import 'package:flutter/material.dart';
import 'package:flutter/cupertino.dart';
import 'package:go_router/go_router.dart';
import 'package:lucide_icons/lucide_icons.dart';
import '../../../../core/di/injection.dart';
import '../../../../core/theme/design_tokens.dart';
import '../calendar_state_manager.dart';
import '../calendar_time_utils.dart';
import '../widgets/bottom_dock.dart';
import '../widgets/create_event_sheet.dart';
import '../../data/services/mock_calendar_service.dart';

class CalendarMonthScreen extends StatefulWidget {
  final bool resetToToday;

  const CalendarMonthScreen({super.key, this.resetToToday = false});

  @override
  State<CalendarMonthScreen> createState() => _CalendarMonthScreenState();
}

class _CalendarMonthScreenState extends State<CalendarMonthScreen> {
  late final CalendarStateManager _calendarManager;
  late DateTime _currentMonth;
  late DateTime _selectedDate;
  Key _eventsKey = UniqueKey();

  @override
  void initState() {
    super.initState();
    _calendarManager = sl<CalendarStateManager>();

    if (widget.resetToToday) {
      _calendarManager.resetToToday();
    }

    final savedDate = _calendarManager.selectedDate;
    _selectedDate = savedDate;
    _currentMonth = DateTime(savedDate.year, savedDate.month, 1);
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: AppColors.todoBg,
      body: SafeArea(
        child: Column(
          children: [
            _buildHeader(),
            Expanded(
              child: SingleChildScrollView(
                child: Padding(
                  padding: const EdgeInsets.only(bottom: 84),
                  child: _buildMonthContent(),
                ),
              ),
            ),
            _buildBottomDock(),
          ],
        ),
      ),
    );
  }

  Widget _buildHeader() {
    return SizedBox(
      height: 76,
      child: Padding(
        padding: const EdgeInsets.only(left: 16, right: 16, top: 14, bottom: 6),
        child: Column(
          children: [
            SizedBox(
              height: 56,
              child: Row(
                children: [
                  GestureDetector(
                    onTap: () => _showMonthPicker(),
                    child: Row(
                      children: [
                        Text(
                          '${_currentMonth.month}月',
                          style: const TextStyle(
                            fontSize: 22,
                            fontWeight: FontWeight.w700,
                            color: AppColors.slate900,
                          ),
                        ),
                        const SizedBox(width: 6),
                        const Icon(
                          LucideIcons.chevronDown,
                          size: 16,
                          color: AppColors.slate900,
                        ),
                      ],
                    ),
                  ),
                  const Spacer(),
                  GestureDetector(
                    onTap: () => CreateEventSheet.show(
                      context,
                      onSaved: () {
                        setState(() {
                          _eventsKey = UniqueKey();
                        });
                      },
                    ),
                    child: Container(
                      width: 36,
                      height: 36,
                      decoration: BoxDecoration(
                        color: AppColors.blue600,
                        borderRadius: BorderRadius.circular(18),
                      ),
                      child: const Icon(
                        LucideIcons.plus,
                        size: 20,
                        color: Colors.white,
                      ),
                    ),
                  ),
                ],
              ),
            ),
          ],
        ),
      ),
    );
  }

  Widget _buildMonthContent() {
    return Column(
      children: [
        _buildWeekdayHeader(),
        Container(height: 1, color: AppColors.border),
        ..._buildWeeks(),
      ],
    );
  }

  Widget _buildWeekdayHeader() {
    const weekdays = ['日', '一', '二', '三', '四', '五', '六'];
    return SizedBox(
      height: 40,
      child: Padding(
        padding: const EdgeInsets.symmetric(horizontal: 16),
        child: Row(
          mainAxisAlignment: MainAxisAlignment.spaceBetween,
          children: weekdays
              .map(
                (day) => SizedBox(
                  width: 36,
                  child: Center(
                    child: Text(
                      day,
                      style: const TextStyle(
                        fontSize: 11,
                        fontWeight: FontWeight.w600,
                        color: AppColors.slate400,
                      ),
                    ),
                  ),
                ),
              )
              .toList(),
        ),
      ),
    );
  }

