import 'package:flutter/foundation.dart';

import '../data/remote/question_source_remote_store.dart';
import '../models/question_source_preference.dart';

/// Question source mix persisted via `/v1/me/question-sources`.
class QuestionSourceConfigRepository {
  QuestionSourceConfigRepository._();

  static final QuestionSourceConfigRepository instance =
      QuestionSourceConfigRepository._();

  static const List<QuestionSourcePreference> defaultPreferences =
      <QuestionSourcePreference>[
    QuestionSourcePreference(
      id: 'market_history',
      label: 'Market question',
      description: 'Prospective price-move guessing game',
      ratio: 50,
    ),
    QuestionSourcePreference(
      id: 'spelling',
      label: 'Spelling',
      description: 'Spell-check quiz from curated word lists',
      ratio: 50,
    ),
  ];

  final QuestionSourceRemoteStore _remote = QuestionSourceRemoteStore();

  final ValueNotifier<List<QuestionSourcePreference>> preferences =
      ValueNotifier<List<QuestionSourcePreference>>(
    List<QuestionSourcePreference>.from(defaultPreferences),
  );

  String? _activeUid;

  List<QuestionSourcePreference> get current =>
      mergeWithDefaults(preferences.value);

  Future<void> startSession(String firebaseUid) async {
    if (_activeUid == firebaseUid) {
      return;
    }
    _activeUid = firebaseUid;
    await loadFromRemote();
  }

  Future<void> endSession() async {
    _activeUid = null;
    resetToDefaults();
  }

  Future<void> loadFromRemote() async {
    try {
      final List<QuestionSourcePreference>? remote =
          await _remote.fetchPreferences();
      if (remote != null) {
        replaceAll(remote);
      }
    } catch (_) {
      replaceAll(defaultPreferences);
    }
  }

  Future<void> saveAll(List<QuestionSourcePreference> next) async {
    final List<QuestionSourcePreference> normalized = mergeWithDefaults(next);
    if (_activeUid == null) {
      replaceAll(normalized);
      return;
    }

    final List<QuestionSourcePreference> saved =
        await _remote.savePreferences(normalized);
    replaceAll(saved);
  }

  void replaceAll(List<QuestionSourcePreference> next) {
    preferences.value = mergeWithDefaults(next);
  }

  /// Keeps saved toggles/weights while picking up new default sources and labels.
  static List<QuestionSourcePreference> mergeWithDefaults(
    List<QuestionSourcePreference> saved,
  ) {
    final Map<String, QuestionSourcePreference> byId =
        <String, QuestionSourcePreference>{
      for (final QuestionSourcePreference source in saved) source.id: source,
    };

    return defaultPreferences
        .map((QuestionSourcePreference defaults) {
          final QuestionSourcePreference? existing = byId[defaults.id];
          if (existing == null) {
            return defaults;
          }
          return existing.copyWith(
            label: defaults.label,
            description: defaults.description,
            comingSoon: defaults.comingSoon,
            enabled: defaults.comingSoon ? false : existing.enabled,
          );
        })
        .toList(growable: false);
  }

  void resetToDefaults() {
    replaceAll(defaultPreferences);
  }

  /// True when spelling is the only enabled, non–coming-soon source.
  static bool isSpellingOnlyEnabled(List<QuestionSourcePreference> sources) {
    final Iterable<QuestionSourcePreference> enabled = sources.where(
      (QuestionSourcePreference s) => s.enabled && !s.comingSoon,
    );
    return enabled.length == 1 && enabled.first.id == 'spelling';
  }

  /// True when market history is the only enabled, non–coming-soon source.
  static bool isMarketOnlyEnabled(List<QuestionSourcePreference> sources) {
    final Iterable<QuestionSourcePreference> enabled = sources.where(
      (QuestionSourcePreference s) => s.enabled && !s.comingSoon,
    );
    return enabled.length == 1 && enabled.first.id == 'market_history';
  }

  static bool isMarketHistoryEnabled(List<QuestionSourcePreference> sources) {
    for (final QuestionSourcePreference source in sources) {
      if (source.id == 'market_history') {
        return source.enabled && !source.comingSoon;
      }
    }
    return false;
  }

  static bool isSpellingEnabled(List<QuestionSourcePreference> sources) {
    for (final QuestionSourcePreference source in sources) {
      if (source.id == 'spelling') {
        return source.enabled && !source.comingSoon;
      }
    }
    return false;
  }

  /// True when spelling is enabled and its effective mix is 100%.
  static bool isSpellingFullyWeighted(List<QuestionSourcePreference> sources) {
    if (!isSpellingEnabled(sources)) {
      return false;
    }
    return (effectiveMix(sources)['spelling'] ?? 0) >= 100;
  }

  /// Effective share (0–100) for each enabled source; empty when none enabled.
  static Map<String, int> effectiveMix(
    List<QuestionSourcePreference> sources,
  ) {
    final Iterable<QuestionSourcePreference> enabled =
        sources.where((QuestionSourcePreference s) => s.enabled);
    final int totalWeight =
        enabled.fold<int>(0, (int sum, QuestionSourcePreference s) => sum + s.ratio);
    if (totalWeight <= 0) {
      return <String, int>{};
    }

    return <String, int>{
      for (final QuestionSourcePreference source in enabled)
        source.id: ((source.ratio / totalWeight) * 100).round(),
    };
  }
}