package crypto

import (
	"crypto/aes"
	"crypto/cipher"
	"crypto/rand"
	"encoding/base64"
	"fmt"
	"io"
)

type Encryptor struct {
	key []byte
}

func New(key []byte) *Encryptor {
	return &Encryptor{key: key}
}

func (e *Encryptor) Encrypt(plaintext string) (string, error) {
	block, err := aes.NewCipher(e.key)
	if err != nil {
		return "", err
	}
	gcm, err := cipher.NewGCM(block)
	if err != nil {
		return "", err
	}
	nonce := make([]byte, gcm.NonceSize())
	if _, err = io.ReadFull(rand.Reader, nonce); err != nil {
		return "", err
	}
	ciphertext := gcm.Seal(nonce, nonce, []byte(plaintext), nil)
	return base64.StdEncoding.EncodeToString(ciphertext), nil
}

func (e *Encryptor) Decrypt(encoded string) (string, error) {
	data, err := base64.StdEncoding.DecodeString(encoded)
	if err != nil {
		return "", err
	}
	block, err := aes.NewCipher(e.key)
	if err != nil {
		return "", err
	}
	gcm, err := cipher.NewGCM(block)
	if err != nil {
		return "", err
	}
	if len(data) < gcm.NonceSize() {
		return "", fmt.Errorf("ciphertext too short")
	}
	nonce, ciphertext := data[:gcm.NonceSize()], data[gcm.NonceSize():]
	plain, err := gcm.Open(nil, nonce, ciphertext, nil)
	if err != nil {
		return "", err
	}
	return string(plain), nil
}