private decimal TryAssignPurchase(IDemandToProvider demand, decimal amount)
{
var purchaseParts = _context.PurchaseParts.Where(a => a.State != State.Finished && a.ArticleId == demand.ArticleId).ToList();
var amountAlreadyReserved = purchaseParts.Select(a => a.DemandProviderPurchaseParts.Sum(b => b.Quantity)).Sum();
var amountReservable = purchaseParts.Select(a => a.Quantity).Sum() - amountAlreadyReserved;
if (amountReservable == 0)
{
return(amount);
}
var amountReserving = amountReservable > amount ? amount : amountReservable;
_context.CreateDemandProviderStock(demand, amountReserving);
amount -= amountReserving;
return(amount);
}