<?php

// +----------------------------------------------------------------------
// | WeChatDeveloper
// +----------------------------------------------------------------------
// | 版权所有 2014~2020 广州楚才信息科技有限公司 [ http://www.cuci.cc ]
// +----------------------------------------------------------------------
// | 官方网站: http://think.ctolog.com
// +----------------------------------------------------------------------
// | 开源协议 ( https://mit-license.org )
// +----------------------------------------------------------------------
// | github开源项目：https://github.com/zoujingli/WeChatDeveloper
// +----------------------------------------------------------------------

namespace WePayV3\Contracts;

use WeChat\Exceptions\InvalidArgumentException;
use WeChat\Exceptions\InvalidDecryptException;

/**
 * Aes 解密工具类
 * Class DecryptAes
 * @package WePayV3\Contracts
 */
class DecryptAes
{

    private $aesKey;

    const KEY_LENGTH_BYTE = 32;
    const AUTH_TAG_LENGTH_BYTE = 16;

    /**
     * Constructor
     * @param string $aesKey
     */
    public function __construct($aesKey)
    {
        if (strlen($aesKey) != self::KEY_LENGTH_BYTE) {
            throw new InvalidArgumentException('无效的ApiV3Key，长度应为32个字节');
        }
        $this->aesKey = $aesKey;
    }

    /**
     * Decrypt AEAD_AES_256_GCM ciphertext
     * @param string $associatedData AES GCM additional authentication data
     * @param string $nonceStr AES GCM nonce
     * @param string $ciphertext AES GCM cipher text
     * @return string|bool      Decrypted string on success or FALSE on failure
     * @throws InvalidDecryptException
     */
    public function decryptToString($associatedData, $nonceStr, $ciphertext)
    {
        $ciphertext = \base64_decode($ciphertext);
        if (strlen($ciphertext) <= self::AUTH_TAG_LENGTH_BYTE) {
            return false;
        }
        try {
            // ext-sodium (default installed on >= PHP 7.2)
            if (function_exists('\sodium_crypto_aead_aes256gcm_is_available') && \sodium_crypto_aead_aes256gcm_is_available()) {
                return \sodium_crypto_aead_aes256gcm_decrypt($ciphertext, $associatedData, $nonceStr, $this->aesKey);
            }
            // ext-libsodium (need install libsodium-php 1.x via pecl)
            if (function_exists('\Sodium\crypto_aead_aes256gcm_is_available') && \Sodium\crypto_aead_aes256gcm_is_available()) {
                return \Sodium\crypto_aead_aes256gcm_decrypt($ciphertext, $associatedData, $nonceStr, $this->aesKey);
            }
            // openssl (PHP >= 7.1 support AEAD)
            if (PHP_VERSION_ID >= 70100 && in_array('aes-256-gcm', \openssl_get_cipher_methods())) {
                $ctext = substr($ciphertext, 0, -self::AUTH_TAG_LENGTH_BYTE);
                $authTag = substr($ciphertext, -self::AUTH_TAG_LENGTH_BYTE);
                return \openssl_decrypt($ctext, 'aes-256-gcm', $this->aesKey, \OPENSSL_RAW_DATA, $nonceStr, $authTag, $associatedData);
            }
        } catch (\Exception $exception) {
            throw new InvalidDecryptException($exception->getMessage(), $exception->getCode());
        } catch (\SodiumException $exception) {
            throw new InvalidDecryptException($exception->getMessage(), $exception->getCode());
        }
        throw new InvalidDecryptException('AEAD_AES_256_GCM 需要 PHP 7.1 以上或者安装 libsodium-php');
    }
}