function reEstablishSessionInIframe()

in public/lib/user.js [44:112]
25 lines of code
4 McCabe index (conditional complexity)

        function reEstablishSessionInIframe() {

            if (!$sessionCheckFrame) {
                // singleton iframe
                $sessionCheckFrame = angular.element('<iframe class="login-check__frame">');

                angular.element($window.document.body).append($sessionCheckFrame);
            }

            return new Promise((resolve, reject) => {

                var timeout;

                function postMessageListener(event) {
                    // checks for "originalEvent" object, available when jquery is in the page
                    var eventData = event.originalEvent && event.originalEvent.data || event.data;

                    if (eventData) { // TODO: check for sessionCheck identifier in message data

                        $$window.off('message', postMessageListener);
                        $timeout.cancel(timeout);

                        resolve(eventData);
                    }

                }


                $$window.on('message', postMessageListener);


                // Timeout fallback
                timeout = $timeout(function () {

                    $$window.off('message', postMessageListener);

                    reject(new Error('Timeout loading URL in iframe: ' + SESSION_CHECK_URL));

                }, IFRAME_TIMEOUT);


                $sessionCheckFrame.one('load', function () {

                    try {
                        // When logged out, google auth refuses to load in an iframe by setting the X-Frame-Options header
                        // we can sort of detect this by checking the location of the iframe
                        // if the contentDocument object cannot be accessed, its due to a security error.
                        // security error will occur when the frame is on a different origin

                        if ($sessionCheckFrame[0].contentDocument.location) {
                            // loaded successfully - now wait for a postMessage with the user object.
                        }

                    } catch (err) {

                        $$window.off('message', postMessageListener);
                        $timeout.cancel(timeout);

                        reject(err);
                    }


                });


                $sessionCheckFrame.attr('src', SESSION_CHECK_URL);

            });
        }