// 日历页面 — 月视图(心情色彩) + 周视图 + 时间轴
// 对齐 Open Design 原型稿: 日历格子用心情颜色填充背景 + 月/周/时间轴切换

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/core/theme/app_radius.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(心情色彩) + 周视图 + 时间轴
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));
              },
            ),

            // 视图模式切换
            Padding(
              padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 4),
              child: SegmentedButton<CalendarViewMode>(
                segments: const [
                  ButtonSegment(value: CalendarViewMode.month, label: Text('月')),
                  ButtonSegment(value: CalendarViewMode.week, label: Text('周')),
                  ButtonSegment(value: CalendarViewMode.timeline, label: Text('时间轴')),
                ],
                selected: {loaded.viewMode},
                onSelectionChanged: (modes) {
                  context.read<CalendarBloc>()
                      .add(CalendarViewModeChanged(modes.first));
                },
                style: ButtonStyle(
                  visualDensity: VisualDensity.compact,
                  textStyle: WidgetStatePropertyAll(theme.textTheme.labelSmall),
                ),
              ),
            ),

            // 根据视图模式切换内容
            switch (loaded.viewMode) {
              CalendarViewMode.month => _MonthView(loaded: loaded),
              CalendarViewMode.week => _WeekView(loaded: loaded),
              CalendarViewMode.timeline => _TimelineView(loaded: loaded),
            },
          ],
        );
      },
    );
  }
}

// ===== 月视图 =====

class _MonthView extends StatelessWidget {
  const _MonthView({required this.loaded});

  final CalendarLoaded loaded;

  @override
  Widget build(BuildContext context) {
    return Expanded(
      child: Column(
        children: [
          // 星期标题行
          _WeekdayHeader(colorScheme: Theme.of(context).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),
          ),
        ],
      ),
    );
  }
}

// ===== 周视图 =====

class _WeekView extends StatelessWidget {
  const _WeekView({required this.loaded});

  final CalendarLoaded loaded;

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

    // 计算选中日期所在周
    final selected = loaded.selectedDay;
    final startOfWeek = selected.subtract(Duration(days: selected.weekday - 1));

    return Expanded(
      child: ListView(
        padding: const EdgeInsets.all(16),
        children: [
          // 7 天条目
          ...List.generate(7, (i) {
            final day = startOfWeek.add(Duration(days: i));
            final dayKey = DateTime(day.year, day.month, day.day);
            final journals = loaded.journalsByDate[dayKey] ?? [];
            final isToday = _isToday(day);
            final isSelected = _isSameDay(day, loaded.selectedDay);
            final hasEntry = journals.isNotEmpty;

            return Padding(
              padding: const EdgeInsets.only(bottom: 8),
              child: InkWell(
                onTap: () {
                  context.read<CalendarBloc>().add(CalendarDaySelected(day));
                },
                borderRadius: AppRadius.mdBorder,
                child: Container(
                  padding: const EdgeInsets.all(16),
                  decoration: BoxDecoration(
                    color: isSelected
                        ? colorScheme.primaryContainer
                        : hasEntry
                            ? _getMoodBgColor(journals.first.mood.value)
                            : colorScheme.surface,
                    borderRadius: AppRadius.mdBorder,
                    border: Border.all(
                      color: isToday
                          ? colorScheme.primary
                          : colorScheme.outlineVariant,
                      width: isToday ? 2 : 1,
                    ),
                  ),
                  child: Row(
                    children: [
                      // 日期
                      SizedBox(
                        width: 48,
                        child: Column(
                          children: [
                            Text(
                              _weekdayName(day.weekday),
                              style: theme.textTheme.labelSmall?.copyWith(
                                color: colorScheme.onSurfaceVariant,
                              ),
                            ),
                            Text(
                              '${day.day}',
                              style: theme.textTheme.titleLarge?.copyWith(
                                fontWeight: isToday ? FontWeight.bold : FontWeight.normal,
                                color: isToday ? colorScheme.primary : null,
                              ),
                            ),
                          ],
                        ),
                      ),
                      const SizedBox(width: 16),
                      // 内容
                      Expanded(
                        child: hasEntry
                            ? Column(
                                crossAxisAlignment: CrossAxisAlignment.start,
                                children: [
                                  Text(
                                    journals.first.title,
                                    style: theme.textTheme.titleSmall?.copyWith(
                                      fontWeight: FontWeight.w600,
                                    ),
                                    maxLines: 1,
                                    overflow: TextOverflow.ellipsis,
                                  ),
                                  if (journals.length > 1)
                                    Text(
                                      '还有 ${journals.length - 1} 篇日记',
                                      style: theme.textTheme.bodySmall?.copyWith(
                                        color: colorScheme.onSurfaceVariant,
                                      ),
                                    ),
                                ],
                              )
                            : Text(
                                '无日记',
                                style: theme.textTheme.bodySmall?.copyWith(
                                  color: colorScheme.onSurface.withValues(alpha: 0.4),
                                ),
                              ),
                      ),
                      // 心情 emoji
                      if (hasEntry)
                        Text(
                          _moodEmoji(journals.first.mood),
                          style: const TextStyle(fontSize: 24),
                        ),
                    ],
                  ),
                ),
              ),
            );
          }),
        ],
      ),
    );
  }
}

