A wrapper which uses lasso-loader to enable google oauth flow asynchronously

google-auth.js

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

/* globals gapi, _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://apis.google.com/js/platform.js'
            ]
        }, function () {
            if (!gapi) {
                let err = new Error('Google client is not instantiated');
                err.message = 'session.googleAuthFailed';
                return reject(err);
            }
            if (!(_sdk && _sdk.config && _sdk.config.oauth && _sdk.config.oauth.google)) {
                let err = new Error('Global namespace _sdk is not instantiated');
                _sdk.slError(err, 'warn');
                err.message = 'error.general';
                return reject(err);
            }
            gapi.load('auth2', function () {
                /**
                 * This is an alternate way of logging the user in without using the usual Google Button Flow
                 * Reference:
                 * https://developers.google.com/identity/sign-in/web/reference#gapiauth2authorizeparams-callback
                 */
                gapi.auth2.authorize(_sdk.config.oauth.google,
                    function (response) {
                        if (response.error) {
                            // An error happened!
                            /*
                             * Handle error codes as given by google auth flow
                             * https://developers.google.com/identity/sign-in/web/reference#gapiauth2authorize-errorcodes
                             */
                            let errorMap = {
                                /**
                                 * Failed to initialize a required iframe from Google, for instance, due to an
                                 * unsupported environment. A details property will give more information on the error
                                 * raised.
                                 */
                                'idpiframe_initialization_failed': 'session.googleAuthFailed',

                                /**
                                 * The user closed the popup before finishing the sign in flow.
                                 */
                                'popup_closed_by_user': 'session.popupClosed',

                                /**
                                 * The user denied the permission to the scopes required.
                                 */
                                'access_denied': 'session.accessDenied',

                                /**
                                 * No user could be automatically selected without prompting the consent flow. Error
                                 * raised when using signIn with prompt: 'none' option.
                                 * raised when using signIn with prompt: 'none' option.
                                 */
                                'immediate_failed': 'session.googleAuthFailed'
                            };
                            return reject(new Error(errorMap[response.error] || 'session.loginFailure'));
                        }
                        resolve({
                            //The provider name is google in this case
                            provider: 'google',
                            // The user authorized the application for the scopes requested.
                            token: response.id_token
                        });

                    });
            });
        });
    });
}

module.exports = {
    authenticate
};