import 'dart:io';

import 'package:file_selector/file_selector.dart';
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:http/http.dart' as http;
import 'package:path_provider/path_provider.dart';
import 'package:share_plus/share_plus.dart';
import 'package:url_launcher/url_launcher.dart';

import '../data/note_repository.dart';
import '../sync/github_client.dart';
import '../sync/github_device_auth.dart';
import '../sync/notes_markdown.dart';
import '../sync/sync_settings.dart';

/// Settings screen for GitHub sync configuration and note backup.
///
/// Primary sync path: the "Connect GitHub" button runs the OAuth **device
/// flow** (authorize in a browser, no token pasting). The manual token field
/// remains as a fallback. The Backup section exports/imports all notes as a
/// single Markdown file (see [NotesMarkdown]).
class SettingsScreen extends StatefulWidget {
  const SettingsScreen({
    required this.initial,
    required this.repository,
    this.httpClient,
    super.key,
  });

  final SyncSettings initial;
  final NoteRepository repository;

  /// Optional HTTP client for the GitHub calls (test-connection and device
  /// flow). Injected by tests; production uses each client's default.
  final http.Client? httpClient;

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

class _SettingsScreenState extends State<SettingsScreen> {
  late final TextEditingController _owner = TextEditingController(
    text: widget.initial.owner,
  );
  late final TextEditingController _repo = TextEditingController(
    text: widget.initial.repo,
  );
  late final TextEditingController _token = TextEditingController(
    text: widget.initial.token,
  );
  late final TextEditingController _clientId = TextEditingController(
    text: widget.initial.clientId,
  );

  bool _testing = false;
  String? _status;

  @override
  void dispose() {
    _owner.dispose();
    _repo.dispose();
    _token.dispose();
    _clientId.dispose();
    super.dispose();
  }

  SyncSettings get _current => SyncSettings(
    owner: _owner.text.trim(),
    repo: _repo.text.trim(),
    token: _token.text.trim(),
    clientId: _clientId.text.trim(),
  );

  /// Runs the OAuth device flow and, on success, fills in the token field.
  Future<void> _connectGitHub() async {
    final clientId = _clientId.text.trim();
    if (clientId.isEmpty) {
      setState(() => _status = 'Enter the OAuth App client id first.');
      return;
    }
    final auth = GitHubDeviceAuth(
      clientId: clientId,
      httpClient: widget.httpClient,
    );
    try {
      final device = await auth.requestDeviceCode();
      if (!mounted) return;
      final token = await showDialog<String>(
        context: context,
        barrierDismissible: false,
        builder: (_) => _DeviceCodeDialog(device: device, auth: auth),
      );
      if (token != null && token.isNotEmpty) {
        setState(() {
          _token.text = token;
          _status = 'Connected via GitHub. Token saved on Save.';
        });
        await _current.save();
      }
    } catch (e) {
      if (mounted) setState(() => _status = 'Could not start device flow: $e');
    } finally {
      auth.close();
    }
  }

  Future<void> _test() async {
    setState(() {
      _testing = true;
      _status = null;
    });
    final s = _current;
    final client = GitHubClient(
      owner: s.owner,
      repo: s.repo,
      token: s.token,
      httpClient: widget.httpClient,
    );
    try {
      final ok = await client.canAccessRepo();
      setState(
        () => _status = ok
            ? 'Connected — repo is reachable.'
            : 'Could not access ${s.owner}/${s.repo}. Check token scope.',
      );
    } catch (e) {
      setState(() => _status = 'Error: $e');
    } finally {
      client.close();
      if (mounted) setState(() => _testing = false);
    }
  }

  Future<void> _save() async {
    final s = _current;
    await s.save();
    if (mounted) Navigator.of(context).pop(s);
  }

  /// Exports every note to a single Markdown file. On mobile this opens the
  /// system share sheet; on desktop it writes the canonical `~/todo/
  /// BACKLOG.md` so a future tool/agent has a stable path to read.
  Future<void> _export() async {
    try {
      final notes = await widget.repository.listNotes();
      final markdown = NotesMarkdown.export(notes);

