import 'dart:async';

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

import '../../l10n/app_localizations.dart';
import '../places/location_flow.dart';
import '../places/location_service.dart';
import '../places/saved_places.dart';
import '../sources/sources_screen.dart';

/// Settings, currently just location.
class SettingsScreen extends ConsumerStatefulWidget {
  const SettingsScreen({super.key});

  @override
  ConsumerState<SettingsScreen> createState() => _SettingsScreenState();
}

class _SettingsScreenState extends ConsumerState<SettingsScreen> {
  LocationAvailability? _availability;

  @override
  void initState() {
    super.initState();
    unawaited(_refreshAvailability());
  }

  Future<void> _refreshAvailability() async {
    final availability = await ref.read(locationServiceProvider).availability();
    if (!mounted) return;
    setState(() => _availability = availability);
  }

  @override
  Widget build(BuildContext context) {
    final l10n = AppLocalizations.of(context);
    final theme = Theme.of(context);
    final places = ref.watch(savedPlacesProvider).value ?? const [];

    return Scaffold(
      appBar: AppBar(title: Text(l10n.settingsTitle)),
      body: ListView(
        children: [
          _SectionHeader(l10n.settingsLocationSection),

          // The disclosure text is shown here too, not only before the system
          // dialog: someone who already granted or refused should still be able
          // to read what the permission is actually used for.
          Padding(
            padding: const EdgeInsets.fromLTRB(16, 0, 16, 12),
            child: Text(
              l10n.locationDisclosureBody,
              style: theme.textTheme.bodyMedium,
            ),
          ),

          ListTile(
            leading: Icon(_iconFor(_availability)),
            title: Text(_statusLabel(l10n, _availability)),
            subtitle: _availability == LocationAvailability.granted
                ? null
                : Text(l10n.locateMe),
            trailing: switch (_availability) {
              LocationAvailability.denied => FilledButton(
                onPressed: () async {
                  await requestPosition(context, ref);
                  await _refreshAvailability();
                },
                child: Text(l10n.locationDisclosureContinue),
              ),
              LocationAvailability.deniedForever => TextButton(
                onPressed: () async {
                  await Geolocator.openAppSettings();
                  await _refreshAvailability();
                },
                child: Text(l10n.locationOpenSystemSettings),
              ),
              LocationAvailability.serviceDisabled => TextButton(
                onPressed: () async {
                  await Geolocator.openLocationSettings();
                  await _refreshAvailability();
                },
                child: Text(l10n.locationOpenSystemSettings),
              ),
              _ => null,
            },
          ),

          const Divider(),
          _SectionHeader(l10n.placesTitle),
          ListTile(
            leading: const Icon(Icons.place_outlined),
            title: Text(l10n.placesTitle),
            subtitle: Text('${places.length} / ${SavedPlaces.maxPlaces}'),
          ),

          const Divider(),
          // The map no longer carries a permanent credit line, so this is the
          // route the attribution guidelines require. It must stay easy to
          // find: do not bury it deeper or drop the subtitle that says what it
          // holds.
          ListTile(
            leading: const Icon(Icons.info_outline),
            title: Text(l10n.sourcesTitle),
            subtitle: Text(l10n.settingsSourcesHint),
            trailing: const Icon(Icons.chevron_right),
            onTap: () => Navigator.of(context).push(
              MaterialPageRoute<void>(builder: (_) => const SourcesScreen()),
            ),
          ),
        ],
      ),
    );
  }

  static IconData _iconFor(LocationAvailability? availability) =>
      switch (availability) {
        LocationAvailability.granted => Icons.my_location,
        LocationAvailability.serviceDisabled => Icons.location_disabled,
        null => Icons.location_searching,
        _ => Icons.location_off,
      };

  static String _statusLabel(
    AppLocalizations l10n,
    LocationAvailability? availability,
  ) => switch (availability) {
    LocationAvailability.granted => l10n.locationStatusGranted,
    LocationAvailability.denied => l10n.locationStatusDenied,
    LocationAvailability.deniedForever => l10n.locationStatusDeniedForever,
    LocationAvailability.serviceDisabled => l10n.locationStatusServiceDisabled,
    null => l10n.loading,
  };
}

class _SectionHeader extends StatelessWidget {
  const _SectionHeader(this.title);

  final String title;

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);

    return Padding(
      padding: const EdgeInsets.fromLTRB(16, 16, 16, 8),
      child: Text(
        title,
        style: theme.textTheme.titleSmall?.copyWith(
          color: theme.colorScheme.primary,
        ),
      ),
    );
  }
}