import 'dart:async';
import 'dart:developer' as developer;
import 'dart:typed_data';
import 'package:flutter_blue_plus/flutter_blue_plus.dart';
import 'package:permission_handler/permission_handler.dart';
import 'bytes_util.dart';
import 'protocol_parser.dart';

class BleManager {
  static final BleManager instance = BleManager._internal();
  BleManager._internal();

  BluetoothDevice? _connectedDevice;
  BluetoothDevice? _connectingDevice;
  BluetoothCharacteristic? _writeCharacteristic;
  BluetoothCharacteristic? _readCharacteristic;

  /// 有状态的协议解析器（支持 BLE 分片）
  final ProtocolParser _parser = ProtocolParser();

  final Map<DeviceIdentifier, ScanResult> _scanResults = {};
  final StreamController<List<ScanResult>> _scanController =
      StreamController.broadcast();
  final StreamController<BlePacket> _packetController =
      StreamController.broadcast();
  final StreamController<BluetoothDevice?> _connectionController =
      StreamController.broadcast();
  final StreamController<BluetoothDevice?> _connectingController =
      StreamController.broadcast();

  StreamSubscription<List<ScanResult>>? _scanSubscription;
  StreamSubscription<List<int>>? _readSubscription;
  StreamSubscription<BluetoothAdapterState>? _adapterStateSubscription;
  StreamSubscription<BluetoothConnectionState>? _deviceConnectionSubscription;

  /// 防止异步竞态：stopScan() 后 in-flight 的 startScan() 不应生效
  int _scanGen = 0;

  /// 协商后的 MTU 值，用于分片写入
  int _negotiatedMtu = 23;

  /// 已收到的数据包存储（跨页面持久化）
  final List<BlePacket> receivedPacketStore = [];
  static const int _maxStoredPackets = 100;

  void clearReceivedPackets() {
    receivedPacketStore.clear();
  }

  bool get isConnected => _connectedDevice != null;
  BluetoothDevice? get connectedDevice => _connectedDevice;
  BluetoothDevice? get connectingDevice => _connectingDevice;
  Stream<List<ScanResult>> get scanResults => _scanController.stream;
  Stream<BlePacket> get packetStream => _packetController.stream;
  Stream<BluetoothAdapterState> get adapterState =>
      FlutterBluePlus.adapterState;

  /// 连接状态变化流：连接成功时发出 device，断开时发出 null
  Stream<BluetoothDevice?> get connectionStream => _connectionController.stream;

  /// 连接中状态流：开始连接时发出 device，连接完成/失败时发出 null
  Stream<BluetoothDevice?> get connectingStream => _connectingController.stream;

  Future<bool> checkBluetooth() async {
    final state = await FlutterBluePlus.adapterState.first;
    return state == BluetoothAdapterState.on;
  }

  Future<bool> requestPermissions() async {
    final connStatus = await Permission.bluetoothConnect.status;
    developer.log(
      '[BLE] bluetoothConnect status: $connStatus',
      name: 'BleManager',
    );
    if (connStatus.isDenied) {
      developer.log('[BLE] requesting bluetoothConnect...', name: 'BleManager');
      await Permission.bluetoothConnect.request();
    }

    final scanStatus = await Permission.bluetoothScan.status;
    developer.log(
      '[BLE] bluetoothScan status: $scanStatus',
      name: 'BleManager',
    );
    if (scanStatus.isDenied) {
      developer.log('[BLE] requesting bluetoothScan...', name: 'BleManager');
      await Permission.bluetoothScan.request();
    }

    final locStatus = await Permission.locationWhenInUse.status;
    developer.log(
      '[BLE] locationWhenInUse status: $locStatus',
      name: 'BleManager',
    );
    if (locStatus.isDenied) {
      developer.log(
        '[BLE] requesting locationWhenInUse...',
        name: 'BleManager',
      );
      await Permission.locationWhenInUse.request();
    }

    final allGranted =
        await Permission.bluetoothConnect.isGranted &&
        await Permission.bluetoothScan.isGranted;
    developer.log(
      '[BLE] all permissions granted: $allGranted',
      name: 'BleManager',
    );
    return allGranted;
  }

