<?php
namespace ebcms;

class Crypt
{

    public static function encode($data, $key, $expire = 0)
    {
        if ((int)$expire) {
            $expire = (int)$expire + time();
            $data = $expire . '_' . serialize($data);
        }else{
            $data = '0_' . serialize($data);
        }
        $key = md5($key);
        $x = 0;
        $len = strlen($data);
        $l = strlen($key);
        $char = '';
        for ($i = 0; $i < $len; $i++) {
            if ($x == $l) {
                $x = 0;
            }
            $char .= $key{$x};
            $x++;
        }
        $str = '';
        for ($i = 0; $i < $len; $i++) {
            $str .= chr(ord($data{$i}) + (ord($char{$i})) % 256);
        }
        return base64_encode($str);
    }

    public static function decode($data, $key)
    {
        $key = md5($key);
        $x = 0;
        $data = base64_decode($data);
        $len = strlen($data);
        $l = strlen($key);
        $char = '';
        for ($i = 0; $i < $len; $i++) {
            if ($x == $l) {
                $x = 0;
            }
            $char .= substr($key, $x, 1);
            $x++;
        }
        $str = '';
        for ($i = 0; $i < $len; $i++) {
            if (ord(substr($data, $i, 1)) < ord(substr($char, $i, 1))) {
                $str .= chr((ord(substr($data, $i, 1)) + 256) - ord(substr($char, $i, 1)));
            } else {
                $str .= chr(ord(substr($data, $i, 1)) - ord(substr($char, $i, 1)));
            }
        }
        $pos = mb_strpos($str, '_');
        $expire = (int)mb_substr($str, 0, $pos);
        if ($expire == 0 || $expire > time()) {
            return unserialize(mb_substr($str, $pos + 1));
        }
        return false;
    }

}