      // coverage:ignore-start
      // Mobile-only share path: Platform.isAndroid/isIOS are always false on
      // the Linux test host, so these lines are structurally unreachable in
      // CI and excluded from the coverage denominator. Verified on-device.
      if (Platform.isAndroid || Platform.isIOS) {
        final dir = await getTemporaryDirectory();
        final file = File('${dir.path}/todo-backlog.md');
        await file.writeAsString(markdown);
        await SharePlus.instance.share(
          ShareParams(
            files: [XFile(file.path, mimeType: 'text/markdown')],
            subject: 'todo backlog (${notes.length} notes)',
          ),
        );
      } else {
        // coverage:ignore-end
        final home = Platform.environment['HOME'] ?? Directory.current.path;
        final dir = Directory('$home/todo');
        if (!dir.existsSync()) dir.createSync(recursive: true);
        final file = File('${dir.path}/BACKLOG.md');
        await file.writeAsString(markdown);
        if (mounted) {
          setState(
            () => _status = 'Exported ${notes.length} notes to ${file.path}',
          );
        }
      }
    } catch (e) {
      if (mounted) setState(() => _status = 'Export failed: $e');
    }
  }

  /// Imports notes from a user-picked Markdown file, merging by id so a
  /// stale backup never clobbers a newer local edit (see
  /// [NoteRepository.importNotes]).
  Future<void> _import() async {
    try {
      const group = XTypeGroup(
        label: 'Markdown',
        extensions: ['md', 'markdown', 'txt'],
        // UTIs/MIME so the picker accepts the file on iOS/Android too.
        uniformTypeIdentifiers: ['net.daringfireball.markdown', 'public.text'],
        mimeTypes: ['text/markdown', 'text/plain'],
      );
      final file = await openFile(acceptedTypeGroups: const [group]);
      if (file == null) return; // user cancelled
      final content = await file.readAsString();

      final notes = NotesMarkdown.parse(content);
      final outcome = await widget.repository.importNotes(notes);
      if (mounted) {
        setState(
          () => _status =
              'Imported ${outcome.total}: ${outcome.added} new, '
              '${outcome.updated} updated, ${outcome.skipped} unchanged',
        );
      }
    } catch (e) {
      if (mounted) setState(() => _status = 'Import failed: $e');
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('Sync settings')),
      body: ListView(
        padding: const EdgeInsets.all(16),
        children: [
          TextField(
            controller: _owner,
            decoration: const InputDecoration(
              labelText: 'GitHub owner',
              border: OutlineInputBorder(),
            ),
          ),
          const SizedBox(height: 12),
          TextField(
            controller: _repo,
            decoration: const InputDecoration(
              labelText: 'Repository name',
              border: OutlineInputBorder(),
            ),
          ),
          const SizedBox(height: 24),
          Text(
            'Connect with GitHub',
            style: Theme.of(context).textTheme.titleMedium,
          ),
          const SizedBox(height: 8),
          TextField(
            controller: _clientId,
            decoration: const InputDecoration(
              labelText: 'OAuth App client id',
              helperText: 'From your GitHub OAuth App (device flow enabled)',
              border: OutlineInputBorder(),
            ),
          ),
          const SizedBox(height: 12),
          FilledButton.icon(
            onPressed: _connectGitHub,
            icon: const Icon(Icons.login),
            label: const Text('Connect GitHub'),
          ),
          const SizedBox(height: 24),
          const Divider(),
          const SizedBox(height: 8),
          Text(
            'Or paste a token (fallback)',
            style: Theme.of(context).textTheme.titleMedium,
          ),
          const SizedBox(height: 8),
          TextField(
            controller: _token,
            obscureText: true,
            decoration: const InputDecoration(
              labelText: 'Access token (fine-grained PAT)',
              helperText: 'Contents: read/write on the sync repo only',
              border: OutlineInputBorder(),
            ),
          ),
          const SizedBox(height: 16),
          Row(
            children: [
              OutlinedButton.icon(
                onPressed: _testing ? null : _test,
                icon: _testing
                    ? const SizedBox(
                        width: 16,
                        height: 16,
                        child: CircularProgressIndicator(strokeWidth: 2),
                      )
                    : const Icon(Icons.wifi_tethering),
                label: const Text('Test connection'),
              ),
              const Spacer(),
              FilledButton.icon(
                onPressed: _save,
                icon: const Icon(Icons.save),
                label: const Text('Save'),
              ),
            ],
          ),
          const SizedBox(height: 24),
          const Divider(),
          const SizedBox(height: 8),
          Text('Backup', style: Theme.of(context).textTheme.titleMedium),
          const SizedBox(height: 4),
          Text(
            'Export all notes to a single Markdown file, or import/merge a '
            'file back (matching ids are merged, never duplicated).',
            style: Theme.of(context).textTheme.bodySmall,
          ),
          const SizedBox(height: 12),
          Row(
            children: [
              OutlinedButton.icon(
                onPressed: _export,
                icon: const Icon(Icons.upload_file),
                label: const Text('Export notes'),
              ),
              const SizedBox(width: 12),
              OutlinedButton.icon(
                onPressed: _import,
                icon: const Icon(Icons.download),
                label: const Text('Import notes'),
              ),
            ],
          ),
          if (_status != null) ...[
            const SizedBox(height: 16),
            Text(_status!, style: Theme.of(context).textTheme.bodyMedium),
          ],
        ],
      ),
    );
  }
}

