prefix method

ResultPrefix prefix(String previousRank, String nextRank)

Return a string between previousRank and nextRank as a condition, both params must be of the same length

Implementation

ResultPrefix prefix(String previousRank, String nextRank) {
  var response = '';

  // if (previousRank.isEmpty) return '';
  // if (nextRank.isEmpty) return '';

  for (var i = 0; i < previousRank.length; i++) {
    var current = '';

    if (nextRank.at(i) == wildcard) {
      current = wildcard;
    } else if (previousRank.at(i) == wildcard) {
      if (nextRank.at(i) == alphabet.first()) {
        current = wildcard;
      } else {
        current = alphabet.between(alphabet.first(), nextRank.at(i));
      }
    } else {
      current = alphabet.between(previousRank.at(i), nextRank.at(i));
    }

    response += current;

    if (current != previousRank.at(i)) {
      return ResultPrefix(response: response, hasSuffix: false);
    }
  }
  return ResultPrefix(response: response, hasSuffix: true);
}