import 'package:flutter/material.dart';
import 'package:flutter/services.dart'; // 用于复制功能

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

  @override
  State<TodoPage> createState() => _TodoPageState();
}

// 待办事项数据模型
class TodoItem {
  String id;
  String title;
  String? description;
  bool isCompleted;
  DateTime createdAt;
  DateTime? dueDate;
  Priority priority;
  String? category;

  TodoItem({
    required this.id,
    required this.title,
    this.description,
    this.isCompleted = false,
    DateTime? createdAt,
    this.dueDate,
    this.priority = Priority.medium,
    this.category,
  }) : createdAt = createdAt ?? DateTime.now();

  TodoItem copyWith({
    String? id,
    String? title,
    String? description,
    bool? isCompleted,
    DateTime? createdAt,
    DateTime? dueDate,
    Priority? priority,
    String? category,
  }) {
    return TodoItem(
      id: id ?? this.id,
      title: title ?? this.title,
      description: description ?? this.description,
      isCompleted: isCompleted ?? this.isCompleted,
      createdAt: createdAt ?? this.createdAt,
      dueDate: dueDate ?? this.dueDate,
      priority: priority ?? this.priority,
      category: category ?? this.category,
    );
  }
}

enum Priority {
  low('低', Colors.grey, Icons.low_priority),
  medium('中', Colors.orange, Icons.flag),
  high('高', Colors.red, Icons.warning);

  final String label;
  final Color color;
  final IconData icon;

  const Priority(this.label, this.color, this.icon);
}

enum TodoFilter {
  all('全部'),
  active('待完成'),
  completed('已完成'),
  today('今天');

  final String label;
  const TodoFilter(this.label);
}

class _TodoPageState extends State<TodoPage> {
  // 待办事项列表
  List<TodoItem> _todos = [];
  TodoFilter _currentFilter = TodoFilter.all;
  final TextEditingController _titleController = TextEditingController();
  final TextEditingController _descriptionController = TextEditingController();
  DateTime? _selectedDueDate;
  Priority _selectedPriority = Priority.medium;
  String? _selectedCategory;

  // 获取过滤后的待办事项
  List<TodoItem> get _filteredTodos {
    switch (_currentFilter) {
      case TodoFilter.active:
        return _todos.where((todo) => !todo.isCompleted).toList();
      case TodoFilter.completed:
        return _todos.where((todo) => todo.isCompleted).toList();
      case TodoFilter.today:
        final today = DateTime.now();
        return _todos.where((todo) =>
        todo.dueDate != null &&
            todo.dueDate!.year == today.year &&
            todo.dueDate!.month == today.month &&
            todo.dueDate!.day == today.day
        ).toList();
      default:
        return _todos;
    }
  }

  // 统计数据
  int get _totalCount => _todos.length;
  int get _activeCount => _todos.where((todo) => !todo.isCompleted).length;
  int get _completedCount => _todos.where((todo) => todo.isCompleted).length;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('待办事项'),
        backgroundColor: Colors.orange,
        foregroundColor: Colors.white
      ),
      body: Column(
        children: [
          // 统计信息卡片
          _buildStatsCard(),

          // 过滤器选项卡
          _buildFilterTabs(),

          // 待办事项列表
          Expanded(
            child: _filteredTodos.isEmpty ? _buildEmptyState() : _buildTodoList(),
          ),
        ],
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _showAddTodoDialog,
        backgroundColor: Colors.orange,
        child: const Icon(Icons.add),
      ),
    );
  }

  // 构建统计信息卡片
  Widget _buildStatsCard() {
    return Card(
      margin: const EdgeInsets.all(12),
      child: Padding(
        padding: const EdgeInsets.all(16),
        child: Row(
          mainAxisAlignment: MainAxisAlignment.spaceAround,
          children: [
            _buildStatItem('总计', _totalCount, Colors.blue),
            _buildStatItem('待完成', _activeCount, Colors.orange),
            _buildStatItem('已完成', _completedCount, Colors.green),
          ],
        ),
      ),
    );
  }

  Widget _buildStatItem(String label, int count, Color color) {
    return Column(
      children: [
        Text(
          count.toString(),
          style: TextStyle(
            fontSize: 24,
            fontWeight: FontWeight.bold,
            color: color,
          ),
        ),
        const SizedBox(height: 4),
        Text(
          label,
          style: const TextStyle(fontSize: 12, color: Colors.grey),
        ),
      ],
    );
  }

