import 'package:flutter_riverpod/flutter_riverpod.dart';

import '../data/models/briefing_feed.dart';
import '../data/models/news_item.dart';
import 'api_client_provider.dart';

// ─── NewsState ────────────────────────────────────────────────────────────────

class NewsState {
  final List<NewsItem> items;
  final int offset;
  final bool hasMore;
  final bool loadingMore;
  final int? selectedFeedId;
  final Map<int, String?> reactions;

  const NewsState({
    required this.items,
    required this.offset,
    required this.hasMore,
    required this.loadingMore,
    required this.selectedFeedId,
    required this.reactions,
  });

  NewsState copyWith({
    List<NewsItem>? items,
    int? offset,
    bool? hasMore,
    bool? loadingMore,
    Object? selectedFeedId = _sentinel,
    Map<int, String?>? reactions,
  }) {
    return NewsState(
      items: items ?? this.items,
      offset: offset ?? this.offset,
      hasMore: hasMore ?? this.hasMore,
      loadingMore: loadingMore ?? this.loadingMore,
      selectedFeedId: selectedFeedId == _sentinel
          ? this.selectedFeedId
          : selectedFeedId as int?,
      reactions: reactions ?? this.reactions,
    );
  }
}

const _sentinel = Object();

// ─── NewsNotifier ─────────────────────────────────────────────────────────────

final newsProvider =
    AsyncNotifierProvider<NewsNotifier, NewsState>(NewsNotifier.new);

class NewsNotifier extends AsyncNotifier<NewsState> {
  static const _limit = 40;

  @override
  Future<NewsState> build() async {
    final items = await ref.watch(newsApiProvider).getNewsItems(
          days: 90,
          limit: _limit,
          offset: 0,
        );
    return NewsState(
      items: items,
      offset: items.length,
      hasMore: items.length == _limit,
      loadingMore: false,
      selectedFeedId: null,
      reactions: {for (final item in items) item.id: item.reaction},
    );
  }

  /// Re-fetch the first page without clearing state (no flicker).
  Future<void> refresh() async {
    final current = state.value;
    final items = await ref.read(newsApiProvider).getNewsItems(
          days: 90,
          limit: _limit,
          offset: 0,
          feedId: current?.selectedFeedId,
        );
    state = AsyncData(NewsState(
      items: items,
      offset: items.length,
      hasMore: items.length == _limit,
      loadingMore: false,
      selectedFeedId: current?.selectedFeedId,
      reactions: {for (final item in items) item.id: item.reaction},
    ));
  }

  Future<void> loadMore() async {
    final current = state.value;
    if (current == null || current.loadingMore || !current.hasMore) return;
    state = AsyncData(current.copyWith(loadingMore: true));
    try {
      final items = await ref.read(newsApiProvider).getNewsItems(
            days: 90,
            limit: _limit,
            offset: current.offset,
            feedId: current.selectedFeedId,
          );
      final updatedReactions = Map<int, String?>.from(current.reactions);
      for (final item in items) {
        updatedReactions.putIfAbsent(item.id, () => item.reaction);
      }
      state = AsyncData(current.copyWith(
        items: [...current.items, ...items],
        offset: current.offset + items.length,
        hasMore: items.length == _limit,
        loadingMore: false,
        reactions: updatedReactions,
      ));
    } catch (e) {
      final recovered = state.value ?? current;
      state = AsyncData(recovered.copyWith(loadingMore: false));
      rethrow;
    }
  }

  Future<void> setFeed(int? feedId) async {
    state = const AsyncLoading();
    try {
      final items = await ref.read(newsApiProvider).getNewsItems(
            days: 90,
            limit: _limit,
            offset: 0,
            feedId: feedId,
          );
      state = AsyncData(NewsState(
        items: items,
        offset: items.length,
        hasMore: items.length == _limit,
        loadingMore: false,
        selectedFeedId: feedId,
        reactions: {for (final item in items) item.id: item.reaction},
      ));
    } catch (e, st) {
      state = AsyncError(e, st);
    }
  }

  void toggleReaction(int itemId, String reaction) {
    final current = state.value;
    if (current == null) return;
    final prev = current.reactions[itemId];
    final next = prev == reaction ? null : reaction;
    state = AsyncData(current.copyWith(
      reactions: {...current.reactions, itemId: next},
    ));
    final briefingApi = ref.read(briefingApiProvider);
    final future = next == null
        ? briefingApi.deleteRssReaction(itemId)
        : briefingApi.postRssReaction(itemId, next);
    future.catchError((_) {
      final s = state.value;
      if (s != null) {
        state = AsyncData(s.copyWith(
          reactions: {...s.reactions, itemId: prev},
        ));
      }
    });
  }
}

// ─── FeedsNotifier ────────────────────────────────────────────────────────────

final feedsProvider =
    AsyncNotifierProvider<FeedsNotifier, List<BriefingFeed>>(FeedsNotifier.new);

class FeedsNotifier extends AsyncNotifier<List<BriefingFeed>> {
  @override
  Future<List<BriefingFeed>> build() async {
    return ref.watch(newsApiProvider).getFeeds();
  }
}