import 'dart:async';
import 'dart:math';
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:shared_preferences/shared_preferences.dart';
import '../models/vocabulary_item.dart';
import '../models/srs_item.dart';
import 'package:hirameki_srs/src/services/vocab_deck_repository.dart';
import '../services/distractor_generator.dart';
import '../widgets/kanji_card.dart';
import '../widgets/options_grid.dart';
import 'package:audioplayers/audioplayers.dart';
import 'settings_screen.dart';

class _QuizState {
  VocabularyItem? current;
  List<String> options = [];
  List<String> correctAnswers = [];
  int score = 0;
  int asked = 0;
  Key key = UniqueKey();
  String? selectedOption;
  bool showResult = false;
  Set<int> wrongItems = {};
}

class VocabScreen extends StatefulWidget {
  const VocabScreen({super.key});

  @override
  State<VocabScreen> createState() => _VocabScreenState();
}

class _VocabScreenState extends State<VocabScreen>
    with SingleTickerProviderStateMixin {
  late TabController _tabController;
  List<VocabularyItem> _deck = [];
  bool _loading = false;
  bool _isAnswering = false;
  String _status = 'Loading deck...';
  final DistractorGenerator _dg = DistractorGenerator();
  final Random _random = Random();
  final _audioPlayer = AudioPlayer();

  final _quizStates = [_QuizState(), _QuizState(), _QuizState()];
  _QuizState get _currentQuizState => _quizStates[_tabController.index];
  final _sessionDecks = <int, List<VocabularyItem>>{};
  final _sessionDeckSizes = <int, int>{};

  bool _playIncorrectSound = true;
  bool _playCorrectSound = true;
  bool _playNarrator = true;
  bool _apiKeyMissing = false;

  @override
  void initState() {
    super.initState();
    _tabController = TabController(length: 3, vsync: this);
    _tabController.addListener(() {
      if (_tabController.index == 2 && !_tabController.indexIsChanging) {
        _playCurrentAudio();
      }
      setState(() {});
    });
    _loadSettings();
    _loadDeck();
  }

  @override
  void dispose() {
    _tabController.dispose();
    super.dispose();
  }

  Future<void> _loadSettings() async {
    final prefs = await SharedPreferences.getInstance();
    setState(() {
      _playIncorrectSound = prefs.getBool('playIncorrectSound') ?? true;
      _playCorrectSound = prefs.getBool('playCorrectSound') ?? true;
      _playNarrator = prefs.getBool('playNarrator') ?? true;
    });
  }

  Future<void> _loadDeck() async {
    setState(() {
      _loading = true;
      _status = 'Loading deck...';
    });

    try {
      final repo = Provider.of<VocabDeckRepository>(context, listen: false);
      await repo.loadApiKey();
      final apiKey = repo.apiKey;

      if (apiKey == null || apiKey.isEmpty) {
        setState(() {
          _apiKeyMissing = true;
          _loading = false;
        });
        return;
      }

      var items = await repo.loadVocabulary();
      if (items.isEmpty ||
          items.every((item) => item.pronunciationAudios.isEmpty)) {
        setState(() {
          _status = 'Fetching deck...';
        });
        items = await repo.fetchAndCacheVocabularyFromWk(apiKey);
      }

      setState(() {
        _deck = items;
        _status = 'Loaded ${items.length} vocabulary';
        _loading = false;
        _apiKeyMissing = false;
      });

      final disabledLevels = <int>{};
      final itemsByLevel = <int, List<VocabularyItem>>{};
      for (final item in _deck) {
        (itemsByLevel[item.level] ??= []).add(item);
      }

      itemsByLevel.forEach((level, items) {
        final allSrsItems = items
            .expand((item) => item.srsItems.values)
            .toList();
        if (allSrsItems.isNotEmpty &&
            allSrsItems.every((srs) => srs.disabled)) {
          disabledLevels.add(level);
        }
      });

