package encrypt

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

// PKCS5 填充
func pkcs5Padding(src []byte, blockSize int) []byte {
	padding := blockSize - len(src)%blockSize
	padText := bytes.Repeat([]byte{byte(padding)}, padding)
	return append(src, padText...)
}

func AesEncryptCBCPKCS5(plainText, key, iv []byte) ([]byte, error) {

	block, err := aes.NewCipher(key)
	if err != nil {
		return nil, err
	}

	// PKCS5 填充（与 PKCS7 相同，只是 block size 为 8）
	paddedText := pkcs5Padding(plainText, block.BlockSize())

	cipherText := make([]byte, len(paddedText))
	mode := cipher.NewCBCEncrypter(block, iv)
	mode.CryptBlocks(cipherText, paddedText)

	return cipherText, nil
}