  // 构建过滤器选项卡
  Widget _buildFilterTabs() {
    return SizedBox(
      height: 50,
      child: ListView(
        scrollDirection: Axis.horizontal,
        children: TodoFilter.values.map((filter) {
          return Padding(
            padding: const EdgeInsets.symmetric(horizontal: 4),
            child: FilterChip(
              label: Text(filter.label),
              selected: _currentFilter == filter,
              onSelected: (selected) {
                setState(() {
                  _currentFilter = filter;
                });
              },
            ),
          );
        }).toList(),
      ),
    );
  }

  // 构建空状态
  Widget _buildEmptyState() {
    final messages = {
      TodoFilter.all: '还没有待办事项\n点击+号添加第一个任务',
      TodoFilter.active: '没有待完成的任务\n享受轻松时光吧',
      TodoFilter.completed: '还没有完成的任务\n加油哦！',
      TodoFilter.today: '今天没有安排任务\n好好放松一下吧',
    };

    return Center(
      child: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: [
          Icon(Icons.checklist, size: 80, color: Colors.grey.shade300),
          const SizedBox(height: 20),
          Text(
            messages[_currentFilter] ?? '暂无数据',
            textAlign: TextAlign.center,
            style: TextStyle(
              fontSize: 16,
              color: Colors.grey.shade500,
            ),
          ),
        ],
      ),
    );
  }

  // 构建待办事项列表
  Widget _buildTodoList() {
    return ListView.builder(
      itemCount: _filteredTodos.length,
      itemBuilder: (context, index) {
        final todo = _filteredTodos[index];
        return _buildTodoItem(todo);
      },
    );
  }

  // 构建单个待办事项项
  Widget _buildTodoItem(TodoItem todo) {
    final isOverdue = todo.dueDate != null &&
        todo.dueDate!.isBefore(DateTime.now()) &&
        !todo.isCompleted;

    return Dismissible(
      key: Key(todo.id),
      direction: DismissDirection.endToStart,
      background: Container(
        color: Colors.red,
        alignment: Alignment.centerRight,
        padding: const EdgeInsets.only(right: 20),
        child: const Icon(Icons.delete, color: Colors.white),
      ),
      confirmDismiss: (direction) async {
        return await _showDeleteConfirmation(todo);
      },
      onDismissed: (direction) => _deleteTodo(todo.id),
      child: Card(
        margin: const EdgeInsets.symmetric(horizontal: 12, vertical: 4),
        color: todo.isCompleted ? Colors.grey.shade50 : null,
        child: ListTile(
          leading: Checkbox(
            value: todo.isCompleted,
            onChanged: (value) => _toggleTodo(todo.id),
          ),
          title: Text(
            todo.title,
            style: TextStyle(
              decoration: todo.isCompleted ? TextDecoration.lineThrough : null,
              color: todo.isCompleted ? Colors.grey : null,
              fontWeight: FontWeight.w500,
            ),
          ),
          subtitle: _buildTodoSubtitle(todo, isOverdue),
          trailing: _buildPriorityBadge(todo.priority),
          onTap: () => _showEditTodoDialog(todo),
          onLongPress: () => _showTodoOptions(todo),
        ),
      ),
    );
  }

  // 构建待办事项副标题
  Widget? _buildTodoSubtitle(TodoItem todo, bool isOverdue) {
    final hasContent = todo.description?.isNotEmpty == true || todo.dueDate != null;

    if (!hasContent) return null;

    return Column(
      crossAxisAlignment: CrossAxisAlignment.start,
      children: [
        if (todo.description?.isNotEmpty == true)
          Text(
            todo.description!,
            maxLines: 1,
            overflow: TextOverflow.ellipsis,
            style: TextStyle(
              fontSize: 12,
              color: Colors.grey.shade600,
            ),
          ),
        if (todo.dueDate != null)
          Text(
            '截止: ${_formatDate(todo.dueDate!)}',
            style: TextStyle(
              fontSize: 11,
              color: isOverdue ? Colors.red : Colors.grey,
              fontWeight: isOverdue ? FontWeight.bold : FontWeight.normal,
            ),
          ),
      ],
    );
  }

  // 构建优先级徽章
  Widget _buildPriorityBadge(Priority priority) {
    return Chip(
      label: Text(priority.label),
      backgroundColor: priority.color.withOpacity(0.1),
      labelStyle: TextStyle(
        color: priority.color,
        fontSize: 10,
        fontWeight: FontWeight.bold,
      ),
      materialTapTargetSize: MaterialTapTargetSize.shrinkWrap,
      visualDensity: VisualDensity.compact,
    );
  }