      for (var i = 0; i < _tabController.length; i++) {
        final mode = _modeForIndex(i);
        var filteredDeck = _deck.where((item) {
          if (disabledLevels.contains(item.level)) {
            return false;
          }
          final srsItem = item.srsItems[mode.toString()];
          return srsItem == null || !srsItem.disabled;
        }).toList();

        if (mode == QuizMode.audioToEnglish) {
          filteredDeck = filteredDeck
              .where((item) => item.pronunciationAudios.isNotEmpty)
              .toList();
        }

        filteredDeck.shuffle(_random);
        _sessionDecks[i] = filteredDeck;
        _sessionDeckSizes[i] = filteredDeck.length;
      }

      for (var i = 0; i < _tabController.length; i++) {
        _nextQuestion(i);
      }
    } catch (e) {
      setState(() {
        _status = 'Error: $e';
        _loading = false;
      });
    }
  }

  String _toTitleCase(String s) {
    if (s.isEmpty) return s;
    return s
        .split(' ')
        .map((w) => w.isEmpty ? w : w[0].toUpperCase() + w.substring(1))
        .join(' ');
  }

  QuizMode _modeForIndex(int index) {
    switch (index) {
      case 0:
        return QuizMode.vocabToEnglish;
      case 1:
        return QuizMode.englishToVocab;
      case 2:
        return QuizMode.audioToEnglish;
      default:
        return QuizMode.vocabToEnglish;
    }
  }

  void _nextQuestion([int? index]) {
    final tabIndex = index ?? _tabController.index;
    final quizState = _quizStates[tabIndex];
    final sessionDeck = _sessionDecks[tabIndex];
    final mode = _modeForIndex(tabIndex);

    if (sessionDeck == null || sessionDeck.isEmpty) {
      setState(() {
        quizState.current = null;
        _status = 'Quiz complete!';
      });
      return;
    }

    quizState.current = sessionDeck.removeAt(0);
    quizState.key = UniqueKey();
    quizState.correctAnswers = [];
    quizState.options = [];
    quizState.selectedOption = null;
    quizState.showResult = false;

    switch (mode) {
      case QuizMode.vocabToEnglish:
      case QuizMode.audioToEnglish:
        quizState.correctAnswers = [quizState.current!.meanings.first];
        quizState.options = [
          quizState.correctAnswers.first,
          ..._dg.generateVocabMeanings(quizState.current!, _deck, 3),
        ].map(_toTitleCase).toList()..shuffle();
        break;

      case QuizMode.englishToVocab:
        quizState.correctAnswers = [quizState.current!.characters];
        quizState.options = [
          quizState.correctAnswers.first,
          ..._dg.generateVocab(quizState.current!, _deck, 3),
        ]..shuffle();
        break;
      default:
        break;
    }

    setState(() {
      _isAnswering = false;
    });

    if (mode == QuizMode.audioToEnglish) {
      _playCurrentAudio(playOnLoad: true);
    }
  }

  Future<void> _playCurrentAudio({bool playOnLoad = false}) async {
    final current = _currentQuizState.current;
    if (current == null || current.pronunciationAudios.isEmpty) return;

    if (playOnLoad && !_playNarrator) return;

    final maleAudios = current.pronunciationAudios.where(
      (a) => a.gender == 'male',
    );
    final audioUrl = (maleAudios.isNotEmpty
        ? maleAudios.first.url
        : current.pronunciationAudios.first.url);

    try {
      await _audioPlayer.play(UrlSource(audioUrl));
    } finally {}
  }

  void _answer(String option) async {
    final quizState = _currentQuizState;
    final mode = _modeForIndex(_tabController.index);
    final isCorrect = quizState.correctAnswers
        .map((a) => a.toLowerCase().trim())
        .contains(option.toLowerCase().trim());

    final repo = Provider.of<VocabDeckRepository>(context, listen: false);
    final current = quizState.current!;
    final tabIndex = _tabController.index;
    final sessionDeck = _sessionDecks[tabIndex]!;

