import 'dart:async';
import 'dart:math';
import 'package:flutter_blue_plus/flutter_blue_plus.dart';
import '../models/bp_reading.dart';

/// 欧姆龙蓝牙血压计 BLE 服务
class OmronBleService {
  static const bpServiceUuid = '00001810-0000-1000-8000-00805F9B34FB';
  static const bpMeasurementUuid = '00002A35-0000-1000-8000-00805F9B34FB';
  static const bpFeatureUuid = '00002A49-0000-1000-8000-00805F9B34FB';
  static const dateTimeUuid = '00002A08-0000-1000-8000-00805F9B34FB';

  BluetoothDevice? _device;
  StreamSubscription<List<int>>? _subscription;
  final _readingsController = StreamController<BpReading>.broadcast();
  Stream<BpReading> get readings => _readingsController.stream;

  bool get isConnected => _device?.isConnected ?? false;

  /// 扫描血压计设备
  Stream<ScanResult> scan({Duration timeout = const Duration(seconds: 15)}) async* {
    await FlutterBluePlus.startScan(timeout: timeout);
    await for (final list in FlutterBluePlus.scanResults) {
      for (final r in list) {
        yield r;
      }
    }
  }

  /// 判断是否为血压计设备
  static bool isBpDevice(ScanResult r) {
    final name = [
      r.advertisementData.localName,
      r.device.platformName,
    ].where((n) => n.isNotEmpty).join(' ').toUpperCase();
    return name.contains('OMRON') ||
           name.contains('HEM') ||
           name.contains('BLESMART') ||
           name.contains('J735') ||
           name.contains('BPM') ||
           name.contains('BP');
  }

  /// 连接设备并订阅测量数据
  Future<void> connect(BluetoothDevice device) async {
    _device = device;
    await device.connect(autoConnect: false);
    await device.discoverServices();

    final services = await device.discoverServices();
    final bpService = services.firstWhere(
      (s) => s.uuid.str128.toUpperCase() == bpServiceUuid.toUpperCase(),
    );

    final measurementChar = bpService.characteristics.firstWhere(
      (c) => c.uuid.str128.toUpperCase() == bpMeasurementUuid.toUpperCase(),
    );

    await measurementChar.setNotifyValue(true);
    _subscription = measurementChar.lastValueStream.listen(_parseReading);
    await _syncTime(bpService);
  }

  /// 断开连接
  Future<void> disconnect() async {
    _subscription?.cancel();
    _subscription = null;
    await _device?.disconnect();
    _device = null;
  }

  void dispose() {
    disconnect();
    _readingsController.close();
  }

  // ── 解析 BLE 测量数据（Bluetooth SIG BP Service 1.1） ──

  void _parseReading(List<int> raw) {
    if (raw.length < 7) return;

    final flags = raw[0];
    final isKpa = (flags & 0x01) != 0;
    final hasTimestamp = (flags & 0x02) != 0;
    final hasPulse = (flags & 0x04) != 0;
    final hasUserId = (flags & 0x08) != 0;
    final hasStatus = (flags & 0x10) != 0;

    int systolic = _decodeSFloat(raw[1] | (raw[2] << 8)).round();
    int diastolic = _decodeSFloat(raw[3] | (raw[4] << 8)).round();

    if (isKpa) {
      systolic = (systolic * 7.50062).round();
      diastolic = (diastolic * 7.50062).round();
    }

    int offset = 7;
    DateTime timestamp = DateTime.now();

    if (hasTimestamp && raw.length >= offset + 7) {
      int year = raw[offset] | (raw[offset + 1] << 8);
      int month = raw[offset + 2];
      int day = raw[offset + 3];
      int hour = raw[offset + 4];
      int minute = raw[offset + 5];
      int second = raw[offset + 6];
      timestamp = DateTime(year, month, day, hour, minute, second);
      offset += 7;
    }

    int? pulse;
    if (hasPulse && raw.length >= offset + 2) {
      pulse = _decodeSFloat(raw[offset] | (raw[offset + 1] << 8)).round();
      offset += 2;
    }

    String? userId;
    if (hasUserId && raw.length > offset) {
      userId = raw[offset].toString();
      offset += 1;
    }

    bool bodyMovement = false, irregularPulse = false;
    if (hasStatus && raw.length >= offset + 2) {
      int status = raw[offset] | (raw[offset + 1] << 8);
      bodyMovement = (status & 0x0001) != 0;
      irregularPulse = (status & 0x0800) != 0;
    }

    _readingsController.add(BpReading(
      systolic: systolic,
      diastolic: diastolic,
      pulse: pulse,
      timestamp: timestamp,
      userId: userId,
      isKpa: isKpa,
      hasBodyMovement: bodyMovement,
      hasIrregularPulse: irregularPulse,
    ));
  }

  /// SFLOAT IEEE-11073 16-bit 解码
  static double _decodeSFloat(int raw) {
    int mantissa = raw & 0x0FFF;
    if (mantissa & 0x0800 != 0) mantissa |= 0xFFFFF000;
    int exponent = (raw >> 12) & 0x0F;
    if (exponent & 0x08 != 0) exponent |= 0xFFFFFFF0;
    return (mantissa * pow(10, exponent)).toDouble();
  }

  /// 同步当前时间到设备
  Future<void> _syncTime(BluetoothService service) async {
    try {
      final dtChar = service.characteristics.firstWhere(
        (c) => c.uuid.str128.toUpperCase() == dateTimeUuid.toUpperCase(),
      );
      final now = DateTime.now();
      await dtChar.write([
        now.year & 0xFF, now.year >> 8,
        now.month, now.day,
        now.hour, now.minute, now.second,
      ]);
    } catch (e) { print('[BLE]读取数据失败: $e'); }
  }
}