CreateOrderCommandHandler.cs

using System.Linq;

namespace Microsoft.eShopOnContainers.Services.Ordering.API.Application.Commands
{
    using Domain.AggregatesModel.OrderAggregate;
    using global::Ordering.API.Application.IntegrationEvents;
    using global::Ordering.API.Application.IntegrationEvents.Events;
    using MediatR;
    using Microsoft.eShopOnContainers.Services.Ordering.API.Infrastructure.Services;
    using Microsoft.eShopOnContainers.Services.Ordering.Infrastructure.Idempotency;
    using Microsoft.Extensions.Logging;
    using System;
    using System.Threading;
    using System.Threading.Tasks;

    // Regular CommandHandler
    public class CreateOrderCommandHandler
        : IRequestHandler<CreateOrderCommand, bool>
    {
        private readonly IOrderRepository _orderRepository;
        private readonly IIdentityService _identityService;
        private readonly IMediator _mediator;
        private readonly IOrderingIntegrationEventService _orderingIntegrationEventService;
        private readonly ILogger<CreateOrderCommandHandler> _logger;

        // Using DI to inject infrastructure persistence Repositories
        public CreateOrderCommandHandler(IMediator mediator,
            IOrderingIntegrationEventService orderingIntegrationEventService,
            IOrderRepository orderRepository,
            IIdentityService identityService,
            ILogger<CreateOrderCommandHandler> logger)
        {
            _orderRepository = orderRepository ?? throw new ArgumentNullException(nameof(orderRepository));
            _identityService = identityService ?? throw new ArgumentNullException(nameof(identityService));
            _mediator = mediator ?? throw new ArgumentNullException(nameof(mediator));
            _orderingIntegrationEventService = orderingIntegrationEventService ?? throw new ArgumentNullException(nameof(orderingIntegrationEventService));
            _logger = logger ?? throw new ArgumentNullException(nameof(logger));
        }

        public async Task<bool> Handle(CreateOrderCommand message, CancellationToken cancellationToken)
        {
            // Add Integration event to clean the basket
            var orderStartedIntegrationEvent = new OrderStartedIntegrationEvent(message.UserId);
            await _orderingIntegrationEventService.AddAndSaveEventAsync(orderStartedIntegrationEvent);

            // Add/Update the Buyer AggregateRoot
            // DDD patterns comment: Add child entities and value-objects through the Order Aggregate-Root
            // methods and constructor so validations, invariants and business logic 
            // make sure that consistency is preserved across the whole aggregate
            var address = new Address(message.Street, message.City, message.State, message.Country, message.ZipCode);
            var orderItems = message.OrderItems.Select(item => new OrderItem(item.ProductId, item.ProductName,
                item.UnitPrice, item.Discount, item.PictureUrl, item.Units));

            var order = new Order(
                message.UserId,
                message.UserName,
                address,
                message.CardTypeId,
                message.CardNumber,
                message.CardSecurityNumber,
                message.CardHolderName,
                message.CardExpiration,
                orderItems.ToList());

            _logger.LogInformation("----- Creating Order - Order: {@Order}", order);

            _orderRepository.Add(order);

            return await _orderRepository.UnitOfWork
                .SaveEntitiesAsync(cancellationToken);
        }
    }


    // Use for Idempotency in Command process
    public class CreateOrderIdentifiedCommandHandler : IdentifiedCommandHandler<CreateOrderCommand, bool>
    {
        public CreateOrderIdentifiedCommandHandler(
            IMediator mediator,
            IRequestManager requestManager,
            ILogger<IdentifiedCommandHandler<CreateOrderCommand, bool>> logger)
            : base(mediator, requestManager, logger)
        {
        }

        protected override bool CreateResultForDuplicateRequest()
        {
            return true;                // Ignore duplicate requests for creating order.
        }
    }
}