function getClient() {
        $client = new Google_Client();
        $client->setApplicationName("DL Calendar");
        $client->setAuthConfig('application/client_secrets.json');
        $client->addScope('profile');
        $client->setIncludeGrantedScopes(true);
        $client->setAccessType('offline');

        return $client;
}

  function gcalendar() {
    $this->load->add_package_path(APPPATH . 'vendor/autoload');

    $client = $this->getClient();
    //$client->setRedirectUri(site_url('calendar/index'));
    $client->addScope(Google_Service_Calendar::CALENDAR);

    if (isset($_SESSION['access_token']) && $_SESSION['access_token']) {

        $client->setAccessToken($_SESSION['access_token']);
        $access_token = $_SESSION['access_token'];

        $service = new ]Google_Service_Calendar($client);
        $calendar = new Google_Service_Calendar_Calendar();
                //$calendarList = $service->calendarList->listCalendarList();
        $calendar = $service->calendars->get('primary');

               $params = array(
                    'owner_id' => get_current_user_id(),
                    'title' => get_current_user(). ' ' .'Google Calendar',
                    'type' => 'gcal',
                    'url' => $calendar->id,
                );

        $calendar_id = $this->Calendar_model->add_calendar($params);
        redirect('calendar/index');

    } else {

        $redirect_uri = site_url('calendar/oauth2callback');
        header('Location: ' . filter_var($redirect_uri, FILTER_SANITIZE_URL));
     }
        $this->session->set_flashdata('success', 'Event Successfully Added');
}

//Build the client object
        $client = $this->getClient();
        $client->addScope(Google_Service_Calendar::CALENDAR);
        $service = new Google_Service_Calendar($client);

        $url = parse_url($_SERVER['REQUEST_URI']); parse_str($url['query'], $params);
        $code = $params['code'];

    //To exchange an authorization code for an access token, use the authenticate method:
        if (! isset($code)) {
            $auth_url = $client->createAuthUrl();
            header('Location: ' . filter_var($auth_url, FILTER_SANITIZE_URL));

        } else {

            $token = $client->fetchAccessTokenWithAuthCode($code);
            $client->setAccessToken($token);
            $client->authenticate($code);
            $_SESSION['access_token'] = $client->getAccessToken();
            $redirect_uri = site_url('calendar/gcalendar');
            header('Location: ' . filter_var($redirect_uri, FILTER_SANITIZE_URL));
         }

function gcalendar_events() {
    $client = $this->getClient();

    $client->addScope(Google_Service_Calendar::CALENDAR);
   // $client->setRedirectUri(site_url('calendar/gcalendar'));
    $client->setAccessType('offline'); //need calendar events to appear even if not logged in to google
    if (isset($_SESSION['access_token']) && $_SESSION['access_token']) {

        $client->setAccessToken($_SESSION['access_token']);
        $access_token = $_SESSION['access_token'];

        $service = new Google_Service_Calendar($client);
        $id = 'primary';
        $calendar = new Google_Service_Calendar_Calendar();
        $calendar = $service->calendars->get('primary');

        $event = new Google_Service_Calendar_Event();

        $events = $service->events->listEvents($id);

            foreach ($events->getItems() as $event) {

                $startTime = strtotime($event->getStart()->dateTime)  ;
                $endTime = strtotime($event->getEnd()->dateTime);
                $start = date('Y-m-d H:i:s', $startTime);
                $end = date('Y-m-d H:i:s', $endTime);

                $eventsArr[] = array(
                                'title' => $event->getSummary(),
                                'start'=> $start,
                                'end' =>  $end,
                            );
                        }
                        // Return a single `events` with all the `$eventsArr`
                        echo json_encode($eventsArr);


    }
}

if ($client->isAccessTokenExpired()) {
                            $refresh_token =     $client->fetchAccessTokenWithRefreshToken($client->getRefreshToken());
                            $client->setAccessToken($refresh_token);
                            $_SESSION['access_token'] = $refresh_token;
                            $this->load->helper('file');
                         write_file('application/client_secrets.json',   json_encode($client->getAccessToken()));
     } else {
        $access_token = $_SESSION['access_token'];
            }

$token = $client->getAccessToken();
$authObj = json_decode($token);
if(isset($authObj->refresh_token)) {
save_refresh_token($authObj->refresh_token);
}

$client->refreshToken($your_saved_refresh_token);

$_SESSION['access_token'] = $client->getAccessToken();