<?php

/*
 * This file is part of the overtrue/wechat.
 *
 * (c) overtrue <i@overtrue.me>
 *
 * This source file is subject to the MIT license that is bundled
 * with this source code in the file LICENSE.
 */

namespace douyin;

use app\common\exception\Exception;
use douyin\AES;

/**
 * Class Encryptor.
 *
 * @author mingyoung <mingyoungcheung@gmail.com>
 */
class Encryptor
{
    /**
     * Decrypt data.
     *
     * @param string $sessionKey
     * @param string $iv
     * @param string $encrypted
     *
     * @return array
     */
    public function decryptData(string $sessionKey, string $iv, string $encrypted): array
    {

        $decrypted = AES::decrypt(
            base64_decode($encrypted, false), base64_decode($sessionKey, false), base64_decode($iv, false)
        );

        $decrypted = json_decode($this->pkcs7Unpad($decrypted), true);
        if (!$decrypted) {
            throw new Exception('The given payload is invalid.');
        }

        return $decrypted;
    }


    const ERROR_INVALID_SIGNATURE = -40001; // Signature verification failed
    const ERROR_CALC_SIGNATURE = -40003; // Calculating the signature failed
    const ERROR_INVALID_AES_KEY = -40004; // Invalid AESKey
    const ERROR_INVALID_APP_ID = -40005; // Check AppID failed
    const ERROR_ENCRYPT_AES = -40006; // AES EncryptionInterface failed
    const ERROR_DECRYPT_AES = -40007; // AES decryption failed
    const ERROR_BASE64_ENCODE = -40009; // Base64 encoding failed
    const ERROR_BASE64_DECODE = -40010; // Base64 decoding failed
    const ILLEGAL_BUFFER = -41003; // Illegal buffer

    /**
     * @var string
     */
    protected $aesKey;

    /**
     * Block size.
     *
     * @var int
     */
    protected $blockSize = 32;

    /**
     * Constructor.
     *
     * @param string      $appId
     * @param string|null $token
     * @param string|null $aesKey
     */
    public function __construct(string $aesKey = null)
    {
        $this->aesKey = base64_decode($aesKey.'=', true);
    }


    /**
     * Get SHA1.
     *
     * @return string
     *
     * @throws self
     */
    public function signature(): string
    {
        $array = func_get_args();
        sort($array, SORT_STRING);

        return sha1(implode($array));
    }

    /**
     * PKCS#7 pad.
     *
     * @param string $text
     * @param int    $blockSize
     *
     * @return string
     *
     */
    public function pkcs7Pad($text, $blockSize)
    {
        if ($blockSize > 256) {
            throw new Exception('$blockSize may not be more than 256');
        }
        $padding = $blockSize - (strlen($text) % $blockSize);
        $pattern = chr($padding);

        return $text.str_repeat($pattern, $padding);
    }

    /**
     * PKCS#7 unpad.
     *
     * @param string $text
     *
     * @return string
     */
    public function pkcs7Unpad($text)
    {
        $pad = ord(substr($text, -1));
        if ($pad < 1 || $pad > $this->blockSize) {
            $pad = 0;
        }

        return substr($text, 0, (strlen($text) - $pad));
    }
}