Overview

The CompleteOrderCommand is an integration event published by the Finance service when an order transitions to the Completed state. This command is part of the order processing saga and is used to notify other services about order completion, particularly for sending confirmation notifications to customers.

Architecture

Message Structure

The command contains the following properties:

Workflow Context

This command is published by the Order State Machine when the following conditions are met:

1. The order is in the Placed state
2. An OrderStatusChangedToCompleteIntegrationEvent is received
3. The order transitions to the Completed state
4. The customer’s email is available (not null)

Technical Implementation

The CompleteOrderCommand is implemented as follows:

[AsyncApi]
[Channel("notification-complete-order")]
[SubscribeOperation(
    typeof(CompleteOrderCommand),
    OperationId = nameof(CompleteOrderCommand),
    Summary = "Complete order notification"
)]
public sealed record CompleteOrderCommand(Guid OrderId, string? Email, decimal TotalMoney)
    : IntegrationEvent;

Within the Order State Machine, the command is published during the state transition:

When(OrderCompleted)
    .Then(context =>
    {
        context.Saga.OrderId = context.Message.OrderId;
        context.Saga.BasketId = context.Message.BasketId;
        context.Saga.Email = context.Message.Email;
        context.Saga.TotalMoney = context.Message.TotalMoney;

      logger.LogInformation(
          "[{Event}] Order completed for {OrderId}",
          nameof(OrderCompleted),
          context.Message.OrderId
      );
  })
  .TransitionTo(Completed)
  .If(
      context => context.Saga.Email is not null,
      x =>
          x.Publish(context => new CompleteOrderCommand(
              context.Saga.OrderId,
              context.Saga.Email,
              context.Saga.TotalMoney.GetValueOrDefault(0.0M)
          ))
  )

Consuming Services

This command is typically consumed by:

• Notification Service: To send order completion emails to customers
• Ordering Service: To update the order status in the database