  Future<void> openBluetooth() async {
    try {
      await FlutterBluePlus.turnOn();
    } catch (e) {
      await _goToSystemSettings();
    }
  }

  Future<void> _goToSystemSettings() async {
    await openAppSettings();
  }

  Future<void> _openLocationSettings() async {
    await openAppSettings();
  }

  Future<bool> _checkLocationService() async {
    final locStatus = await Permission.location.serviceStatus;
    developer.log(
      '[BLE] location service status: $locStatus',
      name: 'BleManager',
    );
    return locStatus == ServiceStatus.enabled;
  }

  Future<void> startScan({bool continuous = true}) async {
    final int myGen = ++_scanGen;
    developer.log(
      '[BLE] startScan called, gen=$myGen, continuous=$continuous',
      name: 'BleManager',
    );
    // 先停止任何残留扫描，确保干净启动
    try { await FlutterBluePlus.stopScan(); } catch (_) {}
    _scanResults.clear();
    _scanController.add([]);

    final isOn = await checkBluetooth();
    if (myGen != _scanGen) return;
    developer.log('[BLE] Bluetooth adapter on: $isOn', name: 'BleManager');
    if (!isOn) {
      developer.log(
        '[BLE] Bluetooth is OFF, aborting scan',
        name: 'BleManager',
      );
      return;
    }

    final granted = await requestPermissions();
    if (myGen != _scanGen) return;
    developer.log('[BLE] Permissions granted: $granted', name: 'BleManager');
    if (!granted) {
      developer.log(
        '[BLE] Permissions not granted, aborting scan',
        name: 'BleManager',
      );
      return;
    }

    final locEnabled = await _checkLocationService();
    if (myGen != _scanGen) return;
    if (!locEnabled) {
      developer.log(
        '[BLE] Location service OFF, directing to settings',
        name: 'BleManager',
      );
      await _openLocationSettings();
      return;
    }

    _scanSubscription?.cancel();
    _scanSubscription = FlutterBluePlus.scanResults.listen(
      (results) {
        for (final result in results) {
          _scanResults[result.device.remoteId] = result;
        }
        developer.log(
          '[BLE] 📡 扫描到 ${results.length} 个设备: ${results.map((r) => '${r.device.platformName.isNotEmpty ? r.device.platformName : r.device.advName.isNotEmpty ? r.device.advName : r.device.remoteId} (${r.rssi}dBm)').join(', ')}',
          name: 'BleManager',
        );
        _scanController.add(_scanResults.values.toList());
      },
      onError: (e) {
        developer.log('[BLE] scanResults error: $e', name: 'BleManager');
      },
    );

    try {
      if (continuous) {
        developer.log('[BLE] Starting continuous scan...', name: 'BleManager');
        await FlutterBluePlus.startScan(
          timeout: const Duration(days: 1),
          androidUsesFineLocation: true,
          androidScanMode: AndroidScanMode.lowLatency,
          androidLegacy: true,
        );
      } else {
        developer.log('[BLE] Starting 10s scan...', name: 'BleManager');
        await FlutterBluePlus.startScan(
          timeout: const Duration(seconds: 10),
          androidUsesFineLocation: true,
          androidScanMode: AndroidScanMode.lowLatency,
          androidLegacy: true,
        );
      }
      developer.log('[BLE] startScan completed', name: 'BleManager');
    } catch (e, stackTrace) {
      developer.log(
        '[BLE] startScan error: $e\n$stackTrace',
        name: 'BleManager',
      );
    }
  }

  Future<void> refreshScan() async {
    await stopScan();
    await Future.delayed(const Duration(milliseconds: 200));
    await startScan(continuous: true);
  }

