import 'package:flutter_riverpod/flutter_riverpod.dart';

import '../services/notification_service.dart';

/// 未读消息数（我的页角标）：登录后加载，标记已读后同步
final unreadCountProvider =
    StateNotifierProvider<UnreadCountNotifier, int>((_) => UnreadCountNotifier());

class UnreadCountNotifier extends StateNotifier<int> {
  UnreadCountNotifier() : super(0);

  Future<void> refresh() async {
    try {
      state = await NotificationService.fetchUnreadCount();
    } catch (_) {
      // 未登录/网络异常：保持原值
    }
  }

  /// 本地 decrement（标记单条已读后角标即时 -1，后台再 refresh 校准）
  void decrement([int count = 1]) {
    state = state > count ? state - count : 0;
  }

  void clear() => state = 0;
}

/// 通知列表状态：type 筛选 + 触底分页
class NotificationsState {
  const NotificationsState({
    this.items = const [],
    this.total = 0,
    this.type,
    this.isLoading = false,
    this.loadFailed = false,
    this.loadingMore = false,
    this.markingAll = false,
  });

  final List<NotificationItem> items;
  final int total;

  /// null = 全部
  final int? type;
  final bool isLoading;
  final bool loadFailed;
  final bool loadingMore;
  final bool markingAll;

  bool get hasMore => items.length < total;
  int get unreadCount => items.where((e) => !e.isRead).length;

  NotificationsState copyWith({
    List<NotificationItem>? items,
    int? total,
    int? Function()? type,
    bool? isLoading,
    bool? loadFailed,
    bool? loadingMore,
    bool? markingAll,
  }) =>
      NotificationsState(
        items: items ?? this.items,
        total: total ?? this.total,
        type: type != null ? type() : this.type,
        isLoading: isLoading ?? this.isLoading,
        loadFailed: loadFailed ?? this.loadFailed,
        loadingMore: loadingMore ?? this.loadingMore,
        markingAll: markingAll ?? this.markingAll,
      );
}

class NotificationsNotifier extends StateNotifier<NotificationsState> {
  NotificationsNotifier(this._ref) : super(const NotificationsState()) {
    load();
  }

  final Ref _ref;
  static const _pageSize = 20;

  Future<void> load() async {
    state = state.copyWith(isLoading: true, loadFailed: false);
    try {
      final page = await NotificationService.fetchNotifications(
        page: 1,
        pageSize: _pageSize,
        type: state.type,
      );
      state = state.copyWith(
        items: page.items,
        total: page.total,
        isLoading: false,
      );
    } catch (_) {
      state = state.copyWith(isLoading: false, loadFailed: true);
    }
  }

  /// 切换类型筛选并重载
  Future<void> setType(int? type) async {
    if (type == state.type) return;
    state = state.copyWith(type: () => type);
    await load();
  }

  /// 触底加载下一页
  Future<void> loadMore() async {
    if (state.loadingMore || !state.hasMore || state.isLoading) return;
    state = state.copyWith(loadingMore: true);
    try {
      final page = await NotificationService.fetchNotifications(
        page: state.items.length ~/ _pageSize + 1,
        pageSize: _pageSize,
        type: state.type,
      );
      state = state.copyWith(
        items: [...state.items, ...page.items],
        total: page.total,
        loadingMore: false,
      );
    } catch (_) {
      state = state.copyWith(loadingMore: false);
    }
  }

  /// 单条已读：乐观更新本地，失败静默（下次进入重拉）
  Future<void> markOneRead(NotificationItem item) async {
    if (item.isRead) return;
    state = state.copyWith(
      items: [
        for (final e in state.items)
          if (e.id == item.id) e.copyWith(isRead: true) else e,
      ],
    );
    _ref.read(unreadCountProvider.notifier).decrement();
    try {
      await NotificationService.markRead(ids: [item.id]);
    } catch (_) {
      // 静默：以服务端为准，下次进入页面会重拉
    }
  }

  /// 全部已读
  Future<void> markAllRead() async {
    if (state.markingAll) return;
    state = state.copyWith(markingAll: true);
    try {
      await NotificationService.markRead(all: true);
      if (!mounted) return;
      state = state.copyWith(
        items: [for (final e in state.items) e.copyWith(isRead: true)],
        markingAll: false,
      );
      _ref.read(unreadCountProvider.notifier).clear();
    } catch (_) {
      if (mounted) state = state.copyWith(markingAll: false);
      rethrow;
    }
  }
}

final notificationsProvider =
    StateNotifierProvider.autoDispose<NotificationsNotifier, NotificationsState>(
  (ref) => NotificationsNotifier(ref),
);