parsePrereqGaps function

Implementation

PrereqGapParseResult parsePrereqGaps(String text) {
  final matches = _kPrereqGapPattern.allMatches(text).toList();
  if (matches.isEmpty) {
    return PrereqGapParseResult(cleanedText: text, concepts: const []);
  }

  // Order-preserving dedupe (case-insensitive comparison).
  final seen = <String>{};
  final concepts = <String>[];
  for (final m in matches) {
    final raw = m.group(1)?.trim();
    if (raw == null || raw.isEmpty) continue;
    final key = raw.toLowerCase();
    if (seen.add(key)) concepts.add(raw);
  }

  // Strip every tag from the text. Then collapse runs of whitespace that
  // the removal may have left behind (e.g. "foo [tag] bar" → "foo  bar").
  var cleaned = text.replaceAll(_kPrereqGapPattern, '');
  cleaned = cleaned.replaceAll(RegExp(r'[ \t]{2,}'), ' ');
  // Trim trailing spaces on each line; collapse 3+ blank lines to 2.
  cleaned = cleaned
      .split('\n')
      .map((line) => line.replaceAll(RegExp(r'[ \t]+$'), ''))
      .join('\n');
  cleaned = cleaned.replaceAll(RegExp(r'\n{3,}'), '\n\n').trim();

  return PrereqGapParseResult(cleanedText: cleaned, concepts: concepts);
}