  // 显示添加待办事项对话框
  void _showAddTodoDialog() {
    _resetForm();
    showDialog(
      context: context,
      builder: (context) => _buildTodoDialog(isEditing: false),
    );
  }

  // 显示编辑待办事项对话框
  void _showEditTodoDialog(TodoItem todo) {
    _titleController.text = todo.title;
    _descriptionController.text = todo.description ?? '';
    _selectedDueDate = todo.dueDate;
    _selectedPriority = todo.priority;
    _selectedCategory = todo.category;

    showDialog(
      context: context,
      builder: (context) => _buildTodoDialog(isEditing: true, todo: todo),
    );
  }

  // 构建待办事项对话框
  Widget _buildTodoDialog({bool isEditing = false, TodoItem? todo}) {
    return AlertDialog(
      title: Text(isEditing ? '编辑待办事项' : '添加待办事项'),
      content: SingleChildScrollView(
        child: Column(
          mainAxisSize: MainAxisSize.min,
          children: [
            TextField(
              controller: _titleController,
              decoration: const InputDecoration(
                labelText: '标题*',
                border: OutlineInputBorder(),
              ),
              maxLength: 100,
            ),
            const SizedBox(height: 12),
            TextField(
              controller: _descriptionController,
              decoration: const InputDecoration(
                labelText: '描述',
                border: OutlineInputBorder(),
              ),
              maxLines: 2,
              maxLength: 200,
            ),
            const SizedBox(height: 12),
            // 截止日期选择
            ListTile(
              leading: const Icon(Icons.calendar_today),
              title: Text(_selectedDueDate == null
                  ? '选择截止日期'
                  : '截止: ${_formatDate(_selectedDueDate!)}'),
              trailing: _selectedDueDate != null
                  ? IconButton(
                icon: const Icon(Icons.clear),
                onPressed: () => setState(() => _selectedDueDate = null),
              )
                  : null,
              onTap: () => _selectDueDate(),
            ),
            // 优先级选择
            ListTile(
              leading: const Icon(Icons.flag),
              title: const Text('优先级'),
              trailing: DropdownButton<Priority>(
                value: _selectedPriority,
                onChanged: (value) => setState(() => _selectedPriority = value!),
                items: Priority.values.map((priority) {
                  return DropdownMenuItem(
                    value: priority,
                    child: Row(
                      children: [
                        Icon(priority.icon, color: priority.color, size: 16),
                        const SizedBox(width: 8),
                        Text(priority.label),
                      ],
                    ),
                  );
                }).toList(),
              ),
            ),
          ],
        ),
      ),
      actions: [
        TextButton(
          onPressed: () => Navigator.pop(context),
          child: const Text('取消'),
        ),
        ElevatedButton(
          onPressed: _validateForm() ? () => _saveTodo(isEditing, todo) : null,
          child: Text(isEditing ? '保存' : '添加'),
        ),
      ],
    );
  }

  // 选择截止日期
  Future<void> _selectDueDate() async {
    final DateTime? picked = await showDatePicker(
      context: context,
      initialDate: DateTime.now(),
      firstDate: DateTime.now(),
      lastDate: DateTime(2100),
    );

    if (picked != null) {
      setState(() {
        _selectedDueDate = picked;
      });
    }
  }

  // 验证表单
  bool _validateForm() {
    return _titleController.text.trim().isNotEmpty;
  }

  // 重置表单
  void _resetForm() {
    _titleController.clear();
    _descriptionController.clear();
    _selectedDueDate = null;
    _selectedPriority = Priority.medium;
    _selectedCategory = null;
  }

  // 保存待办事项
  void _saveTodo(bool isEditing, TodoItem? todo) {
    if (!_validateForm()) return;

    final newTodo = TodoItem(
      id: isEditing ? todo!.id : DateTime.now().millisecondsSinceEpoch.toString(),
      title: _titleController.text.trim(),
      description: _descriptionController.text.trim().isEmpty ?
      null : _descriptionController.text.trim(),
      dueDate: _selectedDueDate,
      priority: _selectedPriority,
      category: _selectedCategory,
    );

    setState(() {
      if (isEditing) {
        final index = _todos.indexWhere((t) => t.id == todo!.id);
        if (index != -1) {
          _todos[index] = newTodo.copyWith(isCompleted: _todos[index].isCompleted);
        }
      } else {
        _todos.insert(0, newTodo);
      }
    });

