isEmpty()) return

            handler.post {
                val existing = discoveredDevices.indexOfFirst { it.address == device.address }
                if (existing >= 0) {
                    discoveredDevices[existing] = discoveredDevices[existing].copy(rssi = result.rssi)
                } else {
                    discoveredDevices.add(BleDevice(device, result.rssi))
                    Log.d(TAG, "Discovered: $name (${device.address}) rssi=${result.rssi}")
                }
            }
        }

        override fun onScanFailed(errorCode: Int) {
            Log.e(TAG, "Scan failed with error code: $errorCode")
            handler.post {
                isScanning.value = false
                connectionError.value = "Scan failed (error $errorCode)"
            }
        }
    }

    // Connection
    fun connect(bleDevice: BleDevice) {
        stopScan()
        Log.d(TAG, "Connecting to ${bleDevice.name} (${bleDevice.address})")

        // Clean up any existing GATT connection
        bluetoothGatt?.let { gatt ->
            Log.d(TAG, "Closing existing GATT connection")
            try {
                gatt.disconnect()
                gatt.close()
            } catch (e: Exception) {
                Log.w(TAG, "Error closing old GATT: ${e.message}")
            }
            bluetoothGatt = null
            txCharacteristic = null
            rxCharacteristic = null
        }

        val idx = discoveredDevices.indexOfFirst { it.address == bleDevice.address }
        if (idx >= 0) discoveredDevices[idx] = discoveredDevices[idx].copy(isConnecting = true)

        connectionError.value = null

        try {
            bluetoothGatt = bleDevice.device.connectGatt(context, false, gattCallback, BluetoothDevice.TRANSPORT_LE)
            Log.d(TAG, "connectGatt called, gatt=${bluetoothGatt != null}")
        } catch (e: Exception) {
            Log.e(TAG, "connectGatt failed: ${e.message}")
            handler.post {
                connectionError.value = "Connection failed: ${e.message}"
                if (idx >= 0) discoveredDevices[idx] = discoveredDevices[idx].copy(isConnecting = false)
            }
            return
        }

        // Connection timeout
        connectionTimer?.let { handler.removeCallbacks(it) }
        val timeout = Runnable {
            if (!isConnected.value) {
                Log.w(TAG, "Connection timeout")
                bluetoothGatt?.let { gatt ->
                    try {
                        gatt.disconnect()
                        gatt.close()
                    } catch (_: Exception) {}
                }
                bluetoothGatt = null
                connectionError.value = "Connection timed out. Try again."
                if (idx >= 0 && idx < discoveredDevices.size) {
                    discoveredDevices[idx] = discoveredDevices[idx].copy(isConnecting = false)
                }
            }
        }
        connectionTimer = timeout
        handler.postDelayed(timeout, 10000)
    }

    fun disconnect() {
        isUserDisconnect = true
        connectionTimer?.let { handler.removeCallbacks(it) }
        connectionTimer = null
        bluetoothGatt?.disconnect()
    }

    // Reconnection
    fun reconnectToLastDevice(lastDeviceAddress: String?) {
        if (lastDeviceAddress == null || bluetoothAdapter?.isEnabled != true) {
            onReconnectionFailed?.invoke()
            return
        }

        // Clean up existing
        bluetoothGatt?.let { gatt ->
            try { gatt.disconnect(); gatt.close() } catch (_: Exception) {}
            bluetoothGatt = null
        }

        isReconnecting.value = true
        val device = bluetoothAdapter.getRemoteDevice(lastDeviceAddress)
        bluetoothGatt = device.connectGatt(context, false, gattCallback, BluetoothDevice.TRANSPORT_LE)

        handler.postDelayed({
            if (isReconnecting.value) {
                isReconnecting.value = false
                bluetoothGatt?.let { gatt ->
                    try { gatt.disconnect(); gatt.close() } catch (_: Exception) {}
                }
                bluetoothGatt = null
                onReconnectionFailed?.invoke()
            }
        }, 10000)
    }

    // Send
    fun sendRaw(data: ByteArray) {
        val characteristic = txCharacteristic ?: return
        val gatt = bluetoothGatt ?: return
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
            gatt.writeCharacteristic(characteristic, data, BluetoothGattCharacteristic.WRITE_TYPE_NO_RESPONSE)
        } else {
            @Suppress("DEPRECATION")
            characteristic.value = data
            characteristic.writeType = BluetoothGattCharacteristic.WRITE_TYPE_NO_RESPONSE
            @Suppress("DEPRECATION")
            gatt.writeCharacteristic(characteristic)
        }
    }

