getLargestUnit method

TUnit getLargestUnit({ required Set<TUnit> permissibleUnits, })

Determines the largest unit that has a value of at least 1.

This method will determine which unit within permissibleUnits is the largest unit that has a value of at least 1. This is typically useful to determine which unit should be used to visualize a unit of measurement.

Implementation

TUnit getLargestUnit({
  required Set<TUnit> permissibleUnits,
}) {
  if (permissibleUnits.isEmpty) {
    throw ArgumentError('permissibleUnits cannot be empty');
  }

  TUnit? largestUnit;
  Rational? largestUnits;
  TUnit? smallestUnit;
  Rational? smallestUnits;

  for (final unit in permissibleUnits) {
    final units = getUnits(unit);

    // Logic is counterintuitive. If the number of units for a given unit is less than the current largest units,
    // and is more than one, that means we have at least one of those units and it is larger than the currently
    // selected unit because there are fewer of them.
    if (units >= Rationals.one &&
        (largestUnits == null || units < largestUnits)) {
      largestUnit = unit;
      largestUnits = units;
    }

    if (smallestUnits == null || units > smallestUnits) {
      smallestUnit = unit;
      smallestUnits = units;
    }
  }

  if (largestUnit != null) {
    return largestUnit;
  } else {
    // None of the units has at least a value of 1, so return the smallest unit instead.
    return smallestUnit!;
  }
}