1.7 Run it

Program.cs:

using Shopfront.Inventory;
using Shopfront.Payments;
using Shopfront.Trains.PlaceOrder;
using Trax.Core.Exceptions;
using Trax.Effect.Data.InMemory.Extensions;
using Trax.Effect.Extensions;
using Trax.Effect.Provider.Parameter.Extensions;
using Trax.Mediator.Extensions;
 
var builder = WebApplication.CreateBuilder(args);
 
builder.Services.AddSingleton<Catalogue>();
builder.Services.AddSingleton<IPaymentProvider, FakePaymentProvider>();
 
builder.Services.AddTrax(trax =>
    trax.AddEffects(effects => effects.UseInMemory().SaveTrainParameters())
        .AddMediator(typeof(Program).Assembly)
);
 
var app = builder.Build();
 
app.MapPost(
    "/orders",
    async (PlaceOrderInput input, IPlaceOrderTrain train, CancellationToken cancellationToken) =>
    {
        try
        {
            return Results.Ok(await train.Run(input, cancellationToken));
        }
        catch (TrainException ex)
        {
            return Results.UnprocessableEntity(ex.Message);
        }
    }
);
 
app.Run();

AddMediator finds PlaceOrderTrain in the assembly and registers it under IPlaceOrderTrain. The junctions get the catalogue, the payment provider and their loggers from the container, like any other class. SaveTrainParameters keeps each run's input and output with its record, which chapter 2's tests read back.

The endpoint passes the request's CancellationToken to Run, which is where every junction's token comes from, and turns a TrainException into a 422 with its message. Anything else is a bug, and ASP.NET Core answers it with a 500.

Start it:

dotnet run --urls http://localhost:5080

In a second terminal, buy two mugs and a T-shirt:

curl -X POST http://localhost:5080/orders -H 'Content-Type: application/json' \
  -d '{"customerId":"ada","lines":[{"sku":"MUG","quantity":2},{"sku":"TEE","quantity":1}]}'

{"orderId":"dc74b072-253f-42c8-8f3c-7e7a92110932","total":49.00,"transactionId":"tx_d95607af"}

The application's log shows the four junctions in order:

info: Shopfront.Trains.PlaceOrder.Junctions.PriceCartJunction[0]
      Priced 2 lines at 49.00
info: Shopfront.Trains.PlaceOrder.Junctions.ReserveStockJunction[0]
      Reserved stock as 23978801-97ad-4259-b404-b7bb5176f27d
info: Shopfront.Trains.PlaceOrder.Junctions.TakePaymentJunction[0]
      Charged 49.00 as tx_d95607af
info: Shopfront.Trains.PlaceOrder.Junctions.ConfirmOrderJunction[0]
      Confirmed order dc74b072-253f-42c8-8f3c-7e7a92110932

Your ids will differ.

SDK Reference

Junctions | Chain | Run / RunEither | TrainException | AddTrax / AddEffects | UseInMemory | SaveTrainParameters | AddMediator

Next: 1.8 When an order fails