import 'package:flutter/material.dart';
import 'package:intl/intl.dart';
import 'package:provider/provider.dart';

import '../services/app_state.dart';
import '../services/cloud/cloud_storage_provider.dart';
import '../services/onboarding_keys.dart';
import 'cloud_folder_browser_screen.dart';

/// "Data" settings submenu, reached from [SettingsScreen]: cloud storage
/// connection, the two photo-handling switches, and an Advanced section
/// (stale sync lock timeout, plus the destructive purge actions — grouped
/// there rather than given their own top-level "Danger Zone" so they sit
/// behind the same disclosure as other rarely-touched settings).
class DataSettingsScreen extends StatefulWidget {
  const DataSettingsScreen({super.key});

  @override
  State<DataSettingsScreen> createState() => _DataSettingsScreenState();
}

class _DataSettingsScreenState extends State<DataSettingsScreen> {
  static final _dateFormat = DateFormat.yMMMd();

  bool _busy = false;
  String? _error;

  DateTime? _purgeRangeStart;
  DateTime? _purgeRangeEnd;
  String? _purgeRangeError;

  Future<void> _connect(CloudProviderId id) async {
    setState(() {
      _busy = true;
      _error = null;
    });
    try {
      await context.read<AppState>().connectProvider(id);
    } catch (e) {
      setState(() => _error = 'Could not sign in: $e');
    } finally {
      if (mounted) setState(() => _busy = false);
    }
  }

  Future<void> _connectManual(CloudProviderId id, String providerName) async {
    final credentials = await showDialog<_WebDavCredentials>(
      context: context,
      builder: (_) => _WebDavCredentialsDialog(providerName: providerName),
    );
    if (credentials == null || !mounted) return;

    setState(() {
      _busy = true;
      _error = null;
    });
    try {
      await context.read<AppState>().connectProviderWithCredentials(
            id,
            serverUrl: credentials.serverUrl,
            username: credentials.username,
            password: credentials.password,
          );
    } catch (e) {
      setState(() => _error = 'Could not connect: $e');
    } finally {
      if (mounted) setState(() => _busy = false);
    }
  }

  Future<void> _disconnect() async {
    setState(() => _busy = true);
    try {
      await context.read<AppState>().disconnectCloud();
    } finally {
      if (mounted) setState(() => _busy = false);
    }
  }

  void _chooseFolder() {
    Navigator.of(context).push(
      MaterialPageRoute(builder: (_) => const CloudFolderBrowserScreen()),
    );
  }

  Future<void> _syncNow() async {
    setState(() => _busy = true);
    try {
      await context.read<AppState>().syncNow();
    } finally {
      if (mounted) setState(() => _busy = false);
    }
  }

  /// Shared warning-dialog shell for both purge actions — [message] is the
  /// caller's job to make specific and unambiguous, since this is the only
  /// thing standing between the user and an unrecoverable delete.
  Future<bool> _confirmPurge({required String title, required String message}) async {
    final confirmed = await showDialog<bool>(
      context: context,
      builder: (dialogContext) => AlertDialog(
        title: Text(title),
        content: Text(message),
        actions: [
          TextButton(
            onPressed: () => Navigator.of(dialogContext).pop(false),
            child: const Text('Cancel'),
          ),
          TextButton(
            style: TextButton.styleFrom(
              foregroundColor: Theme.of(dialogContext).colorScheme.error,
            ),
            onPressed: () => Navigator.of(dialogContext).pop(true),
            child: const Text('Delete'),
          ),
        ],
      ),
    );
    return confirmed ?? false;
  }

  /// Extra context appended to a purge warning when a cloud account is
  /// connected — a purely local delete would otherwise just get silently
  /// re-imported from the remote copy on the very next sync, which isn't
  /// obvious from the app's normal behavior.
  String _cloudSyncCaveat(AppState appState) {
    if (!appState.isCloudConnected) return '';
    return '\n\nThis device is connected to ${appState.activeProvider!.displayName}. The '
        'deletion will be pushed there on the next sync, same as any other delete.';
  }

  Future<void> _purgeAllData() async {
    final appState = context.read<AppState>();
    final confirmed = await _confirmPurge(
      title: 'Purge all data?',
      message: 'This permanently deletes every vehicle, fuel entry, and receipt photo on '
          "this device — starting completely fresh. This can't be undone."
          '${_cloudSyncCaveat(appState)}',
    );
    if (!confirmed || !mounted) return;

    setState(() => _busy = true);
    try {
      await appState.purgeAllData();
      if (mounted) {
        ScaffoldMessenger.of(context).showSnackBar(
          const SnackBar(content: Text('All data purged.')),
        );
      }
    } finally {
      if (mounted) setState(() => _busy = false);
    }
  }

