Fix part of oppia#18470: Improve the user experience for adding topic…

…s to the list of topics in the classroom admin page. (oppia#19000)

core/controllers/classroom.py

@@ -172,6 +172,34 @@ def get(self) -> None:
         self.render_json(self.values)
 
 
+class UnusedTopicsHandler(
+    base.BaseHandler[Dict[str, str], Dict[str, str]]
+):
+    """Handler for fetching topics not associated with any classroom."""
+
+    GET_HANDLER_ERROR_RETURN_TYPE = feconf.HANDLER_TYPE_JSON
+    URL_PATH_ARGS_SCHEMAS: Dict[str, str] = {}
+    HANDLER_ARGS_SCHEMAS: Dict[str, Dict[str, str]] = {'GET': {}}
+
+    @acl_decorators.can_access_classroom_admin_page
+    def get(self) -> None:
+        """Retrieves topics not associated with any classroom."""
+        all_topics = topic_fetchers.get_all_topics()
+        all_classrooms = classroom_config_services.get_all_classrooms()
+
+        topics_not_in_classroom = [
+            topic.to_dict() for topic in all_topics
+            if not any(
+                topic.id in classroom.topic_id_to_prerequisite_topic_ids
+                for classroom in all_classrooms
+            )
+        ]
+        self.values.update({
+            'unused_topics': topics_not_in_classroom
+        })
+        self.render_json(self.values)
+
+
 class NewClassroomIdHandler(
     base.BaseHandler[Dict[str, str], Dict[str, str]]
 ):

core/controllers/classroom_test.py

@@ -402,3 +402,134 @@ def test_get_classroom_id_from_url_fragment_works_correctly(
 
