class Bob {
  String response(String input) {
    if (input.isQuestion && input.isUppercase)
      return "Calm down, I know what I'm doing!";
    if (input.isQuestion) return "Sure.";
    if (input.isUppercase) return "Whoa, chill out!";
    if (input.isNothing) return "Fine. Be that way!";
    return "Whatever.";
  }
}

extension on String {
  bool get isQuestion => this.trim().endsWith('?');
  bool get isUppercase =>
      this == this.toUpperCase() && this != this.toLowerCase();
  bool get isNothing => this.contains('silence') || this.trim().isEmpty;
}