import React, {useState, useEffect, useRef} from 'react';
import {
  StyleSheet,
  View,
  Text,
  TouchableOpacity,
  FlatList,
  Platform,
  PermissionsAndroid,
  DeviceEventEmitter,
  NativeModules,
} from 'react-native';
import {SafeAreaProvider, SafeAreaView} from 'react-native-safe-area-context';

// Device type string names accepted by startDiscovery on both platforms
const DEVICE_TYPE_KEYS = [
  'AM3S', 'AM4', 'PO3', 'BP5', 'BP5S', 'BP3L', 'BP7', 'BP7S',
  'KN550', 'HS2', 'HS2S', 'HS4S', 'BG1', 'BG1S', 'BG5', 'BG5S',
  'ECG3', 'BTM', 'TS28B', 'NT13B',
] as const;

type DeviceTypeName = (typeof DEVICE_TYPE_KEYS)[number];

// The native module exports string constants on iOS, number constants on Android.
type DiscoveryConstant = string | number;

interface IHealthDeviceManager {
  // Device type constants (string on iOS, number on Android)
  AM3S: DiscoveryConstant;
  AM4: DiscoveryConstant;
  PO3: DiscoveryConstant;
  BP5: DiscoveryConstant;
  BP5S: DiscoveryConstant;
  BP3L: DiscoveryConstant;
  BP7: DiscoveryConstant;
  BP7S: DiscoveryConstant;
  KN550: DiscoveryConstant;
  HS2: DiscoveryConstant;
  HS2S: DiscoveryConstant;
  HS4S: DiscoveryConstant;
  BG1: DiscoveryConstant;
  BG1S: DiscoveryConstant;
  BG5: DiscoveryConstant;
  BG5S: DiscoveryConstant;
  ECG3: DiscoveryConstant;
  BTM: DiscoveryConstant;
  TS28B: DiscoveryConstant;
  NT13B: DiscoveryConstant;
  // Event name constants
  Event_Scan_Device: string;
  Event_Scan_Finish: string;
  Event_Device_Connected: string;
  Event_Device_Connect_Failed: string;
  Event_Device_Disconnect: string;
  Event_Authenticate_Result: string;
  // Methods — startDiscovery takes a device type name string per official docs
  startDiscovery(type: DeviceTypeName | string): void;
  stopDiscovery(): void;
  connectDevice(mac: string, type: string): void;
  disconnectDevice(mac: string, type: string): void;
  sdkAuthWithLicense(license: string): void;
  authenConfigureInfo(userName: string, clientID: string, clientSecret: string): void;
  getDevicesIDPS(mac: string, callback: (idps: Record<string, string>) => void): void;
}

const iHealthDeviceManagerModule =
  NativeModules.iHealthDeviceManagerModule as IHealthDeviceManager;

type Device = {
  mac: string;
  type: string;
  rssi?: number;
  timestamp: number;
};

async function requestAndroidPermissions(): Promise<boolean> {
  if (Platform.OS !== 'android') return true;

  const apiLevel = Platform.Version;
  const permissions: string[] = [];

  if (apiLevel >= 31) {
    permissions.push(
      PermissionsAndroid.PERMISSIONS.BLUETOOTH_SCAN,
      PermissionsAndroid.PERMISSIONS.BLUETOOTH_CONNECT,
    );
  }
  permissions.push(PermissionsAndroid.PERMISSIONS.ACCESS_FINE_LOCATION);

  const results = await PermissionsAndroid.requestMultiple(permissions as any);
  return Object.values(results).every(
    r => r === PermissionsAndroid.RESULTS.GRANTED,
  );
}

function DeviceIcon({type}: {type: string}) {
  const icons: Record<string, string> = {
    BP: 'BP',
    AM: 'AM',
    PO: 'PO',
    BG: 'BG',
    HS: 'HS',
    ECG: 'ECG',
    BTM: 'BTM',
  };
  const prefix = Object.keys(icons).find(k => type.startsWith(k)) || '?';
  return (
    <View style={styles.deviceIcon}>
      <Text style={styles.deviceIconText}>{icons[prefix] || '?'}</Text>
    </View>
  );
}

function App() {
  const [devices, setDevices] = useState<Device[]>([]);
  const [scanning, setScanning] = useState(false);
  const [error, setError] = useState<string | null>(null);
  const devicesRef = useRef<Device[]>([]);

  useEffect(() => {
    if (!iHealthDeviceManagerModule) {
      setError('iHealth native module not found. Check linking.');
      return;
    }

    // The iHealth SDK uses the global DeviceEventEmitter (not NativeEventEmitter)
    // because the iOS native module doesn't subclass RCTEventEmitter.
    const scanSub = DeviceEventEmitter.addListener(
      iHealthDeviceManagerModule.Event_Scan_Device ?? 'event_scan_device',
      (event: {mac: string; type: string; rssi?: number}) => {
        const {mac = '', type = 'Unknown', rssi} = event;

