import 'courses/courses.dart';

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

  final bool complete;
  final String message;
}

/// A deliberately small offline checker for teaching tasks. The rule and the
/// hint come from the segment's writing task in the course JSON; it
/// checks only the essential information and never claims to grade
/// pronunciation or nuanced grammar.
class WritingFeedback {
  const WritingFeedback._();

  static WritingCheckResult check(String segmentId, String input) {
    final activity = activityBySegmentId(segmentId);
    final rule = activity.writingRequiredTerms;
    final complete = rule.isEmpty
        ? RegExp(r"[a-z]+(?:'[a-z]+)?")
                  .allMatches(normalizeAnswer(input))
                  .map((match) => match.group(0))
                  .toSet()
                  .length >=
              2
        : matchesRule(input, rule);
    if (complete) {
      return const WritingCheckResult(
        complete: true,
        message: '这句已经表达完整。继续在对话里用一次吧。',
      );
    }
    return WritingCheckResult(
      complete: false,
      message: activity.writingHint.isNotEmpty
          ? activity.writingHint
          : '再补充一个完整英文句子。',
    );
  }
}