create optimized course tree query API endpoint

lms/djangoapps/api_manager/courses_urls.py

@@ -17,5 +17,6 @@ urlpatterns = patterns(
     url(r'^(?P<course_id>[^/]+/[^/]+/[^/]+)/static_tabs/(?P<tab_id>[a-zA-Z0-9/_:]+)$', 'static_tab_detail'),
     url(r'^(?P<course_id>[^/]+/[^/]+/[^/]+)/static_tabs$', 'static_tabs_list'),
     url(r'^(?P<course_id>[^/]+/[^/]+/[^/]+)/users$', 'course_users_list'),
+    url(r'^(?P<course_id>[^/]+/[^/]+/[^/]+)/tree/(?P<depth>[0-9]+)$', 'course_tree'),
     url(r'^(?P<course_id>[^/]+/[^/]+/[^/]+)$', 'courses_detail'),
 )

lms/djangoapps/api_manager/courses_views.py

@@ -16,7 +16,7 @@ from api_manager.models import CourseGroupRelationship
 from xmodule.modulestore.django import modulestore
 from xmodule.modulestore import Location, InvalidLocationError
 
-from courseware.courses import get_course_about_section, get_course_info_section
+from courseware.courses import get_course_about_section, get_course_info_section, get_course_by_id
 from courseware.views import get_static_tab_contents
 from student.models import CourseEnrollment, CourseEnrollmentAllowed
 
@@ -226,6 +226,40 @@ def courses_detail(request, course_id):
     return Response(response_data, status=status_code)
 
 
+@api_view(['GET'])
+@permission_classes((ApiKeyHeaderPermission,))
+def course_tree(request, course_id, depth):
+    """
+    GET retrieves an existing course from the system and returns summary information about the submodules
+    to the specified depth
+    """
+    response_data = {}
+
+    depth_int = int(depth)
+
+    # note, passing in depth=N optimizes the number of round trips to the database
+    course_descriptor = get_course_by_id(course_id, depth=depth_int)
+    if not course_descriptor:
+        return Response({}, status.HTTP_404_NOT_FOUND)
+
+    def _serialize_node_with_children(descriptor, depth):
+        data = _serialize_module(
+            request,
+            course_descriptor.id,
+            descriptor
+        )
+
+        if depth > 0:
+            data['modules'] = []
+            for child in descriptor.get_children():
+                data['modules'].append(_serialize_node_with_children(child, depth-1))
+
+        return data
+
+    response_data = _serialize_node_with_children(course_descriptor, depth_int)
+    return Response(response_data)
+
+
 @api_view(['POST'])
 @permission_classes((ApiKeyHeaderPermission,))
 def courses_groups_list(request, course_id):

lms/djangoapps/api_manager/tests/test_courses_views.py

@@ -170,6 +170,36 @@ class CoursesApiTests(TestCase):
         response = self.do_get(test_uri)
         self.assertEqual(response.status_code, 404)
 
+    def test_course_tree_get(self):
+        # query the course tree to quickly get naviation information
+        test_uri = self.base_courses_uri + '/' + self.test_course_id + '/tree/2'
+        response = self.do_get(test_uri)
+        self.assertEqual(response.status_code, 200)
+        self.assertGreater(len(response.data), 0)
+        self.assertEqual(response.data['category'], 'course')
+        self.assertEqual(response.data['name'], self.course.display_name)
+        self.assertEqual(len(response.data['modules']), 1)
+
+        chapter = response.data['modules'][0]
+        self.assertEqual(chapter['category'], 'chapter')
+        self.assertEqual(chapter['name'], 'Overview')
+        self.assertEqual(len(chapter['modules']), 1)
+
+        sequence = chapter['modules'][0]
+        self.assertEqual(sequence['category'], 'videosequence')
+        self.assertEqual(sequence['name'], 'Video_Sequence')
+        self.assertNotIn('modules', sequence)
+
+    def test_course_tree_get_root(self):
+        # query the course tree to quickly get naviation information
+        test_uri = self.base_courses_uri + '/' + self.test_course_id + '/tree/0'
+        response = self.do_get(test_uri)
+        self.assertEqual(response.status_code, 200)
+        self.assertGreater(len(response.data), 0)
+        self.assertEqual(response.data['category'], 'course')
+        self.assertEqual(response.data['name'], self.course.display_name)
+        self.assertNotIn('modules', response.data)
+
     def test_chapter_list_get(self):
         test_uri = self.base_chapters_uri
         response = self.do_get(test_uri)