package utils

import (
	"crypto/cipher"
	"crypto/des"
	"encoding/base64"
)

func DesBase64Decrypt(crypted []byte, desKey string) []byte {
	result, _ := base64.StdEncoding.DecodeString(string(crypted))
	remain := len(result) % 8
	if remain > 0 {
		mod := 8 - remain
		for i := 0; i < mod; i++ {
			result = append(result, 0)
		}
	}
	origData, err := TripleDesDecrypt(result, []byte(desKey))
	if err != nil {
		panic(any(err))
	}
	return origData
}

func TripleDesDecrypt(crypted, key []byte) ([]byte, error) {
	block, err := des.NewTripleDESCipher(key)
	if err != nil {
		return nil, err
	}
	blockMode := cipher.NewCBCDecrypter(block, key[:8])
	origData := make([]byte, len(crypted))
	blockMode.CryptBlocks(origData, crypted)
	origData = PKCS5UnPadding(origData)
	return origData, nil
}

func PKCS5UnPadding(origData []byte) []byte {
	length := len(origData)
	unpadding := int(origData[length-1])
	return origData[:(length - unpadding)]
}