// 日历页面 — 月视图 + 日记列表

import 'package:flutter/material.dart';
import 'package:flutter_bloc/flutter_bloc.dart';
import 'package:go_router/go_router.dart';
import 'package:nuanji_app/core/theme/app_colors.dart';
import 'package:nuanji_app/data/models/journal_entry.dart';
import 'package:nuanji_app/data/repositories/journal_repository.dart';
import '../bloc/calendar_bloc.dart';

/// 日历页面 — 月视图 + 选中日期的日记列表
class CalendarPage extends StatelessWidget {
  const CalendarPage({super.key});

  @override
  Widget build(BuildContext context) {
    return BlocProvider(
      create: (context) => CalendarBloc(
        journalRepository: context.read<JournalRepository>(),
      )..add(CalendarMonthChanged(DateTime.now())),
      child: const _CalendarView(),
    );
  }
}

class _CalendarView extends StatelessWidget {
  const _CalendarView();

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    final colorScheme = theme.colorScheme;

    return BlocBuilder<CalendarBloc, CalendarState>(
      builder: (context, state) {
        if (state is CalendarInitial) {
          return const Center(child: CircularProgressIndicator());
        }

        if (state is CalendarError) {
          return Center(
            child: Column(
              mainAxisSize: MainAxisSize.min,
              children: [
                Icon(Icons.error_outline, size: 48, color: colorScheme.error),
                const SizedBox(height: 16),
                Text(state.message, style: theme.textTheme.bodyLarge),
                const SizedBox(height: 16),
                FilledButton.tonal(
                  onPressed: () => context.read<CalendarBloc>()
                      .add(CalendarMonthChanged(DateTime.now())),
                  child: const Text('重试'),
                ),
              ],
            ),
          );
        }

        if (state is! CalendarLoaded) return const SizedBox.shrink();
        final loaded = state;

        return Column(
          children: [
            // 月份导航
            _MonthNavigator(
              month: loaded.focusedMonth,
              onPrevious: () {
                final prev = DateTime(
                  loaded.focusedMonth.year,
                  loaded.focusedMonth.month - 1,
                );
                context.read<CalendarBloc>().add(CalendarMonthChanged(prev));
              },
              onNext: () {
                final next = DateTime(
                  loaded.focusedMonth.year,
                  loaded.focusedMonth.month + 1,
                );
                context.read<CalendarBloc>().add(CalendarMonthChanged(next));
              },
            ),

            // 星期标题行
            _WeekdayHeader(colorScheme: colorScheme),

            // 日历网格
            _CalendarGrid(
              month: loaded.focusedMonth,
              selectedDay: loaded.selectedDay,
              journalsByDate: loaded.journalsByDate,
              onDaySelected: (day) {
                context.read<CalendarBloc>().add(CalendarDaySelected(day));
              },
            ),

            const Divider(height: 1),

            // 选中日期的日记列表
            Expanded(
              child: loaded.selectedDayJournals.isEmpty
                  ? _EmptyDayView(selectedDay: loaded.selectedDay)
                  : _DayJournalList(journals: loaded.selectedDayJournals),
            ),
          ],
        );
      },
    );
  }
}

/// 月份导航栏
class _MonthNavigator extends StatelessWidget {
  const _MonthNavigator({
    required this.month,
    required this.onPrevious,
    required this.onNext,
  });

  final DateTime month;
  final VoidCallback onPrevious;
  final VoidCallback onNext;

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    final monthName = _formatMonth(month);

    return Padding(
      padding: const EdgeInsets.symmetric(horizontal: 8, vertical: 4),
      child: Row(
        mainAxisAlignment: MainAxisAlignment.spaceBetween,
        children: [
          IconButton(
            onPressed: onPrevious,
            icon: const Icon(Icons.chevron_left),
            tooltip: '上个月',
          ),
          Text(
            monthName,
            style: theme.textTheme.titleMedium?.copyWith(
              fontWeight: FontWeight.bold,
            ),
          ),
          IconButton(
            onPressed: onNext,
            icon: const Icon(Icons.chevron_right),
            tooltip: '下个月',
          ),
        ],
      ),
    );
  }

  String _formatMonth(DateTime date) {
    const months = [
      '1月', '2月', '3月', '4月', '5月', '6月',
      '7月', '8月', '9月', '10月', '11月', '12月',
    ];
    return '${date.year}年 ${months[date.month - 1]}';
  }
}

/// 星期标题行
class _WeekdayHeader extends StatelessWidget {
  const _WeekdayHeader({required this.colorScheme});

  final ColorScheme colorScheme;

