Allow to change payment term (closes #10)

src/pretix/base/models.py

@@ -1568,22 +1568,27 @@ class Order(Versionable):
         order.save()
         return order
 
-    def _can_be_paid(self):
+    def _can_be_paid(self, keep_locked=False):
         error_messages = {
-            'unavailable': _('Some of the ordered products were no longer available.'),
-            'busy': _('We were not able to process the request completely as the '
-                      'server was too busy. Please try again.'),
             'late': _("The payment is too late to be accepted."),
         }
 
         if self.event.settings.get('payment_term_last') \
                 and now() > self.event.settings.get('payment_term_last'):
-            return error_messages['late']
+            return error_messages['late'], None
         if now() < self.expires:
-            return True
+            return True, None
         if not self.event.settings.get('payment_term_accept_late'):
-            return error_messages['late']
+            return error_messages['late'], None
 
+        return self._is_still_available(keep_locked)
+
+    def _is_still_available(self, keep_locked=False):
+        error_messages = {
+            'unavailable': _('Some of the ordered products were no longer available.'),
+            'busy': _('We were not able to process the request completely as the '
+                      'server was too busy. Please try again.'),
+        }
         positions = list(self.positions.all().select_related(
             'item', 'variation'
         ).prefetch_related(
@@ -1591,6 +1596,7 @@ class Order(Versionable):
             'item__questions', 'answers'
         ))
         quotas_locked = set()
+        release = True
 
         try:
             for i, op in enumerate(positions):
@@ -1613,16 +1619,19 @@ class Order(Versionable):
                         # This quota is sold out/currently unavailable, so do not sell this at all
                         raise Quota.QuotaExceededException(error_messages['unavailable'])
         except Quota.QuotaExceededException as e:
-            return str(e)
+            return str(e), None
         except Quota.LockTimeoutException:
             # Is raised when there are too many threads asking for quota locks and we were
             # unaible to get one
-            return error_messages['busy']
+            return error_messages['busy'], None
+        else:
+            release = False
         finally:
             # Release the locks. This is important ;)
-            for quota in quotas_locked:
+            if release or not keep_locked:
-                quota.release()
+                for quota in quotas_locked:
-        return True
+                    quota.release()
+        return True, quotas_locked
 
     def mark_paid(self, provider=None, info=None, date=None, manual=None, force=False):
         """
@@ -1641,7 +1650,7 @@ class Order(Versionable):
         :type force: boolean
         :raises Quota.QuotaExceededException: if the quota is exceeded and ``force`` is ``False``
         """
-        can_be_paid = self._can_be_paid()
+        can_be_paid, quotas_locked = self._can_be_paid(keep_locked=True)
         if not force and can_be_paid is not True:
             raise Quota.QuotaExceededException(can_be_paid)
         order = self.clone()
@@ -1653,6 +1662,10 @@ class Order(Versionable):
         order.status = Order.STATUS_PAID
         order.save()
 
+        if quotas_locked:
+            for quota in quotas_locked:
+                quota.release()
+
         from pretix.base.mail import mail
         mail(
             order.user, _('Payment received for your order: %(code)s') % {'code': order.code},

src/pretix/control/templates/pretixcontrol/order/index.html

@@ -20,6 +20,9 @@
                 <div class="btn-group" role="group">
                     {% if order.status == 'n' %}
                         <button name="status" value="p" class="btn btn-default">{% trans "Mark as paid" %}</button>
+                        <a href="{% url "control:event.order.extend" event=request.event.slug organizer=request.event.organizer.slug code=order.code %}" class="btn btn-default">
+                            {% trans "Extend payment term" %}
+                        </a>
                         <a href="{% url "control:event.order.transition" event=request.event.slug organizer=request.event.organizer.slug code=order.code %}?status=c" class="btn btn-default">
                             {% trans "Cancel order" %}
                         </a>

