components/LiteCharms.Features.MidrandBooks/Payments/Events/Handlers/PayfastPaymentConfirmationReceivedEventHandler.cs

using LiteCharms.Features.Hasher;
using LiteCharms.Features.MidrandBooks.Orders;

namespace LiteCharms.Features.MidrandBooks.Payments.Events.Handlers;

public sealed class PayfastPaymentConfirmationReceivedEventHandler(PaymentService paymentService,
    HashService hashService, OrderService orderService, ILogger<PayfastPaymentConfirmationReceivedEvent> logger) : 
    INotificationHandler<PayfastPaymentConfirmationReceivedEvent>
{
    public async ValueTask Handle(PayfastPaymentConfirmationReceivedEvent notification, CancellationToken cancellationToken)
    {
        var hashResult = hashService.DecodeLongIdHash(notification.Payload?.MPaymentId!);
        if (hashResult.IsFailed)
        {
            logger.LogError("Failed to decode payment ID hash: {Hash}. Errors: {Errors}", notification.Payload?.MPaymentId, string.Join(", ", hashResult.Errors.Select(e => e.Message)));
            throw new Exception($"Failed to decode payment ID hash: {notification.Payload?.MPaymentId}.");
        }

        var orderResult = await orderService.GetOrderAsync(hashResult.Value, cancellationToken);
        if (orderResult.IsFailed)
        {
            logger.LogError("Failed to retrieve order for payment ID: {PaymentId}. Errors: {Errors}", notification.Payload?.MPaymentId, string.Join(", ", orderResult.Errors.Select(e => e.Message)));
            throw new Exception($"Failed to retrieve order for payment ID: {notification.Payload?.MPaymentId}.");
        }

        var paymentResult = await paymentService.GetOrderPaymentAsync(orderResult.Value.CustomerId, cancellationToken);
        if (paymentResult.IsFailed)
        {
            logger.LogError("Failed to retrieve payment for order ID: {OrderId}. Errors: {Errors}", orderResult.Value.Id, string.Join(", ", paymentResult.Errors.Select(e => e.Message)));
            throw new Exception($"Failed to retrieve payment for order ID: {orderResult.Value.Id}.");
        }

        var isAlreadyProcessed = await paymentService.HasLedgerEntryAsync(orderResult.Value.Id, paymentResult.Value.Id, 1, cancellationToken);

        if (isAlreadyProcessed.IsFailed)
        {
            logger.LogError("Failed to check existing ledger entry for order ID: {OrderId} and payment ID: {PaymentId}. Errors: {Errors}", orderResult.Value.Id, paymentResult.Value.Id, string.Join(", ", isAlreadyProcessed.Errors.Select(e => e.Message)));
            throw new Exception($"Failed to check existing ledger entry for order ID: {orderResult.Value.Id} and payment ID: {paymentResult.Value.Id}.");
        }

        if (isAlreadyProcessed.Value)
        {
            logger.LogInformation("Payment confirmation for payment ID: {PaymentId} has already been processed. Skipping.", notification.Payload?.MPaymentId);
            return;
        }

        var ledgerResult = await paymentService.WriteLedgerEntryAsync(new Models.CreateLedgerEntry
        {
            CustomerId = orderResult.Value.CustomerId,
            OrderId = orderResult.Value.Id,
            PaymentId = paymentResult.Value.Id,
            Status = LedgerStatuses.Received,
            PaymentGatewayId = 1,
            PaymentGatewayReference = notification.CorrelationId,
        }, cancellationToken);

        if (ledgerResult.IsFailed)
        {
            logger.LogError("Failed to write ledger entry for payment ID: {PaymentId}. Errors: {Errors}", notification.Payload?.MPaymentId, string.Join(", ", ledgerResult.Errors.Select(e => e.Message)));
            throw new Exception($"Failed to write ledger entry for payment ID: {notification.Payload?.MPaymentId}.");   
        }

        var paymentCompletedResult = await paymentService.CompletePaymentAsync(paymentResult.Value.Id, PaymentStatuses.Paid, cancellationToken);
        if (paymentCompletedResult.IsFailed)
        {
            logger.LogError("Failed to complete payment for order ID: {OrderId}. Errors: {Errors}", orderResult.Value.Id, string.Join(", ", paymentCompletedResult.Errors.Select(e => e.Message)));
            throw new Exception($"Failed to complete payment for order ID: {orderResult.Value.Id}.");
        }

        var orderCompletedResult = await orderService.UpdateOrderStatusAsync(orderResult.Value.Id, OrderStatus.Completed, cancellationToken);
        if (orderCompletedResult.IsFailed)
        {
            logger.LogError("Failed to update order status to Completed for order ID: {OrderId}. Errors: {Errors}", orderResult.Value.Id, string.Join(", ", orderCompletedResult.Errors.Select(e => e.Message)));
            throw new Exception($"Failed to update order status to Completed for order ID: {orderResult.Value.Id}.");
        }

        logger.LogInformation("Received Payfast payment confirmation for payment ID: {PaymentId}", notification.Payload?.MPaymentId);

        // TODO: Publish MediatR notifications or queue downstream Quartz jobs (Discord, Shipping, Customer Email, Royalties)
    }
}