  List<Widget> _buildWeeks() {
    final firstDayOfMonth = DateTime(
      _currentMonth.year,
      _currentMonth.month,
      1,
    );
    final lastDayOfMonth = DateTime(
      _currentMonth.year,
      _currentMonth.month + 1,
      0,
    );
    final startWeekday = firstDayOfMonth.weekday % 7;

    final daysInMonth = lastDayOfMonth.day;
    final totalCells = ((daysInMonth + startWeekday) / 7).ceil() * 7;

    final weeks = <Widget>[];
    for (var weekStart = 0; weekStart < totalCells; weekStart += 7) {
      weeks.add(_buildWeekRow(weekStart, startWeekday, daysInMonth));
      if (weekStart + 7 < totalCells) {
        weeks.add(Container(height: 1, color: AppColors.border));
      }
    }

    return weeks;
  }

  Widget _buildWeekRow(int weekStart, int startWeekday, int daysInMonth) {
    return Padding(
      padding: const EdgeInsets.only(left: 16, right: 16, top: 14, bottom: 0),
      child: Column(
        children: [
          Row(
            mainAxisAlignment: MainAxisAlignment.spaceBetween,
            children: List.generate(7, (index) {
              final dayIndex = weekStart + index - startWeekday + 1;
              if (dayIndex < 1 || dayIndex > daysInMonth) {
                return SizedBox(width: 36, height: 36);
              }

              final date = DateTime(
                _currentMonth.year,
                _currentMonth.month,
                dayIndex,
              );
              final isSelected = isSameDay(_selectedDate, date);

              return GestureDetector(
                onTap: () {
                  setState(() {
                    _selectedDate = date;
                  });
                  _calendarManager.setSelectedDate(date);
                  _calendarManager.setViewType(CalendarViewType.month);
                  final ymd = formatYmd(date);
                  context.push('/calendar/dayweek?date=$ymd');
                },
                child: Container(
                  width: 36,
                  height: 36,
                  decoration: BoxDecoration(
                    color: isSelected ? AppColors.blue100 : Colors.transparent,
                    borderRadius: BorderRadius.circular(18),
                  ),
                  child: Center(
                    child: Text(
                      '$dayIndex',
                      style: TextStyle(
                        fontSize: 15,
                        fontWeight: isSelected
                            ? FontWeight.w600
                            : FontWeight.normal,
                        color: isSelected
                            ? AppColors.blue600
                            : AppColors.slate900,
                      ),
                    ),
                  ),
                ),
              );
            }),
          ),
          const SizedBox(height: 10),
          KeyedSubtree(
            key: _eventsKey,
            child: _buildWeekEvents(weekStart, startWeekday, daysInMonth),
          ),
        ],
      ),
    );
  }

  Widget _buildWeekEvents(int weekStart, int startWeekday, int daysInMonth) {
    final firstDayOfMonth = DateTime(
      _currentMonth.year,
      _currentMonth.month,
      1,
    );
    final weekFirstDate = firstDayOfMonth.add(
      Duration(days: weekStart - startWeekday),
    );

    return SizedBox(
      height: 70,
      child: Row(
        mainAxisAlignment: MainAxisAlignment.spaceBetween,
        children: List.generate(7, (index) {
          final dayIndex = weekStart + index - startWeekday + 1;
          if (dayIndex < 1 || dayIndex > daysInMonth) {
            return const SizedBox(width: 38, height: 1);
          }

          final date = weekFirstDate.add(Duration(days: index));
          final events = CalendarService().getEventsForDay(date);
          final displayEvents = events.take(2).toList();
          final remainingCount = events.length - 2;

