Simple wrapper which uses lasso-loader to enable facebook oauth asynchronously

facebook-auth.js

const lassoLoader = require('lasso-loader');

/* globals FB, _sdk */
/**
 * Performs a one time OAuth 2.0 authorization.
 * Depending on the parameters used, this will open a popup to the Google sign-in flow
 * or try to load the requested response silently, without user interaction.
 */
function authenticate() {
    return new Promise(function (resolve, reject) {
        lassoLoader.load({
            js: [
                'https://connect.facebook.net/en_US/sdk.js'
            ]
        }, function () {
            if (!FB) {
                let err = new Error('Facebook sdk is not instantiated');
                _sdk.slError(err, 'error');
                err.message = 'session.fbAuthFailed';
                return reject(err);
            }
            if (!(_sdk && _sdk.config && _sdk.config.oauth && _sdk.config.oauth.facebook)) {
                let err = new Error('Global namespace _sdk is not instantiated');
                _sdk.slError(err, 'error');
                err.message = 'error.general';
                return reject(err);
            }
            /*
             * Initialize the FB SDK
             * https://developers.facebook.com/docs/javascript/reference/FB.init/v2.10
             */
            FB.init(_sdk.config.oauth.facebook);

            /*
             * Get login status and login if needed
             * https://developers.facebook.com/docs/reference/javascript/FB.getLoginStatus
             */
            FB.getLoginStatus(function (response) {
                if (response.status === 'connected') {
                    /*
                     * the user is logged in and has authenticated your
                     * app, and response.authResponse supplies
                     * the user's ID, a valid access token, a signed
                     * request, and the time the access token
                     * and signed request each expire
                     * let uid = response.authResponse.userID;
                     * let accessToken = response.authResponse.accessToken;
                     */
                    resolve({
                        'provider': 'facebook',
                        'token': response.authResponse.accessToken
                    });
                } else {
                    /*
                     * The user isn't logged in to Facebook, attempt login
                     * https://developers.facebook.com/docs/reference/javascript/FB.login/v2.10
                     */
                    FB.login(function (response) {
                        if (response.authResponse) {
                            resolve({
                                'provider': 'facebook',
                                'token': response.authResponse.accessToken
                            });
                        } else {
                            let err = new Error('session.popupClosed');
                            _sdk.slError(err, 'warn');
                            return reject(err);
                        }
                    });
                }
            });
        });
    });
}

module.exports = {
    authenticate
};