Added post-save and post-delete signals to manage Embed instances. Added the delete...

[philo.git] / contrib / penfield / embed.py

diff --git a/contrib/penfield/embed.py b/contrib/penfield/embed.py
index b279fc7..7f875cc 100644 (file)
--- a/contrib/penfield/embed.py
+++ b/contrib/penfield/embed.py
@@ -32,7 +32,57 @@ class TemplateField(models.TextField):
                return Template(value)
 
 
+class Embed(models.Model):
+       embedder_content_type = models.ForeignKey(ContentType, related_name="embedder_related")
+       embedder_object_id = models.PositiveIntegerField()
+       embedder = generic.GenericForeignKey("embedder_content_type", "embedder_object_id")
+       
+       embedded_content_type = models.ForeignKey(ContentType, related_name="embedded_related")
+       embedded_object_id = models.PositiveIntegerField()
+       embedded = generic.GenericForeignKey("embedded_content_type", "embedded_object_id")
+       
+       def delete(self):
+               # This needs to be called manually.
+               super(Embed, self).delete()
+               
+               # Cycle through all the fields in the embedder and remove all references
+               # to the embedded object.
+               embedder = self.embedder
+               for field in embedder._meta.fields:
+                       if isinstance(field, EmbedField):
+                               attr = getattr(embedder, field.attname)
+                               setattr(embedder, field.attname, attr.replace(self.get_embed_tag(), ''))
+               
+               embedder.save()
+       
+       def get_embed_tag(self):
+               """Convenience function to construct the embed tag that would create this instance."""
+               ct = self.embedded_content_type
+               return "{%% embed %s.%s %s %%}" % (ct.app_label, ct.model, self.embedded_object_id)
+       
+       class Meta:
+               app_label = 'penfield'
+
+
+def sync_embedded_instances(model_instance, embedded_instances):
+       model_instance_ct = ContentType.objects.get_for_model(model_instance)
+       
+       # Cycle through all the embedded instances and make sure that they are linked to
+       # the model instance. Track their pks.
+       new_embed_pks = []
+       for embedded_instance in embedded_instances:
+               embedded_instance_ct = ContentType.objects.get_for_model(embedded_instance)
+               new_embed = Embed.objects.get_or_create(embedder_content_type=model_instance_ct, embedder_object_id=model_instance.id, embedded_content_type=embedded_instance_ct, embedded_object_id=embedded_instance.id)[0]
+               new_embed_pks.append(new_embed.pk)
+       
+       # Then, delete all embed objects related to this model instance which do not relate
+       # to one of the newly embedded instances.
+       Embed.objects.filter(embedder_content_type=model_instance_ct, embedder_object_id=model_instance.id).exclude(pk__in=new_embed_pks).delete()
+
+
 class EmbedField(TemplateField):
+       _embedded_instances = set()
+       
        def validate_template(self, template):
                """Check to be sure that the embedded instances and templates all exist."""
                for node in template.nodelist:
@@ -47,30 +97,32 @@ class EmbedField(TemplateField):
                                        embedded_template = loader.get_template(node.template_name)
                                        self.validate_template(embedded_template)
                                elif node.object_pk is not None:
-                                       embedded_instance = node.model.objects.get(pk=node.object_pk)
+                                       self._embedded_instances.add(node.model.objects.get(pk=node.object_pk))
        
-       def to_template(self, value):
-               return Template("{% load embed %}" + value)
+       def pre_save(self, model_instance, add):
+               if not hasattr(model_instance, '_embedded_instances'):
+                       model_instance._embedded_instances = set()
+               model_instance._embedded_instances |= self._embedded_instances
+               return getattr(model_instance, self.attname)
 
 
-class Embed(models.Model):
-       embedder_embed_field = models.CharField(max_length=255)
-       
-       embedder_contenttype = models.ForeignKey(ContentType, related_name="embedder_related")
-       embedder_object_id = models.PositiveIntegerField()
-       embedder = generic.GenericForeignKey("embedder_contenttype", "embedder_object_id")
-       
-       embedded_contenttype = models.ForeignKey(ContentType, related_name="embedded_related")
-       embedded_object_id = models.PositiveIntegerField()
-       embedded = generic.GenericForeignKey("embedded_contenttype", "embedded_object_id")
-       
-       def delete(self):
-               # Unclear whether this would be called by a cascading deletion.
-               
-               super(Embed, self).delete()
-       
-       class Meta:
-               app_label = 'penfield'
+# Add a post-save signal function to run the syncer.
+def post_save_embed_sync(sender, instance, **kwargs):
+       if hasattr(instance, '_embedded_instances') and instance._embedded_instances:
+               sync_embedded_instances(instance, instance._embedded_instances)
+models.signals.post_save.connect(post_save_embed_sync)
+
+
+# Deletions can't cascade automatically without a GenericRelation - but there's no good way of
+# knowing what models should have one. Anything can be embedded! Also, cascading would probably
+# bypass the Embed model's delete method.
+def post_delete_cascade(sender, instance, **kwargs):
+       ct = ContentType.objects.get_for_model(sender)
+       embeds = Embed.objects.filter(embedded_content_type=ct, embedded_object_id=instance.id)
+       for embed in embeds:
+               embed.delete()
+       Embed.objects.filter(embedder_content_type=ct, embedder_object_id=instance.id).delete()
+models.signals.post_delete.connect(post_delete_cascade)
 
 
 class Test(models.Model):