src/pretix/control/urls.py

@@ -48,6 +48,8 @@ urlpatterns = [
         url(r'^quotas/add$', item.QuotaCreate.as_view(), name='event.items.quotas.add'),
         url(r'^orders/(?P<code>[0-9A-Z]+)/transition$', orders.OrderTransition.as_view(),
             name='event.order.transition'),
+        url(r'^orders/(?P<code>[0-9A-Z]+)/extend$', orders.OrderExtend.as_view(),
+            name='event.order.extend'),
         url(r'^orders/(?P<code>[0-9A-Z]+)/$', orders.OrderDetail.as_view(), name='event.order'),
         url(r'^orders/$', orders.OrderList.as_view(), name='event.orders'),
     ])),

src/pretix/control/views/orders.py

@@ -2,11 +2,13 @@ from itertools import groupby
 from django.contrib import messages
 from django.core.urlresolvers import reverse
 from django.db.models import Q
+from django.utils.timezone import now
 from django.utils.translation import ugettext_lazy as _
 from django.http import HttpResponse
 from django.shortcuts import redirect, render
 from django.utils.functional import cached_property
 from django.views.generic import ListView, DetailView
+from pretix.base.forms import VersionedModelForm
 
 from pretix.base.models import Order, Quota
 from pretix.base.signals import register_payment_providers
@@ -26,7 +28,7 @@ class OrderList(EventPermissionRequiredMixin, ListView):
         ).select_related("user")
 
 
-class OrderView(DetailView):
+class OrderView(EventPermissionRequiredMixin, DetailView):
     context_object_name = 'order'
     model = Order
 
@@ -49,7 +51,13 @@ class OrderView(DetailView):
                 return provider
 
 
-class OrderDetail(EventPermissionRequiredMixin, OrderView):
+class ExtendForm(VersionedModelForm):
+    class Meta:
+        model = Order
+        fields = ['expires']
+
+
+class OrderDetail(OrderView):
     template_name = 'pretixcontrol/order/index.html'
     permission = 'can_view_orders'
 
@@ -99,8 +107,8 @@ class OrderDetail(EventPermissionRequiredMixin, OrderView):
         }
 
 
-class OrderTransition(EventPermissionRequiredMixin, OrderView):
+class OrderTransition(OrderView):
-    permission = 'can_view_orders'
+    permission = 'can_change_orders'
 
     def post(self, *args, **kwargs):
         to = self.request.POST.get('status', '')
@@ -148,3 +156,51 @@ class OrderTransition(EventPermissionRequiredMixin, OrderView):
             })
         else:
             return HttpResponse(status=405)
+
+
+class OrderExtend(OrderView):
+    permission = 'can_change_orders'
+
+    def post(self, *args, **kwargs):
+        if self.order.status != Order.STATUS_PENDING:
+            messages.error(self.request, _('This action is only allowed for pending orders.'))
+            return self._redirect_back()
+        oldvalue = self.order.expires
+
+        if self.form.is_valid():
+            if oldvalue > now():
+                self.form.save()
+            else:
+                is_available, _quotas_locked = self.order._is_still_available(keep_locked=False)
+                if is_available is True:
+                    self.form.save()
+                    messages.success(self.request, _('The payment term has been changed.'))
+                else:
+                    messages.error(self.request, is_available)
+            return self._redirect_back()
+        else:
+            return self.get(*args, **kwargs)
+
+    def _redirect_back(self):
+        return redirect(reverse(
+            'control:event.order',
+            kwargs={
+                'event': self.request.event.slug,
+                'organizer': self.request.event.organizer.slug,
+                'code': self.order.code,
+            }
+        ))
+
+    def get(self, *args, **kwargs):
+        if self.order.status != Order.STATUS_PENDING:
+            messages.error(self.request, _('This action is only allowed for pending orders.'))
+            return self._redirect_back()
+        return render(self.request, 'pretixcontrol/order/extend.html', {
+            'order': self.order,
+            'form': self.form,
+        })
+
+    @cached_property
+    def form(self):
+        return ExtendForm(instance=self.order,
+                          data=self.request.POST if self.request.method == "POST" else None)