7.2 PlaceOrder becomes a mutation

[TraxMutation] puts a train in the schema as a mutation. GraphQLOperation.Run says the mutation runs the train and answers with its output, as POST /orders did; the other operation, queueing, comes with the worker later in the book. [TraxRunProgress] lets whoever started a run follow it.

Trains/PlaceOrder/PlaceOrderTrain.cs:

using Shopfront.Auth;
using Shopfront.Fraud;
using Shopfront.Trains.PlaceOrder.Junctions;
using Trax.Core.Functional;
using Trax.Effect.Attributes;
using Trax.Effect.Services.ServiceTrain;
 
namespace Shopfront.Trains.PlaceOrder;
 
[TraxMutation(GraphQLOperation.Run)]
[TraxAuthorize(Roles = Roles.Customer)]
[TraxRunProgress]
public class PlaceOrderTrain : ServiceTrain<PlaceOrderInput, PlaceOrderOutput>, IPlaceOrderTrain
{
    protected override Task<Either<Exception, PlaceOrderOutput>> Junctions() =>
        Chain<IdentifyCustomerJunction>()
            .Chain<PriceCartJunction>()
            .Chain<AssessRiskJunction>()
            .Gate<OrderRisk, LooksFraudulent>(gate =>
                gate.Yes(hold => hold.Chain<RefuseOrderJunction>())
                    .No(take => take)
                    .Shadow<ICandidateFraudDecider>()
                    .WaitForShadows(TimeSpan.FromSeconds(1))
            )
            .Chain<ReserveStockJunction>()
            .Chain<TakePaymentJunction>()
            .Chain<ConfirmOrderJunction>()
            .Resolve();
}

The field's name comes from the interface: IPlaceOrderTrain without its I and Train is placeOrder. Its argument is the train's input, PlaceOrderInput, which has no customer in it, so the schema has none either: there is nothing a caller could send to order as someone else.

SDK Reference

AddTraxGraphQL | TraxMutation | Query models | Run progress | AddJunctionEvents | dispatch mutations

Next: 7.3 The catalogue and the orders become queries