public void AddDemand(Demand oneDemand, Quantity reservedQuantity)
{
if (_demands.GetDemandById(oneDemand.GetId()) != null)
{
throw new MrpRunException("You cannot add an already added demand.");
}
// if it has quantity that is not reserved, remember it for later reserving
if (oneDemand.GetType() == typeof(StockExchangeDemand) &&
reservedQuantity.IsSmallerThan(oneDemand.GetQuantity()))
{
_openDemands.Add(oneDemand.GetArticle(),
new OpenNode <Demand>(oneDemand, oneDemand.GetQuantity().Minus(reservedQuantity),
oneDemand.GetArticle()));
}
// save demand
_demands.Add(oneDemand);
}