From 326f82721e7b7bd37feff3ff5ff25c4d551812b0 Mon Sep 17 00:00:00 2001
From: Arunmozhi <arun@arunmozhi.in>
Date: Thu, 6 Jan 2022 16:26:11 +0530
Subject: [PATCH] feat: reset a Randomized Content Block via AJAX

This makes the reset button to refresh the contents of a Randomized
Content Block (RCB) without reloading the full page by fetching a new
set of problems in the "reset" response and replacing the DOM contents.

The reset button returns the student view as a string and the client
uses the HtmlUtils package to replace the contents and reinitializes the
XBlock.

This allows students to use the RCB as a flash card system.
---
 .../library_content/public/js/library_content_reset.js | 10 ++++++++--
 common/lib/xmodule/xmodule/library_content_module.py   |  2 +-
 .../lib/xmodule/xmodule/tests/test_library_content.py  |  8 +++++++-
 3 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/common/lib/xmodule/xmodule/assets/library_content/public/js/library_content_reset.js b/common/lib/xmodule/xmodule/assets/library_content/public/js/library_content_reset.js
index 81eb7d2105e7..e985d3c2a692 100644
--- a/common/lib/xmodule/xmodule/assets/library_content/public/js/library_content_reset.js
+++ b/common/lib/xmodule/xmodule/assets/library_content/public/js/library_content_reset.js
@@ -4,8 +4,14 @@ function LibraryContentReset(runtime, element) {
     e.preventDefault();
     $.post({
       url: runtime.handlerUrl(element, 'reset_selected_children'),
-      success() {
-        location.reload();
+      success(data) {
+        edx.HtmlUtils.setHtml(element, edx.HtmlUtils.HTML(data));
+        // Rebind the reset button for the block
+        XBlock.initializeBlock(element);
+        // Render the new set of problems (XBlocks)
+        $(".xblock", element).each(function(i, child) {
+          XBlock.initializeBlock(child);
+        });
       },
     });
   });
diff --git a/common/lib/xmodule/xmodule/library_content_module.py b/common/lib/xmodule/xmodule/library_content_module.py
index 29e772f8bee1..5e54ea9b201b 100644
--- a/common/lib/xmodule/xmodule/library_content_module.py
+++ b/common/lib/xmodule/xmodule/library_content_module.py
@@ -375,7 +375,7 @@ def reset_selected_children(self, _, __):
                 block.save()
 
         self.selected = []
-        return Response()
+        return Response(json.dumps(self.student_view({}).content))
 
     def _get_selected_child_blocks(self):
         """
diff --git a/common/lib/xmodule/xmodule/tests/test_library_content.py b/common/lib/xmodule/xmodule/tests/test_library_content.py
index a2d057b984c3..748a962f1d65 100644
--- a/common/lib/xmodule/xmodule/tests/test_library_content.py
+++ b/common/lib/xmodule/xmodule/tests/test_library_content.py
@@ -4,7 +4,7 @@
 Higher-level tests are in `cms/djangoapps/contentstore/tests/test_libraries.py`.
 """
 import ddt
-from unittest.mock import Mock, patch
+from unittest.mock import MagicMock, Mock, patch
 
 from bson.objectid import ObjectId
 from fs.memoryfs import MemoryFS
@@ -405,13 +405,19 @@ def test_reset_selected_children_capa_blocks(self, allow_resetting_children, max
         self._create_capa_problems()
         self.lc_block.refresh_children()
         self.lc_block = self.store.get_item(self.lc_block.location)
+        # Mock the student view to return an empty dict to be returned as response
+        self.lc_block.student_view = MagicMock()
+        self.lc_block.student_view.return_value.content = {}
 
         with patch.object(ProblemBlock, 'reset_problem', return_value={'success': True}) as reset_problem:
             response = self.lc_block.reset_selected_children(None, None)
 
         if allow_resetting_children:
+            self.lc_block.student_view.assert_called_once_with({})
             assert reset_problem.call_count == len(self.problem_types)
             assert response.status_code == status.HTTP_200_OK
+            assert response.content_type == "text/html"
+            assert response.body == b"{}"
         else:
             reset_problem.assert_not_called()
             assert response.status_code == status.HTTP_400_BAD_REQUEST