formatDuration function
Implementation
String formatDuration(Duration d) {
if (d.inHours > 0)
return '${d.inHours}h ${(d.inMinutes % 60).toString().padLeft(2, '0')}m';
if (d.inMinutes > 0)
return '${d.inMinutes}m ${(d.inSeconds % 60).toString().padLeft(2, '0')}s';
return '${d.inSeconds}s';
}