durationToString function

String durationToString(Map<String, Object?> duration)

Converts a google.protobuf.Duration to its canonical string form.

A Duration contains "seconds" (int64) and optional "nanos" (int32, same sign as seconds or zero, absolute value in [0, 999999999]).

Output: "1.000340012s", "-0.500s", "0s". Negative durations have a leading - and both seconds and nanos share the sign.

Implementation

String durationToString(Map<String, Object?> duration) {
  final seconds = _toInt(duration['seconds'] ?? 0);
  final nanos = _toInt(duration['nanos'] ?? 0);

  if (nanos == 0) {
    return '${seconds}s';
  }

  // Determine sign: the canonical form has a single leading '-' when the
  // overall duration is negative.
  final negative = seconds < 0 || (seconds == 0 && nanos < 0);
  final absSeconds = seconds.abs();
  final absNanos = nanos.abs();

  final nanoStr = absNanos.toString().padLeft(9, '0');
  // Trim trailing zeros.
  String fractional = nanoStr;
  while (fractional.length > 1 && fractional.endsWith('0')) {
    fractional = fractional.substring(0, fractional.length - 1);
  }

  final sign = negative ? '-' : '';
  return '$sign$absSeconds.${fractional}s';
}