# Merchant side invoicing

{% hint style="info" %}
Implementation is **OPTIONAL**
{% endhint %}

### General Flow

1. Customer scans products to shopping cart.
2. Smarts will send shopping cart to merchant when customer is ready to pay for the purchase.
3. Merchant will response with generated receipt
4. Customer will pay for receipt.
5. Smarts will send receipt payment confirmation to merchant.

### Configuration

Visit your store configuration page in Smarts manager UI. Switch store side invoicing to **ON** position and implement SDK required methods.

### Implementation

You only need to create a new class, implement **`ReceiptAdapter`** interface and fill all required methods.  API endpoints for merchant side invoicing are created automatically and secured with token. 

It is important to add `@Component` annotation on top of the class. There is no restriction for class name or location in your project. Our SDK will find your implementation based on the interface (DI).

```java
import ee.smarts.common.v1.Entities.receipt.Receipt;
import ee.smarts.common.v1.requests.CreateReceiptRequest;
import ee.smarts.common.v1.requests.ReceiptPaymentConfirmationRequest;
import ee.smarts.starter.adapter.ReceiptAdapter;
import org.springframework.stereotype.Component;
@Component
public class ReceiptAdapterImpl implements ReceiptAdapter {
    @Override
    public Receipt create(CreateReceiptRequest request) {
        // implement this method
        return null;
    }
    @Override
    public void confirmationListener(ReceiptPaymentConfirmationRequest request) {
        // implement this method
    } 
}
```

{% hint style="info" %}
There is **additional step** for customer in payment process when using merchant side invoicing. Smarts shows generated receipt to customer before they are able to pay for the purchase.
{% endhint %}


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