          return SizedBox(
            width: 38,
            height: 70,
            child: Column(
              crossAxisAlignment: CrossAxisAlignment.start,
              children: [
                ...displayEvents.map((event) {
                  final color = _parseColor(event.metadata?.color);
                  return GestureDetector(
                    onTap: () {
                      _calendarManager.setSelectedDate(date);
                      context.push('/calendar/events/${event.id}');
                    },
                    child: Container(
                      margin: const EdgeInsets.only(bottom: 2),
                      padding: const EdgeInsets.symmetric(
                        horizontal: 4,
                        vertical: 2,
                      ),
                      decoration: BoxDecoration(
                        color: color.withValues(alpha: 0.2),
                        borderRadius: BorderRadius.circular(4),
                      ),
                      child: Text(
                        event.title,
                        style: TextStyle(
                          fontSize: 9,
                          color: color,
                          fontWeight: FontWeight.w500,
                        ),
                        maxLines: 1,
                        overflow: TextOverflow.ellipsis,
                      ),
                    ),
                  );
                }),
                if (remainingCount > 0)
                  GestureDetector(
                    onTap: () {
                      _calendarManager.setSelectedDate(date);
                      _calendarManager.setViewType(CalendarViewType.day);
                      context.push('/calendar/dayweek?date=${formatYmd(date)}');
                    },
                    child: Text(
                      '+$remainingCount',
                      style: const TextStyle(
                        fontSize: 9,
                        color: AppColors.slate500,
                        fontWeight: FontWeight.w500,
                      ),
                    ),
                  ),
              ],
            ),
          );
        }),
      ),
    );
  }

  Color _parseColor(String? hex) {
    if (hex == null || hex.isEmpty) return AppColors.blue600;
    try {
      return Color(int.parse(hex.replaceFirst('#', '0xFF')));
    } catch (_) {
      return AppColors.blue600;
    }
  }

  void _showMonthPicker() {
    showModalBottomSheet(
      context: context,
      builder: (context) => Container(
        height: 300,
        color: Colors.white,
        child: Column(
          children: [
            Row(
              mainAxisAlignment: MainAxisAlignment.spaceBetween,
              children: [
                TextButton(
                  onPressed: () => Navigator.pop(context),
                  child: const Text('取消'),
                ),
                TextButton(
                  onPressed: () => Navigator.pop(context),
                  child: const Text('确定'),
                ),
              ],
            ),
            Expanded(
              child: Row(
                children: [
                  Expanded(
                    child: CupertinoPicker(
                      itemExtent: 40,
                      scrollController: FixedExtentScrollController(
                        initialItem: _currentMonth.year - 2020,
                      ),
                      onSelectedItemChanged: (index) {
                        setState(() {
                          _currentMonth = DateTime(
                            2020 + index,
                            _currentMonth.month,
                            1,
                          );
                        });
                      },
                      children: List.generate(20, (index) {
                        return Center(child: Text('${2020 + index}年'));
                      }),
                    ),
                  ),
                  Expanded(
                    child: CupertinoPicker(
                      itemExtent: 40,
                      scrollController: FixedExtentScrollController(
                        initialItem: _currentMonth.month - 1,
                      ),
                      onSelectedItemChanged: (index) {
                        setState(() {
                          _currentMonth = DateTime(
                            _currentMonth.year,
                            index + 1,
                            1,
                          );
                        });
                      },
                      children: List.generate(12, (index) {
                        return Center(child: Text('${index + 1}月'));
                      }),
                    ),
                  ),
                ],
              ),
            ),
          ],
        ),
      ),
    );
  }

  Widget _buildBottomDock() {
    return BottomDock(
      activeTab: DockTab.calendar,
      onTodoTap: () {
        _calendarManager.setViewType(CalendarViewType.month);
        context.push('/todo');
      },
      onCalendarTap: () {},
      onHomeTap: () => context.go('/home'),
    );
  }
}