import 'package:flutter/material.dart';
import 'package:flutter_bluetooth_serial/flutter_bluetooth_serial.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:permission_handler/permission_handler.dart';
import '../../../core/bluetooth/bt_poller.dart';
import '../../../core/providers/bt_provider.dart';
import '../../../core/providers/settings_provider.dart';
import '../../widgets/main_nav.dart';

class BtPickerScreen extends ConsumerStatefulWidget {
  const BtPickerScreen({super.key});

  @override
  ConsumerState<BtPickerScreen> createState() => _BtPickerScreenState();
}

class _BtPickerScreenState extends ConsumerState<BtPickerScreen> {
  String? _error;
  bool _initDone = false;

  @override
  void initState() {
    super.initState();
    WidgetsBinding.instance.addPostFrameCallback((_) => _initBluetooth());
  }

  Future<void> _initBluetooth() async {
    setState(() => _error = null);

    final statuses = await [
      Permission.bluetoothConnect,
      Permission.bluetoothScan,
      Permission.locationWhenInUse,
    ].request();

    final denied = statuses.entries
        .where((e) => e.value.isDenied || e.value.isPermanentlyDenied)
        .map((e) => e.key.toString())
        .toList();

    if (denied.isNotEmpty) {
      setState(() {
        _error = 'Permissions denied: ${denied.join(", ")}\n\n'
            'Go to Settings → Apps → HV BT Dashboard → Permissions.';
        _initDone = true;
      });
      return;
    }

    final btState = await FlutterBluetoothSerial.instance.state;
    if (btState != BluetoothState.STATE_ON) {
      await FlutterBluetoothSerial.instance.requestEnable();
      await Future<void>.delayed(const Duration(seconds: 1));
    }

    setState(() => _initDone = true);
    ref.invalidate(pairedDevicesProvider);
  }

  Future<void> _connect(BluetoothDevice device, EcuType ecuType) async {
    ref.read(settingsProvider.notifier).setEcuType(ecuType);
    await ref.read(btProvider.notifier).connect(device);
    if (!mounted) return;
    if (ref.read(btProvider).isConnected) {
      Navigator.of(context).pushReplacement(
        MaterialPageRoute(builder: (_) => const MainNav()),
      );
    }
  }

  void _showProtocolDialog(BluetoothDevice device) {
    showDialog<void>(
      context: context,
      builder: (ctx) => AlertDialog(
        title: Text(device.name ?? device.address),
        content: const Text('Select ECU protocol:'),
        actions: [
          TextButton(
            onPressed: () { Navigator.pop(ctx); _connect(device, EcuType.s300); },
            child: const Text('S300'),
          ),
          TextButton(
            onPressed: () { Navigator.pop(ctx); _connect(device, EcuType.kpro); },
            child: const Text('KPro'),
          ),
          TextButton(
            onPressed: () => Navigator.pop(ctx),
            child: const Text('Cancel'),
          ),
        ],
      ),
    );
  }

  @override
  Widget build(BuildContext context) {
    final btState = ref.watch(btProvider);
    final devicesAsync = ref.watch(pairedDevicesProvider);

    return Scaffold(
      appBar: AppBar(
        title: const Text('Connect to ECU'),
        actions: [
          IconButton(
            icon: const Icon(Icons.refresh),
            onPressed: _loading ? null : _initBluetooth,
          ),
        ],
      ),
      body: Column(
        children: [
          if (btState.status == BtStatus.error)
            _banner('Connection failed: ${btState.error}'),
          if (_error != null) _banner(_error!),
          Expanded(
            child: !_initDone
                ? const Center(child: CircularProgressIndicator())
                : devicesAsync.when(
                    loading: () => const Center(
                        child: CircularProgressIndicator()),
                    error: (e, _) =>
                        Center(child: _banner('Failed to load: $e')),
                    data: (devices) => devices.isEmpty
                        ? const Center(
                            child: Padding(
                              padding: EdgeInsets.all(24),
                              child: Text(
                                'No paired BT devices.\nPair your ECU in Android Settings first.',
                                textAlign: TextAlign.center,
                                style: TextStyle(color: Colors.grey),
                              ),
                            ),
                          )
                        : ListView.separated(
                            itemCount: devices.length,
                            separatorBuilder: (_, __) =>
                                const Divider(height: 1),
                            itemBuilder: (_, i) {
                              final d = devices[i];
                              final connecting = btState.isConnecting &&
                                  btState.deviceName ==
                                      (d.name ?? d.address);
                              return ListTile(
                                leading: const Icon(Icons.bluetooth),
                                title: Text(d.name ?? 'Unknown'),
                                subtitle: Text(d.address),
                                trailing: connecting
                                    ? const SizedBox(
                                        width: 20,
                                        height: 20,
                                        child: CircularProgressIndicator(
                                            strokeWidth: 2))
                                    : const Icon(
                                        Icons.arrow_forward_ios,
                                        size: 14),
                                onTap: connecting
                                    ? null
                                    : () => _showProtocolDialog(d),
                              );
                            },
                          ),
                  ),
          ),
        ],
      ),
    );
  }

  bool get _loading => !_initDone || ref.read(btProvider).isConnecting;

  Widget _banner(String msg) => Container(
        width: double.infinity,
        color: const Color(0xFF4A0000),
        padding: const EdgeInsets.all(12),
        child: Text(msg,
            style: const TextStyle(color: Colors.redAccent, fontSize: 12)),
      );
}