nj/app/lib/features/class_/bloc/class_bloc.dart

// 班级 BLoC — 管理班级状态、成员、日记墙、主题布置和评语

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

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

sealed class ClassEvent {
  const ClassEvent();
}

/// 加载我的班级列表
final class ClassLoadMyClasses extends ClassEvent {
  const ClassLoadMyClasses();
}

/// 选择当前班级
final class ClassSelected extends ClassEvent {
  final String classId;
  const ClassSelected(this.classId);
}

/// 加载班级成员列表
final class ClassLoadMembers extends ClassEvent {
  final String classId;
  const ClassLoadMembers(this.classId);
}

/// 加载班级日记墙（已分享到班级的日记）
final class ClassLoadDiaryWall extends ClassEvent {
  final String classId;
  const ClassLoadDiaryWall(this.classId);
}

/// 加载主题布置列表
final class ClassLoadTopics extends ClassEvent {
  final String classId;
  const ClassLoadTopics(this.classId);
}

/// 创建班级（老师）
final class ClassCreate extends ClassEvent {
  final String name;
  final String? schoolName;
  const ClassCreate({required this.name, this.schoolName});
}

/// 布置主题（老师）
final class TopicAssign extends ClassEvent {
  final String classId;
  final String title;
  final String? description;
  final DateTime? dueDate;
  const TopicAssign({
    required this.classId,
    required this.title,
    this.description,
    this.dueDate,
  });
}

/// 加载日记评语
final class ClassLoadComments extends ClassEvent {
  final String journalId;
  const ClassLoadComments(this.journalId);
}

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

/// 班级成员模型
class ClassMember {
  final String userId;
  final String role;
  final String? nickname;
  final DateTime joinedAt;

  const ClassMember({
    required this.userId,
    required this.role,
    this.nickname,
    required this.joinedAt,
  });
}

/// 主题布置模型
class TopicAssignment {
  final String id;
  final String classId;
  final String teacherId;
  final String title;
  final String? description;
  final DateTime? dueDate;
  final bool isActive;

  const TopicAssignment({
    required this.id,
    required this.classId,
    required this.teacherId,
    required this.title,
    this.description,
    this.dueDate,
    this.isActive = true,
  });
}

/// 评语模型
class Comment {
  final String id;
  final String journalId;
  final String authorId;
  final String content;
  final DateTime createdAt;

  const Comment({
    required this.id,
    required this.journalId,
    required this.authorId,
    required this.content,
    required this.createdAt,
  });
}

/// 班级状态
sealed class ClassState {
  const ClassState();
}

/// 初始状态
final class ClassInitial extends ClassState {
  const ClassInitial();
}

/// 加载中
final class ClassLoading extends ClassState {
  const ClassLoading();
}

/// 班级列表已加载
final class ClassListLoaded extends ClassState {
  final List<SchoolClass> classes;
  final bool isLoading;

  const ClassListLoaded({
    this.classes = const [],
    this.isLoading = false,
  });

  ClassListLoaded copyWith({
    List<SchoolClass>? classes,
    bool? isLoading,
  }) =>
      ClassListLoaded(
        classes: classes ?? this.classes,
        isLoading: isLoading ?? this.isLoading,
      );
}

/// 班级详情已加载（日记墙 / 成员 / 主题 / 评语）
final class ClassDetailLoaded extends ClassState {
  final SchoolClass classInfo;
  final List<ClassMember> members;
  final List<JournalEntry> diaryWall;
  final List<TopicAssignment> topics;
  final List<Comment> comments;
  final bool isLoadingWall;
  final bool isLoadingMembers;
  final String? selectedJournalId;

  const ClassDetailLoaded({
    required this.classInfo,
    this.members = const [],
    this.diaryWall = const [],
    this.topics = const [],
    this.comments = const [],
    this.isLoadingWall = false,
    this.isLoadingMembers = false,
    this.selectedJournalId,
  });

  ClassDetailLoaded copyWith({
    SchoolClass? classInfo,
    List<ClassMember>? members,
    List<JournalEntry>? diaryWall,
    List<TopicAssignment>? topics,
    List<Comment>? comments,
    bool? isLoadingWall,
    bool? isLoadingMembers,
    String? selectedJournalId,
    bool clearSelectedJournal = false,
  }) =>
      ClassDetailLoaded(
        classInfo: classInfo ?? this.classInfo,
        members: members ?? this.members,
        diaryWall: diaryWall ?? this.diaryWall,
        topics: topics ?? this.topics,
        comments: comments ?? this.comments,
        isLoadingWall: isLoadingWall ?? this.isLoadingWall,
        isLoadingMembers: isLoadingMembers ?? this.isLoadingMembers,
        selectedJournalId: clearSelectedJournal
            ? null
            : (selectedJournalId ?? this.selectedJournalId),
      );
}

/// 错误状态
final class ClassError extends ClassState {
  final String message;
  const ClassError(this.message);
}

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

class ClassBloc extends Bloc<ClassEvent, ClassState> {
  ClassBloc() : super(const ClassInitial()) {
    on<ClassLoadMyClasses>(_onLoadMyClasses);
    on<ClassSelected>(_onClassSelected);
    on<ClassLoadMembers>(_onLoadMembers);
    on<ClassLoadDiaryWall>(_onLoadDiaryWall);
    on<ClassLoadTopics>(_onLoadTopics);
    on<ClassCreate>(_onCreateClass);
    on<TopicAssign>(_onTopicAssign);
    on<ClassLoadComments>(_onLoadComments);
  }