/// Dialog shown during the device flow: displays the user code, opens the
/// verification page, and polls until authorized — popping the token (or
/// null if cancelled / failed).
class _DeviceCodeDialog extends StatefulWidget {
  const _DeviceCodeDialog({required this.device, required this.auth});

  final DeviceCodeResponse device;
  final GitHubDeviceAuth auth;

  @override
  State<_DeviceCodeDialog> createState() => _DeviceCodeDialogState();
}

class _DeviceCodeDialogState extends State<_DeviceCodeDialog> {
  String? _error;

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

  Future<void> _poll() async {
    try {
      final token = await widget.auth.pollForToken(widget.device);
      if (mounted) Navigator.of(context).pop(token);
    } catch (e) {
      if (mounted) setState(() => _error = '$e');
    }
  }

  Future<void> _openPage() async {
    await Clipboard.setData(ClipboardData(text: widget.device.userCode));
    await launchUrl(
      Uri.parse(widget.device.verificationUri),
      mode: LaunchMode.externalApplication,
    );
  }

  @override
  Widget build(BuildContext context) {
    return AlertDialog(
      title: const Text('Authorize on GitHub'),
      content: Column(
        mainAxisSize: MainAxisSize.min,
        crossAxisAlignment: CrossAxisAlignment.start,
        children: [
          const Text('Enter this code on GitHub:'),
          const SizedBox(height: 8),
          SelectableText(
            widget.device.userCode,
            style: Theme.of(context).textTheme.headlineSmall,
          ),
          const SizedBox(height: 16),
          if (_error == null)
            const Row(
              children: [
                SizedBox(
                  width: 16,
                  height: 16,
                  child: CircularProgressIndicator(strokeWidth: 2),
                ),
                SizedBox(width: 12),
                Expanded(child: Text('Waiting for authorization…')),
              ],
            )
          else
            Text(_error!, style: const TextStyle(color: Colors.red)),
        ],
      ),
      actions: [
        TextButton(
          onPressed: () => Navigator.of(context).pop(),
          child: const Text('Cancel'),
        ),
        FilledButton.icon(
          onPressed: _openPage,
          icon: const Icon(Icons.open_in_new),
          label: const Text('Open GitHub & copy code'),
        ),
      ],
    );
  }
}