public class CheckoutProcessor : ICheckoutProcessor

{

    public BlockingCollection<CheckoutItem> CheckoutQueue { get; }

​

    public CheckoutProcessor()

    {

        CheckoutQueue = new BlockingCollection<CheckoutItem>(new ConcurrentQueue<CheckoutItem>());

    }

​

    public Task<CheckoutResponse> ProcessCheckoutAsync(CheckoutRequest request)

    {

        var response = new CheckoutResponse

        {

            OrderId = Guid.NewGuid(),

            OrderStatus = OrderStatus.Inprogress,

            Message = "Your order is in progress," 

                         + "you will receive an email with all details."

        };

​

        var item = new CheckoutItem

        {

           OrderId = response.OrderId,

           Request = request

        };

​

        CheckoutQueue.Add(item);

​

        return Task.FromResult(response);

    }

}