timeLeft function
Implementation
String timeLeft(int seconds) {
int diff = seconds;
int hours = diff ~/ (60 * 60);
diff -= hours * (60 * 60);
int minutes = diff ~/ (60);
diff -= minutes * (60);
String result =
"${twoDigitNumber(hours)}:${twoDigitNumber(minutes)}:${twoDigitNumber(diff)}";
return result;
}