  Future<void> _pickPurgeRangeDate({required bool isStart}) async {
    final now = DateTime.now();
    final picked = await showDatePicker(
      context: context,
      initialDate: (isStart ? _purgeRangeStart : _purgeRangeEnd) ?? now,
      firstDate: DateTime(2000),
      lastDate: now,
    );
    if (picked == null) return;
    setState(() {
      _purgeRangeError = null;
      if (isStart) {
        _purgeRangeStart = picked;
      } else {
        _purgeRangeEnd = picked;
      }
    });
  }

  Future<void> _purgeDataInRange() async {
    final start = _purgeRangeStart;
    final end = _purgeRangeEnd;
    if (start == null || end == null) return;
    if (end.isBefore(start)) {
      setState(() => _purgeRangeError = 'End date must be on or after the start date.');
      return;
    }

    final appState = context.read<AppState>();
    final confirmed = await _confirmPurge(
      title: 'Purge data in range?',
      message: 'This permanently deletes every fuel entry and receipt photo dated from '
          '${_dateFormat.format(start)} to ${_dateFormat.format(end)}, across all '
          "vehicles. Vehicles themselves aren't affected. This can't be undone."
          '${_cloudSyncCaveat(appState)}',
    );
    if (!confirmed || !mounted) return;

    setState(() => _busy = true);
    try {
      await appState.purgeFuelEntriesInRange(start, end);
      if (mounted) {
        setState(() {
          _purgeRangeStart = null;
          _purgeRangeEnd = null;
          _purgeRangeError = null;
        });
        ScaffoldMessenger.of(context).showSnackBar(
          const SnackBar(content: Text('Fuel entries in range purged.')),
        );
      }
    } finally {
      if (mounted) setState(() => _busy = false);
    }
  }

