import 'package:local_auth/local_auth.dart';

/// Thin wrapper over [LocalAuthentication] for the login screen. Exposes what
/// the device can do (fingerprint vs. face) and a single [authenticate] call.
class BiometricAuth {
  final LocalAuthentication _auth = LocalAuthentication();

  bool _supported = false;
  bool _canCheck = false;
  List<BiometricType> _types = const <BiometricType>[];

  /// Whether any biometric login can be offered (device supports it and the
  /// user has at least one biometric enrolled).
  bool get available => _supported && _canCheck;

  /// The device advertises a face enrolment. On some Androids the platform only
  /// reports weak/strong instead of the specific modality — see [showFace].
  bool get hasFace => _types.contains(BiometricType.face);

  bool get _hasFingerprint =>
      _types.contains(BiometricType.fingerprint) ||
      _types.contains(BiometricType.strong) ||
      _types.contains(BiometricType.weak);

  /// Show the face button when face is reported, or when the device supports
  /// biometrics but reports no specific modality (BiometricPrompt still lets the
  /// user use whatever strong biometric — often face — is enrolled).
  bool get showFace => available && (hasFace || _types.isEmpty);

  /// Show the fingerprint button when fingerprint is reported, or as the generic
  /// fallback when no specific modality is advertised.
  bool get showFingerprint => available && (_hasFingerprint || _types.isEmpty);

  /// Refreshes the capability flags. Safe to call repeatedly.
  Future<void> refresh() async {
    try {
      _supported = await _auth.isDeviceSupported();
      _canCheck = await _auth.canCheckBiometrics;
      _types = _supported ? await _auth.getAvailableBiometrics() : const <BiometricType>[];
    } catch (_) {
      _supported = false;
      _canCheck = false;
      _types = const <BiometricType>[];
    }
  }

  /// Prompts the OS biometric sheet. Returns true only on a verified match.
  Future<bool> authenticate({required String reason}) {
    return _auth.authenticate(
      localizedReason: reason,
      options: const AuthenticationOptions(
        biometricOnly: true,
        stickyAuth: true,
        useErrorDialogs: true,
      ),
    );
  }
}