import 'package:flutter_test/flutter_test.dart';
import 'package:kouyu_english/core/seed_courses.dart';

const _digitWords = {
  '0': 'zero',
  '1': 'one',
  '2': 'two',
  '3': 'three',
  '4': 'four',
  '5': 'five',
  '6': 'six',
  '7': 'seven',
  '8': 'eight',
  '9': 'nine',
};

const _skipWords = {'a', 'an', 'the', 'my', 'is', 'it', 'im', 'to', 'you'};

String _normalize(String text) =>
    text.toLowerCase().replaceAll(RegExp(r'[^a-z0-9一-龥]'), '');

/// 选项在对话里是否真的出现过。数字选项按英文读法展开（138 → onethreeeight），
/// 逐字母拼写（S-H-E-N）先去掉连字符。
bool _appearsInReading(String reading, String option) {
  final haystack = _normalize(
    reading.replaceAllMapped(
      RegExp(r'\d'),
      (match) => _digitWords[match[0]]!,
    ),
  );
  final tokens = option
      .replaceAll('-', '')
      .replaceAllMapped(RegExp(r'\d'), (match) => _digitWords[match[0]]!)
      .toLowerCase()
      .split(RegExp(r'[^a-z0-9一-龥]+'))
      .where((token) => token.length > 1 && !_skipWords.contains(token));
  return tokens.isNotEmpty && tokens.every(haystack.contains);
}

void main() {
  final activities = <String, LessonActivity>{
    ...a0Activities,
    ...a0SegmentActivities,
  };

  group('阅读找答案题', () {
    test('每题三个选项，第一项是标准答案', () {
      for (final entry in activities.entries) {
        final activity = entry.value;
        expect(activity.answers, hasLength(3), reason: entry.key);
        expect(activity.readingOptions, hasLength(3), reason: entry.key);
        expect(
          activity.readingOptions.first,
          activity.readingAnswer,
          reason: '${entry.key}：readingOptions 第一项应是标准答案',
        );
        expect(
          activity.readingOptions.toSet(),
          hasLength(3),
          reason: '${entry.key}：选项不能重复',
        );
      }
    });

    test('至少两个选项在对话中出现，必须读懂才能选', () {
      for (final entry in activities.entries) {
        final activity = entry.value;
        final present = activity.readingOptions
            .where((option) => _appearsInReading(activity.reading, option))
            .toList();
        expect(
          _appearsInReading(activity.reading, activity.readingAnswer),
          isTrue,
          reason: '${entry.key}：答案必须能在对话里找到',
        );
        expect(
          present.length,
          greaterThanOrEqualTo(2),
          reason:
              '${entry.key}：只有 ${present.length} 个选项出现在对话中，'
              '学习者不读对话也能挑出唯一出现过的那个',
        );
      }
    });

    test('选项之间不构成子串，避免判分时误判', () {
      for (final entry in activities.entries) {
        final options = entry.value.readingOptions.map(_normalize).toList();
        for (var i = 0; i < options.length; i++) {
          for (var j = i + 1; j < options.length; j++) {
            expect(
              options[i].contains(options[j]) ||
                  options[j].contains(options[i]),
              isFalse,
              reason: '${entry.key}：“${entry.value.readingOptions[i]}”与'
                  '“${entry.value.readingOptions[j]}”互为子串，会被判分逻辑当成同一个答案',
            );
          }
        }
      }
    });

    test('打乱后的选项内容不变且顺序稳定', () {
      for (final entry in activities.entries) {
        final activity = entry.value;
        final seed = '${activity.readingQuestion}-reading';
        final first = shuffledOptions(activity.readingOptions, seed);
        final second = shuffledOptions(activity.readingOptions, seed);
        expect(first, second, reason: entry.key);
        expect(
          first.toSet(),
          activity.readingOptions.toSet(),
          reason: entry.key,
        );
      }
    });

    test('正确答案在三个位置上都出现，不集中在某一位', () {
      final readingSlots = <int, int>{};
      final listeningSlots = <int, int>{};
      for (final activity in activities.values) {
        final reading = shuffledOptions(
          activity.readingOptions,
          '${activity.readingQuestion}-reading',
        );
        final readingSlot = reading.indexOf(activity.readingAnswer);
        readingSlots[readingSlot] = (readingSlots[readingSlot] ?? 0) + 1;
        final listening = shuffledOptions(
          activity.answers,
          '${activity.listening}-listening',
        );
        final listeningSlot = listening.indexOf(activity.answers.first);
        listeningSlots[listeningSlot] = (listeningSlots[listeningSlot] ?? 0) + 1;
      }
      for (final slots in [readingSlots, listeningSlots]) {
        expect(slots.keys.toSet(), {0, 1, 2});
        for (final count in slots.values) {
          expect(count, lessThan(activities.length ~/ 2));
        }
      }
    });

    test('题干不重复，复习时不会撞题', () {
      final questions = activities.values
          .map((activity) => activity.readingQuestion)
          .toList();
      expect(questions.toSet(), hasLength(questions.length));
    });
  });
}