    final srsKey = mode.toString();

    var srsItemNullable = current.srsItems[srsKey];
    final isNew = srsItemNullable == null;
    final srsItem =
        srsItemNullable ?? SrsItem(subjectId: current.id, quizMode: mode);

    quizState.selectedOption = option;
    quizState.showResult = true;
    setState(() {});

    if (isCorrect) {
      quizState.asked += 1;
      if (!quizState.wrongItems.contains(current.id)) {
        quizState.score += 1;
      }
      srsItem.srsStage += 1;
    } else {
      srsItem.srsStage = max(0, srsItem.srsStage - 1);
      sessionDeck.add(current);
      sessionDeck.shuffle(_random);
      quizState.wrongItems.add(current.id);
      if (_playIncorrectSound) {
        await _audioPlayer.play(AssetSource('sfx/incorrect.wav'));
      }
    }
    srsItem.lastAsked = DateTime.now();
    current.srsItems[srsKey] = srsItem;

    if (isNew) {
      await repo.insertVocabSrsItem(srsItem);
    } else {
      await repo.updateVocabSrsItem(srsItem);
    }

    final correctDisplay = (mode == QuizMode.vocabToEnglish)
        ? _toTitleCase(quizState.correctAnswers.first)
        : quizState.correctAnswers.first;

    if (!mounted) return;
    final snack = SnackBar(
      content: Text(
        isCorrect ? 'Correct!' : 'Wrong — correct: $correctDisplay',
        style: TextStyle(
          color: isCorrect
              ? Theme.of(context).colorScheme.tertiary
              : Theme.of(context).colorScheme.error,
          fontWeight: FontWeight.bold,
        ),
      ),
      backgroundColor: Theme.of(context).colorScheme.surfaceContainerHighest,
      duration: const Duration(milliseconds: 900),
    );
    ScaffoldMessenger.of(context).showSnackBar(snack);

    if (isCorrect) {
      if (_playCorrectSound && !_playNarrator) {
        await _audioPlayer.play(AssetSource('sfx/correct.wav'));
      } else if (_playNarrator) {
        final maleAudios = current.pronunciationAudios.where(
          (a) => a.gender == 'male',
        );
        if (maleAudios.isNotEmpty) {
          final completer = Completer<void>();
          final sub = _audioPlayer.onPlayerComplete.listen((event) {
            if (!completer.isCompleted) completer.complete();
          });

          try {
            await _audioPlayer.play(UrlSource(maleAudios.first.url));
            await completer.future.timeout(const Duration(seconds: 5));
          } finally {
            await sub.cancel();
          }
        }
      }
    }

    setState(() {
      _isAnswering = true;
    });

    Future.delayed(const Duration(milliseconds: 900), () {
      if (mounted) {
        _nextQuestion();
      }
    });
  }

  @override
  Widget build(BuildContext context) {
    if (_apiKeyMissing) {
      return Scaffold(
        appBar: AppBar(title: const Text('Vocabulary Quiz')),
        body: Center(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: [
              Text(
                'WaniKani API key is not set.',
                style: TextStyle(
                  color: Theme.of(context).colorScheme.onSurface,
                ),
              ),
              const SizedBox(height: 16),
              ElevatedButton(
                onPressed: () async {
                  await Navigator.of(context).push(
                    MaterialPageRoute(builder: (_) => const SettingsScreen()),
                  );
                  if (!mounted) return;
                  _loadDeck();
                },
                child: const Text('Go to Settings'),
              ),
            ],
          ),
        ),
      );
    }

    if (_loading) {
      return Scaffold(
        appBar: AppBar(
          title: const Text('Vocabulary Quiz'),
          bottom: TabBar(
            controller: _tabController,
            tabs: const [
              Tab(text: 'Vocab→English'),
              Tab(text: 'English→Vocab'),
              Tab(text: 'Listening'),
            ],
          ),
        ),
        body: const Center(child: CircularProgressIndicator()),
      );
    }

