Impersonation system implementation

nonpacks/common/context_processors.py

@@ -14,4 +14,37 @@ def app_version(request):
         'OS_ICON': os_icon,
         'OS_NAME': os_name,
         'PAGE_GEN_TIME': page_gen_time,
+    }
+
+
+def impersonation(request):
+    """Expose the impersonation state for the UI (user-bar chip + menu).
+
+    Reads the impersonator id stored in the session when a staff member is
+    acting as another user.
+    """
+    from django.contrib.auth import get_user_model
+    from django.core.exceptions import ObjectDoesNotExist
+    from django.urls import reverse
+
+    impersonator_id = request.session.get('impersonator_id')
+    impersonator = None
+    avatar_url = None
+    if impersonator_id:
+        impersonator = (
+            get_user_model().objects.filter(pk=impersonator_id).first()
+        )
+        if impersonator is None:
+            request.session.pop('impersonator_id', None)
+        else:
+            try:
+                profile = impersonator.userprofile
+            except ObjectDoesNotExist:
+                profile = None
+            if profile is not None and profile.avatar_id:
+                avatar_url = reverse('library:file_request', args=[profile.avatar.uuid])
+    return {
+        'impersonating': impersonator is not None,
+        'impersonator': impersonator,
+        'impersonator_avatar_url': avatar_url,
     }