if self.invoice.cart is not None:

            cart = CartController(self.invoice.cart)

            cart.validate_cart()  # Raises ValidationError if invalid

        ''' Adds a payment '''

        payment = rego.Payment.objects.create(

            invoice=self.invoice,

            reference=reference,

            amount=amount,

        )

        payment.save()

        agg = payments.aggregate(Sum("amount"))

        total = agg["amount__sum"]

        if total == self.invoice.value:

            self.invoice.paid = True

            cart = self.invoice.cart

            cart.active = False

            cart.save()

            self.invoice.save()

      <td>{{line_item.price}}</td>

      <td><!-- multiply --> FIXME</td>

    </tr>

  {% endfor %}

  <tr>

    <th>TOTAL</th>

    <td></td>

    <td></td>

    <td>{{ invoice.value }}</td>

  </tr>

</table>

{% endblock %}

    return render(request, "invoice.html", data)

@login_required

def pay_invoice(request, invoice_id):

    ''' Marks the invoice with the given invoice id as paid.

    WORK IN PROGRESS FUNCTION. Must be replaced with real payment workflow.

    '''

    invoice_id = int(invoice_id)

    inv = rego.Invoice.objects.get(pk=invoice_id)

    current_invoice = InvoiceController(inv)

        current_invoice.pay("Demo invoice payment", inv.value)

    return redirect("invoice", current_invoice.invoice.id)