import 'package:flutter_test/flutter_test.dart';
import 'package:kouyu_english/core/app_state.dart';
import 'package:kouyu_english/core/courses/courses.dart';
import 'package:kouyu_english/core/models.dart';

/// The word bank exists so vocabulary is not capped by lesson progress: a
/// learner still on A0 must have words to recognise from the first day.
void main() {
  TestWidgetsFlutterBinding.ensureInitialized();

  setUp(() async {
    clearCoreItems();
    WordBank.instance.resetForTest();
    await WordBank.instance.load();
  });

  tearDown(() {
    clearCoreItems();
    WordBank.instance.resetForTest();
  });

  test('the bank carries a few thousand words with gloss and IPA', () {
    final ids = receptiveWordRegistry.keys.where(
      (id) => WordBank.isBankUnit(receptiveWordRegistry[id]!.unit),
    );
    expect(ids.length, greaterThan(2000));
    for (final id in ids) {
      expect(wordEnglish(id), isNotEmpty, reason: id);
      expect(wordMeaning(id), isNotEmpty, reason: id);
    }
    final withIpa = ids.where((id) => wordIpa(id).isNotEmpty);
    expect(withIpa.length / ids.length, greaterThan(0.98));
  });

  test('every level pool is filed under its own unit', () {
    final units = receptiveWordRegistry.values
        .map((word) => word.unit)
        .where(WordBank.isBankUnit)
        .toSet();
    expect(units, containsAll(['bank-A1', 'bank-A2', 'bank-B1']));
    expect(WordBank.levelOfUnit('bank-A2'), 'A2');
  });

  test('new words are handed out by spoken frequency, not alphabetically', () {
    final state = AppState();
    final first = state.unstartedBankWords.take(12);
    final words = first.map(wordEnglish).toList();
    // Alphabetical order would open with `a.m.`, `ability`, `able`.
    expect(words, contains('know'));
    expect(words.first, isNot('a.m.'));
    final ranks = first.map(WordBank.instance.rankOf).toList();
    expect(ranks, orderedEquals(ranks.toList()..sort()));
  });

  test('almost every word has a real frequency rank', () {
    final ids = receptiveWordRegistry.keys.where(
      (id) => WordBank.isBankUnit(receptiveWordRegistry[id]!.unit),
    );
    final ranked = ids.where(
      (id) => WordBank.instance.rankOf(id) != WordBank.unranked,
    );
    expect(ranked.length / ids.length, greaterThan(0.99));
  });

  test('a fresh learner has bank words waiting and none started', () {
    final state = AppState();
    expect(state.wordKnowledge, isEmpty);
    expect(state.unstartedBankWordCount, greaterThan(2000));
    expect(state.wordSessionPreviewSize, state.newWordsPerDay);
  });

  test('a round hands out new bank words, easiest level first', () {
    final state = AppState();
    final plan = state.wordSession(size: 5);
    expect(plan, hasLength(5));
    for (final question in plan) {
      expect(question.options, contains(question.answer));
      expect(question.options, hasLength(3));
      expect(receptiveWordRegistry[question.id]!.level, 'A1');
      expect(state.wordStatus(question.id), WordStatus.newWord);
    }
  });

  test('the day has a cap on how many new words the bank starts', () {
    final state = AppState();
    expect(state.newWordsPerDay, 15, reason: 'the 20-minute default');
    final first = state.wordSession(size: 20);
    expect(first, hasLength(15), reason: 'a round stops at the cap');
    expect(state.newWordQuota, 0);
    // A second round adds nothing new. It re-offers the same words, which is
    // right: a round left half-finished should be finishable.
    final second = state.wordSession(size: 20);
    expect(second.map((q) => q.id), first.map((q) => q.id));
    expect(state.newWordsStartedToday, 15);
  });

  test('the cap follows the daily time budget', () {
    final state = AppState();
    state.setDailyMinutes(10);
    expect(state.newWordsPerDay, 8);
    expect(state.wordSession(size: 20), hasLength(8));
    state.setDailyMinutes(30);
    // The cap moved, so the rest of today's allowance opens up.
    expect(state.newWordQuota, 12);
  });

