contrib/penfield/embed.py

   1 from django.contrib.contenttypes import generic
   2 from django.contrib.contenttypes.models import ContentType
   3 from django.core.exceptions import ValidationError
   4 from django.db import models
   5 from django.template import loader, loader_tags, Parser, Lexer, Template
   6 import re
   7 from philo.models.fields import TemplateField
   8 from philo.contrib.penfield.templatetags.embed import EmbedNode
   9 from philo.utils import nodelist_crawl, ContentTypeRegistryLimiter
  10
  11
  12 embeddable_content_types = ContentTypeRegistryLimiter()
  13
  14
  15 class Embed(models.Model):
  16         embedder_content_type = models.ForeignKey(ContentType, related_name="embedder_related")
  17         embedder_object_id = models.PositiveIntegerField()
  18         embedder = generic.GenericForeignKey("embedder_content_type", "embedder_object_id")
  19
  20         embedded_content_type = models.ForeignKey(ContentType, related_name="embedded_related")
  21         embedded_object_id = models.PositiveIntegerField()
  22         embedded = generic.GenericForeignKey("embedded_content_type", "embedded_object_id")
  23
  24         def delete(self):
  25                 # This needs to be called manually.
  26                 super(Embed, self).delete()
  27
  28                 # Cycle through all the fields in the embedder and remove all references
  29                 # to the embedded object.
  30                 embedder = self.embedder
  31                 for field in embedder._meta.fields:
  32                         if isinstance(field, EmbedField):
  33                                 attr = getattr(embedder, field.attname)
  34                                 setattr(embedder, field.attname, self.embed_re.sub('', attr))
  35
  36                 embedder.save()
  37
  38         def get_embed_re(self):
  39                 """Convenience function to return a compiled regular expression to find embed tags that would create this instance."""
  40                 if not hasattr(self, '_embed_re'):
  41                         ct = self.embedded_content_type
  42                         self._embed_re = re.compile("{%% ?embed %s.%s %s( .*?)? ?%%}" % (ct.app_label, ct.model, self.embedded_object_id))
  43                 return self._embed_re
  44         embed_re = property(get_embed_re)
  45
  46         class Meta:
  47                 app_label = 'penfield'
  48
  49
  50 def sync_embedded_instances(model_instance, embedded_instances):
  51         model_instance_ct = ContentType.objects.get_for_model(model_instance)
  52
  53         # Cycle through all the embedded instances and make sure that they are linked to
  54         # the model instance. Track their pks.
  55         new_embed_pks = []
  56         for embedded_instance in embedded_instances:
  57                 embedded_instance_ct = ContentType.objects.get_for_model(embedded_instance)
  58                 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]
  59                 new_embed_pks.append(new_embed.pk)
  60
  61         # Then, delete all embed objects related to this model instance which do not relate
  62         # to one of the newly embedded instances.
  63         Embed.objects.filter(embedder_content_type=model_instance_ct, embedder_object_id=model_instance.id).exclude(pk__in=new_embed_pks).delete()
  64
  65
  66 class EmbedField(TemplateField):
  67         def process_node(self, node, results):
  68                 if isinstance(node, EmbedNode) and node.instance is not None:
  69                         if node.content_type.model_class() not in embeddable_content_types.classes:
  70                                 raise ValidationError("Class %s.%s cannot be embedded." % (node.content_type.app_label, node.content_type.model))
  71
  72                         if not node.instance:
  73                                 raise ValidationError("Instance with content type %s.%s and id %s does not exist." % (node.content_type.app_label, node.content_type.model, node.object_pk))
  74
  75                         results.append(node.instance)
  76
  77         def clean(self, value, model_instance):
  78                 value = super(EmbedField, self).clean(value, model_instance)
  79
  80                 if not hasattr(model_instance, '_embedded_instances'):
  81                         model_instance._embedded_instances = set()
  82
  83                 model_instance._embedded_instances |= set(nodelist_crawl(Template(value).nodelist, self.process_node))
  84
  85                 return value
  86
  87
  88 try:
  89         from south.modelsinspector import add_introspection_rules
  90 except ImportError:
  91         pass
  92 else:
  93         add_introspection_rules([], ["^philo\.contrib\.penfield\.embed\.EmbedField"])
  94
  95
  96 # Add a post-save signal function to run the syncer.
  97 def post_save_embed_sync(sender, instance, **kwargs):
  98         if hasattr(instance, '_embedded_instances') and instance._embedded_instances:
  99                 sync_embedded_instances(instance, instance._embedded_instances)
 100 models.signals.post_save.connect(post_save_embed_sync)
 101
 102
 103 # Deletions can't cascade automatically without a GenericRelation - but there's no good way of
 104 # knowing what models should have one. Anything can be embedded! Also, cascading would probably
 105 # bypass the Embed model's delete method.
 106 def post_delete_cascade(sender, instance, **kwargs):
 107         if sender in embeddable_content_types.classes:
 108                 # Don't bother looking for Embed objects that embed a contenttype that can't be embedded.
 109                 ct = ContentType.objects.get_for_model(sender)
 110                 embeds = Embed.objects.filter(embedded_content_type=ct, embedded_object_id=instance.id)
 111                 for embed in embeds:
 112                         embed.delete()
 113
 114         if not hasattr(sender._meta, '_has_embed_fields'):
 115                 sender._meta._has_embed_fields = False
 116                 for field in sender._meta.fields:
 117                         if isinstance(field, EmbedField):
 118                                 sender._meta._has_embed_fields = True
 119                                 break
 120
 121         if sender._meta._has_embed_fields:
 122                 # If it doesn't have embed fields, then it can't be an embedder.
 123                 Embed.objects.filter(embedder_content_type=ct, embedder_object_id=instance.id).delete()
 124 models.signals.post_delete.connect(post_delete_cascade)