  Future<void> stopScan() async {
    _scanGen++;
    developer.log('[BLE] stopScan, gen=$_scanGen', name: 'BleManager');
    _scanSubscription?.cancel();
    await FlutterBluePlus.stopScan();
  }

  /// 连接设备，返回 null 表示成功，返回错误信息字符串表示失败
  Future<String?> connect(BluetoothDevice device) async {
    // 标记正在连接，通知所有监听者
    _connectingDevice = device;
    _connectingController.add(device);
    try {
      await device
          .connect(license: License.nonprofit, mtu: 512)
          .timeout(const Duration(seconds: 15));
      _connectedDevice = device;
      // 连接成功，立即停止扫描（避免扫描射频干扰导致连接断开）
      await stopScan();
      // 清除连接中状态
      _connectingDevice = null;
      _connectingController.add(null);
      // 监听设备连接状态，任何一方断开都能感知
      _deviceConnectionSubscription?.cancel();
      _deviceConnectionSubscription = device.connectionState.listen((state) {
        developer.log(
          '[BLE] device connectionState: $state',
          name: 'BleManager',
        );
        if (state == BluetoothConnectionState.disconnected) {
          _onDeviceDisconnected();
        }
      });
      _connectionController.add(device);
      await _discoverServices(device);
      // 确认协商后的 MTU
      try {
        final mtu = await device.requestMtu(512);
        _negotiatedMtu = mtu;
        developer.log('[BLE] MTU: $mtu', name: 'BleManager');
      } catch (e) {
        developer.log('[BLE] requestMtu failed: $e', name: 'BleManager');
      }
      return null; // 成功
    } catch (e) {
      // 连接失败，清除连接中状态
      _connectingDevice = null;
      _connectingController.add(null);
      // 返回具体的错误原因
      if (e is TimeoutException) {
        return '连接超时（15秒），请确认设备在附近且已开启';
      }
      return '连接失败: $e';
    }
  }

  void _onDeviceDisconnected() {
    _connectedDevice = null;
    _connectingDevice = null;
    _writeCharacteristic = null;
    _readCharacteristic = null;
    _negotiatedMtu = 23;
    _readSubscription?.cancel();
    _deviceConnectionSubscription?.cancel();
    _connectionController.add(null);
    _connectingController.add(null);
    // 清空协议解析器缓冲区
    _parser.clear();
  }

  Future<void> disconnect() async {
    final device = _connectedDevice;
    if (device == null) return;
    developer.log('[BLE] 发起断开连接...', name: 'BleManager');
    await device.disconnect();
    // 等待连接状态流确认已断开，设置超时防止无限等待
    try {
      await device.connectionState
          .firstWhere((s) => s == BluetoothConnectionState.disconnected)
          .timeout(const Duration(seconds: 3));
      developer.log('[BLE] 连接已确认断开', name: 'BleManager');
    } catch (_) {
      developer.log('[BLE] 等待断开超时，强制清理', name: 'BleManager');
    }
    _onDeviceDisconnected();
  }

  Future<void> _discoverServices(BluetoothDevice device) async {
    final services = await device.discoverServices();
    for (final service in services) {
      for (final characteristic in service.characteristics) {
        if (characteristic.properties.write) {
          _writeCharacteristic = characteristic;
        }
        if (characteristic.properties.notify) {
          _readCharacteristic = characteristic;
          await characteristic.setNotifyValue(true);
          _readSubscription?.cancel();
          _readSubscription = characteristic.lastValueStream.listen((value) {
            _onDataReceived(value);
          });
        }
      }
    }
  }

