vscode_search_regex.dart

bool _hasMatch(String target, String text) {
  text = text.replaceAll(' ', '');
  target = target.replaceAll(' ', '');
  text = text.toLowerCase();
  target = target.toLowerCase();

  final query = text.split('');

  final ids = <int>[];

  for (var i = 0; i < query.length; i++) {
    final q = query[i];

    final id = target.indexOf(q);

    if (id == -1) return false;

    ids.add(id);

    if (id + 1 >= target.length) break;

    target = target.substring(id + 1);
  }

  return ids.length == query.length;
}

// Usage:

void main() {
  final target1 = 'A normal string with letters';
  final target2 = 'Other random string';

  final search1 = 'nwl';
  final search2 = 'normal letters';
  final search3 = 'oth str';
  final search4 = 'dom sng';
  final search5 = 'atts';

  print(_hasMatch(target1, search1)); // true
  print(_hasMatch(target2, search1)); // false

  print(_hasMatch(target1, search2)); // true
  print(_hasMatch(target2, search2)); // false

  print(_hasMatch(target1, search3)); // false
  print(_hasMatch(target2, search3)); // true

  print(_hasMatch(target1, search4)); // false
  print(_hasMatch(target2, search4)); // true

  print(_hasMatch(target1, search5)); // true
  print(_hasMatch(target2, search5)); // false
}