package utils

import (
	"crypto/aes"
	"crypto/cipher"
	"crypto/rand"
	"crypto/sha256"
	"encoding/base64"
	"errors"
	"io"
	"os"
)

var EncryptionKey = ")ZLxR6X@h5tYGhkwin<j"

// use sha256 to get 32 bytes key
func getAESKey(key string) []byte {
	selfSecretKey := os.Getenv("ENCRYPTION_KEY")
	if selfSecretKey != "" {
		key = selfSecretKey
	} else {
		key = EncryptionKey
	}
	hash := sha256.Sum256([]byte(key))
	return hash[:]
}

func Encrypt(plaintext, secret string) (string, error) {
	key := getAESKey(secret)
	block, err := aes.NewCipher(key)
	if err != nil {
		return "", err
	}
	ciphertext := make([]byte, aes.BlockSize+len(plaintext))
	iv := ciphertext[:aes.BlockSize]
	if _, err := io.ReadFull(rand.Reader, iv); err != nil {
		return "", err
	}

	stream := cipher.NewCFBEncrypter(block, iv)
	stream.XORKeyStream(ciphertext[aes.BlockSize:], []byte(plaintext))
	return base64.StdEncoding.EncodeToString(ciphertext), nil
}

func Decrypt(encryptedText, secret string) (string, error) {
	key := getAESKey(secret)
	ciphertext, err := base64.StdEncoding.DecodeString(encryptedText)
	if err != nil {
		return "", err
	}
	if len(ciphertext) < aes.BlockSize {
		return "", errors.New("the ciphertext is too short")
	}
	iv := ciphertext[:aes.BlockSize]
	ciphertext = ciphertext[aes.BlockSize:]
	block, err := aes.NewCipher(key)
	if err != nil {
		return "", err
	}
	stream := cipher.NewCFBDecrypter(block, iv)
	stream.XORKeyStream(ciphertext, ciphertext)
	return string(ciphertext), nil
}