<?php
/**
 * Created by PhpStorm.
 * User: jianjun
 * Date: 2016/11/17
 * Time: 17:12
 */

namespace api\libs;
use yii\base\Exception;

/**
 * 微信小程序加密解密包
 * Class WxBizDecrypt
 * @package api\lib
 */
class WxBizDecrypt
{

    public static $OK = 0;
    public static $IllegalAesKey = -41001;
    public static $IllegalIv = -41002;
    public static $IllegalBuffer = -41003;
    public static $DecodeBase64Error = -41004;

    public static $IllegalSessionKey = -41005;

    public static $block_size = 16;

    public static $appid = '';
    public static $appSecret = '';


    /**
     * 获取SessionKey 以及Openid
     * SessionKey 获取更多加密信息，如unionId
     * @param $code
     * @return Int
     */
    static function getSessionkey($code,&$data){
        $url = "https://api.weixin.qq.com/sns/jscode2session?appid=".self::$appid."&secret=".self::$appSecret."&js_code=$code&grant_type=authorization_code";
        $result = self::getHtml($url);
        $resultObj = json_decode($result);
        if($resultObj== null){
            return self::$IllegalSessionKey;
        }
        $data = $result;
        return self::$OK;
    }

    protected static function getHtml($url){
        $ch = curl_init();
        $timeout = 5;
        curl_setopt($ch, CURLOPT_URL, $url);
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
        curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, $timeout);
        $result = curl_exec($ch);
        curl_close($ch);
        return $result;
    }


    /**
     * 检验数据的真实性，并且获取解密后的明文.
     * @param $encryptedData string 加密的用户数据
     * @param $iv string 与用户数据一同返回的初始向量
     * @param $data string 解密后的原文
     *
     * @return int 成功0，失败返回对应的错误码
     */
    static function decryptData( $encryptedData, $iv,$sessionKey, &$data )
    {
        if (strlen($sessionKey) != 24) {
            return self::$IllegalAesKey;
        }
        $aesKey=base64_decode($sessionKey);


        if (strlen($iv) != 24) {
            return self::$IllegalIv;
        }
        $aesIV=base64_decode($iv);

        $aesCipher=base64_decode($encryptedData);


        $result = self::decrypt($aesCipher,$aesIV,$aesKey);

        if ($result[0] != 0) {
            return $result[0];
        }
        $dataObj=json_decode( $result[1] );

        if( $dataObj  == NULL )
        {
            return self::$IllegalBuffer;
        }
        if( $dataObj->watermark->appid != self::$appid )
        {

            return self::$IllegalBuffer;
        }
        $data = $result[1];
        return self::$OK;
    }


    /**
     * 对需要加密的明文进行填充补位
     * @param $text 需要进行填充补位操作的明文
     * @return 补齐明文字符串
     */
    static function encode( $text )
    {
        $text_length = strlen( $text );
        //计算需要填充的位数
        $amount_to_pad = self::$block_size - ( $text_length % self::$block_size );
        if ( $amount_to_pad == 0 ) {
            $amount_to_pad = self::$block_size;
        }
        //获得补位所用的字符
        $pad_chr = chr( $amount_to_pad );
        $tmp = "";
        for ( $index = 0; $index < $amount_to_pad; $index++ ) {
            $tmp .= $pad_chr;
        }
        return $text . $tmp;
    }

    /**
     * 对解密后的明文进行补位删除
     * @param decrypted 解密后的明文
     * @return 删除填充补位后的明文
     */
    static function decode($text)
    {

        $pad = ord(substr($text, -1));
        if ($pad < 1 || $pad > 32) {
            $pad = 0;
        }
        return substr($text, 0, (strlen($text) - $pad));
    }

    /**
     * 对密文进行解密
     * @param string $aesCipher 需要解密的密文
     * @param string $aesIV 解密的初始向量
     * @return string 解密得到的明文
     */
    static function decrypt( $aesCipher, $aesIV ,$key)
    {
        try {

            $module = mcrypt_module_open(MCRYPT_RIJNDAEL_128, '', MCRYPT_MODE_CBC, '');

            mcrypt_generic_init($module, $key, $aesIV);

            //解密
            $decrypted = mdecrypt_generic($module, $aesCipher);
            mcrypt_generic_deinit($module);
            mcrypt_module_close($module);
        } catch (Exception $e) {
            return array(self::$IllegalBuffer, null);
        }


        try {
            //去除补位字符
            $result = self::decode($decrypted);

        } catch (Exception $e) {
            //print $e;
            return array(self::$IllegalBuffer, null);
        }
        return array(0, $result);
    }
}