Auto Complete in 65 Lines of Dart

autocomplete.dart

class Node {
  String prefix;
  List<Node> children = List<Node>();

  bool _addNewChild(String rest) {
    final child = Node();
    var added = child.add(rest);
    if (added) children.add(child);
    return added;
  }

  bool add(String word) {
    if (word == null || word.length == 0) return true;

    final first = word[0];
    final rest = word.substring(1);
    if (prefix == null) {
      prefix = first;
      return _addNewChild(rest);
    } else {
      if (prefix == first) {
        for (var n in children) {
          var added = n.add(rest);
          if (added) return added;
        }
        return _addNewChild(rest);
      }
      return false;
    }
  }

  List<String> find(String partialWord) {
    return _find("", partialWord);
  }

  // Finds partial matches
  List<String> _find(String sofar, String partialWord) {
    final result = List<String>();
    if (partialWord == null || partialWord.length == 0) return result;

    final first = partialWord[0];
    final rest = partialWord.substring(1);

    if (prefix == first) {
      for (var n in children) {
        var result = n._find(sofar + prefix, rest);
        if (result.length != 0) return result;
      }
      return getWords(sofar, result);
    }
    return result;
  }

  List<String> getWords(String sofar, List<String> words) {
    if (prefix == null) {
      words.add(sofar);
      return words;
    }
    sofar += prefix;
    for (var ch in children) {
      words = ch.getWords(sofar, words);
    }
    return words;
  }
}