class Diamond {
  List<String> rows(String input) {
    List<String> result = [];

    int rows = (input.codeUnitAt(0) - 64) * 2 - 1;
    int padding = (rows / 2).floor();
    int center = 0;
    bool halfWay = false;
    int currentChar = 65;

    for (int i = 0; i < rows; i++) {
      String x = '';
      x = addPad(x, padding, halfWay);
      x += String.fromCharCode(currentChar);
      if (center > 0) {
        for (int i = 0; i < center; i++) {
          x += ' ';
        }
        x += String.fromCharCode(currentChar);
      }
      x = addPad(x, padding, halfWay);
      (halfWay) ? padding++ : padding--;
      (halfWay)
          ? (center > 0)
              ? center = center - 2
              : center--
          : (center > 0)
              ? center = center + 2
              : center++;
      (halfWay) ? currentChar-- : currentChar++;
      if (i > rows / 2 - 2) halfWay = true;
      result.add(x);
    }

    return result;
  }

  String addPad(String input, int padSize, bool halfWay) {
    for (int i = 0; i < padSize; i++) {
      input += ' ';
    }
    return input;
  }
}

void main(List<String> args) {
  print(Diamond().rows('Z'));
}