// ===== 时间轴视图 =====

class _TimelineView extends StatelessWidget {
  const _TimelineView({required this.loaded});

  final CalendarLoaded loaded;

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

    // 获取当月所有日记，按日期排序
    final allJournals = loaded.journalsByDate.entries
        .expand((e) => e.value.map((j) => MapEntry(e.key, j)))
        .toList()
      ..sort((a, b) => b.key.compareTo(a.key));

    if (allJournals.isEmpty) {
      return Center(
        child: Column(
          mainAxisSize: MainAxisSize.min,
          children: [
            Icon(Icons.timeline_outlined, size: 48,
                color: colorScheme.onSurface.withValues(alpha: 0.2)),
            const SizedBox(height: 16),
            Text('本月还没有日记', style: theme.textTheme.bodyLarge),
          ],
        ),
      );
    }

    return Expanded(
      child: ListView.builder(
        padding: const EdgeInsets.all(16),
        itemCount: allJournals.length,
        itemBuilder: (context, index) {
          final entry = allJournals[index];
          final date = entry.key;
          final journal = entry.value;
          final isLast = index == allJournals.length - 1;

          return IntrinsicHeight(
            child: Row(
              crossAxisAlignment: CrossAxisAlignment.start,
              children: [
                // 时间轴线
                SizedBox(
                  width: 60,
                  child: Column(
                    children: [
                      // 圆点 + emoji
                      Container(
                        width: 36,
                        height: 36,
                        decoration: BoxDecoration(
                          color: _getMoodBgColor(journal.mood.value),
                          shape: BoxShape.circle,
                        ),
                        alignment: Alignment.center,
                        child: Text(_moodEmoji(journal.mood), style: const TextStyle(fontSize: 18)),
                      ),
                      // 竖线
                      if (!isLast)
                        Expanded(
                          child: Container(
                            width: 2,
                            color: colorScheme.outlineVariant,
                          ),
                        ),
                    ],
                  ),
                ),
                // 内容卡片
                Expanded(
                  child: Padding(
                    padding: const EdgeInsets.only(bottom: 12),
                    child: Card(
                      elevation: 0,
                      shape: RoundedRectangleBorder(
                        borderRadius: AppRadius.mdBorder,
                        side: BorderSide(color: colorScheme.outlineVariant),
                      ),
                      child: InkWell(
                        onTap: () => context.push('/editor?id=${journal.id}'),
                        borderRadius: AppRadius.mdBorder,
                        child: Padding(
                          padding: const EdgeInsets.all(16),
                          child: Column(
                            crossAxisAlignment: CrossAxisAlignment.start,
                            children: [
                              Text(
                                '${date.month}月${date.day}日',
                                style: theme.textTheme.labelSmall?.copyWith(
                                  color: colorScheme.onSurfaceVariant,
                                ),
                              ),
                              const SizedBox(height: 4),
                              Text(
                                journal.title,
                                style: theme.textTheme.titleSmall?.copyWith(
                                  fontWeight: FontWeight.w600,
                                ),
                                maxLines: 1,
                                overflow: TextOverflow.ellipsis,
                              ),
                              // 日记内容通过 JournalElement 管理，日历视图仅显示标题
                              // 后续可通过 elements 预览首段文字
                            ],
                          ),
                        ),
                      ),
                    ),
                  ),
                ),
              ],
            ),
          );
        },
      ),
    );
  }
}

