import 'dart:io';
import 'package:flutter/material.dart';
import 'package:file_picker/file_picker.dart';
import 'package:path/path.dart' as p;
import 'package:permission_handler/permission_handler.dart';
import '../../utils/user_prefs.dart';
import 'md_viewer_page.dart';

/// Markdown 阅读器 - 文件浏览器
class MdReaderTabPage extends StatefulWidget {
  const MdReaderTabPage({super.key});

  @override
  State<MdReaderTabPage> createState() => _MdReaderTabPageState();
}

class _MdReaderTabPageState extends State<MdReaderTabPage> {
  String? _rootPath;
  String? _currentPath;
  List<_FileEntry> _entries = [];
  bool _isLoading = false;
  String? _error;

  bool _showEmptyDirs = true;
  bool _showImageOnlyDirs = true;

  @override
  void initState() {
    super.initState();
    _loadSettings();
    _init();
  }

  void _loadSettings() {
    final prefs = UserPrefs();
    _showEmptyDirs = prefs.showEmptyDirs;
    _showImageOnlyDirs = prefs.showImageOnlyDirs;
  }

  Future<void> _init() async {
    final saved = UserPrefs().lastMdFolder;
    if (saved != null && saved.isNotEmpty) {
      final dir = Directory(saved);
      if (await dir.exists()) {
        _rootPath = saved;
        _currentPath = saved;
        await _loadDirectory();
        return;
      }
    }
    if (mounted) setState(() {});
  }

  /// 请求存储权限（Android 11+ 需要 MANAGE_EXTERNAL_STORAGE）
  Future<bool> _requestStoragePermission() async {
    if (!Platform.isAndroid) return true;

    var status = await Permission.manageExternalStorage.status;
    if (status.isGranted) return true;

    status = await Permission.manageExternalStorage.request();
    if (status.isGranted) return true;

    status = await Permission.storage.status;
    if (status.isGranted) return true;

    status = await Permission.storage.request();
    return status.isGranted;
  }

  Future<void> _pickDirectory() async {
    final hasPermission = await _requestStoragePermission();
    if (!hasPermission) {
      if (mounted) {
        _showPermissionDeniedDialog();
      }
      return;
    }

    final result = await FilePicker.platform.getDirectoryPath();
    if (result == null) return;

    UserPrefs().setLastMdFolder(result);
    _rootPath = result;
    _currentPath = result;
    _error = null;
    await _loadDirectory();
  }

  void _showPermissionDeniedDialog() {
    showDialog(
      context: context,
      builder: (ctx) => AlertDialog(
        title: const Text('需要存储权限', style: TextStyle(fontSize: 16, fontWeight: FontWeight.w600)),
        content: const Text(
          'Android 11+ 需要在系统设置中授予"所有文件访问权限"才能读取目录中的 Markdown 文件。\n\n是否前往设置？',
          style: TextStyle(fontSize: 14, color: Color(0xFF666666), height: 1.6),
        ),
        actions: [
          TextButton(
            onPressed: () => Navigator.pop(ctx),
            child: const Text('取消', style: TextStyle(color: Color(0xFF999999))),
          ),
          TextButton(
            onPressed: () {
              Navigator.pop(ctx);
              openAppSettings();
            },
            child: const Text('前往设置', style: TextStyle(color: Color(0xFF1A1A1A))),
          ),
        ],
      ),
    );
  }

  /// 递归检查目录（含子目录）是否包含 Markdown 文件
  bool _hasMarkdownFiles(String dirPath) {
    try {
      final dir = Directory(dirPath);
      if (!dir.existsSync()) return false;
      for (final entity in dir.listSync(recursive: true, followLinks: false)) {
        if (entity is File) {
          final lower = p.basename(entity.path).toLowerCase();
          if (lower.endsWith('.md') || lower.endsWith('.markdown') || lower.endsWith('.mdown') || lower.endsWith('.txt')) {
            return true;
          }
        }
      }
    } catch (_) {}
    return false;
  }

