MDL-36224: Add support for pluggable extensions to add new LTI services

mod/lti/lib.php

@@ -172,6 +172,22 @@ function lti_delete_instance($id) {
     return $DB->delete_records("lti", array("id" => $basiclti->id));
 }
 
+function lti_get_types() {
+    $type = new stdClass();
+    $type->modclass = MOD_CLASS_ACTIVITY;
+    $type->type = 'lti';
+    $type->typestr = get_string('modulename', 'mod_lti');
+
+    $types = array($type);
+
+    foreach (get_plugin_list('ltisource') as $name => $dir) {
+        if ($moretypes = component_callback("ltisource_$name", 'get_types')) {
+            $types = array_merge($types, $moretypes);
+        }
+    }
+    return $types;
+}
+
 /**
  * Given a coursemodule object, this function returns the extra
  * information needed to print this activity in various places.

mod/lti/mod_form.php

@@ -57,6 +57,10 @@ class mod_lti_mod_form extends moodleform_mod {
     public function definition() {
         global $DB, $PAGE, $OUTPUT, $USER, $COURSE;
 
+        if ($type = optional_param('type', false, PARAM_ALPHA)) {
+            component_callback("ltisource_$type", 'add_instance_hook');
+        }
+        
         $this->typeid = 0;
 
         $mform =& $this->_form;

mod/lti/service.php

@@ -150,10 +150,16 @@ switch ($messagetype) {
         $eventdata = array();
         $eventdata['other'] = array();
         $eventdata['other']['body'] = $rawbody;
+        $eventdata['other']['messageid'] = lti_parse_message_id($xml);
         $eventdata['other']['messagetype'] = $messagetype;
         $eventdata['other']['consumerkey'] = $consumerkey;
         $eventdata['other']['sharedsecret'] = $sharedsecret;
 
+        // Before firing the event, allow subplugins a chance to handle.
+        if (lti_extend_lti_services((object) $eventdata['other'])) {
+            break;
+        }
+
         //If an event handler handles the web service, it should set this global to true
         //So this code knows whether to send an "operation not supported" or not.
         global $lti_web_service_handled;

mod/lti/servicelib.php

@@ -223,3 +223,38 @@ function lti_verify_sourcedid($ltiinstance, $parsed) {
         throw new Exception('SourcedId hash not valid');
     }
 }
+
+/**
+ * Extend the LTI services through the ltisource plugins
+ *
+ * @param stdClass $data LTI request data
+ * @return bool
+ * @throws coding_exception
+ */
+function lti_extend_lti_services($data) {
+    $plugins = get_plugin_list_with_function('ltisource', $data->messagetype);
+    if (!empty($plugins)) {
+        try {
+            // There can only be one
+            if (count($plugins) > 1) {
+                throw new coding_exception('More than one ltisource plugin handler found');
+            }
+            $callback = current($plugins);
+            call_user_func($callback, $data);
+        } catch (moodle_exception $e) {
+            $error = $e->getMessage();
+            if (debugging('', DEBUG_DEVELOPER)) {
+                $error .= ' '.format_backtrace(get_exception_info($e)->backtrace);
+            }
+            $responsexml = lti_get_response_xml(
+                'failure',
+                $error,
+                $data->messageid,
+                $data->messagetype
+            );
+            echo $responsexml->asXML();
+        }
+        return true;
+    }
+    return false;
+}