closes #4368 - extras features model registration

netbox/extras/utils.py

@@ -1,6 +1,12 @@
+import collections
+
+from django.db.models import Q
+from django.utils.deconstruct import deconstructible
 from taggit.managers import _TaggableManager
 from utilities.querysets import DummyQuerySet
 
+from extras.constants import EXTRAS_FEATURES
+
 
 def is_taggable(obj):
     """
@@ -13,3 +19,65 @@ def is_taggable(obj):
         if isinstance(obj.tags, DummyQuerySet):
             return True
     return False
+
+
+#
+# Dynamic feature registration
+#
+
+class Registry:
+    """
+    The registry is a place to hook into for data storage across components
+    """
+
+    def add_store(self, store_name, initial_value=None):
+        """
+        Given the name of some new data parameter and an optional initial value, setup the registry store
+        """
+        if not hasattr(Registry, store_name):
+            setattr(Registry, store_name, initial_value)
+
+
+registry = Registry()
+
+
+@deconstructible
+class FeatureQuerySet:
+    """
+    Helper class that delays evaluation of the registry contents for the functionaility store
+    until it has been populated.
+    """
+
+    def __init__(self, feature):
+        self.feature = feature
+
+    def __call__(self):
+        return self.get_queryset()
+
+    def get_queryset(self):
+        """
+        Given an extras feature, return a Q object for content type lookup
+        """
+        query = Q()
+        for app_label, models in registry.model_feature_store[self.feature].items():
+            query |= Q(app_label=app_label, model__in=models)
+
+        return query
+
+
+registry.add_store('model_feature_store', {f: collections.defaultdict(list) for f in EXTRAS_FEATURES})
+
+
+def extras_features(*features):
+    """
+    Decorator used to register extras provided features to a model
+    """
+    def wrapper(model_class):
+        for feature in features:
+            if feature in EXTRAS_FEATURES:
+                app_label, model_name = model_class._meta.label_lower.split('.')
+                registry.model_feature_store[feature][app_label].append(model_name)
+            else:
+                raise ValueError('{} is not a valid extras feature!'.format(feature))
+        return model_class
+    return wrapper