  /// 递归检查目录是否只有图片文件（无 markdown、无非图片文件）
  bool _isImageOnlyDir(String dirPath) {
    try {
      final dir = Directory(dirPath);
      if (!dir.existsSync()) return false;
      const imageExts = ['.png', '.jpg', '.jpeg', '.gif', '.webp', '.bmp', '.svg', '.ico', '.tiff', '.heic', '.webm'];
      bool hasAnyFile = false;
      for (final entity in dir.listSync(recursive: true, followLinks: false)) {
        if (entity is File) {
          hasAnyFile = true;
          final lower = p.basename(entity.path).toLowerCase();
          if (lower.endsWith('.md') || lower.endsWith('.markdown') || lower.endsWith('.mdown') || lower.endsWith('.txt')) {
            return false;
          }
          if (!imageExts.any((ext) => lower.endsWith(ext))) {
            return false;
          }
        }
      }
      return hasAnyFile;
    } catch (_) {}
    return false;
  }

  /// 判断目录是否应该被过滤掉
  bool _shouldFilterDir(String dirPath) {
    if (!_showEmptyDirs && !_hasMarkdownFiles(dirPath)) return true;
    if (!_showImageOnlyDirs && _isImageOnlyDir(dirPath)) return true;
    return false;
  }

  Future<void> _loadDirectory() async {
    if (_currentPath == null) return;
    setState(() {
      _isLoading = true;
      _error = null;
      _entries = [];
    });

    try {
      final dir = Directory(_currentPath!);
      final exists = await dir.exists();
      if (!exists) {
        if (mounted) {
          setState(() {
            _error = '目录不存在: $_currentPath';
            _isLoading = false;
          });
        }
        return;
      }

      final list = dir.listSync(recursive: false, followLinks: false);

      final entries = <_FileEntry>[];
      for (final entity in list) {
        final name = p.basename(entity.path);
        if (entity is Directory) {
          if (!_shouldFilterDir(entity.path)) {
            entries.add(_FileEntry(name: name, path: entity.path, isDir: true));
          }
        } else if (entity is File) {
          final lower = name.toLowerCase();
          if (lower.endsWith('.md') || lower.endsWith('.markdown') || lower.endsWith('.mdown') || lower.endsWith('.txt')) {
            final stat = entity.statSync();
            entries.add(_FileEntry(name: name, path: entity.path, isDir: false, size: stat.size));
          }
        }
      }

      entries.sort((a, b) {
        if (a.isDir != b.isDir) return a.isDir ? -1 : 1;
        return a.name.toLowerCase().compareTo(b.name.toLowerCase());
      });

      if (mounted) {
        setState(() {
          _entries = entries;
          _isLoading = false;
        });
      }
    } catch (e) {
      if (mounted) {
        setState(() {
          _error = '读取失败: $e';
          _isLoading = false;
        });
      }
    }
  }

  void _enterDirectory(String path) {
    _currentPath = path;
    _loadDirectory();
  }

  void _goBack() {
    if (_currentPath == null || _rootPath == null || _currentPath == _rootPath) return;
    final parent = Directory(_currentPath!).parent.path;
    if (parent == _currentPath!) return;
    if (!parent.startsWith(_rootPath!)) return;
    _currentPath = parent;
    _loadDirectory();
  }

  void _openFile(_FileEntry entry) {
    Navigator.push(context, MaterialPageRoute(
      builder: (context) => MdViewerPage(filePath: entry.path),
    ));
  }