// ===== 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（带心情色彩背景）=====

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 days = _generateDays(month);

    return Padding(
      padding: const EdgeInsets.symmetric(horizontal: 16),
      child: Column(
        children: days.map((week) {
          return Row(
            children: week.map((dayInfo) {
              final dayKey = DateTime(
                dayInfo.date.year, dayInfo.date.month, dayInfo.date.day);
              final journals = journalsByDate[dayKey] ?? [];
              final moodValue = journals.isNotEmpty ? journals.first.mood.value : null;

              return Expanded(
                child: _DayCell(
                  dayInfo: dayInfo,
                  isToday: _isToday(dayInfo.date),
                  isSelected: _isSameDay(dayInfo.date, selectedDay),
                  hasJournals: journals.isNotEmpty,
                  moodValue: moodValue,
                  onTap: () => onDaySelected(dayInfo.date),
                ),
              );
            }).toList(),
          );
        }).toList(),
      ),
    );
  }

  List<List<_DayInfo>> _generateDays(DateTime month) {
    final firstDay = DateTime(month.year, month.month, 1);
    final startOffset = firstDay.weekday - 1;
    final daysInMonth = DateTime(month.year, month.month + 1, 0).day;

    final allDays = <_DayInfo>[];

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

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

    while (allDays.length % 7 != 0) {
      final last = allDays.last.date;
      allDays.add(_DayInfo(date: last.add(const Duration(days: 1)), isCurrentMonth: false));
    }

    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（带心情色彩背景）=====

class _DayCell extends StatelessWidget {
  const _DayCell({
    required this.dayInfo,
    required this.isToday,
    required this.isSelected,
    required this.hasJournals,
    required this.moodValue,
    required this.onTap,
  });

  final _DayInfo dayInfo;
  final bool isToday;
  final bool isSelected;
  final bool hasJournals;
  final String? moodValue;
  final VoidCallback onTap;

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

    // 心情色彩背景
    final moodBg = hasJournals && moodValue != null
        ? _getMoodBgColor(moodValue!)
        : Colors.transparent;

    return GestureDetector(
      onTap: onTap,
      behavior: HitTestBehavior.opaque,
      child: Container(
        height: 48,
        margin: const EdgeInsets.all(2),
        decoration: BoxDecoration(
          color: isSelected
              ? colorScheme.primary
              : moodBg != Colors.transparent
                  ? moodBg
                  : isToday
                      ? colorScheme.primaryContainer
                      : null,
          borderRadius: AppRadius.xsBorder,
          border: isToday && !isSelected
              ? Border.all(color: colorScheme.primary, width: 2)
              : null,
        ),
        alignment: Alignment.center,
        child: Column(
          mainAxisSize: MainAxisSize.min,
          children: [
            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,
              ),
            ),
            // 心情小圆点（仅在有日记但无背景色时显示）
            if (hasJournals && moodBg == Colors.transparent)
              Container(
                width: 4,
                height: 4,
                margin: const EdgeInsets.only(top: 1),
                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.push('/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: AppRadius.mdBorder,
            side: BorderSide(color: colorScheme.outlineVariant),
          ),
          child: InkWell(
            onTap: () => context.push('/editor?id=${journal.id}'),
            borderRadius: AppRadius.mdBorder,
            child: Padding(
              padding: const EdgeInsets.all(16),
              child: Row(
                children: [
                  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),
                  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),
                  ),
                ],
              ),
            ),
          ),
        );
      },
    );
  }
}

// ===== 辅助函数 =====

/// 获取心情对应的日历格子背景色
Color _getMoodBgColor(String mood) {
  return AppColors.moodCellColors[mood] ?? AppColors.secondarySoftLight;
}

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

/// 是否是今天
bool _isToday(DateTime date) {
  final now = DateTime.now();
  return date.year == now.year && date.month == now.month && date.day == now.day;
}

/// 是否同一天
bool _isSameDay(DateTime a, DateTime b) {
  return a.year == b.year && a.month == b.month && a.day == b.day;
}

/// 周几名称
String _weekdayName(int weekday) {
  return switch (weekday) {
    1 => '周一',
    2 => '周二',
    3 => '周三',
    4 => '周四',
    5 => '周五',
    6 => '周六',
    7 => '周日',
    _ => '',
  };
}