quantity property

Implementation

@override
Quantity get quantity {
  var unit = standardUnit;
  if (unit is ProductUnit) unit = unit._simplifyDeep();
  if (unit == this) {
    if (_elements.isEmpty) return Quantities.dimensionless;

    // Find the quantity that has this unit as definition
    var q = Quantities.values.where(
      (q) =>
          (q.siUnit is UnitForQuantity
              ? (q.siUnit as UnitForQuantity).parent
              : q.siUnit) ==
          unit,
    );
    if (q.length == 1) return q.first;

    // Find the quantity that has the same base unit
    var b = baseUnit;
    q = Quantities.values.where((q) => q.siUnit.baseUnit == b);
    if (q.isEmpty) throw StateError('No quantity found for $b');
    if (q.length > 1) {
      throw StateError('Multiple quantities found for $b: $q');
    }
    return q.first;
  }
  return unit.quantity;
}