/// Lightweight fuzzy matching for product search.
library;

String _normalize(String value) =>
    value.trim().toLowerCase().replaceAll(RegExp(r'\s+'), ' ');

/// True when [query] fuzzily matches [text].
bool fuzzyMatch(String query, String text) {
  final q = _normalize(query);
  if (q.isEmpty) return true;
  final t = _normalize(text);
  if (t.contains(q)) return true;

  for (final word in q.split(' ')) {
    if (word.isEmpty) continue;
    if (!t.contains(word) && !_subsequence(word, t)) return false;
  }
  if (q.contains(' ')) return true;
  return _subsequence(q, t);
}

/// Higher is better. Null when [query] does not match.
int? fuzzyScore(String query, String text) {
  final q = _normalize(query);
  if (q.isEmpty) return 0;
  final t = _normalize(text);
  if (t == q) return 1000;
  if (t.startsWith(q)) return 800;
  if (t.contains(q)) return 600 - t.indexOf(q);
  if (!fuzzyMatch(q, t)) return null;
  return 200 - (t.length - q.length).abs().clamp(0, 150);
}

bool _subsequence(String query, String text) {
  var i = 0;
  for (var c = 0; c < text.length && i < query.length; c++) {
    if (text.codeUnitAt(c) == query.codeUnitAt(i)) i++;
  }
  return i == query.length;
}