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

    return Scaffold(
      appBar: AppBar(title: const Text('Data')),
      body: ListView(
        padding: const EdgeInsets.all(16),
        children: [
          Card(
            key: OnboardingKeys.cloudStorageCard,
            child: Padding(
              padding: const EdgeInsets.all(16),
              child: Column(
                crossAxisAlignment: CrossAxisAlignment.start,
                children: [
                  Text('Cloud Storage', style: Theme.of(context).textTheme.titleMedium),
                  const SizedBox(height: 8),
                  if (!appState.isCloudConnected) ...[
                    Text(
                      'Connect a cloud storage account to share vehicles and fuel '
                      'receipts with other people, and to keep a backup off this device.',
                      style: Theme.of(context).textTheme.bodyMedium,
                    ),
                    const SizedBox(height: 12),
                    if (_error != null) ...[
                      Text(_error!, style: TextStyle(color: Theme.of(context).colorScheme.error)),
                      const SizedBox(height: 8),
                    ],
                    Wrap(
                      spacing: 8,
                      runSpacing: 8,
                      children: [
                        for (final provider in appState.availableProviders)
                          FilledButton.icon(
                            onPressed: _busy
                                ? null
                                : () => provider is ManualCredentialCloudStorageProvider
                                    ? _connectManual(provider.id, provider.displayName)
                                    : _connect(provider.id),
                            icon: const Icon(Icons.login),
                            label: Text('Connect ${provider.displayName}'),
                          ),
                      ],
                    ),
                  ] else ...[
                    Text('${appState.activeProvider!.displayName}: ${appState.cloudAccountLabel}'),
                    const SizedBox(height: 4),
                    Text(
                      appState.cloudFolderPath == null
                          ? 'No folder selected yet.'
                          : 'Folder: ${appState.cloudFolderPath}',
                      style: Theme.of(context).textTheme.bodySmall,
                    ),
                    const SizedBox(height: 12),
                    Wrap(
                      spacing: 8,
                      runSpacing: 8,
                      children: [
                        OutlinedButton.icon(
                          onPressed: _busy ? null : _chooseFolder,
                          icon: const Icon(Icons.folder_open),
                          label: Text(appState.cloudFolderPath == null
                              ? 'Choose Folder'
                              : 'Change Folder'),
                        ),
                        OutlinedButton.icon(
                          onPressed: (_busy || appState.cloudFolderPath == null)
                              ? null
                              : _syncNow,
                          icon: appState.isSyncing
                              ? const SizedBox(
                                  height: 16,
                                  width: 16,
                                  child: CircularProgressIndicator(strokeWidth: 2))
                              : const Icon(Icons.sync),
                          label: const Text('Sync Now'),
                        ),
                        TextButton.icon(
                          onPressed: _busy ? null : _disconnect,
                          icon: const Icon(Icons.logout),
                          label: const Text('Disconnect'),
                        ),
                      ],
                    ),
                    const SizedBox(height: 8),
                    if (appState.lastSyncedAt != null)
                      Text(
                        'Last synced ${DateFormat.yMMMd().add_jm().format(appState.lastSyncedAt!)}',
                        style: Theme.of(context).textTheme.bodySmall,
                      ),
                    if (appState.lastSyncError != null)
                      Padding(
                        padding: const EdgeInsets.only(top: 4),
                        child: Text(
                          'Last sync failed: ${appState.lastSyncError}',
                          style: TextStyle(color: Theme.of(context).colorScheme.error),
                        ),
                      ),
                  ],
                ],
              ),
            ),
          ),
          const SizedBox(height: 16),
          Card(
            child: SwitchListTile(
              title: const Text('Keep photos on this phone after syncing'),
              subtitle: const Text(
                'Otherwise, a receipt photo is removed from this device once '
                "it's safely uploaded to the cloud.",
              ),
              value: appState.keepReceiptPhotosLocally,
              onChanged: (value) => context.read<AppState>().setKeepReceiptPhotosLocally(value),
            ),
          ),
          const SizedBox(height: 16),
          Card(
            child: SwitchListTile(
              title: const Text('Keep max quality images'),
              subtitle: const Text(
                'Otherwise, receipt photos are downscaled to a reasonable size '
                'before storing — smaller cloud storage and faster syncs, with '
                'no loss of legibility for a printed receipt.',
              ),
              value: appState.keepMaxQualityReceiptPhotos,
              onChanged: (value) =>
                  context.read<AppState>().setKeepMaxQualityReceiptPhotos(value),
            ),
          ),
          const SizedBox(height: 16),
          Card(
            child: ExpansionTile(
              title: const Text('Advanced'),
              childrenPadding: const EdgeInsets.fromLTRB(16, 0, 16, 16),
              children: [
                Align(
                  alignment: Alignment.centerLeft,
                  child: Text('Stale sync lock timeout', style: Theme.of(context).textTheme.titleSmall),
                ),
                const SizedBox(height: 4),
                Text(
                  "If another device disconnects mid-sync without releasing its lock, "
                  "this is how long to wait before treating it as abandoned and clearing "
                  "it so sync can continue.",
                  style: Theme.of(context).textTheme.bodySmall,
                ),
                Slider(
                  value: appState.staleLockMinutes.toDouble(),
                  min: minStaleLockMinutes.toDouble(),
                  max: maxStaleLockMinutes.toDouble(),
                  divisions: maxStaleLockMinutes - minStaleLockMinutes,
                  label: '${appState.staleLockMinutes} min',
                  onChanged: (value) =>
                      context.read<AppState>().setStaleLockMinutes(value.round()),
                ),
                Text('${appState.staleLockMinutes} minute(s)'),
                const Divider(height: 32),
                Text(
                  'Danger Zone',
                  style: Theme.of(context)
                      .textTheme
                      .titleMedium
                      ?.copyWith(color: Theme.of(context).colorScheme.error),
                ),
                const SizedBox(height: 12),
                Text('Purge All Data', style: Theme.of(context).textTheme.titleSmall),
                const SizedBox(height: 4),
                Text(
                  'Deletes every vehicle, fuel entry, and receipt photo on this device '
                  'and starts completely fresh.',
                  style: Theme.of(context).textTheme.bodySmall,
                ),
                const SizedBox(height: 8),
                SizedBox(
                  width: double.infinity,
                  child: OutlinedButton.icon(
                    onPressed: _busy ? null : _purgeAllData,
                    icon: Icon(Icons.delete_forever, color: Theme.of(context).colorScheme.error),
                    label: Text(
                      'Purge All Data',
                      style: TextStyle(color: Theme.of(context).colorScheme.error),
                    ),
                    style: OutlinedButton.styleFrom(
                      side: BorderSide(color: Theme.of(context).colorScheme.error),
                    ),
                  ),
                ),
                const Divider(height: 32),
                Text('Purge Data by Date Range', style: Theme.of(context).textTheme.titleSmall),
                const SizedBox(height: 4),
                Text(
                  'Deletes fuel entries and receipt photos dated within a range, across '
                  'all vehicles. Vehicles themselves are kept.',
                  style: Theme.of(context).textTheme.bodySmall,
                ),
                const SizedBox(height: 8),
                Row(
                  children: [
                    Expanded(
                      child: OutlinedButton(
                        onPressed: _busy ? null : () => _pickPurgeRangeDate(isStart: true),
                        child: Text(
                          _purgeRangeStart == null
                              ? 'Start date'
                              : _dateFormat.format(_purgeRangeStart!),
                        ),
                      ),
                    ),
                    const SizedBox(width: 12),
                    Expanded(
                      child: OutlinedButton(
                        onPressed: _busy ? null : () => _pickPurgeRangeDate(isStart: false),
                        child: Text(
                          _purgeRangeEnd == null ? 'End date' : _dateFormat.format(_purgeRangeEnd!),
                        ),
                      ),
                    ),
                  ],
                ),
                if (_purgeRangeError != null) ...[
                  const SizedBox(height: 8),
                  Text(
                    _purgeRangeError!,
                    style: TextStyle(color: Theme.of(context).colorScheme.error),
                  ),
                ],
                const SizedBox(height: 8),
                SizedBox(
                  width: double.infinity,
                  child: OutlinedButton.icon(
                    onPressed: (_busy || _purgeRangeStart == null || _purgeRangeEnd == null)
                        ? null
                        : _purgeDataInRange,
                    icon: Icon(Icons.delete_forever, color: Theme.of(context).colorScheme.error),
                    label: Text(
                      'Purge Range',
                      style: TextStyle(color: Theme.of(context).colorScheme.error),
                    ),
                    style: OutlinedButton.styleFrom(
                      side: BorderSide(color: Theme.of(context).colorScheme.error),
                    ),
                  ),
                ),
              ],
            ),
          ),
        ],
      ),
    );
  }
}

