package utils

import (
	"bytes"
	"crypto/aes"
	"crypto/cipher"
)

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

// PKCS5UnPadding exported
func PKCS5UnPadding(srcBytes []byte) []byte {
	length := len(srcBytes)
	unpadding := int(srcBytes[length-1])
	return srcBytes[:(length - unpadding)]
}

// AesCbcEnc encrypter
func AesCbcEnc(srcBytes []byte, key, iv string) ([]byte, error) {
	block, err := aes.NewCipher([]byte(key))
	if err != nil {
		return nil, err
	}
	blockSize := block.BlockSize()
	srcBytes = PKCS5Padding(srcBytes, blockSize)
	blockMode := cipher.NewCBCEncrypter(block, []byte(iv))
	encrypted := make([]byte, len(srcBytes))
	blockMode.CryptBlocks(encrypted, srcBytes)
	return encrypted, nil
}

// AesCbcDec decrypter
func AesCbcDec(srcBytes []byte, key, iv string) ([]byte, error) {
	block, err := aes.NewCipher([]byte(key))
	if err != nil {
		return nil, err
	}
	blockMode := cipher.NewCBCDecrypter(block, []byte(iv))
	decrypted := make([]byte, len(srcBytes))
	blockMode.CryptBlocks(decrypted, srcBytes)
	decrypted = PKCS5UnPadding(decrypted)
	return decrypted, nil
}

// AesCfbEnc encrypter
func AesCfbEnc(srcBytes []byte, key, iv string) ([]byte, error) {
	block, err := aes.NewCipher([]byte(key))
	if err != nil {
		return nil, err
	}
	encrypter := cipher.NewCFBEncrypter(block, []byte(iv))
	encrypted := make([]byte, len(srcBytes))
	encrypter.XORKeyStream(encrypted, srcBytes)
	return encrypted, nil
}

// AesCfbDec decrypter
func AesCfbDec(srcBytes []byte, key, iv string) ([]byte, error) {
	block, err := aes.NewCipher([]byte(key))
	if err != nil {
		return nil, err
	}
	decrypter := cipher.NewCFBDecrypter(block, []byte(iv))
	decrypted := make([]byte, len(srcBytes))
	decrypter.XORKeyStream(decrypted, srcBytes)
	return decrypted, nil
}