  void _showSettingsSheet() {
    showModalBottomSheet(
      context: context,
      backgroundColor: Colors.white,
      shape: const RoundedRectangleBorder(
        borderRadius: BorderRadius.vertical(top: Radius.circular(16)),
      ),
      builder: (ctx) {
        return StatefulBuilder(
          builder: (ctx, setLocalState) => Padding(
            padding: const EdgeInsets.symmetric(horizontal: 20, vertical: 12),
            child: Column(
              mainAxisSize: MainAxisSize.min,
              children: [
                Container(
                  width: 36, height: 4,
                  decoration: BoxDecoration(
                    color: const Color(0xFFDDDDDD),
                    borderRadius: BorderRadius.circular(2),
                  ),
                ),
                const SizedBox(height: 20),
                const Align(
                  alignment: Alignment.centerLeft,
                  child: Text('目录显示设置', style: TextStyle(fontSize: 16, fontWeight: FontWeight.w600, color: Color(0xFF1A1A1A))),
                ),
                const SizedBox(height: 16),
                SwitchListTile(
                  contentPadding: EdgeInsets.zero,
                  title: const Text('显示空目录', style: TextStyle(fontSize: 14, color: Color(0xFF333333))),
                  subtitle: const Text('关闭后隐藏无 Markdown 文件的目录', style: TextStyle(fontSize: 12, color: Color(0xFF999999))),
                  value: _showEmptyDirs,
                  activeColor: const Color(0xFF1A1A1A),
                  onChanged: (val) {
                    setLocalState(() => _showEmptyDirs = val);
                    UserPrefs().setShowEmptyDirs(val);
                    setState(() {});
                    _loadDirectory();
                  },
                ),
                const Divider(height: 0.5, color: Color(0xFFF0F0F0)),
                SwitchListTile(
                  contentPadding: EdgeInsets.zero,
                  title: const Text('显示纯图片目录', style: TextStyle(fontSize: 14, color: Color(0xFF333333))),
                  subtitle: const Text('关闭后隐藏只含图片、无 Markdown 的目录', style: TextStyle(fontSize: 12, color: Color(0xFF999999))),
                  value: _showImageOnlyDirs,
                  activeColor: const Color(0xFF1A1A1A),
                  onChanged: (val) {
                    setLocalState(() => _showImageOnlyDirs = val);
                    UserPrefs().setShowImageOnlyDirs(val);
                    setState(() {});
                    _loadDirectory();
                  },
                ),
                const SizedBox(height: 20),
              ],
            ),
          ),
        );
      },
    );
  }

  bool get _canGoBack => _currentPath != null && _rootPath != null && _currentPath != _rootPath;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: Colors.white,
      appBar: AppBar(
        backgroundColor: Colors.white,
        elevation: 0,
        title: Text(
          _currentPath != null ? p.basename(_currentPath!) : 'Markdown 阅读',
          style: const TextStyle(fontSize: 17, fontWeight: FontWeight.w600, color: Color(0xFF1A1A1A)),
        ),
        leading: IconButton(
          icon: const Icon(Icons.arrow_back, color: Color(0xFF1A1A1A)),
          onPressed: () => Navigator.pop(context),
        ),
        actions: [
          if (_canGoBack)
            Padding(
              padding: const EdgeInsets.only(right: 8),
              child: GestureDetector(
                onTap: _goBack,
                child: Container(
                  padding: const EdgeInsets.symmetric(horizontal: 12, vertical: 5),
                  decoration: BoxDecoration(
                    color: const Color(0xFFF5F5F5),
                    borderRadius: BorderRadius.circular(14),
                    border: Border.all(color: const Color(0xFFE8E8E8), width: 0.5),
                  ),
                  child: const Text('返回上级', style: TextStyle(fontSize: 12, color: Color(0xFF666666))),
                ),
              ),
            ),
          if (_currentPath != null)
            Padding(
              padding: const EdgeInsets.only(right: 4),
              child: GestureDetector(
                onTap: _pickDirectory,
                child: Container(
                  padding: const EdgeInsets.symmetric(horizontal: 12, vertical: 5),
                  decoration: BoxDecoration(
                    color: const Color(0xFFF5F5F5),
                    borderRadius: BorderRadius.circular(14),
                    border: Border.all(color: const Color(0xFFE8E8E8), width: 0.5),
                  ),
                  child: const Text('更换目录', style: TextStyle(fontSize: 12, color: Color(0xFF888888))),
                ),
              ),
            ),
          IconButton(
            icon: const Icon(Icons.tune, size: 20, color: Color(0xFF888888)),
            onPressed: _showSettingsSheet,
          ),
          const SizedBox(width: 4),
        ],
      ),
      body: _buildBody(),
    );
  }

