midrandbooks-api/MidrandBooksApi/Payments/Endpoints/ConfirmationEndpoint.cs

using LiteCharms.Features.Extensions;
using LiteCharms.Features.Hasher;
using LiteCharms.Features.Models;

namespace MidrandBooksApi.Payments.Endpoints;

[ApiVersionTarget(1)]
public sealed class ConfirmationEndpoint : IEndpoint
{
    public void Map(IEndpointRouteBuilder builder)
    {
        builder.MapPost("payments/confirm", async (HttpRequest request, HashService hashService,
            CancellationToken cancellationToken) =>
        {
            var formCollection = await request.ReadFormAsync(cancellationToken);

            if (!formCollection.TryGetValue("signature", out var signatureValues) || string.IsNullOrWhiteSpace(signatureValues.ToString())) 
                return Results.BadRequest("Missing Payfast validation signature.");

            string incomingSignature = signatureValues.ToString();

            var payload = new PayfastWebhookPayload
            {
                Amount = formCollection.TryGetValue("amount", out var amountValues) ? amountValues.ToString() : null,
                ItemName = formCollection.TryGetValue("item_name", out var itemValues) ? itemValues.ToString() : null,
                MPaymentId = formCollection.TryGetValue("m_payment_id", out var paymentIdValues) ? paymentIdValues.ToString() : null
            };

            var validationResult = hashService.VerifyPayfastWebhookSignature(payload, incomingSignature);

            return validationResult.IsFailed || !validationResult.Value
                ? Results.Unauthorized()
                : Results.Ok();
        })
        .WithDescription("Securely confirm and process an incoming Payfast merchant payment callback.")
        .WithName(typeof(ConfirmationEndpoint).ToEndpointName())
        .MapToApiVersion(new ApiVersion(1))
        .Produces(StatusCodes.Status200OK)
        .Produces(StatusCodes.Status400BadRequest)
        .Produces(StatusCodes.Status401Unauthorized)
        .WithTags(EndpointTags.Payments);
    }
}