  test('what is due is asked even after the new-word cap is used up', () {
    final state = AppState();
    final started = state.wordSession(size: 20);
    expect(state.newWordQuota, 0);
    for (final question in started.take(3)) {
      state.recordWordRecognition(question.id, correct: false);
    }
    // Missed words are due tomorrow, so nothing is due right now -- but the
    // cap must not be what is stopping them.
    state.wordKnowledge[started.first.id] = state
        .wordKnowledge[started.first.id]!
        .copyWith(dueAt: DateTime.now().subtract(const Duration(hours: 1)));
    final next = state.wordSession(size: 20);
    expect(next.map((q) => q.id), contains(started.first.id));
  });

  test('answering a new word does not give the cap back', () {
    final state = AppState();
    for (final question in state.wordSession(size: 20)) {
      state.recordWordRecognition(question.id, correct: true);
    }
    // Answering is what a round is for; if it cleared the word off today's
    // count, one sitting could start the bank's whole A1 list.
    expect(state.newWordsStartedToday, 15);
    expect(state.newWordQuota, 0);
    expect(state.wordSession(size: 20), isEmpty);
  });

  test('a word started today counts against the cap after a reload', () {
    final state = AppState();
    state.wordSession(size: 5);
    final restored = AppState()..restoreForTest(state.snapshotForTest());
    expect(restored.newWordsStartedToday, 5);
    expect(restored.newWordQuota, 10);
  });

  test('a word handed out once is not handed out again next round', () {
    final state = AppState();
    final first = state.wordSession(size: 5).map((q) => q.id).toSet();
    for (final id in first) {
      state.recordWordRecognition(id, correct: true);
    }
    final second = state.wordSession(size: 5).map((q) => q.id).toSet();
    expect(second.intersection(first), isEmpty);
  });

  test('a missed word waits for tomorrow instead of the same round', () {
    final state = AppState();
    final missed = state.wordSession(size: 3).map((q) => q.id).toSet();
    for (final id in missed) {
      state.recordWordRecognition(id, correct: false);
    }
    final next = state.wordSession(size: 10).map((q) => q.id).toSet();
    expect(next.intersection(missed), isEmpty);
    expect(state.shakyWords.toSet(), missed);
  });

  test('a word met in a unit is asked before a new one from the bank', () {
    registerSavedWord('t-unit', en: 'ready', zh: '准备好', level: 'A0');
    final state = AppState();
    state.meetWord('t-unit');
    expect(state.wordSession(size: 4).first.id, 't-unit');
  });

  test('bank words stay out of the checkpoint queue and mastery', () {
    final state = AppState();
    final plan = state.wordSession(size: 3);
    for (final question in plan) {
      state.recordWordRecognition(question.id, correct: false);
    }
    expect(state.reviewQueue, isEmpty);
    expect(state.mastery, isEmpty);
  });

  test('every word carries an example sentence with its Chinese', () {
    final ids = receptiveWordRegistry.keys.where(
      (id) => WordBank.isBankUnit(receptiveWordRegistry[id]!.unit),
    );
    for (final id in ids) {
      final sample = WordBank.instance.exampleOf(id);
      expect(sample, isNotNull, reason: id);
      expect(sample!.en, isNotEmpty, reason: id);
      expect(sample.zh, isNotEmpty, reason: id);
    }
  });

  test('a gloss is short enough to be a quiz option', () {
    final glosses = receptiveWordRegistry.entries
        .where((entry) => WordBank.isBankUnit(entry.value.unit))
        .map((entry) => entry.value.zh);
    for (final gloss in glosses) {
      expect(gloss.length, lessThanOrEqualTo(10), reason: gloss);
      expect(gloss, isNot(contains('（')), reason: gloss);
      expect(gloss, isNot(contains('(')), reason: gloss);
    }
  });

  test('extra senses are kept aside from the quiz answer', () {
    final withMore = receptiveWordRegistry.keys.where(
      (id) => WordBank.instance.moreSenses(id).isNotEmpty,
    );
    expect(withMore, isNotEmpty);
    for (final id in withMore.take(50)) {
      expect(
        WordBank.instance.moreSenses(id).split('；'),
        isNot(contains(wordMeaning(id))),
      );
    }
  });
}