        // Filter out AM3 — likely false positives from non-iHealth heart rate devices
        if (type === 'AM3') return;

        const existing = devicesRef.current.findIndex(d => d.mac === mac);
        let updated: Device[];
        if (existing >= 0) {
          updated = [...devicesRef.current];
          updated[existing] = {mac, type, rssi, timestamp: Date.now()};
        } else {
          updated = [
            ...devicesRef.current,
            {mac, type, rssi, timestamp: Date.now()},
          ];
        }
        devicesRef.current = updated;
        setDevices(updated);
      },
    );

    const finishSub = DeviceEventEmitter.addListener(
      iHealthDeviceManagerModule.Event_Scan_Finish ?? 'event_scan_finish',
      () => {
        setScanning(false);
      },
    );

    return () => {
      scanSub.remove();
      finishSub.remove();
    };
  }, []);

  const startScan = async () => {
    setError(null);

    const granted = await requestAndroidPermissions();
    if (!granted) {
      setError('Bluetooth permissions denied');
      return;
    }

    devicesRef.current = [];
    setDevices([]);
    setScanning(true);

    // Discover all device types. 'ALL' hits the default case in getDiscoveryType()
    // which maps to DiscoveryTypeEnum.All (MIX = BLE + BT Classic + WiFi).
    // Requires ACCESS_NETWORK_STATE permission for WiFi scan.
    try {
      iHealthDeviceManagerModule.startDiscovery('ALL');
    } catch (e) {
      console.log('Failed to start discovery:', e);
    }
  };

  const stopScan = () => {
    try {
      iHealthDeviceManagerModule.stopDiscovery();
    } catch (e) {
      console.log('Failed to stop discovery:', e);
    }
    setScanning(false);
  };

  const renderDevice = ({item}: {item: Device}) => (
    <View style={styles.deviceRow}>
      <DeviceIcon type={item.type} />
      <View style={styles.deviceInfo}>
        <Text style={styles.deviceType}>{item.type}</Text>
        <Text style={styles.deviceMac}>{item.mac}</Text>
      </View>
      {item.rssi != null && (
        <Text style={styles.deviceRssi}>{item.rssi} dBm</Text>
      )}
    </View>
  );

  return (
    <SafeAreaProvider>
      <SafeAreaView style={styles.container}>
        <Text style={styles.title}>iHealth Scanner</Text>
        <Text style={styles.subtitle}>
          {scanning
            ? `Scanning... (${devices.length} found)`
            : `${devices.length} device(s) found`}
        </Text>

        {error && <Text style={styles.error}>{error}</Text>}

        <TouchableOpacity
          style={[styles.button, scanning && styles.buttonStop]}
          onPress={scanning ? stopScan : startScan}>
          <Text style={styles.buttonText}>
            {scanning ? 'Stop Scan' : 'Start Scan'}
          </Text>
        </TouchableOpacity>

        <FlatList
          data={devices}
          keyExtractor={item => item.mac}
          renderItem={renderDevice}
          style={styles.list}
          contentContainerStyle={devices.length === 0 && styles.emptyList}
          ListEmptyComponent={
            <Text style={styles.emptyText}>
              {scanning
                ? 'Looking for iHealth devices...'
                : 'Tap "Start Scan" to find nearby iHealth devices'}
            </Text>
          }
        />
      </SafeAreaView>
    </SafeAreaProvider>
  );
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    backgroundColor: '#f5f5f5',
    paddingHorizontal: 16,
  },
  title: {
    fontSize: 28,
    fontWeight: '700',
    color: '#1a1a1a',
    marginTop: 16,
  },
  subtitle: {
    fontSize: 14,
    color: '#666',
    marginTop: 4,
    marginBottom: 16,
  },
  error: {
    color: '#d32f2f',
    fontSize: 13,
    marginBottom: 8,
    backgroundColor: '#ffebee',
    padding: 8,
    borderRadius: 6,
  },
  button: {
    backgroundColor: '#2196F3',
    paddingVertical: 14,
    borderRadius: 10,
    alignItems: 'center',
    marginBottom: 16,
  },
  buttonStop: {
    backgroundColor: '#f44336',
  },
  buttonText: {
    color: '#fff',
    fontSize: 16,
    fontWeight: '600',
  },
  list: {
    flex: 1,
  },
  emptyList: {
    flex: 1,
    justifyContent: 'center',
    alignItems: 'center',
  },
  emptyText: {
    color: '#999',
    fontSize: 15,
    textAlign: 'center',
  },
  deviceRow: {
    flexDirection: 'row',
    alignItems: 'center',
    backgroundColor: '#fff',
    padding: 14,
    borderRadius: 10,
    marginBottom: 8,
    shadowColor: '#000',
    shadowOffset: {width: 0, height: 1},
    shadowOpacity: 0.05,
    shadowRadius: 2,
    elevation: 1,
  },
  deviceIcon: {
    width: 44,
    height: 44,
    borderRadius: 22,
    backgroundColor: '#e3f2fd',
    justifyContent: 'center',
    alignItems: 'center',
    marginRight: 12,
  },
  deviceIconText: {
    fontSize: 13,
    fontWeight: '700',
    color: '#1565c0',
  },
  deviceInfo: {
    flex: 1,
  },
  deviceType: {
    fontSize: 16,
    fontWeight: '600',
    color: '#1a1a1a',
  },
  deviceMac: {
    fontSize: 12,
    color: '#888',
    fontFamily: Platform.OS === 'ios' ? 'Menlo' : 'monospace',
    marginTop: 2,
  },
  deviceRssi: {
    fontSize: 12,
    color: '#999',
    marginLeft: 8,
  },
});

export default App;