String rot13(String text) {
    var result = new StringBuilder();

    for (var character : text.toCharArray()) {
        if (character >= 'a' && character <= 'z')
            character = (char) ('a' + (character - 'a' + 13) % 26);
        else if (character >= 'A' && character <= 'Z')
            character = (char) ('A' + (character - 'A' + 13) % 26);

        result.append(character);
    }

    return result.toString();
}

void main() throws Exception {
    FileMessageBoard.watch("rot13/inbox", message -> {
        if (!message.type().equals("TEXT"))
            return;

        try {
            FileMessageBoard.publish(
                "rot13/outbox",
                new Message("TEXT", rot13(message.value()))
            );
        } catch (IOException exception) {
            throw new UncheckedIOException(exception);
        }
    });
}