rework redorder tabs so that we account for the fact that static tabs can be in…

rework redorder tabs so that we account for the fact that static tabs can be in any arbitrary order (with respect to non-static tabs) when working with an imported course

cms/djangoapps/contentstore/views.py

@@ -908,30 +908,47 @@ def edit_static(request, org, course, coursename):
 @expect_json
 def reorder_tabs(request):
     tabs = request.POST['tabs']
+    course = get_course_for_item(tabs[0])
 
-    if len(tabs) > 0:
-        course = get_course_for_item(tabs[0])
-
-        if not has_access(request.user, course.location):
-            raise PermissionDenied()
-
-        # first filter out all non-static tabs from the tabs list
-        course_tabs = [t for t in course.tabs if t['type'] != 'static_tab']
+    if not has_access(request.user, course.location):
+        raise PermissionDenied()
 
-        # OK, re-assemble the static tabs in the new order
-        for tab in tabs:
-            item = modulestore('direct').get_item(Location(tab))
+    # get list of course_tabs
+    course_tabs = [t for t in course.tabs if t['type'] == 'static_tab']
 
-            course_tabs.append({ 'type':'static_tab', 
-                'name' : item.metadata.get('display_name'), 
-                'url_slug' : item.location.name}
-                )
-        
-        course.tabs = course_tabs
-        modulestore('direct').update_metadata(course.location, course.metadata)
+    # make sure they are the same lengths (i.e. the number of passed in tabs equals the number
+    # that we know about) otherwise we can drop some!
+    if len(course_tabs) != len(tabs):
+        return HttpResponseBadRequest()
 
+    # load all reference tabs, return BadRequest if we can't find any of them
+    tab_items =[]
+    for tab in tabs:
+        item = modulestore('direct').get_item(Location(tab))
+        if item is None:
+            return HttpResponseBadRequest()
+
+        tab_items.append(item)
+
+    # now just go through the existing course_tabs and re-order the static tabs
+    reordered_tabs = []
+    static_tab_idx = 0
+    for tab in course.tabs:
+        if tab['type'] == 'static_tab':
+            reordered_tabs.append({'type': 'static_tab', 
+                'name' : tab_items[static_tab_idx].metadata.get('display_name'), 
+                'url_slug' : tab_items[static_tab_idx].location.name})
+            static_tab_idx += 1
+        else:
+            reordered_tabs.append(tab)
+
+
+    # OK, re-assemble the static tabs in the new order        
+    course.tabs = reordered_tabs
+    modulestore('direct').update_metadata(course.location, course.metadata)
     return HttpResponse()
 
+
 @login_required
 @ensure_csrf_cookie
 def edit_tabs(request, org, course, coursename):