MDL-75947 ltiservice_gradebookservices: test covering lineitem rescale

This test highlights a problem in which updates to the scoreMaximum will
trigger a grade rescale, resulting in the timemodified value for grades
being set to the current time. Any subsequent score posts to that line
item must set a timestamp greater than this time to be considered valid.

This test will currently fail because the logic is too strict. A tool
should be able to post a subsequent score update, so long as the time
stamp is greater than the most recent update. Since the tool is unaware
of the grade rescale event having taken place, or the requirements to
increase the score timestamp to a value higher than the grade rescale
time, this then causes problems during post, resulting in 409s.

Solutions:
1. It's not as simple as removing the date check logic, as this will
likely result in certification suite failure.
2. We might need to track the last score post time in the grade service
plugin, so that we can check against that, instead of relying on the
grade->timemodified value, which clearly can change for other reasons.
3. Data fix won't be possible for existing grades.

We need to look into this problem further.

mod/lti/service/gradebookservices/tests/lineitem_test.php

@@ -265,6 +265,106 @@ public function test_sequential_score_posts(): void {
         $this->assertEquals(200, json_decode($response->get_code()));
     }
 
+    /**
+     * Test highlighting the impact of lineitem updated on lineitems and on subsquent score posts.
+     *
+     * @return void
+     */
+    public function test_lineitem_update_rescale_grades(): void {
+        global $CFG;
+        require_once($CFG->dirroot . '/mod/lti/locallib.php');
+        $this->resetAfterTest();
+        $resourceid = 'test-resource-id';
+        $tag = 'tag';
+        $course = $this->getDataGenerator()->create_course();
+        $typeid = $this->create_type();
+        $user = $this->getDataGenerator()->create_and_enrol($course);
+
+        // Create mod instance with line item - nothing pushed via services yet.
+        $gbservice = new gradebookservices();
+        $gbservice->set_type(lti_get_type($typeid));
+        $modinstance = $this->create_graded_lti($typeid, $course, $resourceid, $tag);
+        $gradeitems = $gbservice->get_lineitems($course->id, null, null, null, null, null, $typeid);
+        $this->assertEquals(1, $gradeitems[0]); // The 1st item in the array is the items count.
+        $lineitem = gradebookservices::item_for_json($gradeitems[1][0], '', $typeid);
+
+        // Post a score so that there's at least one grade present at the time of lineitem update.
+        $score = new scores($gbservice);
+        $_SERVER['REQUEST_METHOD'] = \mod_lti\local\ltiservice\resource_base::HTTP_POST;
+        $_SERVER['PATH_INFO'] = "/$course->id/lineitems/{$gradeitems[1][0]->id}/lineitem/scores?type_id=$typeid";
+        $token = lti_new_access_token($typeid, ['https://purl.imsglobal.org/spec/lti-ags/scope/score']);
+        $_SERVER['HTTP_Authorization'] = 'Bearer '.$token->token;
+        $_GET['type_id'] = (string)$typeid;
+        $score->scoreGiven = "8.0";
+        $score->scoreMaximum = "10.0";
+        $score->activityProgress = "Completed";
+        $score->timestamp = "2024-08-07T18:54:36.736+00:00";
+        $score->gradingProgress = "FullyGraded";
+        $score->userId = $user->id;
+        $response = new \mod_lti\local\ltiservice\response();
+        $response->set_content_type('application/vnd.ims.lis.v1.score+json');
+        $response->set_request_data(json_encode($score));
+        $score->execute($response);
+
+        // The grade in Moodle should reflect the score->timestamp, not the time of the score post.
+        $grades = grade_get_grades($course->id, 'mod', 'lti', $modinstance->id, $user->id);
+        $studentgrade = array_shift($grades->items[0]->grades);
+        $this->assertEquals(strtotime($score->timestamp), $studentgrade->dategraded);
+
+        // Required, to ensure that the line item update + rescale takes place at a different timestamp to the original score push.
+        sleep(1);
+
+        // Next, push an update to the maximum score for the line item.
+        // This will trigger a rescale, setting grade->timemodified to the time the rescale took place.
+        $lineitemresource = new lineitem($gbservice);
+        $this->set_server_for_put($course, $typeid, $lineitem);
+        $response = new \mod_lti\local\ltiservice\response();
+        $lineitem->resourceId = $resourceid.'modified';
+        $lineitem->tag = $tag.'modified';
+        $lineitem->scoreMaximum = '20'; // Change the lineitem to make sure a rescale is triggered.
+        $response->set_request_data(json_encode($lineitem));
+        $lineitemupdatetime = time();
+        $lineitemresource->execute($response);
+
+        $grades = grade_get_grades($course->id, 'mod', 'lti', $modinstance->id, $user->id);
+        $studentgrade = array_shift($grades->items[0]->grades);
+        // The grade->timemodified value, which dictates the value of $studentgrade->dategraded,
+        // has been updated to the time the rescale took place.
+        $this->assertGreaterThanOrEqual($lineitemupdatetime, $studentgrade->dategraded);
+
+        // Now, try to post a score update with a timestamp that is greater than the one used in the original score post,
+        // but which is less than the timestamp at which the rescale event took place.
+        // I.e. (timestamp > '2024-08-07T18:54:36.736+00:00' && timestamp < $lineitemupdatetime).
+        $_SERVER['REQUEST_METHOD'] = \mod_lti\local\ltiservice\resource_base::HTTP_POST;
+        $_SERVER['PATH_INFO'] = "/$course->id/lineitems/{$gradeitems[1][0]->id}/lineitem/scores?type_id=$typeid";
+        $token = lti_new_access_token($typeid, ['https://purl.imsglobal.org/spec/lti-ags/scope/score']);
+        $_SERVER['HTTP_Authorization'] = 'Bearer '.$token->token;
+        $_GET['type_id'] = (string)$typeid;
+        $score->scoreGiven = "14";
+        $score->timestamp = date('c', $lineitemupdatetime-1);
+        $response = new \mod_lti\local\ltiservice\response();
+        $response->set_content_type('application/vnd.ims.lis.v1.score+json');
+        $response->set_request_data(json_encode($score));
+        $score->execute($response);
+        // The tool should be able to post a score update.
+        $this->assertEquals(200, json_decode($response->get_code()));
+
+        // The only way to post a score update after a rescale event is by setting score->timestamp to a value which is greater than
+        // the time at which the rescale took place (score->timestamp > $lineitemupdatetime).
+        $_SERVER['REQUEST_METHOD'] = \mod_lti\local\ltiservice\resource_base::HTTP_POST;
+        $_SERVER['PATH_INFO'] = "/$course->id/lineitems/{$gradeitems[1][0]->id}/lineitem/scores?type_id=$typeid";
+        $token = lti_new_access_token($typeid, ['https://purl.imsglobal.org/spec/lti-ags/scope/score']);
+        $_SERVER['HTTP_Authorization'] = 'Bearer '.$token->token;
+        $_GET['type_id'] = (string)$typeid;
+        $score->scoreGiven = "14";
+        $score->timestamp = date('c', $lineitemupdatetime+1);
+        $response = new \mod_lti\local\ltiservice\response();
+        $response->set_content_type('application/vnd.ims.lis.v1.score+json');
+        $response->set_request_data(json_encode($score));
+        $score->execute($response);
+        $this->assertEquals(200, json_decode($response->get_code()));
+    }
+
     /**
      * Inserts a graded lti instance, which should create a grade_item and gradebookservices record.
      *