# On-Premises Showcase


This sample implements a fictional e-commerce store. It is different from most samples in that it shows many features of NServiceBus working together.

This variant of the showcase uses the [learning transport](/transports/learning/index.md) and [learning persistence](/persistence/learning/index.md) to have the least friction for running the sample.

## Walk-through

Users can order products from the website. Once orders are submitted, there is a window of time allocated for handling cancellations due to buyer's remorse. Once the order has been accepted, it is provisioned and made available for download. 


### Sales

The web application hosts the **ECommerce** endpoint. When a user presses <kbd>Place Order</kbd> on the website, the **ECommerce** endpoint sends a `SubmitOrder` command to the Sales endpoint. Upon receiving a `SubmitOrder` command the **Sales** endpoint will immediately publish an `OrderPlaced` event with a request to be called back in 20 seconds (`BuyersRemorseIsOver`). If the user does not cancel the order before the end of the buyer's remorse period, the **Sales** endpoint will publish an `OrderAccepted` event.

The **ECommerce** endpoint subscribes to the `OrderPlaced` and `OrderAccepted` events in order to update the web page. It does this by forwarding events to the client using SignalR.

```mermaid
graph LR

  subgraph Sales
    web(ECommerce)
    sales(Sales)
    web --> SubmitOrder 
    sales --> BuyersRemorseIsOver["fa:fa-bell-o BuyersRemorseIsOver"]
    BuyersRemorseIsOver --> sales
  SubmitOrder --> sales
  end
    
  sales -.-> OrderPlaced
  OrderPlaced -.-> web

  sales -.-> OrderAccepted
  OrderAccepted -.-> web  
  
  classDef message fill:#ffe4c2;
  classDef event fill:#ffe4c2,stroke-dasharray: 2,2;

  class SubmitOrder,BuyersRemorseIsOver message;
  class OrderPlaced,OrderAccepted event;
```

If the user presses <kbd>Cancel</kbd> before the buyer's remorse period ends, the **ECommerce** endpoint sends a `CancelOrder` command to the **Sales** endpoint which publishes an `OrderCancelled` event instead of an `OrderAccepted` event. The **ECommerce** endpoint subscribes to `OrderCancelled` and updates the UI via SignalR to mark the order as cancelled.

```mermaid
graph LR

  subgraph Sales
    web(ECommerce)
    sales(Sales)
    web --> SubmitOrder 
    web --> CancelOrder
    sales --> BuyersRemorseIsOver["fa:fa-bell-o BuyersRemorseIsOver"]
    BuyersRemorseIsOver --> sales
    SubmitOrder --> sales
    CancelOrder --> sales
  end
    
  sales -.-> OrderPlaced
  OrderPlaced -.-> web

  sales -.-> OrderCancelled
  OrderCancelled -.-> web  
  
  classDef message fill:#ffe4c2;
  classDef event fill:#ffe4c2,stroke-dasharray: 2,2;

  class SubmitOrder,BuyersRemorseIsOver message;
  class OrderPlaced,OrderCancelled event;
```


### Provisioning

Once an order is accepted, it can be provisioned. The **ContentManagement** endpoint subscribes to the `OrderAccepted` event and sends a `ProvisionDownloadRequest` message to the **Operations** endpoint. When **Operations** handles `ProvisionDownloadRequest` it responds with a `ProvisionDownloadResponse` message. When the response is received by **ContentManagement** it publishes a `DownloadIsReady` event. The **ECommerce** endpoint subscribes to `DownloadIsReady` to update the UI via SignalR.

```mermaid
graph LR

  subgraph Sales
    web(ECommerce)
    sales(Sales)
  end
    
  sales -.-> OrderAccepted
  OrderAccepted -.-> web  

  subgraph Provisioning
    contentManagement(ContentManagement)
    operations(Operations)
    contentManagement --> ProvisionDownloadRequest
    ProvisionDownloadRequest --> operations
    operations --> ProvisionDownloadResponse
    ProvisionDownloadResponse --> contentManagement
  end

  OrderAccepted -.-> contentManagement

  contentManagement -.-> DownloadIsReady
  DownloadIsReady -.-> web

  classDef message fill:#ffe4c2;
  classDef event fill:#ffe4c2,stroke-dasharray: 2,2;

  class ProvisionDownloadRequest,ProvisionDownloadResponse message;
  class OrderAccepted,DownloadIsReady event;
```


### CustomerRelations

The **CustomerRelations** endpoint subscribes to `OrderAccepted` events. When a customer order is accepted, the **CustomerRelations** endpoint publishes a `ClientBecamePreferred` event. This event has only one subscriber, **CustomerRelations** itself, which will send the customer a welcome pack and a limited time offer when a customer becomes preferred.

```mermaid
graph LR

  subgraph Sales
    sales(Sales)
  end

  sales -.-> OrderAccepted
  OrderAccepted -.-> customerRelations

  subgraph Customer Relations
    customerRelations(CustomerRelations)
  end

  customerRelations -.-> ClientBecamePreferred
  ClientBecamePreferred -.-> customerRelations

  classDef event fill:#ffe4c2,stroke-dasharray: 2,2;

  class OrderAccepted,ClientBecamePreferred event;
```



## Feature usage

In implementing the above workflow various aspects are highlighted:



### Sagas

Illustrates the use of the saga pattern to handle the buyer's remorse scenario.


### Request / response

The request/response pattern is illustrated for the product provisioning between the **ContentManagement** endpoint and the **Operations** endpoint.


### ASP MVC and SignalR

The **ecommerce** endpoint is implemented as an ASP.NET application which uses [SignalR](https://learn.microsoft.com/en-us/aspnet/signalr/overview/getting-started/introduction-to-signalr) to show feedback to the user.


### Message mutator

The use of message headers and message mutator is illustrated when the user clicks on the checkbox on the **ECommerce** web page, which stops at the predefined breakpoints in the message handler code on the endpoints.


### Encryption

The use of encryption is illustrated by passing in the credit card number and the expiration date from the website. The [UnobtrusiveConventions](/nservicebus/messaging/conventions.md) defined in the **ECommerce** endpoint show how to treat certain properties as encrypted. Both the **ECommerce** and the **Sales** endpoint use [Rijndael encryption](/nservicebus/security/property-encryption.md) and the encryption key is provided in the config file. If the messages are inspected in the queue, both the credit card number and the expiration date will show the encrypted values.