import 'a0_core.dart';
import 'models.dart';
import 'speech_compare.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 String _normalize(String input) => input
      .toLowerCase()
      .replaceAll('’', "'")
      .replaceAll('‘', "'")
      .replaceAll(RegExp(r'\s+'), ' ')
      .trim();

  static ReviewCheckResult check(ReviewItem item, String input) {
    final dictation = item.skill == dictationSkill
        ? a0DictationSentences[item.id]
        : null;
    if (dictation != null) {
      final comparison = compareSpoken(dictation.sentence, input);
      final missing = comparison.total - comparison.heardCount;
      final wrong = missing + comparison.extraWords.length;
      return ReviewCheckResult(
        complete: comparison.matches,
        message: comparison.matches
            ? '听写正确。'
            : '有 $wrong 处和听到的句子不一致。再听一次，检查拼写和漏掉的词。',
      );
    }
    final complete = a0CoreItems.containsKey(item.id)
        // A word review checks the word it actually shows.
        ? coreItemUsedIn(item.id, input, word: item.target)
        : _tokens(_normalize(input)).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 Set<String> _tokens(String text) => RegExp(
    r"[a-z]+(?:'[a-z]+)?",
  ).allMatches(text).map((match) => match.group(0)!).toSet();

  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。',
  };
}

/// Whether [input] actually contains A0 core item [id]. Lessons, reviews and
/// dialogues use the same rule, so evidence only goes to the items a learner
/// really produced, never to every target a task happens to be attached to.
bool coreItemUsedIn(String id, String input, {String? word}) {
  final text = ReviewFeedback._normalize(input);
  final tokens = ReviewFeedback._tokens(text);
  bool has(String token) => tokens.contains(ReviewFeedback._normalize(token));
  bool phrase(String value) => text.contains(ReviewFeedback._normalize(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;
  const weekdays = [
    'monday',
    'tuesday',
    'wednesday',
    'thursday',
    'friday',
    'saturday',
    'sunday',
  ];

  return switch (id) {
    // "I'm from …" and "I'm good" are other items, not a name.
    'A0-P01' =>
      phrase('my name is') ||
          RegExp(
            r"\bi(?:'m| am) (?!from\b|good\b|okay\b|ok\b|fine\b|great\b|tired\b)[a-z]",
          ).hasMatch(text),
    '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' => numberWords >= 3,
    'A0-P09' => phrase("what's this") || phrase('what is this'),
    'A0-P10' => itIs && hasAny(['book', 'pen', 'bag', 'key', 'phone']),
    '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(weekdays),
    'A0-P16' => phrase('what time is it'),
    'A0-P17' =>
      itIs &&
          (has('clock') ||
              has("o'clock") ||
              has('oclock') ||
              phrase("o'clock")),
    'A0-P18' => (phrase('i like') || phrase('i love')) && tokens.length >= 3,
    'A0-P19' => phrase('do you like'),
    'A0-P20' =>
      phrase('please say that again') || phrase('please speak slowly'),
    _ when a0CoreItems.containsKey(id) && id.startsWith('A0-W') =>
      has(word ?? a0CoreItems[id]!) || phrase(word ?? a0CoreItems[id]!),
    _ => false,
  };
}