package licence

import (
	"bytes"
	"crypto/aes"
	"crypto/cipher"
	"crypto/md5"
	"encoding/hex"
	"fmt"
	"strings"
)

var ivspec = []byte("0000000000000000")

func GetMd5String(s string, upper bool, half bool) string {
	h := md5.New()
	h.Write([]byte(s))
	result := hex.EncodeToString(h.Sum(nil))
	if upper == true {
		result = strings.ToUpper(result)
	}
	if half == true {
		result = result[8:24]
	}
	return result
}

func AESEncodeStr(src []byte, key string) string {
	block, err := aes.NewCipher([]byte(key))
	if err != nil {
		fmt.Println("key error1", err)
	}
	if src == nil {
		fmt.Println("plain content empty")
	}
	ecb := cipher.NewCBCEncrypter(block, ivspec)
	content := PKCS5Padding(src, block.BlockSize())
	crypted := make([]byte, len(content))
	ecb.CryptBlocks(crypted, content)

	return hex.EncodeToString(crypted)
}

func AESDecodeStr(crypt, key string) []byte {
	crypted, err := hex.DecodeString(strings.ToLower(crypt))
	if err != nil || len(crypted) == 0 {
		return nil
	}

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

	decrypted := make([]byte, len(crypted))
	bs := block.BlockSize()
	if len(crypted)%bs != 0 {
		return nil
	}

	ecb := cipher.NewCBCDecrypter(block, ivspec)
	ecb.CryptBlocks(decrypted, crypted)

	return PKCS5Trimming(decrypted)
}

func PKCS5Padding(ciphertext []byte, blockSize int) []byte {
	padding := blockSize - len(ciphertext)%blockSize
	padtext := bytes.Repeat([]byte{byte(padding)}, padding)
	return append(ciphertext, padtext...)
}

func PKCS5Trimming(encrypt []byte) []byte {
	length := len(encrypt)
	number := int(encrypt[length-1])
	if number >= length {
		return nil
	}
	return encrypt[:length-number]
}