import 'dart:async';
import 'dart:typed_data';

import 'package:flutter/material.dart';
import 'package:flutter_blue_plus/flutter_blue_plus.dart';
import 'package:flutter_local_notifications/flutter_local_notifications.dart';
import 'package:permission_handler/permission_handler.dart';
import 'package:provider/provider.dart';
import 'package:sighej/screens/profile_screen.dart';
import 'package:sighej/services/api_service.dart';
import 'package:sighej/services/session_store.dart';

// BLE service UUID that identifies SigHej devices.
const String kSigHejServiceUuid = '1248f5a0-0000-1000-8000-00805f9b34fb';

// Manufacturer ID used in BLE advertising data (Android).
const int kManufacturerId = 0x4E58; // "NX"

final FlutterLocalNotificationsPlugin _notifications =
    FlutterLocalNotificationsPlugin();

const _androidChannel = AndroidNotificationDetails(
  'sighej_nudge',
  'SigHej Nudges',
  channelDescription: 'Notifies when a nearby person shares your interests',
  importance: Importance.high,
  priority: Priority.high,
  icon: '@mipmap/ic_launcher',
);

class HomeScreen extends StatefulWidget {
  const HomeScreen({super.key});

  @override
  State<HomeScreen> createState() => _HomeScreenState();
}

class _HomeScreenState extends State<HomeScreen> {
  bool _openToTalk = false;
  String? _lastNudge;
  StreamSubscription? _bleSub;

  // Track tokens we have already matched this session to avoid spam.
  final Set<String> _matchedTokens = {};

  @override
  void initState() {
    super.initState();
    _initNotifications();
  }

  Future<void> _initNotifications() async {
    const android = AndroidInitializationSettings('@mipmap/ic_launcher');
    const ios = DarwinInitializationSettings(
      requestAlertPermission: true,
      requestBadgePermission: true,
      requestSoundPermission: true,
    );
    await _notifications.initialize(
      const InitializationSettings(android: android, iOS: ios),
    );
  }

  @override
  void dispose() {
    _stopScanning();
    super.dispose();
  }

  Future<void> _toggle(SessionStore store) async {
    if (_openToTalk) {
      _stopScanning();
      return;
    }

    final granted = await _requestPermissions();
    if (!granted) return;

    await registerSession(
      store.bleToken,
      store.interests,
      name: store.name,
      tagline: store.tagline,
    );
    await _startAdvertising(store.bleToken);

    FlutterBluePlus.startScan(timeout: const Duration(minutes: 120));
    _bleSub = FlutterBluePlus.onScanResults.listen((results) async {
      for (final r in results) {
        final detected = _parseSigHejToken(r);
        if (detected == null ||
            detected == store.bleToken ||
            _matchedTokens.contains(detected)) {
          continue;
        }
        _matchedTokens.add(detected);
        await _handlePotentialMatch(store.bleToken, detected, store);
      }
    });

    setState(() => _openToTalk = true);
  }

  Future<void> _startAdvertising(String token) async {
    final tokenBytes = Uint8List.fromList(token.codeUnits);
    try {
      await FlutterBluePlus.startAdvertising(
        AdvertiseData(
          serviceUuids: [Guid(kSigHejServiceUuid)],
          manufacturerData: [ManufacturerData(kManufacturerId, tokenBytes)],
        ),
      );
    } catch (e) {
      debugPrint('BLE advertise error: $e');
    }
  }

  void _stopScanning() {
    FlutterBluePlus.stopScan();
    FlutterBluePlus.stopAdvertising();
    _bleSub?.cancel();
    _bleSub = null;
    _matchedTokens.clear();
    setState(() {
      _openToTalk = false;
      _lastNudge = null;
    });
  }

