login fb

Myuser.loginFacebook = function(fbId, fbToken, userId, options, callback) {
        /**
         * Check if fb id and fb token is exist or not, if exist return error
         */
        var fbUser = {
            fbId: fbId
        };

        Myuser.findOne({ where: fbUser })
            .then(fUser => {
                if (fUser) {
                    /**
                     * If user id is not provided then it will be treated as login
                     * If userId exist but not equal to found user id, then error: fbId already bound
                     * If userId exist and equal => do nothing (return user)
                     */
                    if (!userId) {
                        createToken(fUser);
                    } else if (fUser.userId !== userId) {
                        var err = new Error('Facebook account is already bound to another user');
                        err.statusCode = 400;
                        err.code = 'INFORMATION_NOT_VALID';
                        callback(err);
                    } else {
                        callback(null, fUser);
                    }
                } else {
                    var fbData;

                    axios.get(`https://graph.facebook.com/${fbId}?fields=id,name,email&access_token=${fbToken}`)
                        .then((response) => {
                            if (response.data.id == fbId) {
                                fbData = response.data;

                                validateData();
                            } else {
                                var err = new Error('Facebook Id or Token is not valid');
                                err.statusCode = 400;
                                err.code = 'INFORMATION_NOT_VALID';
                                callback(err);
                            }
                        })
                        .catch(err => {
                            callback(err)
                        });

                    function validateData() {
                        /**
                         * If userId not exist create new user
                         * If userId exist update attributes
                         */
                        if (!userId) {
                            let userCred = {
                                username: `facebook.${fbId}`,
                                email: fbData.email,
                                name: fbData.name,
                                fbId: fbId,
                                fbToken: fbToken,
                                password: randomString()
                            };

                            Myuser.create(userCred)
                                .then(user => {
                                    createToken(user);
                                })
                                .catch(err => {
                                    callback(err);
                                })
                        } else {
                            let where = { userId: userId };
                            Myuser.findOne({ where: where })
                                .then(updateUser => {
                                    updateUser.updateAttributes(fbUser).then(upUser => {
                                        callback(null, upUser);
                                    }).catch(err => {
                                        callback(err);
                                    })
                                })
                                .catch(err => {
                                    callback(err);
                                });
                        }
                    }
                }

                function createToken(user) {
                    user.createAccessToken(DEFAULT_TTL)
                        .then(token => {
                            callback(null, token)
                        })
                        .catch(err => {
                            callback(err);
                        })
                }
            })
            .catch(err => {
                callback(err);
            })
    };