package common

import (
	"bytes"
	"crypto/aes"
	"crypto/cipher"
	"encoding/base64"
)

func Aes_CBC_Decrypt(crypted []byte, key, iv []byte) ([]byte, error) {
	block, err := aes.NewCipher(key)
	if err != nil {
		return nil, err
	}
	blockMode := cipher.NewCBCDecrypter(block, iv)
	origData := make([]byte, len(crypted))
	blockMode.CryptBlocks(origData, crypted)
	origData = unpadding(origData)
	return origData, nil
}

func unpadding(cipherText []byte) []byte {
	end := cipherText[len(cipherText)-1]
	cipherText = cipherText[:len(cipherText)-int(end)]

	return cipherText
}

func Aes_CBC_Encrypt(data []byte, key, iv []byte) (string, error) {
	block, err := aes.NewCipher(key)
	if err != nil {
		return "", err
	}
	origData := padding([]byte(data), block.BlockSize())
	println("block ", block.BlockSize())
	println("block2 ", len(iv))
	blockMode := cipher.NewCBCEncrypter(block, iv)
	crypted := make([]byte, len(origData))
	blockMode.CryptBlocks(crypted, origData)
	return base64.StdEncoding.EncodeToString(crypted), nil
}

func padding(plainText []byte, blockSize int) []byte {
	n := blockSize - len(plainText)%blockSize
	temp := bytes.Repeat([]byte{byte(n)}, n)
	plainText = append(plainText, temp...)

	return plainText
}