         json_response = self.get_json(
             non_existent_classroom_url, expected_status_int=404)
+
+
+class UnusedTopicsHandlerTests(test_utils.GenericTestBase):
+
+    def setUp(self) -> None:
+        super().setUp()
+        self.signup(self.CURRICULUM_ADMIN_EMAIL, self.CURRICULUM_ADMIN_USERNAME)
+        self.set_curriculum_admins([self.CURRICULUM_ADMIN_USERNAME])
+
+        self.owner_id = self.get_user_id_from_email(self.CURRICULUM_ADMIN_EMAIL)
+        self.used_topic1 = topic_domain.Topic.create_default_topic(
+            'used_topic_1', 'used_topic1_name',
+            'frag-used-topic-one', 'description', 'fragm')        
+        topic_services.save_new_topic(self.owner_id, self.used_topic1)
+
+        self.physics_classroom_id = (
+            classroom_config_services.get_new_classroom_id())
+        self.physics_classroom_dict: classroom_config_domain.ClassroomDict = {
+            'classroom_id': self.physics_classroom_id,
+            'name': 'physics',
+            'url_fragment': 'physics',
+            'course_details': 'Curated physics foundations course.',
+            'topic_list_intro': 'Start from the basics with our first topic.',
+            'topic_id_to_prerequisite_topic_ids': {
+                'topic_id_1': ['topic_id_2', 'topic_id_3'],
+                'topic_id_2': [],
+                'topic_id_3': [],
+                'used_topic_1': []
+            }
+        }
+        self.physics_classroom = classroom_config_domain.Classroom.from_dict(
+            self.physics_classroom_dict)
+        classroom_config_services.update_or_create_classroom_model(
+            self.physics_classroom)
+
+    def test_returns_newly_added_unused_topics(self) -> None:
+        self.login(self.CURRICULUM_ADMIN_EMAIL, is_super_admin=True)
+
+        unused_topic1 = topic_domain.Topic.create_default_topic(
+            'unused_topic1', 'unused_topic1_name',
+            'frag-topic-one', 'description', 'fragm')
+        topic_services.save_new_topic(self.owner_id, unused_topic1)
+        unused_topics = [unused_topic1.to_dict()]
+        json_response = self.get_json(feconf.UNUSED_TOPICS_HANDLER_URL)
+        self.assertEqual(
+            json_response['unused_topics'],
+            unused_topics
+        )
+
+        unused_topic2 = topic_domain.Topic.create_default_topic(
+            'unused_topic2', 'unused_topic2_name',
+            'frag-topic-two', 'description', 'fragm')
+        topic_services.save_new_topic(self.owner_id, unused_topic2)
+        unused_topics = [unused_topic1.to_dict(), unused_topic2.to_dict()]
+        json_response = self.get_json(feconf.UNUSED_TOPICS_HANDLER_URL)
+        self.assertEqual(
+            json_response['unused_topics'],
+            unused_topics
+        )
+
+        self.logout()
+
+    def test_does_not_return_deleted_topic(self) -> None:
+        self.login(self.CURRICULUM_ADMIN_EMAIL, is_super_admin=True)
+
+        unused_topic1 = topic_domain.Topic.create_default_topic(
+            'unused_topic1', 'unused_topic1_name',
+            'frag-topic-one', 'description', 'fragm')
+        topic_services.save_new_topic(self.owner_id, unused_topic1)
+
+        unused_topic2 = topic_domain.Topic.create_default_topic(
+            'unused_topic2', 'unused_topic2_name',
+            'frag-topic-two', 'description', 'fragm')
+        topic_services.save_new_topic(self.owner_id, unused_topic2)
+
+        unused_topics = [unused_topic1.to_dict(), unused_topic2.to_dict()]
+        json_response = self.get_json(feconf.UNUSED_TOPICS_HANDLER_URL)
+        self.assertEqual(
+            json_response['unused_topics'],
+            unused_topics
+        )
+
+        topic_services.delete_topic(self.owner_id, unused_topic2.id, True)
+        unused_topics = [unused_topic1.to_dict()]
+        json_response = self.get_json(feconf.UNUSED_TOPICS_HANDLER_URL)
+        self.assertEqual(
+            json_response['unused_topics'],
+            unused_topics
+        )
+
+        self.logout()
+
+    def test_returns_topic_if_unused_in_classroom(self) -> None:
+        self.login(self.CURRICULUM_ADMIN_EMAIL, is_super_admin=True)
+        json_response = self.get_json(feconf.UNUSED_TOPICS_HANDLER_URL)
+        self.assertEqual(
+            json_response['unused_topics'],
+            []
+        )
+
+        self.physics_classroom.topic_id_to_prerequisite_topic_ids.pop(
+            self.used_topic1.id
+            )
+        classroom_config_services.update_or_create_classroom_model(
+            self.physics_classroom)
+        json_response = self.get_json(feconf.UNUSED_TOPICS_HANDLER_URL)
+        self.assertEqual(
+            json_response['unused_topics'],
+            [self.used_topic1.to_dict()]
+        )
+
+        self.logout()
+
+    def test_returns_no_topics_if_no_unused_topics(self) -> None:
+        self.login(self.CURRICULUM_ADMIN_EMAIL, is_super_admin=True)
+        json_response = self.get_json(feconf.UNUSED_TOPICS_HANDLER_URL)
+        self.assertEqual(
+            json_response['unused_topics'],
+            []
+        )
+
+        self.logout()
+
+    def test_not_able_to_get_unused_topics_when_user_is_not_admin(
+        self
+    ) -> None:
+        self.signup(self.VIEWER_EMAIL, self.VIEWER_USERNAME)
+        self.login(self.VIEWER_EMAIL)
+        self.get_json(
+            feconf.UNUSED_TOPICS_HANDLER_URL, expected_status_int=401)
+        self.logout()

core/feconf.py

@@ -1091,6 +1091,7 @@ def get_empty_ratings() -> Dict[str, int]:
 CREATE_LEARNER_GROUP_PAGE_URL = '/create-learner-group'
 EDIT_LEARNER_GROUP_PAGE_URL = '/edit-learner-group'
 CLASSROOM_ADMIN_DATA_HANDLER_URL = '/classroom_admin_data_handler'
+UNUSED_TOPICS_HANDLER_URL = '/unused_topics'
 NEW_CLASSROOM_ID_HANDLER_URL = '/new_classroom_id_handler'
 CLASSROOM_HANDLER_URL = '/classroom'
 CLASSROOM_URL_FRAGMENT_HANDLER = '/classroom_url_fragment_handler'

main.py

@@ -441,6 +441,9 @@ def get_redirect_route(
     get_redirect_route(
         r'%s' % feconf.CLASSROOM_ADMIN_DATA_HANDLER_URL,
         classroom.ClassroomAdminDataHandler),
+    get_redirect_route(
+        r'%s' % feconf.UNUSED_TOPICS_HANDLER_URL,
+        classroom.UnusedTopicsHandler),
     get_redirect_route(
         r'%s' % feconf.NEW_CLASSROOM_ID_HANDLER_URL,
         classroom.NewClassroomIdHandler),