gapi.js

import loadjs from 'loadjs';
import once from 'lodash-es/once';
import promiseRetry from 'promise-retry';

import config from '../config';
import ExtendableError from '../util/ExtendableError';

export const SCOPES = [
  'https://www.googleapis.com/auth/classroom.courses.readonly',
  'https://www.googleapis.com/auth/classroom.coursework.students',
  'https://www.googleapis.com/auth/classroom.coursework.me',
];

const DISCOVERY_DOCS = ['https://classroom.googleapis.com/$discovery/rest?version=v1'];

const RETRY_OPTIONS = {
  retries: 16,
  factor: 2,
  minTimeout: 200,
  maxTimeout: 4000,
};

class LoadError extends ExtendableError {}

let isGapiLoadedAndConfigured = false;

async function loadGapi() {
  return promiseRetry(
    async(retry) => {
      try {
        const gapi = await new Promise((resolve, reject) => {
          loadjs('https://apis.google.com/js/client.js', {
            success() {
              resolve(window.gapi);
            },
            error(failedPaths) {
              reject(new LoadError(`Failed to load ${failedPaths.join(', ')}`));
            },
          });
        });

        return await new Promise((resolve, reject) => {
          gapi.load('client:auth2', {
            callback: () => {
              resolve(gapi);
            },
            onerror: reject,
            timeout: 1000,
            ontimeout: () => {
              reject(new Error('Timed out'));
            },
          });
        });
      } catch (e) {
        Reflect.deleteProperty(window, 'gapi');
        return retry(e);
      }
    },
    RETRY_OPTIONS,
  );
}

export const loadAndConfigureGapi = once(async() => {
  const gapi = await loadGapi();

  await gapi.client.init({
    apiKey: config.firebaseApiKey,
    clientId: config.firebaseClientId,
    discoveryDocs: DISCOVERY_DOCS,
    scope: SCOPES.join(' '),
  });

  isGapiLoadedAndConfigured = true;

  return gapi;
});

export function getGapiSync() {
  if (!isGapiLoadedAndConfigured) {
    throw new Error(
      'Attempted to synchronously access `gapi` before it was loaded',
    );
  }

  return window.gapi;
}