  Future<void> _onLoadMyClasses(
    ClassLoadMyClasses event,
    Emitter<ClassState> emit,
  ) async {
    emit(const ClassListLoaded(isLoading: true));

    // Phase 1: 占位数据，待 API 集成
    await Future.delayed(const Duration(milliseconds: 300));
    final now = DateTime.now();

    emit(ClassListLoaded(classes: [
      SchoolClass(
        id: 'class-1',
        name: '三年二班',
        schoolName: '阳光小学',
        teacherId: 'teacher-1',
        classCode: 'a1b2c3',
        memberCount: 28,
        createdAt: now,
        updatedAt: now,
      ),
    ]));
  }

  Future<void> _onClassSelected(
    ClassSelected event,
    Emitter<ClassState> emit,
  ) async {
    final now = DateTime.now();
    final classInfo = SchoolClass(
      id: event.classId,
      name: '三年二班',
      schoolName: '阳光小学',
      teacherId: 'teacher-1',
      classCode: 'a1b2c3',
      memberCount: 28,
      createdAt: now,
      updatedAt: now,
    );

    emit(ClassDetailLoaded(classInfo: classInfo));

    add(ClassLoadDiaryWall(event.classId));
    add(ClassLoadMembers(event.classId));
    add(ClassLoadTopics(event.classId));
  }

  Future<void> _onLoadMembers(
    ClassLoadMembers event,
    Emitter<ClassState> emit,
  ) async {
    if (state is! ClassDetailLoaded) return;
    final current = state as ClassDetailLoaded;
    emit(current.copyWith(isLoadingMembers: true));

    await Future.delayed(const Duration(milliseconds: 200));
    final now = DateTime.now();

    final members = List.generate(
      28,
      (i) => ClassMember(
        userId: 'user-$i',
        role: i == 0 ? 'teacher' : 'student',
        nickname: i == 0 ? '王老师' : '同学$i',
        joinedAt: now,
      ),
    );

    emit(current.copyWith(members: members, isLoadingMembers: false));
  }

  Future<void> _onLoadDiaryWall(
    ClassLoadDiaryWall event,
    Emitter<ClassState> emit,
  ) async {
    if (state is! ClassDetailLoaded) return;
    final current = state as ClassDetailLoaded;
    emit(current.copyWith(isLoadingWall: true));

    await Future.delayed(const Duration(milliseconds: 200));
    final now = DateTime.now();
    final titles = ['快乐的周末', '春天来了', '我的小猫', '数学课', '好朋友', '下雨天'];

    final diaries = List.generate(
      6,
      (i) => JournalEntry(
        id: 'diary-$i',
        authorId: 'user-${i + 1}',
        classId: event.classId,
        title: titles[i],
        date: now.subtract(Duration(days: i)),
        mood: Mood.values[i % Mood.values.length],
        tags: const ['日常', '心情'],
        createdAt: now,
        updatedAt: now,
      ),
    );

    emit(current.copyWith(diaryWall: diaries, isLoadingWall: false));
  }

  Future<void> _onLoadTopics(
    ClassLoadTopics event,
    Emitter<ClassState> emit,
  ) async {
    if (state is! ClassDetailLoaded) return;
    final current = state as ClassDetailLoaded;

    final topics = [
      TopicAssignment(
        id: 'topic-1',
        classId: event.classId,
        teacherId: 'teacher-1',
        title: '我的周末',
        description: '写一篇关于你周末生活的日记',
        dueDate: DateTime.now().add(const Duration(days: 3)),
      ),
      TopicAssignment(
        id: 'topic-2',
        classId: event.classId,
        teacherId: 'teacher-1',
        title: '最开心的一天',
        description: '回忆一下让你最开心的一天',
      ),
    ];

    emit(current.copyWith(topics: topics));
  }

  Future<void> _onCreateClass(
    ClassCreate event,
    Emitter<ClassState> emit,
  ) async {
    final newClass = SchoolClass.create(
      name: event.name,
      schoolName: event.schoolName ?? '',
      teacherId: 'current-user',
      classCode: 'x1y2z3',
    );

    if (state is ClassListLoaded) {
      final current = state as ClassListLoaded;
      emit(current.copyWith(classes: [...current.classes, newClass]));
    }
  }

  Future<void> _onTopicAssign(
    TopicAssign event,
    Emitter<ClassState> emit,
  ) async {
    if (state is! ClassDetailLoaded) return;
    final current = state as ClassDetailLoaded;
    final newTopic = TopicAssignment(
      id: 'topic-${DateTime.now().millisecondsSinceEpoch}',
      classId: event.classId,
      teacherId: 'current-user',
      title: event.title,
      description: event.description,
      dueDate: event.dueDate,
    );
    emit(current.copyWith(topics: [newTopic, ...current.topics]));
  }

  Future<void> _onLoadComments(
    ClassLoadComments event,
    Emitter<ClassState> emit,
  ) async {
    if (state is! ClassDetailLoaded) return;
    final current = state as ClassDetailLoaded;

    final comments = [
      Comment(
        id: 'comment-1',
        journalId: event.journalId,
        authorId: 'teacher-1',
        content: '写得很好，继续保持！',
        createdAt: DateTime.now(),
      ),
    ];
    emit(current.copyWith(
      comments: comments,
      selectedJournalId: event.journalId,
    ));
  }
}