  Future<void> _handlePotentialMatch(
      String own, String detected, SessionStore store) async {
    try {
      final result = await reportMatch(own, detected);
      if (result == null || !result.match) return;

      final interests = result.sharedInterests;
      final body = interests.isEmpty
          ? '${store.displayName} — nogen i nærheden er åben for en snak!'
          : 'Fælles interesser: ${interests.join(', ')}';

      await _showNudgeNotification('SigHej — sig hej!', body);
      setState(() => _lastNudge = body);
    } catch (e) {
      debugPrint('Match error: $e');
    }
  }

  Future<void> _showNudgeNotification(String title, String body) async {
    const details = NotificationDetails(android: _androidChannel);
    await _notifications.show(
      body.hashCode,
      title,
      body,
      details,
    );
  }

  /// Parses a SigHej BLE token from a scan result.
  /// Android: reads manufacturer data with key [kManufacturerId].
  /// iOS fallback: reads service data for [kSigHejServiceUuid].
  String? _parseSigHejToken(ScanResult result) {
    final ad = result.advertisementData;

    // Filter: only process SigHej advertisers.
    final hasSigHejUuid = ad.serviceUuids
        .map((g) => g.toString().toLowerCase())
        .contains(kSigHejServiceUuid.toLowerCase());
    if (!hasSigHejUuid) return null;

    // Android: manufacturer data.
    final mfr = ad.manufacturerData[kManufacturerId];
    if (mfr != null && mfr.isNotEmpty) {
      try {
        return String.fromCharCodes(mfr);
      } catch (_) {}
    }

    // iOS fallback: service data.
    final svcData = ad.serviceData[Guid(kSigHejServiceUuid)];
    if (svcData != null && svcData.isNotEmpty) {
      try {
        return String.fromCharCodes(svcData);
      } catch (_) {}
    }

    return null;
  }

  Future<bool> _requestPermissions() async {
    final perms = [
      Permission.bluetooth,
      Permission.bluetoothScan,
      Permission.bluetoothAdvertise,
      Permission.bluetoothConnect,
      Permission.location,
      Permission.notification,
    ];
    final statuses = await perms.request();
    return statuses.values.every((s) => s.isGranted || s.isLimited);
  }

  @override
  Widget build(BuildContext context) {
    final store = context.watch<SessionStore>();

    return Scaffold(
      appBar: AppBar(
        title: const Text('SigHej'),
        actions: [
          IconButton(
            icon: const Icon(Icons.person_outline),
            onPressed: () => Navigator.of(context).push(
              MaterialPageRoute(builder: (_) => const ProfileScreen()),
            ),
            tooltip: 'Rediger profil',
          ),
        ],
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            Text(
              _openToTalk ? 'You\'re open to talk' : 'Tap to open up',
              style: Theme.of(context).textTheme.headlineSmall,
            ),
            const SizedBox(height: 32),
            GestureDetector(
              onTap: () => _toggle(store),
              child: AnimatedContainer(
                duration: const Duration(milliseconds: 300),
                width: 150,
                height: 150,
                decoration: BoxDecoration(
                  shape: BoxShape.circle,
                  color: _openToTalk
                      ? Theme.of(context).colorScheme.primary
                      : Theme.of(context).colorScheme.surfaceContainerHighest,
                ),
                child: Icon(
                  _openToTalk ? Icons.record_voice_over : Icons.mic_off,
                  size: 60,
                  color: _openToTalk
                      ? Theme.of(context).colorScheme.onPrimary
                      : Theme.of(context).colorScheme.onSurfaceVariant,
                ),
              ),
            ),
            if (_lastNudge != null) ...[
              const SizedBox(height: 40),
              Card(
                margin: const EdgeInsets.symmetric(horizontal: 24),
                child: Padding(
                  padding: const EdgeInsets.all(16),
                  child: Text(
                    _lastNudge!,
                    textAlign: TextAlign.center,
                    style: Theme.of(context).textTheme.bodyLarge,
                  ),
                ),
              ),
            ],
          ],
        ),
      ),
    );
  }
}