package util

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

var aesKey []byte

func init() {
	aesKey = []byte("11e90a62f2fa07ce9e600242ac110007")
}

func pkcs7Padding(src []byte, blockSize int) []byte {
	padding := blockSize - len(src)%blockSize
	padText := bytes.Repeat([]byte{byte(padding)}, padding)
	return append(src, padText...)
}

func aesEncrypt(src, key []byte) ([]byte, error) {
	block, err := aes.NewCipher(key)
	if err != nil {
		return nil, err
	}
	blockSize := block.BlockSize()
	src = pkcs7Padding(src, blockSize)
	blockMode := cipher.NewCBCEncrypter(block, key[:blockSize])
	encrypted := make([]byte, len(src))
	blockMode.CryptBlocks(encrypted, src)
	return encrypted, nil
}

func aesDecrypt(encrypted, key []byte) ([]byte, error) {
	block, err := aes.NewCipher(key)
	if err != nil {
		return nil, err
	}
	blockSize := block.BlockSize()
	blockMode := cipher.NewCBCDecrypter(block, key[:blockSize])
	src := make([]byte, len(encrypted))
	blockMode.CryptBlocks(src, encrypted)
	src = pkcs7UnPadding(src)
	return src, nil
}

func pkcs7UnPadding(src []byte) []byte {
	length := len(src)
	unPadding := int(src[length-1])
	return src[:(length - unPadding)]
}

func AesEncrypt(src string) (string, error) {
	res, err := aesEncrypt([]byte(src), aesKey)
	if err != nil {
		r := base64.StdEncoding.EncodeToString(res)
		return r, nil
	} else {
		return "", err
	}
}

func AesDecrypt(src string) (string, error) {
	if len(src) == 0 || strings.TrimSpace(src) == "" {
		return "", nil
	}
	s, e := base64.StdEncoding.DecodeString(src)
	if e != nil {
		return "", e
	}
	res, err := aesDecrypt(s, aesKey)
	return string(res), err
}