import 'package:flutter/material.dart';
import 'package:geolocator/geolocator.dart';

import '../../../../api/connect/rmv/rmv_models.dart';
import '../../../../api/errors/error_mapper.dart';
import '../../../../routing/app_routes.dart';
import '../../../../state/app/modules/rmv/repository/rmv_repository.dart';
import '../../../../widget/app_progress_indicator.dart';
import '../../../../widget/centered_leading.dart';

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

  @override
  State<NearbyStationsView> createState() => _NearbyStationsViewState();
}

class _NearbyStationsViewState extends State<NearbyStationsView> {
  final RmvRepository _repo = RmvRepository();
  List<StopLocation>? _stops;
  bool _loading = true;
  String? _userError;
  Object? _apiError;
  int _radiusMeters = 1000;

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

  Future<void> _load() async {
    setState(() {
      _loading = true;
      _userError = null;
      _apiError = null;
    });
    final position = await _resolvePosition();
    if (!mounted) return;
    if (position == null) {
      // _userError is set by _resolvePosition
      setState(() => _loading = false);
      return;
    }
    try {
      final stops = await _repo.nearbyStops(
        lat: position.latitude,
        lon: position.longitude,
        radiusMeters: _radiusMeters,
        max: 30,
      );
      if (!mounted) return;
      stops.sort((a, b) =>
          (a.distanceMeters ?? 0).compareTo(b.distanceMeters ?? 0));
      setState(() {
        _stops = stops;
        _loading = false;
      });
    } catch (e) {
      if (!mounted) return;
      setState(() {
        _apiError = e;
        _loading = false;
      });
    }
  }

  Future<Position?> _resolvePosition() async {
    if (!await Geolocator.isLocationServiceEnabled()) {
      _userError =
          'Bitte aktiviere die Standortdienste in den System-Einstellungen.';
      return null;
    }
    var permission = await Geolocator.checkPermission();
    if (permission == LocationPermission.denied) {
      permission = await Geolocator.requestPermission();
    }
    if (permission == LocationPermission.deniedForever) {
      _userError =
          'Standortzugriff dauerhaft verweigert. Bitte in den App-Einstellungen aktivieren.';
      return null;
    }
    if (permission == LocationPermission.denied) {
      _userError = 'Ohne Standortzugriff können keine Stationen in der Nähe gefunden werden.';
      return null;
    }
    try {
      return await Geolocator.getCurrentPosition(
        locationSettings: const LocationSettings(
          accuracy: LocationAccuracy.medium,
          timeLimit: Duration(seconds: 10),
        ),
      );
    } catch (e) {
      _userError = 'Standort konnte nicht ermittelt werden: $e';
      return null;
    }
  }

  @override
  Widget build(BuildContext context) => Scaffold(
    appBar: AppBar(
      title: const Text('In meiner Nähe'),
      actions: [
        PopupMenuButton<int>(
          tooltip: 'Suchradius',
          icon: const Icon(Icons.tune),
          onSelected: (r) {
            setState(() => _radiusMeters = r);
            _load();
          },
          itemBuilder: (_) => [500, 1000, 2000, 5000]
              .map(
                (r) => CheckedPopupMenuItem<int>(
                  value: r,
                  checked: r == _radiusMeters,
                  child: Text(r >= 1000 ? '${r ~/ 1000} km' : '$r m'),
                ),
              )
              .toList(),
        ),
      ],
    ),
    body: _body(),
  );

  Widget _body() {
    if (_loading) return const Center(child: AppProgressIndicator.large());
    if (_userError != null) {
      return Center(
        child: Padding(
          padding: const EdgeInsets.all(24),
          child: Column(
            mainAxisSize: MainAxisSize.min,
            children: [
              Text(_userError!, textAlign: TextAlign.center),
              const SizedBox(height: 12),
              Wrap(
                spacing: 8,
                children: [
                  OutlinedButton.icon(
                    icon: const Icon(Icons.refresh),
                    onPressed: _load,
                    label: const Text('Erneut versuchen'),
                  ),
                  OutlinedButton.icon(
                    icon: const Icon(Icons.settings),
                    onPressed: Geolocator.openAppSettings,
                    label: const Text('Einstellungen'),
                  ),
                ],
              ),
            ],
          ),
        ),
      );
    }
    if (_apiError != null) {
      return Center(
        child: Padding(
          padding: const EdgeInsets.all(24),
          child: Column(
            mainAxisSize: MainAxisSize.min,
            children: [
              Text(
                errorToUserMessage(_apiError),
                textAlign: TextAlign.center,
                style: TextStyle(color: Theme.of(context).colorScheme.error),
              ),
              const SizedBox(height: 12),
              FilledButton.icon(
                icon: const Icon(Icons.refresh),
                onPressed: _load,
                label: const Text('Erneut versuchen'),
              ),
            ],
          ),
        ),
      );
    }
    final list = _stops ?? const <StopLocation>[];
    if (list.isEmpty) {
      return const Center(
        child: Padding(
          padding: EdgeInsets.all(24),
          child: Text(
            'Keine Stationen im gewählten Umkreis gefunden.',
            textAlign: TextAlign.center,
          ),
        ),
      );
    }
    return RefreshIndicator(
      onRefresh: _load,
      child: ListView.separated(
        itemCount: list.length,
        separatorBuilder: (_, _) => const Divider(height: 1),
        itemBuilder: (_, i) => _tile(list[i]),
      ),
    );
  }

  Widget _tile(StopLocation stop) => ListTile(
    leading: const CenteredLeading(Icon(Icons.directions_transit)),
    title: Text(stop.name),
    subtitle: stop.distanceMeters == null
        ? null
        : Text('${stop.distanceMeters} m entfernt'),
    onTap: () => AppRoutes.openRmvStationDetail(context, stop),
  );
}