    Navigator.pop(context);
    _resetForm();
  }

  // 切换待办事项完成状态
  void _toggleTodo(String id) {
    setState(() {
      final index = _todos.indexWhere((todo) => todo.id == id);
      if (index != -1) {
        _todos[index] = _todos[index].copyWith(
          isCompleted: !_todos[index].isCompleted,
        );
      }
    });
  }

  // 显示删除确认
  Future<bool> _showDeleteConfirmation(TodoItem todo) async {
    return await showDialog<bool>(
      context: context,
      builder: (context) => AlertDialog(
        title: const Text('确认删除'),
        content: Text('确定要删除"${todo.title}"吗？此操作不可撤销。'),
        actions: [
          TextButton(
            onPressed: () => Navigator.pop(context, false),
            child: const Text('取消'),
          ),
          TextButton(
            onPressed: () => Navigator.pop(context, true),
            child: const Text('删除', style: TextStyle(color: Colors.red)),
          ),
        ],
      ),
    ) ?? false;
  }

  // 删除待办事项
  void _deleteTodo(String id) {
    setState(() {
      _todos.removeWhere((todo) => todo.id == id);
    });

    ScaffoldMessenger.of(context).showSnackBar(
      const SnackBar(content: Text('待办事项已删除')),
    );
  }

  // 显示待办事项选项
  void _showTodoOptions(TodoItem todo) {
    showModalBottomSheet(
      context: context,
      builder: (context) => Column(
        mainAxisSize: MainAxisSize.min,
        children: [
          ListTile(
            leading: const Icon(Icons.content_copy),
            title: const Text('复制内容'),
            onTap: () {
              Navigator.pop(context);
              _copyTodoContent(todo);
            },
          ),
          ListTile(
            leading: Icon(todo.isCompleted ? Icons.undo : Icons.done_all),
            title: Text(todo.isCompleted ? '标记为未完成' : '标记为已完成'),
            onTap: () {
              Navigator.pop(context);
              _toggleTodo(todo.id);
            },
          ),
          const Divider(),
          ListTile(
            leading: const Icon(Icons.delete, color: Colors.red),
            title: const Text('删除', style: TextStyle(color: Colors.red)),
            onTap: () {
              Navigator.pop(context);
              _deleteTodo(todo.id);
            },
          ),
        ],
      ),
    );
  }

  // 复制待办事项内容
  void _copyTodoContent(TodoItem todo) {
    final content = '${todo.title}\n${todo.description ?? ''}'.trim();
    Clipboard.setData(ClipboardData(text: content));

    ScaffoldMessenger.of(context).showSnackBar(
      const SnackBar(content: Text('内容已复制到剪贴板')),
    );
  }

  // 清除已完成的任务
  void _clearCompleted() {
    setState(() {
      _todos.removeWhere((todo) => todo.isCompleted);
    });

    ScaffoldMessenger.of(context).showSnackBar(
      const SnackBar(content: Text('已清除所有已完成的任务')),
    );
  }

  // 处理菜单操作
  void _handleMenuAction(String value) {
    switch (value) {
      case 'export':
        _exportTodos();
        break;
      case 'sort':
        _sortTodos();
        break;
    }
  }

  // 导出待办事项
  void _exportTodos() {
    final exportText = _todos.map((todo) {
      return '${todo.isCompleted ? '[✓]' : '[ ]'} ${todo.title}${todo.dueDate != null ? ' (截止: ${_formatDate(todo.dueDate!)})' : ''}';
    }).join('\n');

    Clipboard.setData(ClipboardData(text: exportText));

    ScaffoldMessenger.of(context).showSnackBar(
      const SnackBar(content: Text('待办事项已导出到剪贴板')),
    );
  }

  // 排序待办事项
  void _sortTodos() {
    setState(() {
      _todos.sort((a, b) {
        // 按优先级排序（高优先级在前）
        if (a.priority.index != b.priority.index) {
          return b.priority.index.compareTo(a.priority.index);
        }
        // 按截止日期排序（有截止日期的在前，然后按时间顺序）
        if (a.dueDate != null && b.dueDate != null) {
          return a.dueDate!.compareTo(b.dueDate!);
        } else if (a.dueDate != null) {
          return -1;
        } else if (b.dueDate != null) {
          return 1;
        }
        // 按创建时间排序（新的在前）
        return b.createdAt.compareTo(a.createdAt);
      });
    });
  }

  // 格式化日期
  String _formatDate(DateTime date) {
    return '${date.month}月${date.day}日';
  }

  @override
  void dispose() {
    _titleController.dispose();
    _descriptionController.dispose();
    super.dispose();
  }
}