Programming Jabber

The set_status() function

The set_status() function receives the latest light value as polled from the sensor and compares it with the pivot value. If the status defined in $new_status is different from the current status (in $current_status), then the current status is updated and returned; otherwise, undef is returned:

sub set_status {
  my $val = shift;

  my $new_status = $val < $opts{'l'} ? COFFEE : NOCOFFEE;

  if ($new_status != $current_status) {
    $current_status = $new_status;
    return $current_status;
  }
  else {
    return undef;
  }
}

If this function returns a status value, a new <presence/> element is generated and emitted by the script. Otherwise, there’s no change (“the coffee’s still there,” or “there’s still no coffee!”) and nothing happens.