    // Piezo Commands
    fun sendPiezoPowerOn(freqOption: Int, cycles: Int) {
        sendRaw(CRC16.buildCommand("mpa", intArrayOf(freqOption, cycles)))
    }

    fun sendPiezoStop() {
        sendRaw(CRC16.buildCommand("mps"))
    }

    fun sendBurst(freqOption: Int, cycles: Int, delayUs: Int, piezoCh: Int = 0) {
        sendRaw(CRC16.buildCommand("mec", intArrayOf(freqOption, delayUs, 140, cycles, 1, piezoCh)))
    }

    // NIRS Commands
    fun sendNirsPowerOn() {
        sendRaw(CRC16.buildCommand("mta", intArrayOf(1)))
    }

    fun sendMqqQuery() {
        sendRaw(CRC16.buildCommand("mqq"))
    }

    fun sendMagQuery() {
        sendRaw(CRC16.buildCommand("mag"))
    }

    fun sendMcjQuery() {
        sendRaw(CRC16.buildCommand("mcj"))
    }

    fun sendBatteryQuery() {
        sendRaw(CRC16.buildCommand("msn", intArrayOf(0)))
    }

    fun startBatteryPolling() {
        batteryTimer?.let { handler.removeCallbacks(it) }
        handler.postDelayed({ sendBatteryQuery() }, 1000)
        val poll = object : Runnable {
            override fun run() {
                sendBatteryQuery()
                handler.postDelayed(this, 30000)
            }
        }
        batteryTimer = poll
        handler.postDelayed(poll, 31000)
    }

    private fun stopBatteryPolling() {
        batteryTimer?.let { handler.removeCallbacks(it) }
        batteryTimer = null
    }

    private val gattCallback = object : BluetoothGattCallback() {
        override fun onConnectionStateChange(gatt: BluetoothGatt, status: Int, newState: Int) {
            Log.d(TAG, "onConnectionStateChange: status=$status newState=$newState")
            handler.post {
                // Cancel connection timeout
                connectionTimer?.let { handler.removeCallbacks(it) }
                connectionTimer = null

                if (status != BluetoothGatt.GATT_SUCCESS && newState != BluetoothProfile.STATE_CONNECTED) {
                    // Connection failed with error
                    Log.e(TAG, "GATT connection failed with status: $status")
                    bluetoothGatt = null
                    txCharacteristic = null
                    rxCharacteristic = null
                    isConnected.value = false
                    isServiceReady.value = false
                    isReconnecting.value = false
                    connectionError.value = "Connection failed (status $status). Try again."

                    val idx = discoveredDevices.indexOfFirst { it.address == gatt.device.address }
                    if (idx >= 0) discoveredDevices[idx] = discoveredDevices[idx].copy(isConnected = false, isConnecting = false)

                    gatt.close()
                    return@post
                }

                when (newState) {
                    BluetoothProfile.STATE_CONNECTED -> {
                        Log.d(TAG, "Connected to ${gatt.device.address}")
                        isReconnecting.value = false
                        isUserDisconnect = false
                        connectionError.value = null
                        val idx = discoveredDevices.indexOfFirst { it.address == gatt.device.address }
                        if (idx >= 0) discoveredDevices[idx] = discoveredDevices[idx].copy(isConnected = true, isConnecting = false)
                        isConnected.value = true
                        connectedDeviceName.value = try { gatt.device.name ?: "Unknown" } catch (_: Exception) { "Unknown" }

                        // Save last connected device address
                        try {
                            val prefs = context.getSharedPreferences("medilight_prefs", Context.MODE_PRIVATE)
                            prefs.edit().putString("last_device_address", gatt.device.address).apply()
                        } catch (_: Exception) {}

                        gatt.discoverServices()
                        startBatteryPolling()
                        onConnectionStateChanged?.invoke(true)
                    }
                    BluetoothProfile.STATE_DISCONNECTED -> {
                        Log.d(TAG, "Disconnected from ${gatt.device.address}")
                        stopBatteryPolling()
                        bluetoothGatt = null
                        txCharacteristic = null
                        rxCharacteristic = null
                        isConnected.value = false
                        isServiceReady.value = false
                        connectedDeviceName.value = ""
                        batteryLevel.value = 0

                        val idx = discoveredDevices.indexOfFirst { it.address == gatt.device.address }
                        if (idx >= 0) discoveredDevices[idx] = discoveredDevices[idx].copy(isConnected = false, isConnecting = false)

                        onConnectionStateChanged?.invoke(false)

