Start on a basic registry_model interface and change a single module to use it. This will allow us to completely abstract out how we deal with registry-related tables and ensure that transitioning to the new OCI-like model will be easier to do.

data/registry_model/registry_pre_oci_model.py

@@ -0,0 +1,27 @@
+from data import model
+from data.registry_model.interface import RegistryDataInterface
+from data.registry_model.datatypes import Tag
+
+
+class PreOCIModel(RegistryDataInterface):
+  """
+  PreOCIModel implements the data model for the registry API using a database schema
+  before it was changed to support the OCI specification.
+  """
+
+  def find_matching_tag(self, repository_ref, tag_names):
+    """ Finds an alive tag in the repository matching one of the given tag names and returns it
+        or None if none.
+    """
+    found_tag = model.tag.find_matching_tag(repository_ref.repo_id, tag_names)
+    return Tag.for_repository_tag(found_tag)
+
+  def get_most_recent_tag(self, repository_ref):
+    """ Returns the most recently pushed alive tag in the repository, if any. If none, returns
+        None.
+    """
+    found_tag = model.tag.get_most_recent_tag(repository_ref.repo_id)
+    return Tag.for_repository_tag(found_tag)
+
+
+pre_oci_model = PreOCIModel()