From 2f2aed7e371d11b021432124de8f9bdd436b0832 Mon Sep 17 00:00:00 2001
From: Joseph Spiros <joseph.spiros@ithinksw.com>
Date: Fri, 30 Jul 2010 23:16:52 -0400
Subject: [PATCH] Initial implementation of AttributeField and
 RelationshipField. These objects are not actual Fields, but rather they
 simply add descriptors to Entity subclasses which provide transparent access
 to specific attributes and relationships.

---
 models/__init__.py |  1 +
 models/fields.py   | 96 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 97 insertions(+)
 create mode 100644 models/fields.py

diff --git a/models/__init__.py b/models/__init__.py
index b9ea3ac..5d39ac6 100644
--- a/models/__init__.py
+++ b/models/__init__.py
@@ -2,6 +2,7 @@ from philo.models.base import *
 from philo.models.collections import *
 from philo.models.nodes import *
 from philo.models.pages import *
+from philo.models.fields import *
 from django.contrib.auth.models import User, Group
 from django.contrib.sites.models import Site
 
diff --git a/models/fields.py b/models/fields.py
new file mode 100644
index 0000000..7f76b9c
--- /dev/null
+++ b/models/fields.py
@@ -0,0 +1,96 @@
+from django.db import models
+from django.db.models import signals
+from django.core.exceptions import ObjectDoesNotExist, FieldError
+from django.contrib.contenttypes.models import ContentType
+from functools import partial
+from philo.models.base import Attribute, Relationship, Entity
+
+
+__all__ = ('AttributeField', 'RelationshipField')
+
+
+class AttributeFieldDescriptor(object):
+	def __init__(self, field):
+		self.field = field
+	
+	def __get__(self, instance, owner):
+		if instance:
+			try:
+				return instance.attribute_set.get(key__exact=self.field.key).value
+			except ObjectDoesNotExist:
+				return None
+		else:
+			raise AttributeError('The \'%s\' attribute can only be accessed from %s instances.' % (self.field.name, owner.__name__))
+	
+	def __set__(self, instance, value):
+		try:
+			attribute = instance.attribute_set.get(key__exact=self.field.key)
+		except ObjectDoesNotExist:
+			attribute = Attribute()
+			attribute.entity = instance
+			attribute.key = self.field.key
+		attribute.value = value
+		attribute.save()
+	
+	def __delete__(self, instance):
+		instance.attribute_set.filter(key__exact=self.field.key).delete()
+
+
+class AttributeField(object):
+	def __init__(self, key):
+		self.key = key
+	
+	def actually_contribute_to_class(self, sender, **kwargs):
+		setattr(sender, self.name, AttributeFieldDescriptor(self))
+	
+	def contribute_to_class(self, cls, name):
+		if issubclass(cls, Entity):
+			self.name = name
+			signals.class_prepared.connect(self.actually_contribute_to_class, sender=cls)
+		else:
+			raise FieldError('AttributeFields can only be declared on Entity subclasses.')
+
+
+class RelationshipFieldDescriptor(object):
+	def __init__(self, field):
+		self.field = field
+	
+	def __get__(self, instance, owner):
+		if instance:
+			try:
+				return instance.relationship_set.get(key__exact=self.field.key).value
+			except ObjectDoesNotExist:
+				return None
+		else:
+			raise AttributeError('The \'%s\' attribute can only be accessed from %s instances.' % (self.field.name, owner.__name__))
+	
+	def __set__(self, instance, value):
+		if isinstance(value, (models.Model, type(None))):
+			try:
+				relationship = instance.relationship_set.get(key__exact=self.field.key)
+			except ObjectDoesNotExist:
+				relationship = Relationship()
+				relationship.entity = instance
+				relationship.key = self.field.key
+			relationship.value = value
+			relationship.save()
+		else:
+			raise AttributeError('The \'%\' attribute can only be set using existing Model objects.' % self.field.name)
+	
+	def __delete__(self, instance):
+		instance.relationship_set.filter(key__exact=self.field.key).delete()
+
+
+class RelationshipField(object):
+	def __init__(self, key):
+		self.key = key
+	
+	def actually_contribute_to_class(self, sender, **kwargs):
+		setattr(sender, self.name, RelationshipFieldDescriptor(self))
+	
+	def contribute_to_class(self, cls, name):
+		if issubclass(cls, Entity):
+			self.name = name
+			signals.class_prepared.connect(self.actually_contribute_to_class, sender=cls)
+		else:
+			raise FieldError('RelationshipFields can only be declared on Entity subclasses.')
\ No newline at end of file
-- 
2.20.1