  @override
  Widget build(BuildContext context) {
    const weekdays = ['一', '二', '三', '四', '五', '六', '日'];
    return Padding(
      padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 8),
      child: Row(
        children: weekdays.map((day) {
          return Expanded(
            child: Center(
              child: Text(
                day,
                style: TextStyle(
                  fontSize: 12,
                  color: colorScheme.onSurface.withValues(alpha: 0.6),
                  fontWeight: FontWeight.w500,
                ),
              ),
            ),
          );
        }).toList(),
      ),
    );
  }
}

/// 日历网格 — 6行7列
class _CalendarGrid extends StatelessWidget {
  const _CalendarGrid({
    required this.month,
    required this.selectedDay,
    required this.journalsByDate,
    required this.onDaySelected,
  });

  final DateTime month;
  final DateTime selectedDay;
  final Map<DateTime, List<JournalEntry>> journalsByDate;
  final ValueChanged<DateTime> onDaySelected;

  @override
  Widget build(BuildContext context) {
    final colorScheme = Theme.of(context).colorScheme;
    final today = DateTime.now();
    final days = _generateDays(month);

    return Padding(
      padding: const EdgeInsets.symmetric(horizontal: 16),
      child: Column(
        children: days.map((week) {
          return Row(
            children: week.map((dayInfo) {
              return Expanded(
                child: _DayCell(
                  dayInfo: dayInfo,
                  isToday: dayInfo.date.year == today.year &&
                      dayInfo.date.month == today.month &&
                      dayInfo.date.day == today.day,
                  isSelected: dayInfo.date.year == selectedDay.year &&
                      dayInfo.date.month == selectedDay.month &&
                      dayInfo.date.day == selectedDay.day,
                  hasJournals: journalsByDate.containsKey(
                    DateTime(dayInfo.date.year, dayInfo.date.month, dayInfo.date.day),
                  ),
                  colorScheme: colorScheme,
                  onTap: () => onDaySelected(dayInfo.date),
                ),
              );
            }).toList(),
          );
        }).toList(),
      ),
    );
  }

  /// 生成当月日历数据（包含前后补齐）
  List<List<_DayInfo>> _generateDays(DateTime month) {
    final firstDay = DateTime(month.year, month.month, 1);
    // 周一为第一天：weekday 1=Mon...7=Sun
    final startOffset = firstDay.weekday - 1;
    final daysInMonth = DateTime(month.year, month.month + 1, 0).day;

    final allDays = <_DayInfo>[];

    // 前面的空白
    for (var i = 0; i < startOffset; i++) {
      allDays.add(_DayInfo(date: firstDay.subtract(Duration(days: startOffset - i)), isCurrentMonth: false));
    }

    // 当月日期
    for (var d = 1; d <= daysInMonth; d++) {
      allDays.add(_DayInfo(
        date: DateTime(month.year, month.month, d),
        isCurrentMonth: true,
      ));
    }

    // 后面的补齐到完整行
    while (allDays.length % 7 != 0) {
      final last = allDays.last.date;
      allDays.add(_DayInfo(date: last.add(const Duration(days: 1)), isCurrentMonth: false));
    }

    // 分周
    return List.generate(allDays.length ~/ 7, (i) => allDays.sublist(i * 7, (i + 1) * 7));
  }
}

class _DayInfo {
  const _DayInfo({required this.date, required this.isCurrentMonth});
  final DateTime date;
  final bool isCurrentMonth;
}

/// 单日格子
class _DayCell extends StatelessWidget {
  const _DayCell({
    required this.dayInfo,
    required this.isToday,
    required this.isSelected,
    required this.hasJournals,
    required this.colorScheme,
    required this.onTap,
  });

  final _DayInfo dayInfo;
  final bool isToday;
  final bool isSelected;
  final bool hasJournals;
  final ColorScheme colorScheme;
  final VoidCallback onTap;

