// Author: fruit.com.cn

import 'package:flutter/foundation.dart';

import '../../core/data/models/drama.dart';
import '../../core/data/models/home_feed.dart';

/// Ranking boards backed by the feed sections the server already returns.
enum RankingBoard { hot, newReleases }

/// One ranked title; rank is one-based and mirrors server section order.
class RankingEntry {
  const RankingEntry({required this.rank, required this.drama});

  final int rank;
  final Drama drama;
}

/// Keeps the active board and turns real feed sections into ranked entries.
///
/// The backend does not expose a dedicated ranking endpoint, so this class
/// never invents scores: it preserves the order of the `hot` and `new`
/// sections and only falls back to the catalog when a section is absent.
class RankingLogic extends ChangeNotifier {
  RankingLogic({required this.sections, required this.fallback});

  static const hotSectionCode = 'hot';
  static const newSectionCode = 'new';

  List<FeedSection> sections;
  List<Drama> fallback;
  RankingBoard _board = RankingBoard.hot;

  RankingBoard get board => _board;

  List<RankingEntry> get entries {
    final sectionCode = _board == RankingBoard.hot
        ? hotSectionCode
        : newSectionCode;
    final source = _sectionDramas(sectionCode);
    final dramas = source.isEmpty ? fallback : source;
    final seen = <String>{};
    final unique = [
      for (final drama in dramas)
        if (seen.add(drama.id)) drama,
    ];
    return [
      for (var index = 0; index < unique.length; index++)
        RankingEntry(rank: index + 1, drama: unique[index]),
    ];
  }

  /// Switches boards and notifies only when the visible source changes.
  void select(RankingBoard next) {
    if (_board == next) return;
    _board = next;
    notifyListeners();
  }

  /// Applies refreshed feed data without rebuilding the page state.
  void updateSources({
    required List<FeedSection> sections,
    required List<Drama> fallback,
  }) {
    this.sections = sections;
    this.fallback = fallback;
    notifyListeners();
  }

  List<Drama> _sectionDramas(String code) {
    for (final section in sections) {
      if (section.code == code) return section.dramas;
    }
    return const [];
  }
}