facebook sign in

facebook_signin.dart

  Future<Either<AuthFailure, Unit>> signInWithFacebook({bool reauth = false}) async {
    try {
      final result = await _facebookLogin.logIn(['email']);
      auth.User previousUser;
      switch (result.status) {
        case FacebookLoginStatus.loggedIn:
          final FacebookAccessToken accessToken = result.accessToken;
          final facebookAuthCred =
              auth.FacebookAuthProvider.credential(accessToken.token);
          if (reauth) {
            previousUser = await getCurrentUser();
            await previousUser.linkWithCredential(facebookAuthCred);
          } else {
            await _firebaseAuth.signInWithCredential(facebookAuthCred);
          }
          break;
        case FacebookLoginStatus.cancelledByUser:
          return const Left(AuthFailure.cancelledByUser());
        case FacebookLoginStatus.error:
          return const Left(AuthFailure.serverError());
      }

      return right(unit);
    } on PlatformException catch (e) {
      print(e);
      return const Left(AuthFailure.serverError());
    }
  }