                        if (!isUserDisconnect) {
                            onUnexpectedDisconnect?.invoke()
                        }
                        isUserDisconnect = false
                        gatt.close()
                    }
                }
            }
        }

        override fun onServicesDiscovered(gatt: BluetoothGatt, status: Int) {
            Log.d(TAG, "onServicesDiscovered: status=$status")
            if (status != BluetoothGatt.GATT_SUCCESS) {
                handler.post { connectionError.value = "Service discovery failed (status $status)" }
                return
            }
            val service = gatt.getService(SERVICE_UUID)
            if (service == null) {
                Log.e(TAG, "NUS service not found!")
                handler.post { connectionError.value = "Device service not found" }
                return
            }
            txCharacteristic = service.getCharacteristic(TX_CHAR_UUID)
            rxCharacteristic = service.getCharacteristic(RX_CHAR_UUID)

            Log.d(TAG, "TX=${txCharacteristic != null}, RX=${rxCharacteristic != null}")

            rxCharacteristic?.let { rx ->
                gatt.setCharacteristicNotification(rx, true)
                val descriptor = rx.getDescriptor(CCCD_UUID)
                if (descriptor != null) {
                    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
                        gatt.writeDescriptor(descriptor, BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE)
                    } else {
                        @Suppress("DEPRECATION")
                        descriptor.value = BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE
                        @Suppress("DEPRECATION")
                        gatt.writeDescriptor(descriptor)
                    }
                } else {
                    Log.w(TAG, "CCCD descriptor not found for RX characteristic")
                    // No CCCD but still mark ready if characteristics exist
                    handler.post {
                        if (txCharacteristic != null && rxCharacteristic != null) {
                            isServiceReady.value = true
                            Log.d(TAG, "Service ready (no CCCD)")
                        }
                    }
                }
            } ?: run {
                // No RX characteristic, mark ready if TX exists
                handler.post {
                    if (txCharacteristic != null) {
                        isServiceReady.value = true
                        Log.d(TAG, "Service ready (no RX)")
                    }
                }
            }
        }

        override fun onDescriptorWrite(gatt: BluetoothGatt, descriptor: BluetoothGattDescriptor, status: Int) {
            Log.d(TAG, "onDescriptorWrite: status=$status uuid=${descriptor.uuid}")
            if (descriptor.uuid == CCCD_UUID) {
                handler.post {
                    if (status == BluetoothGatt.GATT_SUCCESS) {
                        if (txCharacteristic != null && rxCharacteristic != null) {
                            isServiceReady.value = true
                            Log.d(TAG, "Service ready! (CCCD written)")
                        }
                    } else {
                        Log.e(TAG, "CCCD write failed with status: $status")
                        connectionError.value = "Notification setup failed (status $status)"
                    }
                }
            }
        }

        override fun onCharacteristicChanged(gatt: BluetoothGatt, characteristic: BluetoothGattCharacteristic, value: ByteArray) {
            if (characteristic.uuid == RX_CHAR_UUID) {
                if (value.size < 4) return
                handler.post { processReceivedData(value) }
            }
        }

        @Deprecated("Deprecated in API 33", ReplaceWith("onCharacteristicChanged(gatt, characteristic, value)"))
        override fun onCharacteristicChanged(gatt: BluetoothGatt, characteristic: BluetoothGattCharacteristic) {
            if (characteristic.uuid == RX_CHAR_UUID) {
                @Suppress("DEPRECATION")
                val data = characteristic.value ?: return
                if (data.size < 4) return
                handler.post { processReceivedData(data) }
            }
        }
    }

    private fun processReceivedData(data: ByteArray) {
        val prefix = String(data, 0, minOf(4, data.size), Charsets.US_ASCII)
        Log.d(TAG, "Received: $prefix (${data.size} bytes)")
        when (prefix) {
            "rta:", "rta!" -> onNirsPowerOnReceived?.invoke()
            "rsh:", "rsh!", "rqq:", "rqq!" -> onNirsSensorActivated?.invoke()
            "rag:", "rag!" -> onNirsMagReceived?.invoke(data)
            "rcj:", "rcj!" -> onNirsMcjReceived?.invoke(data)
            "rpa:" -> onPiezoDataReceived?.invoke(data)
            "rsn:" -> {
                if (data.size >= 6) {
                    val millivolts = ((data[4].toInt() and 0xFF) shl 8) or (data[5].toInt() and 0xFF)
                    batteryLevel.value = ((millivolts - 3700) * 100 / 500).coerceIn(0, 100)
                }
            }
        }
    }
}