    return Scaffold(
      appBar: AppBar(
        title: const Text('Vocabulary Quiz'),
        bottom: TabBar(
          controller: _tabController,
          tabs: const [
            Tab(text: 'Vocab→English'),
            Tab(text: 'English→Vocab'),
            Tab(text: 'Listening'),
          ],
        ),
      ),
      body: TabBarView(
        controller: _tabController,
        children: [_buildQuizPage(0), _buildQuizPage(1), _buildQuizPage(2)],
      ),
    );
  }

  Widget _buildQuizPage(int index) {
    final quizState = _quizStates[index];
    final mode = _modeForIndex(index);

    if (quizState.current == null) {
      return Center(
        child: Text(
          _status,
          style: TextStyle(
            fontSize: 24,
            color: Theme.of(context).colorScheme.onSurface,
          ),
        ),
      );
    }

    Widget promptWidget;

    if (quizState.current == null) {
      promptWidget = const SizedBox.shrink();
    } else if (mode == QuizMode.audioToEnglish) {
      promptWidget = IconButton(
        icon: Icon(
          Icons.volume_up,
          color: Theme.of(context).colorScheme.onSurface,
          size: 64,
        ),
        onPressed: _playCurrentAudio,
      );
    } else {
      String promptText = '';
      switch (mode) {
        case QuizMode.vocabToEnglish:
          promptText = quizState.current!.characters;
          break;
        case QuizMode.englishToVocab:
          promptText = _toTitleCase(quizState.current!.meanings.first);
          break;
        case QuizMode.audioToEnglish:
          break;
        default:
          break;
      }
      promptWidget = Text(
        promptText,
        style: TextStyle(
          fontSize: 48,
          color: Theme.of(context).colorScheme.onSurface,
        ),
      );
    }

    return Padding(
      key: quizState.key,
      padding: const EdgeInsets.all(16.0),
      child: Column(
        children: [
          Column(
            crossAxisAlignment: CrossAxisAlignment.start,
            children: [
              Text(
                '${quizState.asked} / ${_sessionDeckSizes[index] ?? 0}',
                style: TextStyle(
                  color: Theme.of(context).colorScheme.onSurface,
                  fontSize: 18,
                  fontWeight: FontWeight.bold,
                ),
              ),
              const SizedBox(height: 4),
              LinearProgressIndicator(
                value: (_sessionDeckSizes[index] ?? 0) > 0
                    ? quizState.asked / (_sessionDeckSizes[index] ?? 1)
                    : 0,
                backgroundColor: Theme.of(
                  context,
                ).colorScheme.surfaceContainerHighest,
                valueColor: AlwaysStoppedAnimation<Color>(
                  Theme.of(context).colorScheme.primary,
                ),
              ),
            ],
          ),
          const SizedBox(height: 18),
          Expanded(
            flex: 3,
            child: Center(
              child: ConstrainedBox(
                constraints: const BoxConstraints(
                  minWidth: 0,
                  maxWidth: 500,
                  minHeight: 150,
                ),
                child: KanjiCard(characterWidget: promptWidget, subtitle: ''),
              ),
            ),
          ),
          const SizedBox(height: 12),
          SafeArea(
            top: false,
            child: Column(
              children: [
                OptionsGrid(
                  options: quizState.options,
                  onSelected: _isAnswering ? (option) {} : _answer,
                  showResult: quizState.showResult,
                  selectedOption: quizState.selectedOption,
                  correctAnswers: quizState.correctAnswers,
                ),
                const SizedBox(height: 8),
                Text(
                  'Score: ${quizState.score} / ${quizState.asked}',
                  style: TextStyle(
                    color: Theme.of(context).colorScheme.onSurface,
                  ),
                ),
              ],
            ),
          ),
        ],
      ),
    );
  }
}