getRepeatableLetter method

String getRepeatableLetter()

Gets the first uppercase letter for use as a repeatable index.

Returns the first character uppercased if it's a Latin letter (A-Z), otherwise returns the first character as-is.

Implementation

String getRepeatableLetter() {
  if (isEmpty) return '';
  final String trimmed = trim();
  if (trimmed.isEmpty) return '';
  final String first = String.fromCharCode(trimmed.runes.first);
  final String upper = first.toUpperCase();
  final int code = upper.codeUnitAt(0);
  if (code >= 65 && code <= 90) return upper;
  return first;
}