import 'dart:convert';
import 'package:cryptography/cryptography.dart';

class SecurityService {
  // Same 32-byte key
  static const _keyBase64 = "Your32ByteBase64KeyGoesHere/1234567890+XY=";

  static Future<dynamic> decryptResponse(String encryptedBase64) async {
    final algorithm = AesGcm.with256bits();
    
    // 1. Decode Key and Data
    final secretKey = await algorithm.newSecretKeyFromBytes(base64.decode(_keyBase64));
    final encryptedBytes = base64.decode(encryptedBase64);

    // 2. Extract Parts: [Nonce 12] + [Ciphertext] + [Tag 16]
    // The "SecretBox" class helps us organize these parts
    final nonce = encryptedBytes.sublist(0, 12);
    final ciphertext = encryptedBytes.sublist(12, encryptedBytes.length - 16);
    final mac = encryptedBytes.sublist(encryptedBytes.length - 16);

    final secretBox = SecretBox(
      ciphertext,
      nonce: nonce,
      mac: Mac(mac),
    );

    // 3. Decrypt
    try {
      final decryptedBytes = await algorithm.decrypt(
        secretBox,
        secretKey: secretKey,
      );
      
      final decryptedString = utf8.decode(decryptedBytes);
      return json.decode(decryptedString);
    } catch (e) {
      print("Decryption failed: $e");
      return null;
    }
  }
}