  void _onDataReceived(List<int> data) {
    developer.log(
      '[BLE] 📩 收: ${data.length}B ${_bytesToHex(data)}',
      name: 'BleManager',
    );
    _parser.append(data);
    final packets = _parser.parse();
    developer.log(
      '[BLE] 📦 解析 ${packets.length}包 (buf ${_parser.bufferLength}B)',
      name: 'BleManager',
    );
    if (packets.isEmpty && data.isNotEmpty) {
      developer.log(
        '[BLE] ⚠️ 非标准帧 raw(${data.length}B)',
        name: 'BleManager',
      );
      final packet = BlePacket(
        command: 0x00,
        payload: Uint8List.fromList(data),
      );
      _storePacket(packet);
      _packetController.add(packet);
      return;
    }
    for (final packet in packets) {
      developer.log(
        '[BLE]    cmd=0x${packet.command.toRadixString(16).toUpperCase().padLeft(2, '0')} '
        'payload(${packet.payload.length}B): ${_bytesToHex(packet.payload)}',
        name: 'BleManager',
      );
      _storePacket(packet);
      _packetController.add(packet);
    }
  }

  void _storePacket(BlePacket packet) {
    receivedPacketStore.insert(0, packet);
    if (receivedPacketStore.length > _maxStoredPackets) {
      receivedPacketStore.removeLast();
    }
  }

  String _bytesToHex(List<int> bytes) {
    if (bytes.isEmpty) return '';
    return bytes
        .map((b) => b.toRadixString(16).toUpperCase().padLeft(2, '0'))
        .join(' ');
  }

  Future<void> sendCommand(int command, List<int> payload) async {
    final char = _writeCharacteristic;
    if (char == null) {
      developer.log('[BLE] ❌ 写特征为空，无法发送', name: 'BleManager');
      return;
    }
    final frame = ProtocolParser.pack(command, payload);
    final crc = frame.length >= 5
        ? 'CRC16=0x${frame[frame.length - 4].toRadixString(16).padLeft(2, '0')}${frame[frame.length - 3].toRadixString(16).padLeft(2, '0')}'
        : '';
    developer.log(
      '[BLE] 📤 发送: 0x${command.toRadixString(16).toUpperCase().padLeft(2, '0')}, '
      '帧(${frame.length}B) $crc\n'
      '    ${_bytesToHex(frame)}',
      name: 'BleManager',
    );
    // 分片写入：每次最多写 (MTU - 3) 字节，全部走 withResponse 确保可靠性
    final maxWriteLen = _negotiatedMtu - 3;
    final totalChunks = (frame.length + maxWriteLen - 1) ~/ maxWriteLen;
    if (totalChunks > 1) {
      developer.log(
        '[BLE] 🔀 分${totalChunks}片写入 (MTU=$_negotiatedMtu, 每片≤${maxWriteLen}B)',
        name: 'BleManager',
      );
    }
    for (int offset = 0; offset < frame.length; offset += maxWriteLen) {
      final end = (offset + maxWriteLen <= frame.length)
          ? offset + maxWriteLen
          : frame.length;
      final chunk = frame.sublist(offset, end);
      if (totalChunks > 1) {
        final chunkIdx = offset ~/ maxWriteLen + 1;
        developer.log(
          '[BLE]  片$chunkIdx/$totalChunks: offset=$offset len=${chunk.length}B ${_bytesToHex(chunk)}',
          name: 'BleManager',
        );
      }
      await char.write(chunk, withoutResponse: false);
    }
    developer.log('[BLE] ✅ 写入完成', name: 'BleManager');
  }

  Future<void> sendRawBytes(List<int> bytes) async {
    if (_writeCharacteristic == null) return;
    await _writeCharacteristic!.write(bytes, withoutResponse: false);
  }

  Future<void> sendHeartbeat() async {
    await sendCommand(0xFF, []);
  }

  void dispose() {
    _scanSubscription?.cancel();
    _readSubscription?.cancel();
    _adapterStateSubscription?.cancel();
    _deviceConnectionSubscription?.cancel();
    _scanController.close();
    _packetController.close();
    _connectionController.close();
    _connectingController.close();
  }
}