/// <summary>
/// Typically I'd look to handle command execution and these sorts of
/// cross-cutting concerns via a framework e.g. Mediator pipelines.
///
/// This could also include authentication/authorization. If a
/// re-usable domain is not important you could also do these cross
/// cutting concerns in the web api layer via filters etc.
/// </summary>
private async Task InitializeExecution(AddPaymentCommand command)
{
_logger.LogInformation("Executing AddPaymentCommandHandler");
if (command == null)
{
throw new ArgumentNullException(nameof(command));
}
// In this example validation is handled in the API layer first to
// provide user-friendly error messages in the response.
// It's validated again here as a back-stop; I like my command handlers
// not to assume anything, however it could be ommited depending on
// overall approach.
var validator = new AddPaymentCommandValidator();
await validator.ValidateAndThrowAsync(command);
}
public async Task <AddPaymentCommandResult> ExecuteAsync(AddPaymentCommand command)
{
await InitializeExecution(command);
// Assumption: the API would have some kind of auth that would allow us
// to know the merchant making the API call.
var merchantId = _userSessionService.GetCurrentMerchantId();
_logger.LogDebug("Adding payment for merchant {MerchantId}", merchantId);
// store the payment attempt to ensure the request is captured even
// if an exception occurs during payment e.g. the bank payment is successful
// but updating the status in the data store fails due to a network error
var paymentId = await _paymentRepository.StartPaymentAsync(merchantId, command);
// Try and register the payment with the bank
var addBankPaymentCommand = new AddBankPaymentCommand()
{
CreditCard = command.CreditCard,
MerchantId = merchantId,
PaymentId = paymentId
};
var bankPaymentResponse = await _aquiringBankService.MakePaymentAsync(addBankPaymentCommand);
// Update the payment attempt with the result
await _paymentRepository.CompletePaymentAsync(paymentId, bankPaymentResponse);
// return the result
var result = new AddPaymentCommandResult()
{
PaymentId = paymentId,
PaymentResult = bankPaymentResponse.Result
};
_logger.LogDebug("Payment completed with a result of {Result} for paymentId {PaymentId}", bankPaymentResponse.Result, paymentId);
return(result);
}