/// <summary>
/// Calculates the total price of products before discount,
/// </summary>
/// <param name="products"></param>
/// <returns></returns>
public IEnumerable <string> Calculate(string[] products)
{
//Build the basket
var basketItems = _basketBuilder.Build(products).ToList();
//Get discounts that can be applied
var discountsApplied = _discountCalculator.GetDiscountsApplied(basketItems).ToList();
//We now have everything we need, subtract total basket value from discounts and present it to UI
var subtotal = basketItems.Sum(basket => basket.NumberOfItems * basket.PricePerItem);
yield return($"Subtotal: {subtotal.Format()}");
var discountAmount = discountsApplied.Sum(applied => applied.DiscountAmount);
if (!discountsApplied.Any())
{
yield return("(No offers available)");
}
else
{
foreach (var discountApplied in discountsApplied)
{
yield return($"{discountApplied.OfferType.DiscountDetail}: -{discountApplied.DiscountAmount.Format()}");
}
}
yield return($"Total: {(subtotal - discountAmount).Format()}");
}