import 'package:flutter/material.dart';
import 'package:intl/intl.dart';
import './todo_api.dart';
import './todo_model.dart';
import './todo_detail.dart';
import './todo_form.dart';

class TodoManager extends StatefulWidget {
  final String currentUserId;
  const TodoManager({this.currentUserId = 'admin', super.key});

  @override
  State<StatefulWidget> createState() => _TodoManagerState();
}

class _TodoManagerState extends State<TodoManager> {
  late TodoApiService _apiService;
  late Future<List<Todo>> _todosFuture;

  // UI 狀態控制
  int _selectedDateIndex = 3; // 預設選中 index 3 (即「今天」)
  String _selectedFilter = 'All'; // All, To do, In Progress, Done
  late List<DateTime> _dynamicDates; // 儲存動態產生的日期

  final Color primaryPurple = const Color(0xFF6542D0);
  final Color bgLight = const Color(0xFFF8F9FA);

  @override
  void initState() {
    super.initState();
    _apiService = TodoApiService(currentUserId: widget.currentUserId);
    _todosFuture = _apiService.fetchTodos();
    _generateDates();
  }

  // 產生前3天到後1天的日期區間
  void _generateDates() {
    DateTime today = DateTime.now();
    _dynamicDates = List.generate(5, (index) {
      return today.subtract(Duration(days: 3 - index));
    });
  }

  void _refreshTodos() {
    setState(() {
      _todosFuture = _apiService.fetchTodos();
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: bgLight,
      body: SafeArea(
        child: Column(
          children: [
            _buildCustomHeader(),
            _buildDateSelector(),
            _buildFilterChips(),
            Expanded(
              child: _buildTodoListBody(),
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          Navigator.push(context, MaterialPageRoute(builder: (_) => const TodoForm()));
        },
        backgroundColor: primaryPurple,
        elevation: 4,
        shape: const CircleBorder(),
        child: const Icon(Icons.add, color: Colors.white, size: 28),
      ),
      floatingActionButtonLocation: FloatingActionButtonLocation.centerDocked,
      bottomNavigationBar: _buildBottomNav(),
    );
  }

  // --- UI 元件區塊 ---

  Widget _buildCustomHeader() {
    return Padding(
      padding: const EdgeInsets.symmetric(horizontal: 20, vertical: 16),
      child: Row(
        mainAxisAlignment: MainAxisAlignment.spaceBetween,
        children: [
          IconButton(
            icon: const Icon(Icons.arrow_back_ios_new, color: Colors.black87),
            onPressed: () => Navigator.pop(context),
          ),
          const Text(
            "Today's Tasks",
            style: TextStyle(fontSize: 22, fontWeight: FontWeight.bold, color: Colors.black87),
          ),
          // 移除小鈴鐺圖示後，保留一個佔位符號以確保標題能完美置中
          const SizedBox(width: 48),
        ],
      ),
    );
  }

  Widget _buildDateSelector() {
    return SizedBox(
      height: 90,
      child: ListView.builder(
        scrollDirection: Axis.horizontal,
        padding: const EdgeInsets.symmetric(horizontal: 16),
        itemCount: _dynamicDates.length,
        itemBuilder: (context, index) {
          final date = _dynamicDates[index];
          final isSelected = index == _selectedDateIndex;

          return GestureDetector(
            onTap: () => setState(() => _selectedDateIndex = index),
            child: AnimatedContainer(
              duration: const Duration(milliseconds: 300),
              margin: const EdgeInsets.symmetric(horizontal: 8),
              width: 65,
              decoration: BoxDecoration(
                color: isSelected ? primaryPurple : Colors.white,
                borderRadius: BorderRadius.circular(20),
                boxShadow: [
                  if (!isSelected) BoxShadow(color: Colors.grey.withOpacity(0.1), blurRadius: 10, offset: const Offset(0, 5))
                ],
              ),
              child: Column(
                mainAxisAlignment: MainAxisAlignment.center,
                children: [
                  Text(DateFormat('MMM').format(date), style: TextStyle(color: isSelected ? Colors.white70 : Colors.grey, fontSize: 12)),
                  const SizedBox(height: 4),
                  Text(DateFormat('dd').format(date), style: TextStyle(color: isSelected ? Colors.white : Colors.black, fontSize: 20, fontWeight: FontWeight.bold)),
                  const SizedBox(height: 4),
                  Text(DateFormat('EEE').format(date), style: TextStyle(color: isSelected ? Colors.white70 : Colors.grey, fontSize: 12)),
                ],
              ),
            ),
          );
        },
      ),
    );
  }

  Widget _buildFilterChips() {
    final filters = ['All', 'To do', 'In Progress', 'Done'];
    return SizedBox(
      height: 60,
      child: ListView.builder(
        scrollDirection: Axis.horizontal,
        padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 10),
        itemCount: filters.length,
        itemBuilder: (context, index) {
          final isSelected = _selectedFilter == filters[index];
          return Padding(
            padding: const EdgeInsets.only(right: 12),
            child: ChoiceChip(
              label: Text(filters[index]),
              selected: isSelected,
              onSelected: (bool selected) {
                if (selected) setState(() => _selectedFilter = filters[index]);
              },
              selectedColor: primaryPurple,
              backgroundColor: const Color(0xFFF0EFFF),
              labelStyle: TextStyle(
                color: isSelected ? Colors.white : primaryPurple,
                fontWeight: isSelected ? FontWeight.bold : FontWeight.normal,
              ),
              shape: RoundedRectangleBorder(borderRadius: BorderRadius.circular(20), side: BorderSide.none),
            ),
          );
        },
      ),
    );
  }

