From 5e6b99120c38cd14a707c6d839a17630f5829fea Mon Sep 17 00:00:00 2001
From: Raphael Michel <michel@rami.io>
Date: Fri, 31 Jan 2025 19:27:23 +0100
Subject: [PATCH 1/2] Allow setting due amount according to current payments

---
 pretix_zugferd/invoice.py | 14 ++++++++++++++
 tests/conftest.py         |  2 +-
 tests/results/paid.xml    |  3 ++-
 3 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/pretix_zugferd/invoice.py b/pretix_zugferd/invoice.py
index 0b9e541..fe90e64 100644
--- a/pretix_zugferd/invoice.py
+++ b/pretix_zugferd/invoice.py
@@ -19,6 +19,7 @@
 from drafthorse.models.tradelines import LineItem
 from drafthorse.pdf import attach_xml
 from pretix.base.invoice import ClassicInvoiceRenderer, Modern1Renderer
+from pretix.base.models import Order
 from pretix.base.models.tax import EU_COUNTRIES
 from reportlab.lib.units import mm
 from reportlab.pdfgen.canvas import Canvas
@@ -370,6 +371,19 @@ def _zugferd_generate_document(self, invoice):
         doc.trade.settlement.monetary_summation.tax_total = (taxtotal, cc)
         doc.trade.settlement.monetary_summation.grand_total = total
         doc.trade.settlement.monetary_summation.due_amount = total
+
+        if not self.invoice.is_cancellation:
+            payment_refund_sum = self.invoice.order.payment_refund_sum
+            if payment_refund_sum and (
+                self.invoice.event.settings.invoice_show_payments
+                or self.invoice.order.status == Order.STATUS_PAID
+            ):
+                doc.trade.settlement.monetary_summation.prepaid_total = (
+                    payment_refund_sum
+                )
+                doc.trade.settlement.monetary_summation.due_amount = (
+                    total - payment_refund_sum
+                )
         return doc
 
     def _on_first_page(self, canvas: Canvas, doc):
diff --git a/tests/conftest.py b/tests/conftest.py
index 788bbc6..accb9d3 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -87,7 +87,7 @@ def order(event, organizer, item):
         sales_channel=event.organizer.sales_channels.get(identifier="web"),
         datetime=datetime(2024, 12, 1, 10, 0, 0, tzinfo=UTC),
         expires=datetime(2024, 12, 10, 10, 0, 0, tzinfo=UTC),
-        total=Decimal("100.00"),
+        total=Decimal("23.00"),
         locale="en",
     )
     OrderPosition.objects.create(
diff --git a/tests/results/paid.xml b/tests/results/paid.xml
index 26aa85b..6d8ce5f 100644
--- a/tests/results/paid.xml
+++ b/tests/results/paid.xml
@@ -139,7 +139,8 @@ Attendee: Peter</ram:Description>
                 <ram:TaxBasisTotalAmount>19.33</ram:TaxBasisTotalAmount>
                 <ram:TaxTotalAmount currencyID="EUR">3.67</ram:TaxTotalAmount>
                 <ram:GrandTotalAmount>23.00</ram:GrandTotalAmount>
-                <ram:DuePayableAmount>23.00</ram:DuePayableAmount>
+                <ram:TotalPrepaidAmount>23.00</ram:TotalPrepaidAmount>
+                <ram:DuePayableAmount>0.00</ram:DuePayableAmount>
             </ram:SpecifiedTradeSettlementHeaderMonetarySummation>
         </ram:ApplicableHeaderTradeSettlement>
     </rsm:SupplyChainTradeTransaction>

From 448121daef2f27218698a6862ede3d1f3d8861f6 Mon Sep 17 00:00:00 2001
From: Raphael Michel <michel@rami.io>
Date: Thu, 6 Feb 2025 16:44:12 +0100
Subject: [PATCH 2/2] No negative amounts

---
 pretix_zugferd/invoice.py | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/pretix_zugferd/invoice.py b/pretix_zugferd/invoice.py
index fe90e64..369a54d 100644
--- a/pretix_zugferd/invoice.py
+++ b/pretix_zugferd/invoice.py
@@ -378,11 +378,11 @@ def _zugferd_generate_document(self, invoice):
                 self.invoice.event.settings.invoice_show_payments
                 or self.invoice.order.status == Order.STATUS_PAID
             ):
-                doc.trade.settlement.monetary_summation.prepaid_total = (
-                    payment_refund_sum
+                doc.trade.settlement.monetary_summation.prepaid_total = min(
+                    payment_refund_sum, total
                 )
-                doc.trade.settlement.monetary_summation.due_amount = (
-                    total - payment_refund_sum
+                doc.trade.settlement.monetary_summation.due_amount = min(
+                    total - payment_refund_sum, Decimal("0.00")
                 )
         return doc