import 'dart:math';
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import '../models/kanji_item.dart';
import '../services/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 _ReadingInfo {
  final List<String> correctReadings;
  final String hint;

  _ReadingInfo(this.correctReadings, this.hint);
}

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

  @override
  State<HomeScreen> createState() => _HomeScreenState();
}

class _HomeScreenState extends State<HomeScreen> {
  List<KanjiItem> _deck = [];
  bool _loading = false;
  String _status = 'Loading deck...';
  final DistractorGenerator _dg = DistractorGenerator();
  final Random _random = Random();
  final _audioPlayer = AudioPlayer();

  QuizMode _mode = QuizMode.kanjiToEnglish;
  KanjiItem? _current;
  List<String> _options = [];
  List<String> _correctAnswers = [];
  String _readingHint = '';
  int _score = 0;
  int _asked = 0;

  @override
  void initState() {
    super.initState();
    _loadDeck();
  }

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

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

      if (apiKey == null || apiKey.isEmpty) {
        if (mounted) {
          Navigator.of(context).pushReplacement(
            MaterialPageRoute(builder: (_) => const SettingsScreen()),
          );
        }
        return;
      }

      var items = await repo.loadKanji();
      if (items.isEmpty) {
        setState(() {
          _status = 'Fetching deck...';
        });
        items = await repo.fetchAndCacheFromWk(apiKey);
      }

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

      _nextQuestion();
    } 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(' ');
  }

  _ReadingInfo _pickReading(KanjiItem item) {
    final choices = <String>[];
    if (item.onyomi.isNotEmpty) choices.add('onyomi');
    if (item.kunyomi.isNotEmpty) choices.add('kunyomi');
    if (choices.isEmpty) return _ReadingInfo([], '');

    final pickedType = choices[_random.nextInt(choices.length)];
    final readingsList = pickedType == 'onyomi' ? item.onyomi : item.kunyomi;
    final hint = 'Select the ${pickedType == 'onyomi' ? "on'yomi" : "kunyomi"}';

    return _ReadingInfo(readingsList, hint);
  }

  void _nextQuestion() {
    _deck.sort((a, b) {
      final aSrsItem = a.srsItems[_mode.toString()];
      final bSrsItem = b.srsItems[_mode.toString()];

      final aStage = aSrsItem?.srsStage ?? 0;
      final bStage = bSrsItem?.srsStage ?? 0;

      if (aStage != bStage) {
        return aStage.compareTo(bStage);
      }

      final aLastAsked = aSrsItem?.lastAsked ?? DateTime.fromMillisecondsSinceEpoch(0);
      final bLastAsked = bSrsItem?.lastAsked ?? DateTime.fromMillisecondsSinceEpoch(0);

      return aLastAsked.compareTo(bLastAsked);
    });

    _current = _deck.first;

    _correctAnswers = [];
    _options = [];
    _readingHint = '';

    switch (_mode) {
      case QuizMode.kanjiToEnglish:
        _correctAnswers = [_current!.meanings.first];
        _options = [
          _correctAnswers.first,
          ..._dg.generateMeanings(_current!, _deck, 3)
        ].map(_toTitleCase).toList()
          ..shuffle();
        break;

      case QuizMode.englishToKanji:
        _correctAnswers = [_current!.characters];
        _options = [
          _correctAnswers.first,
          ..._dg.generateKanji(_current!, _deck, 3)
        ]..shuffle();
        break;

      case QuizMode.reading:
        final info = _pickReading(_current!);
        _correctAnswers = info.correctReadings;
        _readingHint = info.hint;

        final readingsSource = _readingHint.contains("on'yomi")
            ? _deck.expand((k) => k.onyomi)
            : _deck.expand((k) => k.kunyomi);

        final distractors = readingsSource
            .where((r) => !_correctAnswers.contains(r))
            .toSet()
            .toList()
          ..shuffle();
        _options = ([
          _correctAnswers[_random.nextInt(_correctAnswers.length)],
          ...distractors.take(3)
        ])
          ..shuffle();
        break;
    }

    setState(() {});
  }

  void _answer(String option) async {
    final isCorrect = _correctAnswers
        .map((a) => a.toLowerCase().trim())
        .contains(option.toLowerCase().trim());

    final repo = Provider.of<DeckRepository>(context, listen: false);
    final current = _current!;

