<?php
class DbSession
{
    private static $_instance;

    protected static function log($t) {
        $file = fopen('session.log', 'a+');
        fwrite($file, date('d.m.Y H:i:s ') . $t . PHP_EOL);
        fclose($file);
    }

    public static function setup() {
        self::log('setup');

        require_once('models/sessiondata.php');
        $dbSession = new DbSession(true);
        $dbSession->_sessionModel = new sessiondata();

        session_set_save_handler(array($dbSession, 'open'),
                array($dbSession, 'close'),
                array($dbSession, 'read'),
                array($dbSession, 'write'),
                array($dbSession, 'destroy'),
                array($dbSession, 'clean')
        );
        return $dbSession;
    }

    public static function getInstance() {
        if(empty(self::$_instance)) {
            self::log('instance empty');
            self::$_instance = self::setup();
        } else {
            self::log('instance not empty');
        }
        return self::$_instance;
    }

    public function __construct($firstTime = false)
    {
        $this->log('construct');
        if($firstTime == false) {
            return self::getInstance();
        }
    }

    public function close()
    {
        $this->log('close');
        return true;
    }

    public function open($path, $name)
    {
        $this->log('open '. $path . ' / ' . $name);
        if($this->_sessionModel) {
            return true;
        }
        return true;
    }

    public function read($id)
    {
        $this->log('read ' . $id);
        try {
            $session = $this->_sessionModel->fetch($id);
            $this->log($session->data);
            return $session->data;
        } catch( Exception $e ) {
            return '';
        }
    }

    public function write($id, $data)
    {
        $this->log('write');
        try {
            $session = $this->_sessionModel->fetch($id);
        } catch( Exception $e ) {
            $session = new sessiondata();
        }
        $session->data = $data;
        $session->last_access = time();
        $session->ip = $_SERVER['REMOTE_ADDR'];
        $session->user_agent = $_SERVER['HTTP_USER_AGENT'];
        return $session->save(); //true if ok
    }

    public function destroy($id)
    {
        $this->log('destroy');
        return true;
        try {
            $session = $this->_sessionModel->fetch($id);
            $session->delete();
        } catch( Exception $e ) {

        }
    }

    public function clean($lifetime)
    {
        $this->log('clean');
        return true;
        $old = time() - $lifetime;
        $sessions = $this->_sessionModel->fetchAll("last_access < '$old'");
        if($sessions) {
            foreach($sessions as $session) {
                $session->delete();
            }
        }
    }
}