printDuration function
Implementation
String printDuration(Duration? duration) {
if (duration != null) {
String twoDigits(int n) => n.toString().padLeft(2, "0");
String twoDigitMinutes = twoDigits(duration.inMinutes.remainder(60));
String twoDigitSeconds = twoDigits(duration.inSeconds.remainder(60));
if (duration.inHours == 0) return "$twoDigitMinutes:$twoDigitSeconds";
return "${twoDigits(duration.inHours)}:$twoDigitMinutes:$twoDigitSeconds";
}
return '';
}