parseSteganographyKey function

Uint8List parseSteganographyKey(String value)

Parses a 32-byte steganography key from hex, a key file, or a 32-char UTF-8 string.

Implementation

Uint8List parseSteganographyKey(String value) {
  final trimmed = value.trim();
  if (trimmed.isEmpty) {
    throw ArgumentError('Key must not be empty');
  }

  if (_looksLikeHexKey(trimmed)) {
    return _decodeHexKey(trimmed);
  }

  final file = File(trimmed);
  if (file.existsSync()) {
    final bytes = file.readAsBytesSync();
    if (bytes.length != 32) {
      throw ArgumentError(
        'Key file must contain exactly 32 bytes, got ${bytes.length}',
      );
    }
    return Uint8List.fromList(bytes);
  }

  final utf8Key = utf8.encode(trimmed);
  if (utf8Key.length == 32) {
    return Uint8List.fromList(utf8Key);
  }

  throw ArgumentError(
    'Key must be 64 hex characters, a path to a 32-byte file, '
    'or a UTF-8 string of exactly 32 characters',
  );
}