Cart expiry handling, checkout link

src/pretix/presale/templates/pretixpresale/event/index.html

@@ -9,6 +9,24 @@
         </div>
         <div class="panel-body">
             {% include "pretixpresale/event/fragment_cart.html" with cart=cart event=request.event editable=True %}
+            <div class="row-fluid">
+                <div class="col-md-6 col-xs-12">
+                    {% if cart.minutes_left > 0 %}
+                        <em>{% blocktrans trimmed with minutes=cart.minutes_left %}
+                            The items in your cart are reserved for you for {{ minutes }} minutes.
+                        {% endblocktrans %}</em>
+                    {% else %}
+                        <em>{% trans "The items in your cart are no longer reserved for you." %}</em>
+                    {% endif %}
+                </div>
+                <div class="col-md-4 col-md-offset-2 col-xs-12">
+                    <a class="btn btn-block btn-primary btn-lg"
+                            href="{% url "presale:event.checkout.start" organizer=request.event.organizer.slug event=request.event.slug %}">
+                        <i class="fa fa-shopping-cart"></i> {% trans "Proceed with checkout" %}
+                    </a>
+                </div>
+                <div class="clearfix"></div>
+            </div>
         </div>
     </div>
     {% endif %}

src/pretix/presale/urls.py

@@ -2,6 +2,8 @@ from django.conf.urls import patterns, url, include
 
 import pretix.presale.views.event
 import pretix.presale.views.cart
+import pretix.presale.views.checkout
+
 
 urlpatterns = patterns(
     '',
@@ -11,6 +13,7 @@ urlpatterns = patterns(
             url(r'^$', pretix.presale.views.event.EventIndex.as_view(), name='event.index'),
             url(r'^cart/add$', pretix.presale.views.cart.CartAdd.as_view(), name='event.cart.add'),
             url(r'^cart/remove$', pretix.presale.views.cart.CartRemove.as_view(), name='event.cart.remove'),
+            url(r'^checkout$', pretix.presale.views.checkout.CheckoutStart.as_view(), name='event.checkout.start'),
         )
     )),
 )

src/pretix/presale/views/__init__.py

@@ -1,7 +1,9 @@
 import uuid
 from itertools import groupby
+from datetime import timedelta
 
 from django.db.models import Q
+from django.utils.timezone import now
 
 from pretix.base.models import CartPosition
 
@@ -49,6 +51,10 @@ class CartDisplayMixin(CartMixin):
         return {
             'positions': positions,
             'total': sum(p.total for p in positions),
+            'minutes_left': (
+                max(min(p.expires for p in positions) - now(), timedelta()).seconds // 60
+                if positions else 0
+            ),
         }
 
 

src/pretix/presale/views/cart.py

@@ -57,6 +57,14 @@ class CartActionMixin(CartMixin):
             return False
         return items
 
+    def _re_add_position(self, items, position):
+        for i, tup in enumerate(items):
+            if tup[0] == position.item_id and tup[1] == position.variation_id:
+                items[i] = (tup[0], tup[1], tup[2] + 1)
+                return items
+        items.append((position.item_id, position.variation_id, 1))
+        return items
+
 
 class CartRemove(EventViewMixin, CartActionMixin, View):
 
@@ -94,6 +102,25 @@ class CartAdd(EventViewMixin, CartActionMixin, View):
                            _("You cannot select more than %d items per order") % self.event.max_items_per_order)
             return redirect(self.get_failure_url())
 
+        # Extend this user's cart session to 30 minutes from now to ensure all items in the
+        # cart expire at the same time
+        qw = Q(session=self.get_session_key())
+        if self.request.user.is_authenticated():
+            qw |= Q(user=self.request.user)
+
+        # We can extend the reservation of items which are not yet expired without
+        # risk
+        CartPosition.objects.current.filter(
+            qw & Q(event=self.request.event) & Q(expires__gt=now())
+        ).update(expires=now() + timedelta(minutes=30))
+
+        # For items that are already expired, we have to delete and re-add them, as they might
+        # be no longer available. Sorry!
+        for cp in CartPosition.objects.current.filter(
+                qw & Q(event=self.request.event) & Q(expires__lte=now())):
+            items = self._re_add_position(items, cp)
+            cp.delete()
+
         # Fetch items from the database
         items_cache = {
             i.identity: i for i
@@ -110,14 +137,6 @@ class CartAdd(EventViewMixin, CartActionMixin, View):
             ).select_related("item", "item__event").prefetch_related("quotas", "values", "values__prop")
         }
 
-        # Extend this user's cart session to 30 minutes from now to ensure all items in the
-        # cart expire at the same time
-        qw = Q(session=self.get_session_key())
-        if self.request.user.is_authenticated():
-            qw |= Q(user=self.request.user)
-        CartPosition.objects.current.filter(
-            qw & Q(event=self.request.event)).update(expires=now() + timedelta(minutes=30))
-
         # Process the request itself
         msg_some_unavailable = False
         for i in items:

src/pretix/presale/views/checkout.py

@@ -0,0 +1,23 @@
+from django.contrib import messages
+from django.core.urlresolvers import reverse
+from django.shortcuts import redirect
+from django.views.generic import View
+from django.utils.translation import ugettext_lazy as _
+
+from pretix.presale.views import EventViewMixin, CartDisplayMixin
+
+
+class CheckoutStart(EventViewMixin, CartDisplayMixin, View):
+
+    def get_failure_url(self):
+        return reverse('presale:event.index', kwargs={
+            'event': self.request.event.slug,
+            'organizer': self.request.event.organizer.slug,
+        })
+
+    def get(self, *args, **kwargs):
+        cart = self.get_cart()
+        if not cart['positions']:
+            messages.error(self.request,
+                           _("Your cart is empty") % self.event.max_items_per_order)
+            return redirect(self.get_failure_url())