package meituan_csr

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

type AES struct {
	AesKey string
}

func NewAes(aesKey string) *AES {
	return &AES{
		AesKey: aesKey,
	}
}

func (c *AES) Encode(data string) (string, error) {
	_key := []byte(c.AesKey)

	block, err := aes.NewCipher(_key)
	if err != nil {
		return "", err
	}
	// 计算需要补齐的字节数
	paddingSize := block.BlockSize() - len([]byte(data))%block.BlockSize()
	paddedText := append([]byte(data), bytes.Repeat([]byte{byte(paddingSize)}, paddingSize)...)

	encryptedData := make([]byte, len(paddedText))
	for i := 0; i < len(paddedText); i += block.BlockSize() {
		block.Encrypt(encryptedData[i:], paddedText[i:]) // 分组加密
	}

	encodedString := base64.StdEncoding.EncodeToString(encryptedData) // Base64编码
	return encodedString, nil
}
func (c *AES) Decode(data string) (str string, err error) {
	_key := []byte(c.AesKey)

	decodedBytes, err := base64.StdEncoding.DecodeString(data) // Base64解码
	if err != nil {
		return "", err
	}
	block, err := aes.NewCipher(_key) // 创建AES对象
	if err != nil {
		return "", err
	}
	decryptedData := make([]byte, len(decodedBytes))
	for i := 0; i < len(decodedBytes); i += block.BlockSize() {
		block.Decrypt(decryptedData[i:], decodedBytes[i:]) // 分组解密
	}
	unpadedText := c._PKCS5UnPadding(decryptedData) // 去除填充
	return string(unpadedText), nil
}

func (c *AES) _PKCS5UnPadding(data []byte) []byte {
	length := len(data)
	unpadding := int(data[length-1])
	return data[:(length - unpadding)]
}