public DiscountApplicationResult AddVoucher(IMayApplyDiscount voucher)
{
var applicationResult = _discountValidator.CanApplyDiscount(_vouchers, voucher);
if (applicationResult.IsDiscountAllowed)
{
_vouchers.Add(voucher);
}
return(applicationResult);
}
public DiscountApplicationResult CanApplyDiscount(IEnumerable<IMayApplyDiscount> existingDiscounts, IMayApplyDiscount toAdd)
{
return IsTryingToAddAdditionalOfferVoucher(existingDiscounts, toAdd)
? DiscountApplicationResult.CreateFailed("Only a single offer voucher can be applied to a basket")
: DiscountApplicationResult.CreateSuccess();
}
private static bool IsTryingToAddAdditionalOfferVoucher(IEnumerable<IMayApplyDiscount> existingDiscounts, IMayApplyDiscount toAdd)
{
return
toAdd.GetDiscountType() == DiscountType.OfferVoucher
&& existingDiscounts.Any(discount => discount.GetDiscountType() == DiscountType.OfferVoucher);
}