import 'models.dart';

class ReviewCheckResult {
  const ReviewCheckResult({required this.complete, required this.message});

  final bool complete;
  final String message;
}

/// Checks only the minimum information a learner needs to produce in an A0
/// review. It intentionally accepts common contractions and variable slot
/// values instead of comparing an answer with one fixed sentence.
class ReviewFeedback {
  const ReviewFeedback._();

  static ReviewCheckResult check(ReviewItem item, String input) {
    final text = input.toLowerCase().replaceAll('’', "'");
    final tokens = RegExp(
      r"[a-z]+(?:'[a-z]+)?",
    ).allMatches(text).map((match) => match.group(0)!).toSet();
    bool has(String token) => tokens.contains(token);
    bool phrase(String value) => text.contains(value);
    bool hasAny(Iterable<String> values) => values.any(has);
    final introduction =
        phrase("i'm") || phrase('i am') || phrase('my name is');
    final itIs = phrase("it's") || phrase('it is');
    final numberWords = RegExp(
      r'\b(zero|one|two|three|four|five|six|seven|eight|nine|ten)\b',
    ).allMatches(text).length;

    final complete = switch (item.id) {
      'A0-P01' => introduction && tokens.length >= 2,
      'A0-P02' => (phrase("what's your name") || phrase('what is your name')),
      'A0-P03' => phrase('nice to meet you'),
      'A0-P04' => phrase('how do you spell'),
      'A0-P05' => phrase('how are you'),
      'A0-P06' => introduction && hasAny(['good', 'okay', 'tired']),
      'A0-P07' =>
        phrase("what's your phone number") ||
            phrase('what is your phone number'),
      'A0-P08' =>
        (phrase('my number is') || numberWords >= 3) && numberWords >= 3,
      'A0-P09' => phrase("what's this") || phrase('what is this'),
      'A0-P10' => itIs && hasAny(['book', 'pen', 'bag', 'key']),
      'A0-P11' => phrase('where are you from'),
      'A0-P12' => introduction && has('from') && tokens.length >= 3,
      'A0-P13' => phrase('this is my') && tokens.length >= 4,
      'A0-P14' => phrase('what day is it'),
      'A0-P15' =>
        itIs &&
            hasAny([
              'monday',
              'tuesday',
              'wednesday',
              'thursday',
              'friday',
              'saturday',
              'sunday',
            ]),
      'A0-P16' => phrase('what time is it'),
      'A0-P17' =>
        itIs &&
            (has('clock') ||
                has("o'clock") ||
                has('oclock') ||
                phrase("o'clock")),
      'A0-P18' => introduction && has('like') && tokens.length >= 3,
      'A0-P19' => phrase('do you like'),
      'A0-P20' =>
        phrase('please say that again') || phrase('please speak slowly'),
      _ when item.id.startsWith('A0-W') => tokens.contains(
        item.target.toLowerCase(),
      ),
      _ => tokens.length >= 2,
    };
    return ReviewCheckResult(
      complete: complete,
      message: complete ? '表达已完成，可以进入下一次复习安排。' : _hint(item.id),
    );
  }

  static String _hint(String id) => switch (id) {
    'A0-P01' => '用 I’m / I am 或 My name is 介绍一个名字。',
    'A0-P02' => '试着问：What’s your name?',
    'A0-P04' => '问对方怎样拼写：How do you spell …?',
    'A0-P08' => '说出至少三个英文数字，也可用 My number is … 开头。',
    'A0-P10' => '用 It’s / It is 加上一个物品。',
    'A0-P12' => '用 I’m from … 说出一个地点。',
    'A0-P17' => '用 It’s … o’clock 说整点时间。',
    'A0-P18' => '用 I like … 说一项喜好。',
    _ => '再补充本次目标中的关键英文词或句型。',
  };
}