  @override
  Widget build(BuildContext context) {
    return GestureDetector(
      onTap: onTap,
      behavior: HitTestBehavior.opaque,
      child: Container(
        height: 44,
        alignment: Alignment.center,
        child: Column(
          mainAxisSize: MainAxisSize.min,
          children: [
            Container(
              width: 32,
              height: 32,
              decoration: BoxDecoration(
                shape: BoxShape.circle,
                color: isSelected
                    ? colorScheme.primary
                    : isToday
                        ? colorScheme.primaryContainer
                        : null,
              ),
              alignment: Alignment.center,
              child: Text(
                '${dayInfo.date.day}',
                style: TextStyle(
                  fontSize: 14,
                  fontWeight: isSelected || isToday ? FontWeight.bold : FontWeight.normal,
                  color: !dayInfo.isCurrentMonth
                      ? colorScheme.onSurface.withValues(alpha: 0.3)
                      : isSelected
                          ? colorScheme.onPrimary
                          : colorScheme.onSurface,
                ),
              ),
            ),
            // 日记指示点
            if (hasJournals)
              Container(
                width: 4,
                height: 4,
                margin: const EdgeInsets.only(top: 2),
                decoration: BoxDecoration(
                  shape: BoxShape.circle,
                  color: isSelected
                      ? colorScheme.onPrimary
                      : AppColors.accent,
                ),
              ),
          ],
        ),
      ),
    );
  }
}

/// 无日记的空状态
class _EmptyDayView extends StatelessWidget {
  const _EmptyDayView({required this.selectedDay});

  final DateTime selectedDay;

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    return Center(
      child: Column(
        mainAxisSize: MainAxisSize.min,
        children: [
          Icon(
            Icons.edit_note_rounded,
            size: 64,
            color: theme.colorScheme.onSurface.withValues(alpha: 0.2),
          ),
          const SizedBox(height: 16),
          Text(
            '${selectedDay.month}月${selectedDay.day}日',
            style: theme.textTheme.titleMedium,
          ),
          const SizedBox(height: 8),
          Text(
            '这一天还没有日记',
            style: theme.textTheme.bodyMedium?.copyWith(
              color: theme.colorScheme.onSurface.withValues(alpha: 0.5),
            ),
          ),
          const SizedBox(height: 24),
          FilledButton.tonal(
            onPressed: () => context.go('/editor'),
            child: const Text('写一篇'),
          ),
        ],
      ),
    );
  }
}

/// 日记列表
class _DayJournalList extends StatelessWidget {
  const _DayJournalList({required this.journals});

  final List<JournalEntry> journals;

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    final colorScheme = theme.colorScheme;

    return ListView.builder(
      padding: const EdgeInsets.all(16),
      itemCount: journals.length,
      itemBuilder: (context, index) {
        final journal = journals[index];
        final moodColor = AppColors.moodColors[journal.mood.value] ?? colorScheme.primary;

        return Card(
          margin: const EdgeInsets.only(bottom: 12),
          elevation: 0,
          shape: RoundedRectangleBorder(
            borderRadius: BorderRadius.circular(16),
            side: BorderSide(color: colorScheme.outlineVariant),
          ),
          child: InkWell(
            onTap: () => context.go('/editor?id=${journal.id}'),
            borderRadius: BorderRadius.circular(16),
            child: Padding(
              padding: const EdgeInsets.all(16),
              child: Row(
                children: [
                  // 心情图标
                  Container(
                    width: 40,
                    height: 40,
                    decoration: BoxDecoration(
                      color: moodColor.withValues(alpha: 0.2),
                      shape: BoxShape.circle,
                    ),
                    alignment: Alignment.center,
                    child: Text(
                      _moodEmoji(journal.mood),
                      style: const TextStyle(fontSize: 20),
                    ),
                  ),
                  const SizedBox(width: 12),
                  // 标题和标签
                  Expanded(
                    child: Column(
                      crossAxisAlignment: CrossAxisAlignment.start,
                      children: [
                        Text(
                          journal.title,
                          style: theme.textTheme.titleSmall?.copyWith(
                            fontWeight: FontWeight.w600,
                          ),
                          maxLines: 1,
                          overflow: TextOverflow.ellipsis,
                        ),
                        if (journal.tags.isNotEmpty) ...[
                          const SizedBox(height: 4),
                          Text(
                            journal.tags.take(3).join(' · '),
                            style: theme.textTheme.bodySmall?.copyWith(
                              color: colorScheme.onSurface.withValues(alpha: 0.5),
                            ),
                          ),
                        ],
                      ],
                    ),
                  ),
                  Icon(
                    Icons.chevron_right,
                    color: colorScheme.onSurface.withValues(alpha: 0.3),
                  ),
                ],
              ),
            ),
          ),
        );
      },
    );
  }

  String _moodEmoji(Mood mood) {
    return switch (mood) {
      Mood.happy => '😊',
      Mood.calm => '😌',
      Mood.sad => '😢',
      Mood.angry => '😠',
      Mood.thinking => '🤔',
    };
  }
}