/*
 *  Copyright (c) 2026 Kaiy Ragur
 *
 *  This Source Code Form is subject to the terms of the Mozilla Public
 *  License, v. 2.0. If a copy of the MPL was not distributed with this
 *  file, You can obtain one at http://mozilla.org/MPL/2.0/.
 */
package utils

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

	"golang.org/x/crypto/scrypt"
)

// Get base64 string of encrpted data
// salt [:16]
// nonce [16:28]
// data [28:]
func AESEncrypt(rawKey string, password string) (string, error) {
	salt := make([]byte, 16)
	if _, err := io.ReadFull(rand.Reader, salt); err != nil {
		return "", err
	}

	key, err := scrypt.Key([]byte(password), salt, 32768, 8, 1, 32)
	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
	}

	nonce := make([]byte, gcm.NonceSize())
	if _, err := io.ReadFull(rand.Reader, nonce); err != nil {
		return "", err
	}

	ciphertext := gcm.Seal(nil, nonce, []byte(rawKey), nil)

	result := append(salt, append(nonce, ciphertext...)...)
	return base64.StdEncoding.EncodeToString(result), nil
}

func AESDecrypt(encryptedB64 string, password string) (string, error) {
	data, err := base64.StdEncoding.DecodeString(encryptedB64)
	if err != nil {
		return "", err
	}

	if len(data) < 16+12 { // Salt(16) + Nonce(12)
		return "", fmt.Errorf("invalid encrypted data")
	}

	salt := data[:16]
	nonce := data[16:28]
	ciphertext := data[28:]

	key, err := scrypt.Key([]byte(password), salt, 32768, 8, 1, 32)
	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
	}

	rawKey, err := gcm.Open(nil, nonce, ciphertext, nil)
	if err != nil {
		return "", fmt.Errorf("decryption failed (wrong password?): %w", err)
	}

	return string(rawKey), nil
}