class _WebDavCredentials {
  final String serverUrl;
  final String username;
  final String password;
  _WebDavCredentials({required this.serverUrl, required this.username, required this.password});
}

/// Collects the server URL/username/password a [ManualCredentialCloudStorageProvider]
/// needs, since (unlike the OAuth providers) there's no browser flow to
/// gather these instead.
class _WebDavCredentialsDialog extends StatefulWidget {
  final String providerName;
  const _WebDavCredentialsDialog({required this.providerName});

  @override
  State<_WebDavCredentialsDialog> createState() => _WebDavCredentialsDialogState();
}

class _WebDavCredentialsDialogState extends State<_WebDavCredentialsDialog> {
  final _formKey = GlobalKey<FormState>();
  final _serverController = TextEditingController();
  final _usernameController = TextEditingController();
  final _passwordController = TextEditingController();

  @override
  void dispose() {
    _serverController.dispose();
    _usernameController.dispose();
    _passwordController.dispose();
    super.dispose();
  }

  void _submit() {
    if (!_formKey.currentState!.validate()) return;
    Navigator.of(context).pop(_WebDavCredentials(
      serverUrl: _serverController.text.trim(),
      username: _usernameController.text.trim(),
      password: _passwordController.text,
    ));
  }

  @override
  Widget build(BuildContext context) {
    return AlertDialog(
      title: Text('Connect ${widget.providerName}'),
      content: Form(
        key: _formKey,
        child: Column(
          mainAxisSize: MainAxisSize.min,
          children: [
            TextFormField(
              controller: _serverController,
              decoration: const InputDecoration(
                labelText: 'Server URL',
                hintText: 'https://cloud.example.com/remote.php/dav/files/me/',
              ),
              keyboardType: TextInputType.url,
              validator: (v) => (v == null || v.trim().isEmpty) ? 'Required' : null,
            ),
            const SizedBox(height: 12),
            TextFormField(
              controller: _usernameController,
              decoration: const InputDecoration(labelText: 'Username'),
              validator: (v) => (v == null || v.trim().isEmpty) ? 'Required' : null,
            ),
            const SizedBox(height: 12),
            TextFormField(
              controller: _passwordController,
              decoration: const InputDecoration(labelText: 'Password'),
              obscureText: true,
              validator: (v) => (v == null || v.isEmpty) ? 'Required' : null,
              onFieldSubmitted: (_) => _submit(),
            ),
          ],
        ),
      ),
      actions: [
        TextButton(
          onPressed: () => Navigator.of(context).pop(),
          child: const Text('Cancel'),
        ),
        FilledButton(
          onPressed: _submit,
          child: const Text('Connect'),
        ),
      ],
    );
  }
}