package cryptext

import (
	"crypto/aes"
	"crypto/cipher"
	"crypto/rand"
	"encoding/base64"
	"errors"
	"golang.org/x/crypto/scrypt"
	"io"
)

// https://stackoverflow.com/a/18819040/1761622

func EncryptAESSimple(password, text []byte) ([]byte, error) {

	key, err := scrypt.Key(password, nil, 32768, 8, 1, 32) // this is not 100% correct, rounds too low and salt is missing
	if err != nil {
		return nil, err
	}

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

	b := base64.StdEncoding.EncodeToString(text)
	ciphertext := make([]byte, aes.BlockSize+len(b))

	iv := ciphertext[:aes.BlockSize]
	if _, err := io.ReadFull(rand.Reader, iv); err != nil {
		return nil, err
	}

	cfb := cipher.NewCFBEncrypter(block, iv)
	cfb.XORKeyStream(ciphertext[aes.BlockSize:], []byte(b))

	return ciphertext, nil
}

func DecryptAESSimple(password, text []byte) ([]byte, error) {

	key, err := scrypt.Key(password, nil, 32768, 8, 1, 32) // this is not 100% correct, rounds too low and salt is missing
	if err != nil {
		return nil, err
	}

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

	if len(text) < aes.BlockSize {
		return nil, errors.New("ciphertext too short")
	}

	iv := text[:aes.BlockSize]
	text = text[aes.BlockSize:]
	cfb := cipher.NewCFBDecrypter(block, iv)
	cfb.XORKeyStream(text, text)

	data, err := base64.StdEncoding.DecodeString(string(text))
	if err != nil {
		return nil, err
	}

	return data, nil
}