  Widget _buildBody() {
    if (_currentPath == null) {
      return _buildWelcome();
    }

    if (_isLoading) {
      return const Center(child: CircularProgressIndicator(color: Color(0xFF1A1A1A)));
    }

    if (_error != null) {
      return _buildError();
    }

    return RefreshIndicator(
      onRefresh: _loadDirectory,
      color: const Color(0xFF1A1A1A),
      backgroundColor: Colors.white,
      child: _entries.isEmpty ? _buildEmpty() : ListView.separated(
        padding: EdgeInsets.zero,
        itemCount: (_canGoBack ? 1 : 0) + _entries.length,
        separatorBuilder: (_, __) => const Divider(height: 0.5, thickness: 0.5, color: Color(0xFFF0F0F0)),
        itemBuilder: (context, index) {
          if (_canGoBack && index == 0) {
            return ListTile(
              leading: Container(
                width: 36, height: 36,
                decoration: BoxDecoration(
                  color: const Color(0xFFF5F5F5),
                  borderRadius: BorderRadius.circular(8),
                ),
                child: const Icon(Icons.arrow_upward, size: 18, color: Color(0xFF888888)),
              ),
              title: const Text('..', style: TextStyle(fontSize: 14, color: Color(0xFF888888))),
              onTap: _goBack,
            );
          }
          final entry = _entries[_canGoBack ? index - 1 : index];
          return ListTile(
            leading: Container(
              width: 36, height: 36,
              decoration: BoxDecoration(
                color: entry.isDir ? const Color(0xFFF0F7FF) : const Color(0xFFF5F5F5),
                borderRadius: BorderRadius.circular(8),
              ),
              child: Icon(
                entry.isDir ? Icons.folder_outlined : Icons.description_outlined,
                size: 18,
                color: entry.isDir ? const Color(0xFF4A90D9) : const Color(0xFF666666),
              ),
            ),
            title: Text(entry.name, style: const TextStyle(fontSize: 14, color: Color(0xFF1A1A1A)), maxLines: 1, overflow: TextOverflow.ellipsis),
            subtitle: entry.isDir ? null : Text(_formatSize(entry.size), style: const TextStyle(fontSize: 11, color: Color(0xFF999999))),
            trailing: Icon(entry.isDir ? Icons.chevron_right : Icons.open_in_new_outlined, size: 16, color: const Color(0xFFCCCCCC)),
            onTap: () => entry.isDir ? _enterDirectory(entry.path) : _openFile(entry),
          );
        },
      ),
    );
  }

  Widget _buildWelcome() {
    return Center(
      child: Padding(
        padding: const EdgeInsets.all(40),
        child: Column(
          mainAxisSize: MainAxisSize.min,
          children: [
            Container(
              width: 80, height: 80,
              decoration: BoxDecoration(
                color: const Color(0xFFF5F5F5),
                borderRadius: BorderRadius.circular(20),
              ),
              child: const Icon(Icons.folder_open_outlined, size: 40, color: Color(0xFFCCCCCC)),
            ),
            const SizedBox(height: 24),
            const Text('Markdown 阅读', style: TextStyle(fontSize: 20, fontWeight: FontWeight.w600, color: Color(0xFF1A1A1A))),
            const SizedBox(height: 8),
            const Text('选择一个包含 .md 文件的文件夹', style: TextStyle(fontSize: 14, color: Color(0xFF999999))),
            const SizedBox(height: 32),
            GestureDetector(
              onTap: _pickDirectory,
              child: Container(
                padding: const EdgeInsets.symmetric(horizontal: 32, vertical: 14),
                decoration: BoxDecoration(
                  color: const Color(0xFF1A1A1A),
                  borderRadius: BorderRadius.circular(24),
                ),
                child: const Text('选择目录', style: TextStyle(fontSize: 15, color: Colors.white, fontWeight: FontWeight.w500)),
              ),
            ),
          ],
        ),
      ),
    );
  }

