Fix #278 -- Preview for invoices

src/pretix/base/services/invoices.py

@@ -9,6 +9,7 @@ from django.contrib.staticfiles import finders
 from django.core.files.base import ContentFile
 from django.db import transaction
 from django.utils.formats import date_format
+from django.utils.timezone import now
 from django.utils.translation import pgettext, ugettext as _
 from reportlab.lib import pagesizes
 from reportlab.lib.styles import ParagraphStyle, StyleSheet1
@@ -399,3 +400,53 @@ def invoice_pdf(*args, **kwargs):
     # was committed and therefore fails to find the invoice object. The invoice_pdf_task
     # will prevent this kind of race condition.
     invoice_pdf_task.apply_async(args=args, kwargs=kwargs)
+
+
+class DummyRollbackException(Exception):
+    pass
+
+
+def build_preview_invoice_pdf(event):
+    locale = event.settings.invoice_language
+    pdf = None
+    if not locale or locale == '__user__':
+        locale = event.settings.locale
+
+    try:
+        with transaction.atomic(), language(locale):
+            order = event.orders.create(status=Order.STATUS_PENDING, datetime=now(),
+                                        expires=now(), code="PREVIEW", total=119)
+            invoice = Invoice(
+                order=order, event=event, invoice_no="PREVIEW",
+                date=date.today(), locale=locale
+            )
+            invoice.invoice_from = event.settings.get('invoice_address_from')
+
+            introductory = event.settings.get('invoice_introductory_text', as_type=LazyI18nString)
+            additional = event.settings.get('invoice_additional_text', as_type=LazyI18nString)
+            footer = event.settings.get('invoice_footer_text', as_type=LazyI18nString)
+            payment = _("A payment provider specific text might appear here.")
+
+            invoice.introductory_text = str(introductory).replace('\n', '<br />')
+            invoice.additional_text = str(additional).replace('\n', '<br />')
+            invoice.footer_text = str(footer)
+            invoice.payment_provider_text = str(payment).replace('\n', '<br />')
+            invoice.invoice_to = _("John Doe\n214th Example Street\n012345 Somecity")
+            invoice.file = None
+            invoice.save()
+            invoice.lines.all().delete()
+
+            InvoiceLine.objects.create(
+                invoice=invoice, description=_("Sample product A"),
+                gross_value=119, tax_value=19,
+                tax_rate=19
+            )
+            with tempfile.NamedTemporaryFile(suffix=".pdf") as f:
+                _invoice_generate_german(invoice, f)
+                f.seek(0)
+                pdf = f.read()
+            raise DummyRollbackException()
+    except DummyRollbackException:
+        return pdf
+    else:
+        raise Exception('Invalid state, should have rolled back.')