    String readingType = '';
    if (_mode == QuizMode.reading) {
      readingType = _readingHint.contains("on'yomi") ? 'onyomi' : 'kunyomi';
    }
    final srsKey = _mode.toString() + readingType;

    var srsItem = current.srsItems[srsKey];
    final isNew = srsItem == null;
    final srsItemForUpdate = srsItem ??=
        SrsItem(kanjiId: current.id, quizMode: _mode, readingType: readingType);
    setState(() {
      _asked += 1;
      if (isCorrect) {
        _score += 1;
        _audioPlayer.play(AssetSource('sfx/confirm.mp3'));
      } else {
        srsItemForUpdate.srsStage = max(0, srsItemForUpdate.srsStage - 1);
      }
      srsItemForUpdate.lastAsked = DateTime.now();
      current.srsItems[srsKey] = srsItemForUpdate;
    });

    if (isNew) {
      await repo.insertSrsItem(srsItemForUpdate);
    } else {
      await repo.updateSrsItem(srsItemForUpdate);
    }

    final correctDisplay = (_mode == QuizMode.kanjiToEnglish)
        ? _toTitleCase(_correctAnswers.first)
        : (_mode == QuizMode.reading
            ? _correctAnswers.join(', ')
            : _correctAnswers.first);

    final snack = SnackBar(
      content: Text(
        isCorrect ? 'Correct!' : 'Wrong — correct: $correctDisplay',
        style: TextStyle(
          color: isCorrect ? Colors.greenAccent : Colors.redAccent,
          fontWeight: FontWeight.bold,
        ),
      ),
      backgroundColor: const Color(0xFF222222),
      duration: const Duration(milliseconds: 900),
    );
    if (mounted) {
      ScaffoldMessenger.of(context).showSnackBar(snack);
    }

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

  @override
  Widget build(BuildContext context) {
    String prompt = '';
    String subtitle = '';

    switch (_mode) {
      case QuizMode.kanjiToEnglish:
        prompt = _current?.characters ?? '';
        break;
      case QuizMode.englishToKanji:
        prompt = _current != null ? _toTitleCase(_current!.meanings.first) : '';
        break;
      case QuizMode.reading:
        prompt = _current?.characters ?? '';
        subtitle = _readingHint;
        break;
    }

    return Scaffold(
      backgroundColor: const Color(0xFF121212),
      appBar: AppBar(
        title: const Text('WaniKani Kanji SRS'),
        backgroundColor: const Color(0xFF1F1F1F),
        foregroundColor: Colors.white,
        elevation: 2,
        actions: [
          IconButton(
            icon: const Icon(Icons.settings),
            onPressed: () {
              Navigator.of(context).push(
                MaterialPageRoute(builder: (_) => const SettingsScreen()),
              );
            },
          )
        ],
      ),
      body: Padding(
        padding: const EdgeInsets.all(16.0),
        child: Column(
          children: [
            Row(
              children: [
                Expanded(
                  child: Text(
                    _status,
                    style: const TextStyle(color: Colors.white),
                  ),
                ),
                if (_loading)
                  const CircularProgressIndicator(color: Colors.blueAccent),
              ],
            ),
            const SizedBox(height: 12),
            Wrap(
              spacing: 6,
              runSpacing: 4,
              alignment: WrapAlignment.center,
              children: [
                _buildChoiceChip('Kanji→English', QuizMode.kanjiToEnglish),
                _buildChoiceChip('English→Kanji', QuizMode.englishToKanji),
                _buildChoiceChip('Reading', QuizMode.reading),
              ],
            ),
            const SizedBox(height: 18),
            Expanded(
              flex: 3,
              child: Center(
                child: ConstrainedBox(
                  constraints: const BoxConstraints(
                    minWidth: 0,
                    maxWidth: 500,
                    minHeight: 150,
                  ),
                  child: KanjiCard(
                    characters: prompt,
                    subtitle: subtitle,
                    backgroundColor: const Color(0xFF1E1E1E),
                    textColor: Colors.white,
                  ),
                ),
              ),
            ),
            const SizedBox(height: 12),
            SafeArea(
              top: false,
              child: Column(
                children: [
                  OptionsGrid(
                    options: _options,
                    onSelected: _answer,
                    buttonColor: const Color(0xFF1E1E1E),
                    textColor: Colors.white,
                  ),
                  const SizedBox(height: 8),
                  Text(
                    'Score: $_score / $_asked',
                    style: const TextStyle(color: Colors.white),
                  ),
                ],
              ),
            ),
          ],
        ),
      ),
    );
  }

  ChoiceChip _buildChoiceChip(String label, QuizMode mode) {
    final selected = _mode == mode;
    return ChoiceChip(
      label: Text(
        label,
        style: TextStyle(color: selected ? Colors.white : Colors.grey[400]),
      ),
      selected: selected,
      onSelected: (v) {
        setState(() => _mode = mode);
        _nextQuestion();
      },
      selectedColor: Colors.blueAccent,
      backgroundColor: const Color(0xFF1E1E1E),
    );
  }
}