<?php

/*******************************************************************************
 *
 * CoreSessionHandler.php - Class to handle PHP session data
 *
 * Copyright (c) 2004-2016 NagVis Project (Contact: info@nagvis.org)
 *
 * License:
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 ******************************************************************************/

/**
 * Class for handlin the PHP sessions. The sessions are used to store
 * information between loading different pages.
 *
 * @author Lars Michelsen <lm@larsmichelsen.com>
 */
class CoreSessionHandler
{
    /**
     * @throws ErrorException
     */
    public function __construct()
    {
        $sDomain = cfg('global', 'sesscookiedomain');
        $sPath = cfg('global', 'sesscookiepath');
        $iDuration = cfg('global', 'sesscookieduration');
        $bSecure = cfg('global', 'sesscookiesecure') == 1;
        $bHTTPOnly = cfg('global', 'sesscookiehttponly') == 1;

        // Set the session name (used in params/cookie names)
        session_name(SESSION_NAME);

        // Only add the domain when it is no simple hostname
        // This can be easily detected searching for a dot
        if (!str_contains($sDomain, '.')) {
            $sDomain = null;
        }

        // Opera has problems with ip addresses in domains. So skip them
        if (
            str_contains($_SERVER['HTTP_USER_AGENT'], 'opera')
            && preg_match('/\d.\d+.\d+.\d+/', $sDomain)
        ) {
            $sDomain = null;
        }

        // Set custom params for the session cookie
        if (version_compare(PHP_VERSION, '5.2') >= 0) {
            session_set_cookie_params(0, $sPath, $sDomain, $bSecure, $bHTTPOnly);
        } else {
            session_set_cookie_params(0, $sPath, $sDomain, $bSecure);
        }

        // Start a session for the user when not started yet
        if (!isset($_SESSION)) {
            try {
                session_start();
                // Write/close to release the lock aquired by session_start().
                // Each write to the session needs to perform session_start() again
                session_write_close();
            } catch (ErrorException $e) {
                // Catch and suppress session cleanup errors. This is a problem
                // especially on current debian/ubuntu:
                //   PHP error in ajax request handler: Error: (8) session_start():
                //   ps_files_cleanup_dir: opendir(/var/lib/php5) failed: Permission denied (13)
                if (!str_contains($e->getMessage(), 'ps_files_cleanup_dir')) {
                    throw $e;
                }
            }

            // Store the creation time of the session
            if (!$this->isSetAndNotEmpty('sessionExpires')) {
                $this->set('sessionExpires', time() + $iDuration);
            }
        }

        // Reset the expiration time of the session cookie
        if (isset($_COOKIE[SESSION_NAME])) {
            // Don't reset the expiration time on every page load - only reset when
            // the half of the expiration time has passed
            if (time() >= $this->get('sessionExpires') - ($iDuration / 2)) {
                $exp = time() + $iDuration;
                setcookie(SESSION_NAME, $_COOKIE[SESSION_NAME], $exp, $sPath, $sDomain, $bSecure, $bHTTPOnly);

                // Store the update time of the session cookie
                $this->set('sessionExpires', $exp);
            }
        }
    }

    /**
     * @param string $sKey
     * @return bool
     */
    public function isSetAndNotEmpty($sKey)
    {
        return isset($_SESSION[$sKey]) && $_SESSION[$sKey] != '';
    }

    /**
     * @param string $sKey
     * @return false|mixed
     */
    public function get($sKey)
    {
        if (isset($_SESSION[$sKey])) {
            return $_SESSION[$sKey];
        } else {
            return false;
        }
    }

    /**
     * @param string $sKey
     * @param mixed $sVal
     * @return false|mixed
     */
    public function set($sKey, $sVal)
    {
        if (isset($_SESSION[$sKey])) {
            $sOld = $_SESSION[$sKey];
        } else {
            $sOld = false;
        }

        if (!$sVal) {
            unset($_SESSION[$sKey]);
        } else {
            $_SESSION[$sKey] = $sVal;
        }

        return $sOld;
    }

    /**
     * @param string $key
     * @return void
     */
    public function del($key)
    {
        unset($_SESSION[$key]);
    }

    /**
     * @return void
     */
    public function aquire()
    {
        session_start();
    }

    /**
     * @return void
     */
    public function commit()
    {
        session_write_close();
    }
}
