import 'dart:convert';
import 'dart:math';

import 'package:encrypt/encrypt.dart';

import 'api_config.dart';

/// AES-128-ECB 加解密
abstract final class ApiCrypto {
  static final _key = Key.fromUtf8(ApiConfig.aesKey);

  static final _encrypter = Encrypter(
    AES(
      _key,
      mode: AESMode.ecb,
      padding: 'PKCS7',
    ),
  );

  /// AES 加密，返回 Base64 字符串
  static String encrypt(String plainText) {
    final encrypted = _encrypter.encrypt(plainText);
    return encrypted.base64;
  }

  /// AES 解密，输入 Base64 字符串
  static String decrypt(String base64Cipher) {
    final encrypted = Encrypted.fromBase64(base64Cipher);
    return _encrypter.decrypt(encrypted);
  }

  /// 生成随机 Base64 字符串（用于噪音字段）
  /// 使用 Random.secure() 保证密码学安全随机性
  static String randomBase64([int byteLength = 16]) {
    final random = Random.secure();
    final bytes = List<int>.generate(byteLength, (_) => random.nextInt(256));
    return base64Encode(bytes);
  }

  /// 生成 8 位随机字母数字
  static String randomAlnum() {
    const chars = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789';
    return List.generate(8, (_) => chars[DateTime.now().microsecondsSinceEpoch % chars.length]).join();
  }
}