  Widget _buildTodoListBody() {
    return FutureBuilder<List<Todo>>(
      future: _todosFuture,
      builder: (context, snapshot) {
        if (snapshot.connectionState == ConnectionState.waiting) {
          return const Center(child: CircularProgressIndicator());
        } else if (snapshot.hasError) {
          return Center(child: Text('載入失敗: ${snapshot.error}'));
        } else if (snapshot.hasData) {

          // 取得目前選取的時間
          DateTime selectedDate = _dynamicDates[_selectedDateIndex];

          List<Todo> filteredTodos = snapshot.data!.where((todo) {
            // 1. 狀態過濾邏輯
            bool statusMatch = true;
            if (_selectedFilter != 'All') {
              String status = (todo.status ?? '').toUpperCase();
              if (_selectedFilter == 'Done') statusMatch = status == 'DONE';
              else if (_selectedFilter == 'In Progress') statusMatch = status == 'WIP';
              else if (_selectedFilter == 'To do') statusMatch = status != 'DONE' && status != 'WIP';
            }

            // 2. 日期過濾邏輯 (比對 年、月、日)
            bool dateMatch = false;
            if (todo.endDate != null) {
              dateMatch = (todo.endDate!.year == selectedDate.year) &&
                  (todo.endDate!.month == selectedDate.month) &&
                  (todo.endDate!.day == selectedDate.day);
            }

            return statusMatch && dateMatch;
          }).toList();

          if (filteredTodos.isEmpty) {
            return Center(
              child: Text('此日期沒有「$_selectedFilter」狀態的任務。',
                  style: const TextStyle(color: Colors.grey, fontSize: 16)),
            );
          }

          return RefreshIndicator(
            onRefresh: () async => _refreshTodos(),
            child: ListView.builder(
              padding: const EdgeInsets.fromLTRB(20, 10, 20, 80),
              itemCount: filteredTodos.length,
              itemBuilder: (context, index) => _buildTaskCard(filteredTodos[index]),
            ),
          );
        } else {
          return const Center(child: Text('目前沒有待辦事項。工作很輕鬆！'));
        }
      },
    );
  }

  Widget _buildTaskCard(Todo item) {
    String displayStatus = 'To-do';
    Color chipColor = Colors.blueGrey;
    Color chipBg = Colors.blueGrey.withOpacity(0.1);

    if (item.status?.toUpperCase() == 'DONE') {
      displayStatus = 'Done';
      chipColor = primaryPurple;
      chipBg = primaryPurple.withOpacity(0.1);
    } else if (item.status?.toUpperCase() == 'WIP') {
      displayStatus = 'In Progress';
      chipColor = Colors.orange;
      chipBg = Colors.orange.withOpacity(0.1);
    }

    return Container(
      margin: const EdgeInsets.only(bottom: 16),
      padding: const EdgeInsets.all(16),
      decoration: BoxDecoration(
        color: Colors.white,
        borderRadius: BorderRadius.circular(20),
        boxShadow: [BoxShadow(color: Colors.grey.withOpacity(0.08), blurRadius: 15, offset: const Offset(0, 5))],
      ),
      child: InkWell(
        onTap: () => Navigator.push(context, MaterialPageRoute(builder: (_) => TodoDetail(todo: item))),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            Row(
              mainAxisAlignment: MainAxisAlignment.spaceBetween,
              children: [
                Text(item.className, style: const TextStyle(color: Colors.grey, fontSize: 13, fontWeight: FontWeight.w500)),
                Icon(Icons.work_outline, color: primaryPurple.withOpacity(0.5), size: 18),
              ],
            ),
            const SizedBox(height: 8),
            Text(item.taskName, style: const TextStyle(fontSize: 18, fontWeight: FontWeight.bold, color: Colors.black87)),
            const SizedBox(height: 16),
            Row(
              mainAxisAlignment: MainAxisAlignment.spaceBetween,
              children: [
                Row(
                  children: [
                    const Icon(Icons.access_time_filled, color: Colors.grey, size: 16),
                    const SizedBox(width: 6),
                    Text(item.formattedEndDate, style: const TextStyle(color: Colors.grey, fontSize: 13, fontWeight: FontWeight.w500)),
                  ],
                ),
                Container(
                  padding: const EdgeInsets.symmetric(horizontal: 12, vertical: 6),
                  decoration: BoxDecoration(color: chipBg, borderRadius: BorderRadius.circular(20)),
                  child: Text(displayStatus, style: TextStyle(color: chipColor, fontSize: 12, fontWeight: FontWeight.w700)),
                )
              ],
            )
          ],
        ),
      ),
    );
  }

  // 移除了內部的圖示，但保留了 BottomAppBar 的挖空設計與高度
  Widget _buildBottomNav() {
    return const BottomAppBar(
      shape: CircularNotchedRectangle(),
      notchMargin: 8.0,
      color: Color(0xFFF0EFFF),
      elevation: 0,
      child: SizedBox(
        height: 60, // 維持底部導覽列的高度，留給 FAB 空間
      ),
    );
  }
}