package utils

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

// Encrypt encrypts plain text using AES-GCM with the given 32-byte key.
func Encrypt(plainText string, key []byte) (string, error) {
	if len(key) != 32 {
		return "", fmt.Errorf("encryption key must be 32 bytes")
	}

	block, err := aes.NewCipher(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
	}

	// The nonce should be prepended to the ciphertext
	cipherText := gcm.Seal(nonce, nonce, []byte(plainText), nil)
	return base64.StdEncoding.EncodeToString(cipherText), nil
}

// Decrypt decrypts base64-encoded cipher text using AES-GCM with the given 32-byte key.
func Decrypt(encodedCipherText string, key []byte) (string, error) {
	if len(key) != 32 {
		return "", fmt.Errorf("encryption key must be 32 bytes")
	}

	cipherText, err := base64.StdEncoding.DecodeString(encodedCipherText)
	if err != nil {
		return "", err
	}

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

	gcm, err := cipher.NewGCM(block)
	if err != nil {
		return "", err
	}

	nonceSize := gcm.NonceSize()
	if len(cipherText) < nonceSize {
		return "", fmt.Errorf("cipher text too short")
	}

	nonce, actualCipherText := cipherText[:nonceSize], cipherText[nonceSize:]
	plainText, err := gcm.Open(nil, nonce, actualCipherText, nil)
	if err != nil {
		return "", err
	}

	return string(plainText), nil
}