private decimal GetCheapestTotal(TrolleyVM trolley, List <SpecialVM> potentialSpecials, TrolleyCheckout trolleyCheckout)
{
int indexCheapest = 0;
decimal cheapest = 0;
for (int i = 0; i < potentialSpecials.Count; i++)
{
var special = potentialSpecials[i];
var checkoutForSpecial = new TrolleyCheckout(trolleyCheckout.Total);
var trolleyForSpecial = new TrolleyVM(trolley);
checkoutForSpecial.Total += special.Total;
ApplySpecial(special, trolleyForSpecial.Quantities);
// Recursive call to continue calculating with reduced items
var totalForSpecial = GetTrolleyTotal(trolleyForSpecial, checkoutForSpecial);
if (i == 0)
{
cheapest = totalForSpecial;
}
else if (totalForSpecial < cheapest)
{
indexCheapest = i;
cheapest = totalForSpecial;
}
}
// Apply the special that has cheapest end value
return(cheapest);
}
// Get total for current trolley - Recursive function
private decimal GetTrolleyTotal(TrolleyVM trolley, TrolleyCheckout trolleyCheckout)
{
// 1. Get all specials that apply to trolley.
var potentialSpecials = GetPotentialSpecials(trolley);
// 2. Calculate end cost of each potential special to get the cheapest result
if (potentialSpecials.Count > 0)
{
return(GetCheapestTotal(trolley, potentialSpecials, trolleyCheckout));
}
else
{
return(GetSingularItemsTotal(trolley, trolleyCheckout));
}
}
private decimal GetSingularItemsTotal(TrolleyVM trolley, TrolleyCheckout trolleyCheckout)
{
// finally calculate the remaining trolley items
foreach (ProductQuantityVM item in trolley.Quantities)
{
var product = trolley.Products.Find(p => p.Name == item.Name);
if (product == null)
{
throw new Exception("Item in trolley is not listed as a product");
}
trolleyCheckout.Total += item.Quantity * product.Price;
item.Quantity = 0;
}
return(trolleyCheckout.Total);
}
public decimal CalculateTrolleyTotal(TrolleyVM trolleyVM)
{
var trolleyCheckout = new TrolleyCheckout();
return(GetTrolleyTotal(trolleyVM, trolleyCheckout));
}
