/// <summary>
        /// Does the actual work of refunding a payment
        /// </summary>
        /// <param name="invoice">The <see cref="IInvoice"/></param>
        /// <param name="payment">The previously Authorize payment to be captured</param>
        /// <param name="amount">The amount to be refunded</param>
        /// <param name="args">Any arguments required to process the payment.</param>
        /// <returns>The <see cref="IPaymentResult"/></returns>
        protected override IPaymentResult PerformRefundPayment(IInvoice invoice, IPayment payment, decimal amount, ProcessorArgumentCollection args)
        {
            var result = _processor.RefundPayment(invoice, payment, amount);

            if (!result.Payment.Success)
            {
                GatewayProviderService.ApplyPaymentToInvoice(payment.Key, invoice.Key, AppliedPaymentType.Denied,
                                                             result.Payment.Exception.Message, 0);
                return(result);
            }

            // use the overloaded AppliedPayments method here for testing if we don't have
            // a MerchelloContext
            foreach (var applied in payment.AppliedPayments(GatewayProviderService))
            {
                applied.TransactionType = AppliedPaymentType.Refund;
                applied.Amount          = 0;
                applied.Description    += " - Refunded";
                GatewayProviderService.Save(applied);
            }

            payment.Amount = payment.Amount - amount;

            if (payment.Amount != 0)
            {
                GatewayProviderService.ApplyPaymentToInvoice(payment.Key, invoice.Key, AppliedPaymentType.Debit,
                                                             "To show partial payment remaining after refund", payment.Amount);
            }

            GatewayProviderService.Save(payment);

            return(new PaymentResult(Attempt <IPayment> .Succeed(payment), invoice, false));
        }