import 'package:flutter_secure_storage/flutter_secure_storage.dart';
import 'package:uuid/uuid.dart';

class CryptoService {
  static const String _deviceIdPref = 'device_uuid';
  static const _storage = FlutterSecureStorage();
  static final RegExp _uuidV4 = RegExp(
    r'^[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$',
    caseSensitive: false,
  );

  /// Get or create a persistent device UUID for server-side session tracking.
  /// Corrupted or tampered storage values are replaced instead of being sent
  /// to the public API as arbitrary query data.
  static Future<String> getDeviceId() async {
    final existing = await _storage.read(key: _deviceIdPref);
    if (existing != null && _uuidV4.hasMatch(existing)) return existing;

    final newId = const Uuid().v4();
    await _storage.write(key: _deviceIdPref, value: newId);
    return newId;
  }
}