  Widget _buildEmpty() {
    return Center(
      child: Column(
        mainAxisSize: MainAxisSize.min,
        children: [
          const Icon(Icons.folder_open_outlined, size: 64, color: Color(0xFFE0E0E0)),
          const SizedBox(height: 16),
          const Text('此目录下没有 Markdown 文件', style: TextStyle(fontSize: 15, color: Color(0xFF999999))),
          const SizedBox(height: 4),
          Text(_currentPath ?? '', style: const TextStyle(fontSize: 12, color: Color(0xFFCCCCCC))),
          const SizedBox(height: 24),
          GestureDetector(
            onTap: _canGoBack ? _goBack : () => _pickDirectory(),
            child: Container(
              padding: const EdgeInsets.symmetric(horizontal: 24, vertical: 10),
              decoration: BoxDecoration(
                border: Border.all(color: const Color(0xFFDDDDDD)),
                borderRadius: BorderRadius.circular(20),
              ),
              child: Text(
                _canGoBack ? '返回上级目录' : '换一个目录',
                style: const TextStyle(fontSize: 13, color: Color(0xFF888888)),
              ),
            ),
          ),
        ],
      ),
    );
  }

  Widget _buildError() {
    return Center(
      child: Padding(
        padding: const EdgeInsets.all(40),
        child: Column(
          mainAxisSize: MainAxisSize.min,
          children: [
            const Icon(Icons.error_outline, size: 48, color: Color(0xFFCCCCCC)),
            const SizedBox(height: 16),
            Text(_error!, style: const TextStyle(fontSize: 14, color: Color(0xFF999999)), textAlign: TextAlign.center),
            const SizedBox(height: 8),
            Text('路径: ${_currentPath ?? ""}', style: const TextStyle(fontSize: 12, color: Color(0xFFCCCCCC))),
            const SizedBox(height: 24),
            Row(
              mainAxisSize: MainAxisSize.min,
              children: [
                GestureDetector(
                  onTap: _loadDirectory,
                  child: Container(
                    padding: const EdgeInsets.symmetric(horizontal: 24, vertical: 10),
                    decoration: BoxDecoration(
                      color: const Color(0xFF1A1A1A),
                      borderRadius: BorderRadius.circular(20),
                    ),
                    child: const Text('重试', style: TextStyle(fontSize: 13, color: Colors.white)),
                  ),
                ),
                const SizedBox(width: 12),
                GestureDetector(
                  onTap: _pickDirectory,
                  child: Container(
                    padding: const EdgeInsets.symmetric(horizontal: 24, vertical: 10),
                    decoration: BoxDecoration(
                      border: Border.all(color: const Color(0xFFDDDDDD)),
                      borderRadius: BorderRadius.circular(20),
                    ),
                    child: const Text('更换目录', style: TextStyle(fontSize: 13, color: Color(0xFF888888))),
                  ),
                ),
              ],
            ),
          ],
        ),
      ),
    );
  }

  String _formatSize(int? bytes) {
    if (bytes == null) return '';
    if (bytes < 1024) return '$bytes B';
    if (bytes < 1024 * 1024) return '${(bytes / 1024).toStringAsFixed(1)} KB';
    return '${(bytes / (1024 * 1024)).toStringAsFixed(1)} MB';
  }
}

class _FileEntry {
  final String name;
  final String path;
  final bool isDir;
  final int? size;

  _FileEntry({required this.name, required this.path, required this.isDir, this.size});
}