package security

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

// Encryptor provides encryption/decryption for sensitive data
type Encryptor struct {
	key []byte
}

// NewEncryptor creates a new encryptor with the given key
// The key must be 32 bytes for AES-256
func NewEncryptor(key string) (*Encryptor, error) {
	if len(key) != 32 {
		return nil, errors.New("encryption key must be 32 bytes (256 bits)")
	}
	return &Encryptor{
		key: []byte(key),
	}, nil
}

// Encrypt encrypts data using AES-256-GCM
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
}

// Decrypt decrypts data encrypted with Encrypt
func (e *Encryptor) Decrypt(ciphertext string) (string, error) {
	data, err := base64.StdEncoding.DecodeString(ciphertext)
	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
	}

	nonceSize := gcm.NonceSize()
	if len(data) < nonceSize {
		return "", errors.New("ciphertext too short")
	}

	nonce := data[:nonceSize]
	ciphertextBytes := data[nonceSize:]
	plaintext, err := gcm.Open(nil, nonce, ciphertextBytes, nil)
	if err != nil {
		return "", err
	}

	return string(plaintext), nil
}