package mycrypto

import (
	"bytes"
	"crypto/aes"
	"crypto/cipher"
	"service/library/configcenter"
	"service/library/logger"
)

type AesCrypto struct {
	aesPriKey []byte
}

func NewAesCrypto(cryptoConfig *configcenter.CryptoConfig) (aesCrypto *AesCrypto, err error) {
	aesCrypto = &AesCrypto{}

	//读取私钥
	if aesCrypto.readAESPriKey(cryptoConfig) != nil {
		logger.Error("read rsa primary key failed!", err)
		return
	}
	return
}

func NewAesCryptoFromString(aesPrivateKeyStr string) (aesCrypto *AesCrypto, err error) {
	aesCrypto = &AesCrypto{}

	//读取私钥
	aesCrypto.aesPriKey = []byte(aesPrivateKeyStr)
	return
}

func (aesCrypto *AesCrypto) Encrypt(msg []byte) (encryptedBytes []byte, err error) {
	//CBC加密
	block, err := aes.NewCipher(aesCrypto.aesPriKey) //block
	if err != nil {
		logger.Error("AES NewCipher failed!, err: %v", err)
		return nil, err
	}
	blockSize := block.BlockSize()                                              //密钥块长度
	paddedData := aesCrypto.pkcs5Padding(msg, blockSize)                        //填充
	blockMode := cipher.NewCBCEncrypter(block, aesCrypto.aesPriKey[:blockSize]) //加密模式
	encryptedBytes = make([]byte, len(paddedData))                              //创建数组
	blockMode.CryptBlocks(encryptedBytes, paddedData)                           //加密
	return
}

func (aesCrypto *AesCrypto) Decrypt(encryptedBytes []byte) (decryptedBytes []byte, err error) {
	if len(encryptedBytes) == 0 {
		return
	}
	//CBC解密
	block, _ := aes.NewCipher(aesCrypto.aesPriKey)                              // 分组秘钥
	blockSize := block.BlockSize()                                              // 获取秘钥块的长度
	blockMode := cipher.NewCBCDecrypter(block, aesCrypto.aesPriKey[:blockSize]) // 加密模式
	decryptedBytes = make([]byte, len(encryptedBytes))                          // 创建数组
	blockMode.CryptBlocks(decryptedBytes, encryptedBytes)                       // 解密
	decryptedBytes = aesCrypto.pkcs5UnPadding(decryptedBytes)                   // 去除补全码
	return
}

func (aesCrypto *AesCrypto) readAESPriKey(cryptoConfig *configcenter.CryptoConfig) (err error) {
	//读取私钥
	aesCrypto.aesPriKey = []byte(cryptoConfig.AESPrivateKey)
	return
}

func (aesCrypto *AesCrypto) pkcs5Padding(ciphertext []byte, blockSize int) []byte {
	padding := blockSize - len(ciphertext)%blockSize        //判断缺少几位长度。最少1，最多 blockSize
	padtext := bytes.Repeat([]byte{byte(padding)}, padding) //补足位数。把切片[]byte{byte(padding)}复制padding个
	return append(ciphertext, padtext...)
}

func (aesCrypto *AesCrypto) pkcs5UnPadding(origData []byte) []byte {
	length := len(origData)
	unpadding := int(origData[length-1])
	return origData[:(length - unpadding)]
}