Provide a celery task for notification processing

Author: Hugo Osvaldo Barrera

README.rst

@@ -75,15 +75,19 @@ AUTOPROCESS
 
 **Required**
 
-If set to ``True``, notifications will be processed as soon as they are
-received. Otherwise, it's up to the developer to process them.
+If set to ``'SYNC'``, notifications will be processed as soon as they are
+received. If set to ``'ASYNC'``, notifications will be processed asynchronously.
+Celery is expected to be configured and running for this to works.
+
+If this variable is set to ``False``, notifications will not be processed and
+it will be up to the developer to call their ``process()`` method.
 
 A signal is always fired when a notification has been created, and a common
-pattern if not auto-processing is to have a celery task to process them::
+pattern if not auto-processing is to use your own queue mechanism::
 
     @receiver(notification_received)
     def process_notification(sender, **kwargs):
-        tasks.process_notification.delay(notification=sender)
+        add_to_some_queue(notification=sender)
 
 SUCCESS_URL
 ~~~~~~~~~~~

django_mercadopago/apps.py

@@ -5,3 +5,11 @@ class MercadoPagoConfig(AppConfig):
     name = 'django_mercadopago'
     label = 'mp'
     verbose_name = 'MercadoPago'
+
+    def ready(self):
+        from django_mercadopago import models, signals
+
+        signals.notification_received.connect(
+            signals.process_new_notification,
+            sender=models.Notification,
+        )

django_mercadopago/signals.py

@@ -1,8 +1,23 @@
-from django.dispatch import Signal
+import logging
 
+from django.conf import settings
+from django.dispatch import Signal
 
-payment_received = Signal(
-    providing_args=['payment']
-)
 
+payment_received = Signal(providing_args=['payment'])
 notification_received = Signal()
+
+logger = logging.getLogger(__name__)
+
+
+def process_new_notification(sender, instance, **kwargs):
+    # XXX: what if a user is being redireected and we expect the status to be
+    # updated?
+
+    if settings.MERCADOPAGO['autoprocess'] == 'SYNC':
+        instance.process()
+    elif settings.MERCADOPAGO['autoprocess'] == 'ASYNC':
+        from django_mercadopago import tasks
+        tasks.process_notification.delay(instance.pk)
+    else:
+        logger.debug('Notification not auto-processed.')

django_mercadopago/tasks.py

@@ -0,0 +1,9 @@
+from celery import shared_task
+
+from django_mercadopago import models
+
+
+@shared_task
+def process_notification(notification_id):
+    notification = models.Notification.objects.get(pk=notification_id)
+    notification.process()

django_mercadopago/views.py

@@ -34,8 +34,6 @@ def _create_notification(reference, topic, resource_id):
         },
     )
 
-    if settings.MERCADOPAGO['autoprocess']:
-        notification.process()
     signals.notification_received.send(sender=notification)
 
     return notification, created