Introduce ChoiceSet class for field choices

netbox/utilities/choices.py

@@ -0,0 +1,36 @@
+class ChoiceSetMeta(type):
+    """
+    Metaclass for ChoiceSet
+    """
+    def __call__(cls, *args, **kwargs):
+        # Django will check if a choices value is callable, and if so assume that it returns an iterable
+        return getattr(cls, 'CHOICES', ())
+
+    def __iter__(cls):
+        choices = getattr(cls, 'CHOICES', ())
+        return iter(choices)
+
+
+class ChoiceSet(metaclass=ChoiceSetMeta):
+
+    CHOICES = list()
+    LEGACY_MAP = dict()
+
+    @classmethod
+    def slug_to_id(cls, slug):
+        """
+        Return the legacy integer value corresponding to a slug.
+        """
+        return cls.LEGACY_MAP.get(slug)
+
+    @classmethod
+    def id_to_slug(cls, legacy_id):
+        """
+        Return the slug value corresponding to a legacy integer value.
+        """
+        if legacy_id in cls.LEGACY_MAP.values():
+            # Invert the legacy map to allow lookup by integer
+            legacy_map = dict([
+                (id, slug) for slug, id in cls.LEGACY_MAP.items()
+            ])
+            return legacy_map.get(legacy_id)