nj/app/lib/features/calendar/bloc/calendar_bloc.dart

// 日历 BLoC — 管理日历视图状态和日记列表

import 'package:flutter_bloc/flutter_bloc.dart';
import 'package:nuanji_app/data/models/journal_entry.dart';

// ===== Events =====

sealed class CalendarEvent {
  const CalendarEvent();
}

/// 切换到指定月份
final class CalendarMonthChanged extends CalendarEvent {
  final DateTime month;
  const CalendarMonthChanged(this.month);
}

/// 选择某一天
final class CalendarDaySelected extends CalendarEvent {
  final DateTime day;
  const CalendarDaySelected(this.day);
}

/// 切换视图模式（月/周/时间轴）
final class CalendarViewModeChanged extends CalendarEvent {
  final CalendarViewMode mode;
  const CalendarViewModeChanged(this.mode);
}

/// 加载某月的日记列表
final class CalendarLoadJournals extends CalendarEvent {
  final DateTime month;
  const CalendarLoadJournals(this.month);
}

// ===== State =====

/// 日历视图模式
enum CalendarViewMode { month, week, timeline }

/// 日历状态
sealed class CalendarState {
  const CalendarState();
}

/// 初始加载中
final class CalendarInitial extends CalendarState {
  const CalendarInitial();
}

/// 日历已加载 — 包含当前月份、选中日期、日记列表
final class CalendarLoaded extends CalendarState {
  /// 当前显示的月份
  final DateTime focusedMonth;

  /// 选中的日期
  final DateTime selectedDay;

  /// 当前月份所有日记（按日期索引）
  final Map<DateTime, List<JournalEntry>> journalsByDate;

  /// 当前选中日期的日记列表
  final List<JournalEntry> selectedDayJournals;

  /// 视图模式
  final CalendarViewMode viewMode;

  /// 是否正在加载
  final bool isLoading;

  const CalendarLoaded({
    required this.focusedMonth,
    required this.selectedDay,
    required this.journalsByDate,
    required this.selectedDayJournals,
    this.viewMode = CalendarViewMode.month,
    this.isLoading = false,
  });

  CalendarLoaded copyWith({
    DateTime? focusedMonth,
    DateTime? selectedDay,
    Map<DateTime, List<JournalEntry>>? journalsByDate,
    List<JournalEntry>? selectedDayJournals,
    CalendarViewMode? viewMode,
    bool? isLoading,
  }) =>
      CalendarLoaded(
        focusedMonth: focusedMonth ?? this.focusedMonth,
        selectedDay: selectedDay ?? this.selectedDay,
        journalsByDate: journalsByDate ?? this.journalsByDate,
        selectedDayJournals: selectedDayJournals ?? this.selectedDayJournals,
        viewMode: viewMode ?? this.viewMode,
        isLoading: isLoading ?? this.isLoading,
      );
}

/// 加载失败
final class CalendarError extends CalendarState {
  final String message;
  const CalendarError(this.message);
}

// ===== BLoC =====

class CalendarBloc extends Bloc<CalendarEvent, CalendarState> {
  CalendarBloc() : super(const CalendarInitial()) {
    on<CalendarMonthChanged>(_onMonthChanged);
    on<CalendarDaySelected>(_onDaySelected);
    on<CalendarViewModeChanged>(_onViewModeChanged);
    on<CalendarLoadJournals>(_onLoadJournals);
  }

  void _onMonthChanged(
    CalendarMonthChanged event,
    Emitter<CalendarState> emit,
  ) {
    final currentState = state is CalendarLoaded ? state as CalendarLoaded : null;

    emit(CalendarLoaded(
      focusedMonth: event.month,
      selectedDay: event.month,
      journalsByDate: currentState?.journalsByDate ?? {},
      selectedDayJournals: [],
      viewMode: currentState?.viewMode ?? CalendarViewMode.month,
    ));

    add(CalendarLoadJournals(event.month));
  }

  void _onDaySelected(
    CalendarDaySelected event,
    Emitter<CalendarState> emit,
  ) {
    if (state is! CalendarLoaded) return;
    final current = state as CalendarLoaded;

    // 查找选中日期的日记
    final dayKey = DateTime(event.day.year, event.day.month, event.day.day);
    final dayJournals = current.journalsByDate[dayKey] ?? [];

    emit(current.copyWith(
      selectedDay: event.day,
      selectedDayJournals: dayJournals,
    ));
  }

  void _onViewModeChanged(
    CalendarViewModeChanged event,
    Emitter<CalendarState> emit,
  ) {
    if (state is! CalendarLoaded) return;
    final current = state as CalendarLoaded;
    emit(current.copyWith(viewMode: event.mode));
  }

  Future<void> _onLoadJournals(
    CalendarLoadJournals event,
    Emitter<CalendarState> emit,
  ) async {
    if (state is! CalendarLoaded) return;
    final current = state as CalendarLoaded;

    emit(current.copyWith(isLoading: true));

    // Phase 1: 使用空数据占位，待 Repository 集成后替换
    // 实际将从 JournalRepository.loadByMonth(event.month) 获取
    await Future.delayed(const Duration(milliseconds: 300));

    emit(current.copyWith(
      isLoading: false,
      journalsByDate: current.journalsByDate,
    ));
  }
}