import 'package:flutter/material.dart';
import 'package:table_calendar/table_calendar.dart'; // 建議引入此套件
import 'package:intl/intl.dart';
import './calendar_model.dart';
import './calendar_api.dart';
import './calendar_detail.dart';

class CalendarManager extends StatefulWidget {
  final String userId;
  const CalendarManager({required this.userId, super.key});

  @override
  State<CalendarManager> createState() => _CalendarManagerState();
}

class _CalendarManagerState extends State<CalendarManager> {
  final CalendarApiService _apiService = CalendarApiService();

  // 狀態控制
  CalendarFormat _calendarFormat = CalendarFormat.month;
  DateTime _focusedDay = DateTime.now();
  DateTime? _selectedDay;

  // 資料儲存：將事件按日期分類，方便日曆標點
  Map<DateTime, List<CalendarEvent>> _eventsMap = {};
  bool _isLoading = false;

  @override
  void initState() {
    super.initState();
    _selectedDay = _focusedDay;
    _fetchMonthEvents(_focusedDay);
  }

  // 核心：抓取整個月的資料並進行分類
  Future<void> _fetchMonthEvents(DateTime month) async {
    setState(() => _isLoading = true);
    try {
      final events = await _apiService.fetchEvents(widget.userId, month);

      // 將 List 轉換為 Map<DateTime, List<Event>>
      Map<DateTime, List<CalendarEvent>> newMap = {};
      for (var event in events) {
        if (event.startTime != null) {
          // 只取日期部分作為 Key
          final dateKey = DateTime(event.startTime!.year, event.startTime!.month, event.startTime!.day);
          if (newMap[dateKey] == null) newMap[dateKey] = [];
          newMap[dateKey]!.add(event);
        }
      }

      setState(() {
        _eventsMap = newMap;
        _isLoading = false;
      });
    } catch (e) {
      setState(() => _isLoading = false);
      ScaffoldMessenger.of(context).showSnackBar(SnackBar(content: Text("載入失敗: $e")));
    }
  }

  // 獲取選定日期的行程
  List<CalendarEvent> _getEventsForDay(DateTime day) {
    final dateKey = DateTime(day.year, day.month, day.day);
    return _eventsMap[dateKey] ?? [];
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('企業行事曆'),
        actions: [
          IconButton(icon: const Icon(Icons.today), onPressed: () => setState(() => _focusedDay = DateTime.now())),
        ],
      ),
      body: Column(
        children: [
          // 1. 日曆組件
          TableCalendar<CalendarEvent>(
            firstDay: DateTime.utc(2020, 1, 1),
            lastDay: DateTime.utc(2030, 12, 31),
            focusedDay: _focusedDay,
            calendarFormat: _calendarFormat,
            selectedDayPredicate: (day) => isSameDay(_selectedDay, day),
            eventLoader: _getEventsForDay, // 在有行程的日期顯示小點點

            // 樣式設定
            calendarStyle: CalendarStyle(
              todayDecoration: BoxDecoration(color: Colors.blue.withOpacity(0.5), shape: BoxShape.circle),
              selectedDecoration: const BoxDecoration(color: Colors.blue, shape: BoxShape.circle),
              markerDecoration: const BoxDecoration(color: Colors.orange, shape: BoxShape.circle),
            ),

            // 互動事件
            onDaySelected: (selectedDay, focusedDay) {
              setState(() {
                _selectedDay = selectedDay;
                _focusedDay = focusedDay;
              });
            },
            onFormatChanged: (format) {
              setState(() => _calendarFormat = format);
            },
            onPageChanged: (focusedDay) {
              _focusedDay = focusedDay;
              _fetchMonthEvents(focusedDay); // 切換月份時自動重新抓取 API
            },
          ),

          const Divider(height: 1),

          // 2. 下方行程列表
          Expanded(
            child: _isLoading
                ? const Center(child: CircularProgressIndicator())
                : _buildEventList(),
          ),
        ],
      ),
      floatingActionButton: FloatingActionButton(
        child: const Icon(Icons.add),
        onPressed: () { /* 實重新增行程邏輯 */ },
      ),
    );
  }

  Widget _buildEventList() {
    final dayEvents = _getEventsForDay(_selectedDay!);

    if (dayEvents.isEmpty) {
      return Center(
        child: Text(
          "${DateFormat('MM/dd').format(_selectedDay!)} 沒有行程",
          style: const TextStyle(color: Colors.grey),
        ),
      );
    }

    return ListView.builder(
      padding: const EdgeInsets.all(12),
      itemCount: dayEvents.length,
      itemBuilder: (context, index) {
        final event = dayEvents[index];
        return Card(
          elevation: 2,
          margin: const EdgeInsets.only(bottom: 10),
          child: ListTile(
            leading: Container(
              width: 4,
              height: 40,
              decoration: BoxDecoration(
                color: event.levelColor,
                borderRadius: BorderRadius.circular(2),
              ),
            ),
            title: Text(event.title, style: const TextStyle(fontWeight: FontWeight.bold)),
            subtitle: Text(event.timeRangeText),
            trailing: const Icon(Icons.chevron_right),
            onTap: () => Navigator.push(
                context,
                MaterialPageRoute(builder: (_) => CalendarDetail(event: event))
            ),
          ),
        );
      },
    );
  }
}