(function() {
    'use strict';

    var CHECK_INTERVAL = 30000; 
    var SESSION_CHECK_URL = 'login.cgi';


    function initSessionCheck() {
        if (window.location.pathname.indexOf('login.html') !== -1) {
            return;
        }

        checkSession();

        setInterval(checkSession, CHECK_INTERVAL);

        document.addEventListener('mousemove', resetTimer);
        document.addEventListener('keydown', resetTimer);
        document.addEventListener('click', resetTimer);
    }

    function checkSession() {
        var xhr = new XMLHttpRequest();
        xhr.open('GET', SESSION_CHECK_URL + '?t=' + Date.now(), true);
        xhr.setRequestHeader('Cache-Control', 'no-cache');

        xhr.onreadystatechange = function() {
            if (xhr.readyState === 4) {
                var response = xhr.responseText || '';

                if (response.indexOf('UNAUTHORIZED') !== -1) {
                    redirectToLogin();
                    return;
                }

                if (response.indexOf('OK') !== -1) {
                    return;
                }
            }
        };

        try {
            xhr.send();
        } catch (e) {
            console.log('Session check failed:', e);
        }
    }

    function redirectToLogin() {
        var currentUrl = window.location.href;
        var loginUrl = 'login.html?redirect=' + encodeURIComponent(currentUrl);

        if (window.top !== window.self) {
            window.top.location.href = loginUrl;
        } else {
            window.location.href = loginUrl;
        }
    }

    var sessionTimer;
    function resetTimer() {
        clearTimeout(sessionTimer);
        sessionTimer = setTimeout(function() {
            checkSession();
        }, 60000);
    }

    if (document.readyState === 'loading') {
        document.addEventListener('DOMContentLoaded', initSessionCheck);
    } else {
        initSessionCheck();
    }
})();