import 'package:flutter_riverpod/flutter_riverpod.dart';

import '../models/comment_item.dart';
import '../services/comment_service.dart';
import 'auth_provider.dart';

/// 回复目标（null 表示直接评论视频）
class ReplyTarget {
  const ReplyTarget({
    required this.parentId,
    required this.replyToUserId,
    required this.nickname,
  });

  /// 一级评论 ID（楼中楼统一挂一级楼下）
  final int parentId;

  /// 被回复人 ID（回复一级评论时等于其作者）
  final int replyToUserId;

  /// 被回复人昵称（输入框提示用）
  final String nickname;
}

/// 评论区状态
class CommentState {
  const CommentState({
    this.items = const [],
    this.total = 0,
    this.isLoading = false,
    this.isLoadingMore = false,
    this.loadFailed = false,
    this.page = 1,
    this.replies = const {},
    this.repliesLoading = const {},
    this.replyTarget,
    this.posting = false,
  });

  /// 一级评论列表
  final List<CommentItem> items;
  final int total;
  final bool isLoading;
  final bool isLoadingMore;

  /// 首屏加载失败
  final bool loadFailed;
  final int page;

  /// 已展开的一级评论的二级回复列表
  final Map<int, List<CommentItem>> replies;

  /// 回复加载中的一级评论 ID
  final Set<int> repliesLoading;

  /// 当前回复目标（null = 评论视频本身）
  final ReplyTarget? replyTarget;

  /// 发表中（防重复提交）
  final bool posting;

  static const int pageSize = 20;

  bool get hasMore => items.length < total;

  CommentState copyWith({
    List<CommentItem>? items,
    int? total,
    bool? isLoading,
    bool? isLoadingMore,
    bool? loadFailed,
    int? page,
    Map<int, List<CommentItem>>? replies,
    Set<int>? repliesLoading,
    ReplyTarget? Function()? replyTarget,
    bool? posting,
  }) =>
      CommentState(
        items: items ?? this.items,
        total: total ?? this.total,
        isLoading: isLoading ?? this.isLoading,
        isLoadingMore: isLoadingMore ?? this.isLoadingMore,
        loadFailed: loadFailed ?? this.loadFailed,
        page: page ?? this.page,
        replies: replies ?? this.replies,
        repliesLoading: repliesLoading ?? this.repliesLoading,
        replyTarget: replyTarget != null ? replyTarget() : this.replyTarget,
        posting: posting ?? this.posting,
      );
}

/// 评论区 Notifier（按 videoId 家族隔离）
class CommentNotifier extends StateNotifier<CommentState> {
  CommentNotifier(this._ref, this.videoId) : super(const CommentState()) {
    load();
  }

  final Ref _ref;
  final int videoId;

  /// 首屏加载
  Future<void> load() async {
    state = state.copyWith(isLoading: true, loadFailed: false);
    try {
      final page = await CommentService.list(videoId);
      state = state.copyWith(
        items: page.items,
        total: page.total,
        isLoading: false,
        page: 1,
      );
    } catch (_) {
      state = state.copyWith(isLoading: false, loadFailed: true);
    }
  }

  /// 触底加载更多一级评论
  Future<void> loadMore() async {
    if (!state.hasMore || state.isLoadingMore || state.isLoading) return;
    state = state.copyWith(isLoadingMore: true);
    try {
      final page = await CommentService.list(videoId, page: state.page + 1);
      state = state.copyWith(
        items: [...state.items, ...page.items],
        total: page.total,
        isLoadingMore: false,
        page: state.page + 1,
      );
    } catch (_) {
      state = state.copyWith(isLoadingMore: false);
    }
  }

  /// 展开/收起二级回复；首次展开时加载（一次拉 50 条，超出部分显示总数）
  Future<void> toggleReplies(CommentItem comment) async {
    final replies = Map<int, List<CommentItem>>.from(state.replies);
    if (replies.containsKey(comment.commentId)) {
      replies.remove(comment.commentId);
      state = state.copyWith(replies: replies);
      return;
    }
    state = state.copyWith(
      repliesLoading: {...state.repliesLoading, comment.commentId},
    );
    try {
      final page = await CommentService.list(
        videoId,
        parentId: comment.commentId,
        pageSize: 50,
      );
      state = state.copyWith(
        replies: {...state.replies, comment.commentId: page.items},
        repliesLoading: {...state.repliesLoading}..remove(comment.commentId),
      );
    } catch (_) {
      state = state.copyWith(
        repliesLoading: {...state.repliesLoading}..remove(comment.commentId),
      );
    }
  }

  /// 设置/清除回复目标
  void setReplyTarget(ReplyTarget? target) =>
      state = state.copyWith(replyTarget: () => target);

  /// 发表评论/回复。成功返回结果（含奖励进度），失败抛异常由 UI 提示
  Future<CommentCreateResult> post(String content) async {
    final user = _ref.read(authProvider).user;
    final target = state.replyTarget;
    state = state.copyWith(posting: true);
    try {
      final result = await CommentService.create(
        videoId,
        content,
        parentId: target?.parentId,
        replyToUserId: target?.replyToUserId,
      );
      final item = CommentItem(
        commentId: result.commentId,
        userId: user?.userId ?? 0,
        nickname: user?.nickname ?? '我',
        avatarUrl: user?.avatarUrl ?? '',
        content: content,
        createdAt: '刚刚',
      );
      if (target == null) {
        // 一级评论：插入顶部
        state = state.copyWith(
          items: [item, ...state.items],
          total: state.total + 1,
          posting: false,
        );
      } else {
        // 回复：插入已展开列表，父评论 replyCount+1
        final replies = Map<int, List<CommentItem>>.from(state.replies);
        if (replies.containsKey(target.parentId)) {
          replies[target.parentId] = [item, ...replies[target.parentId]!];
        }
        state = state.copyWith(
          replies: replies,
          items: [
            for (final c in state.items)
              c.commentId == target.parentId
                  ? c.copyWith(replyCount: c.replyCount + 1)
                  : c,
          ],
          total: state.total + 1,
          posting: false,
          replyTarget: () => null,
        );
      }
      return result;
    } catch (_) {
      state = state.copyWith(posting: false);
      rethrow;
    }
  }

  /// 删除评论：parentId=0 为一级评论，否则为某一级楼下的回复
  Future<void> remove(CommentItem comment, {int parentId = 0}) async {
    await CommentService.delete(comment.commentId);
    if (parentId == 0) {
      final replies = Map<int, List<CommentItem>>.from(state.replies)
        ..remove(comment.commentId);
      state = state.copyWith(
        items: state.items.where((c) => c.commentId != comment.commentId).toList(),
        total: (state.total - 1).clamp(0, 1 << 31),
        replies: replies,
      );
    } else {
      final replies = Map<int, List<CommentItem>>.from(state.replies);
      replies[parentId] = (replies[parentId] ?? [])
          .where((c) => c.commentId != comment.commentId)
          .toList();
      state = state.copyWith(
        replies: replies,
        items: [
          for (final c in state.items)
            c.commentId == parentId
                ? c.copyWith(replyCount: (c.replyCount - 1).clamp(0, 1 << 31))
                : c,
        ],
        total: (state.total - 1).clamp(0, 1 << 31),
      );
    }
  }
}

/// 评论区 Provider（按视频 ID 家族）
final commentProvider =
    StateNotifierProvider.family<CommentNotifier, CommentState, int>(
  (ref, videoId) => CommentNotifier(ref, videoId),
);