From c9dbd2c30858736e63a5cc0a672ad6a3c6c57227 Mon Sep 17 00:00:00 2001
From: Calen Pennington <cale@edx.org>
Date: Fri, 24 Apr 2015 09:30:06 -0400
Subject: [PATCH] Add an empty implementation of XBlockUserStateClient backed
 by StudentModule

---
 .../courseware/user_state_client.py           | 63 +++++++++++++++++++
 lms/djangoapps/xblock_user_state/interface.py |  1 +
 2 files changed, 64 insertions(+)
 create mode 100644 lms/djangoapps/courseware/user_state_client.py

diff --git a/lms/djangoapps/courseware/user_state_client.py b/lms/djangoapps/courseware/user_state_client.py
new file mode 100644
index 0000000000..19f522d34b
--- /dev/null
+++ b/lms/djangoapps/courseware/user_state_client.py
@@ -0,0 +1,63 @@
+"""
+An implementation of :class:`XBlockUserStateClient`, which stores XBlock Scope.user_state
+data in a Django ORM model.
+"""
+
+from xblock_user_state.interface import DjangoXBlockUserStateClient
+
+
+class DjangoXBlockUserStateClient(DjangoXBlockUserStateClient):
+    """
+    An interface that uses the Django ORM StudentModule as a backend.
+    """
+
+    class ServiceUnavailable(XBlockUserStateClient.ServiceUnavailable):
+        """
+        This error is raised if the service backing this client is currently unavailable.
+        """
+        pass
+
+    class PermissionDenied(XBlockUserStateClient.PermissionDenied):
+        """
+        This error is raised if the caller is not allowed to access the requested data.
+        """
+        pass
+
+    class DoesNotExist(XBlockUserStateClient.DoesNotExist):
+        """
+        This error is raised if the caller has requested data that does not exist.
+        """
+        pass
+
+    def get(username, block_key, scope=Scope.user_state):
+        return self.get_many(username, [block_key], scope)
+
+    def set(username, block_key, state, scope=Scope.user_state):
+        self.set_many(username, {block_key: state}, scope)
+
+    def get_many(username, block_keys, scope=Scope.user_state):
+        """Returns dict of block_id -> state."""
+        raise NotImplementedError()
+
+    def set_many(username, block_keys_to_state, scope=Scope.user_state):
+        raise NotImplementedError()
+
+    def get_history(username, block_key, scope=Scope.user_state):
+        """We don't guarantee that history for many blocks will be fast."""
+        raise NotImplementedError()
+
+    def iter_all_for_block(block_key, scope=Scope.user_state, batch_size=None):
+        """
+        You get no ordering guarantees. Fetching will happen in batch_size
+        increments. If you're using this method, you should be running in an
+        async task.
+        """
+        raise NotImplementedError()
+
+    def iter_all_for_course(course_key, block_type=None, scope=Scope.user_state, batch_size=None):
+        """
+        You get no ordering guarantees. Fetching will happen in batch_size
+        increments. If you're using this method, you should be running in an
+        async task.
+        """
+        raise NotImplementedError()
diff --git a/lms/djangoapps/xblock_user_state/interface.py b/lms/djangoapps/xblock_user_state/interface.py
index 5d001de4d1..2c7254d00f 100644
--- a/lms/djangoapps/xblock_user_state/interface.py
+++ b/lms/djangoapps/xblock_user_state/interface.py
@@ -10,6 +10,7 @@ from xblock.fields import Scope, ScopeBase
 
 new_contract('UsageKey', UsageKey)
 
+
 class XBlockUserStateClient(object):
     """
     First stab at an interface for accessing XBlock User State. This will have