<?php
/**
 * 可逆加密解密类
 *
 * @author Coeus <r.anerg@gmail.com>
 */

namespace huolib\tool;
class Encrypt {
    /**
     * 获取加密key
     * @return mixed
     */
    private static function getKey() {
        return config('database.authcode');
    }

    /**
     * 加密字符串
     *
     * @param mixed   $data
     * @param integer $expire 有效期（秒）
     * @param string  $key    加密key
     *
     * @return string
     */
    public static function encrypt($data, $expire = 0, $key = '') {
        if (is_array($data)) {
            $data = json_encode($data, JSON_NUMERIC_CHECK | JSON_UNESCAPED_UNICODE);
        }
        $expire = sprintf('%010d', $expire ? $expire + time() : 0);
        if (!$key) {
            $key = self::getKey();
        }
        $key = md5($key);
        $data = base64_encode($expire.$data);
        $x = 0;
        $len = strlen($data);
        $l = strlen($key);
        $char = $str = '';
        for ($i = 0; $i < $len; $i++) {
            if ($x == $l) {
                $x = 0;
            }
            $char .= substr($key, $x, 1);
            $x++;
        }
        for ($i = 0; $i < $len; $i++) {
            $str .= chr(ord(substr($data, $i, 1)) + (ord(substr($char, $i, 1))) % 256);
        }

        return str_replace(array('+', '/', '='), array('-', '_', ''), base64_encode($str));
    }

    /**
     * 解密字符串
     *
     * @param mixed  $data 数据
     * @param string $key  加密key
     *
     * @return string
     */
    public static function decrypt($data, $key = '') {
        if (!$data) {
            return '';
        }
        if (!$key) {
            $key = self::getKey();
        }
        $key = md5($key);
        $data = str_replace(array('-', '_'), array('+', '/'), $data);
        $mod4 = strlen($data) % 4;
        if ($mod4) {
            $data .= substr('====', $mod4);
        }
        $data = base64_decode($data);
        $x = 0;
        $len = strlen($data);
        $l = strlen($key);
        $char = $str = '';
        for ($i = 0; $i < $len; $i++) {
            if ($x == $l) {
                $x = 0;
            }
            $char .= substr($key, $x, 1);
            $x++;
        }
        for ($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)));
            }
        }
        $data = base64_decode($str);
        $expire = substr($data, 0, 10);
        if ($expire > 0 && $expire < time()) {
            return '';
        }
        $data = substr($data, 10);
        $json = json_decode($data, true);

        return json_last_error() === JSON_ERROR_NONE ? $json : $data;
    }
}