package myCrypto

import (
	"bytes"
	"crypto/aes"
	"crypto/cipher"
	"crypto/rand"
	"crypto/rsa"
	"crypto/x509"
	"encoding/base64"
	"encoding/pem"
	"fmt"
	"os"
	"sync"
)

var (
	instance *CryptoService
	once     sync.Once
)

func CryptoServiceInstance() *CryptoService {
	once.Do(func() {
		instance = &CryptoService{}
	})
	return instance
}

type CryptoService struct {
	rsaPriKey *rsa.PrivateKey
	rsaPubKey *rsa.PublicKey
	aesPriKey []byte
}

func (cryptoService *CryptoService) Init() {
	cryptoService.readAESPriKey()
}

func (cryptoService *CryptoService) EncryptByRSA(msg []byte) (encryptedBytes []byte, err error) {
	//公钥加密
	encryptedBytes, err = rsa.EncryptPKCS1v15(rand.Reader, cryptoService.rsaPubKey, msg)
	if err != nil {
		fmt.Printf("EncryptByRSA failed!, err: %v", err)
		return
	}
	return
}

func (cryptoService *CryptoService) DecryptByRSA(encryptedBytes []byte) (decryptedBytes []byte, err error) {
	//私钥解密
	decryptedBytes, err = rsa.DecryptPKCS1v15(rand.Reader, cryptoService.rsaPriKey, encryptedBytes)
	if err != nil {
		fmt.Printf("DecryptByRSA failed!, err: %v", err)
		return
	}

	return
}

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

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

func (cryptoService *CryptoService) readRSAPubKey() (err error) {
	//读取公钥
	file, err := os.Open("public.pem")
	if err != nil {
		fmt.Printf("Decoding rsa public key failed, check your config, please!, err: %v", err)
		return
	}
	fileInfo, err := file.Stat()
	if err != nil {
		fmt.Printf("Decoding rsa public key failed, check your config, please!, err: %v", err)
		return
	}
	rsaPubKeyBytes := make([]byte, fileInfo.Size())
	file.Read(rsaPubKeyBytes) // 读取公钥文件内容
	file.Close()

	// 2 pem解码
	block, _ := pem.Decode(rsaPubKeyBytes) // 解码

	// 3 x509解析得到公钥
	pubInterface, err := x509.ParsePKIXPublicKey(block.Bytes)
	if err != nil {
		fmt.Printf("Decoding rsa public key failed, check your config, please!, err: %v", err)
		return
	}
	// 断言类型转换
	cryptoService.rsaPubKey = pubInterface.(*rsa.PublicKey)
	return
}

func (cryptoService *CryptoService) readRSAPriKey() (err error) {
	//读取私钥
	file, err := os.Open("private.pem")
	if err != nil {
		fmt.Printf("Decoding rsa public key failed, check your config, please!, err: %v", err)
		return
	}
	fileInfo, err := file.Stat()
	if err != nil {
		fmt.Printf("Decoding rsa public key failed, check your config, please!, err: %v", err)
		return
	}
	rsaPriKeyBytes := make([]byte, fileInfo.Size())
	file.Read(rsaPriKeyBytes)
	file.Close()

	block, _ := pem.Decode(rsaPriKeyBytes)

	fmt.Printf("私钥:\n")
	fmt.Printf("%v", base64.StdEncoding.EncodeToString(block.Bytes))

	rsaPriKey, err := x509.ParsePKCS1PrivateKey(block.Bytes)
	if err != nil {
		fmt.Printf("Decoding rsa primary key failed, check your config, please!, err: %v", err)
		return
	}
	cryptoService.rsaPriKey = rsaPriKey
	return
}

func (cryptoService *CryptoService) readAESPriKey() (aesPriKey []byte) {
	//读取私钥
	aesPriKey = []byte("Xbz1145141919810")
	return
}

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