fix collection ordering

atlas/models.py

@@ -816,13 +816,17 @@ class CaseCollection(ExamOrCollectionGenericBase):
 
     #    return False
 
+    def get_cases(self):
+        """Returns the cases in the collection in order of the CaseDetail sort_order"""
+        return self.cases.all().order_by("casedetail__sort_order")
+
     def get_case_by_index(
         self, case_index: int, case_count=False
     ) -> Case | Tuple[Case, int]:
         # Seems to be a bug when case_number is 0 or 1 the same (first) object gets returned
         # forces a list fixes (but is likely inefficient)
         cases = list(
-            self.cases.all().order_by("casedetail__sort_order").prefetch_related()
+            self.get_cases().prefetch_related()
         )
 
         try:
@@ -838,7 +842,7 @@ class CaseCollection(ExamOrCollectionGenericBase):
 
     def get_case_take_url(self, case):
         cases = list(
-            self.cases.all().order_by("casedetail__sort_order").prefetch_related()
+            self.get_cases().prefetch_related()
         )
 
         return reverse(
@@ -878,6 +882,13 @@ class CaseCollection(ExamOrCollectionGenericBase):
             "studies": studies
         }
 
+    def add_case(self, case):
+        """Adds a case to the collection and makes sure order is maintained"""
+        # We might be better off adding via the case detail model direct
+        #CaseDetail.objects.create(case=case, collection=self)
+        self.cases.add(case)
+        self.order_cases()
+
 
     def order_cases(self): 
         """Modifies the casedetail sort_order to sequentially order the cases"""