Gdn::userModel PHP Method

    public static function userModel()
    {
        return self::factory(self::AliasUserModel);
    }

 public function pluginController_quoteMention_create($sender, $discussionID, $commentID, $username)
 {
     $sender->deliveryMethod(DELIVERY_METHOD_JSON);
     $user = Gdn::userModel()->getByUsername($username);
     $discussionModel = new DiscussionModel();
     $discussion = $discussionModel->getID($discussionID);
     if (!$user || !$discussion) {
         throw notFoundException();
     }
     // Make sure this endpoint can't be used to snoop around.
     $sender->permission('Vanilla.Discussions.View', true, 'Category', $discussion->PermissionCategoryID);
     // Find the previous comment of the mentioned user in this discussion.
     $item = Gdn::sql()->getWhere('Comment', ['DiscussionID' => $discussion->DiscussionID, 'InsertUserID' => $user->UserID, 'CommentID <' => $commentID], 'CommentID', 'desc', 1)->firstRow();
     // The items ID in the DOM used for highlighting.
     if ($item) {
         $target = '#Comment_' . $item->CommentID;
         // The mentioned user might be the discussion creator.
     } elseif ($discussion->InsertUserID == $user->UserID) {
         $item = $discussion;
         $target = '#Discussion_' . $item->DiscussionID;
     }
     if (!$item) {
         // A success response code always means that a comment was found.
         $sender->statusCode(404);
     }
     $sender->renderData($item ? ['html' => nl2br(sliceString(Gdn_Format::plainText($item->Body, $item->Format), c('QuoteMention.MaxLength', 400))), 'target' => $target] : []);
 }