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.')

src/pretix/control/templates/pretixcontrol/event/invoicing.html

@@ -19,6 +19,9 @@
             {% bootstrap_field form.invoice_footer_text layout="horizontal" %}
         </fieldset>
         <div class="form-group submit-group">
+            <button type="submit" class="btn btn-default btn-lg" name="preview" value="preview" formtarget="_blank">
+                {% trans "Save and show preview" %}
+            </button>
             <button type="submit" class="btn btn-primary btn-save">
                 {% trans "Save" %}
             </button>

src/pretix/control/urls.py

@@ -44,6 +44,7 @@ urlpatterns = [
         url(r'^settings/tickets$', event.TicketSettings.as_view(), name='event.settings.tickets'),
         url(r'^settings/email$', event.MailSettings.as_view(), name='event.settings.mail'),
         url(r'^settings/invoice$', event.InvoiceSettings.as_view(), name='event.settings.invoice'),
+        url(r'^settings/invoice/preview$', event.InvoicePreview.as_view(), name='event.settings.invoice.preview'),
         url(r'^settings/display', event.DisplaySettings.as_view(), name='event.settings.display'),
         url(r'^items/$', item.ItemList.as_view(), name='event.items'),
         url(r'^items/add$', item.ItemCreate.as_view(), name='event.items.add'),

src/pretix/control/views/event.py

@@ -6,17 +6,19 @@ from django.core.files import File
 from django.core.urlresolvers import reverse
 from django.db import transaction
 from django.forms import modelformset_factory
+from django.http import HttpResponse
 from django.shortcuts import redirect
 from django.utils.functional import cached_property
 from django.utils.translation import ugettext_lazy as _
 from django.views.generic import FormView
-from django.views.generic.base import TemplateView
+from django.views.generic.base import TemplateView, View
 from django.views.generic.detail import SingleObjectMixin
 
 from pretix.base.forms import I18nModelForm
 from pretix.base.models import (
     Event, EventPermission, Item, ItemVariation, User,
 )
+from pretix.base.services.invoices import build_preview_invoice_pdf
 from pretix.base.signals import (
     register_payment_providers, register_ticket_outputs,
 )
@@ -273,12 +275,27 @@ class InvoiceSettings(EventSettingsFormView):
     permission = 'can_change_settings'
 
     def get_success_url(self) -> str:
+        if 'preview' in self.request.POST:
+            return reverse('control:event.settings.invoice.preview', kwargs={
+                'organizer': self.request.event.organizer.slug,
+                'event': self.request.event.slug
+            })
         return reverse('control:event.settings.invoice', kwargs={
             'organizer': self.request.event.organizer.slug,
             'event': self.request.event.slug
         })
 
 
+class InvoicePreview(EventPermissionRequiredMixin, View):
+    permission = 'can_change_settings'
+
+    def get(self, request, *args, **kwargs):
+        pdf = build_preview_invoice_pdf(request.event)
+        resp = HttpResponse(pdf, content_type='application/pdf')
+        resp['Content-Disposition'] = 'attachment; filename="invoice-preview.pdf"'
+        return resp
+
+
 class DisplaySettings(EventSettingsFormView):
     model = Event
     form_class = DisplaySettingsForm