insomnia/packages/insomnia-app/app/network/o-auth-2/grant-implicit.js

// @flow
import * as c from './constants';
import { buildQueryStringFromParams, joinUrlAndQueryString } from 'insomnia-url';
import { responseToObject, authorizeUserInWindow } from './misc';

export default async function(
  requestId: string,
  authorizationUrl: string,
  clientId: string,
  responseType: string = c.RESPONSE_TYPE_TOKEN,
  redirectUri: string = '',
  scope: string = '',
  state: string = '',
  audience: string = '',
): Promise<Object> {
  const params = [
    { name: c.P_RESPONSE_TYPE, value: responseType },
    { name: c.P_CLIENT_ID, value: clientId },
  ];

  // Add optional params
  if (
    responseType === c.RESPONSE_TYPE_ID_TOKEN_TOKEN ||
    responseType === c.RESPONSE_TYPE_ID_TOKEN
  ) {
    const nonce = Math.floor(Math.random() * 9999999999999) + 1;
    params.push({ name: c.P_NONCE, value: nonce });
  }

  redirectUri && params.push({ name: c.P_REDIRECT_URI, value: redirectUri });
  scope && params.push({ name: c.P_SCOPE, value: scope });
  state && params.push({ name: c.P_STATE, value: state });
  audience && params.push({ name: c.P_AUDIENCE, value: audience });

  // Add query params to URL
  const qs = buildQueryStringFromParams(params);
  const finalUrl = joinUrlAndQueryString(authorizationUrl, qs);

  const redirectedTo = await authorizeUserInWindow(
    finalUrl,
    /(access_token=|id_token=)/,
    /(error=)/,
  );
  const fragment = redirectedTo.split('#')[1];

  if (fragment) {
    const results = responseToObject(fragment, [
      c.P_ACCESS_TOKEN,
      c.P_ID_TOKEN,
      c.P_TOKEN_TYPE,
      c.P_EXPIRES_IN,
      c.P_SCOPE,
      c.P_STATE,
      c.P_ERROR,
      c.P_ERROR_DESCRIPTION,
      c.P_ERROR_URI,
    ]);
    results[c.P_ACCESS_TOKEN] = results[c.P_ACCESS_TOKEN] || results[c.P_ID_TOKEN];
    return results;
  } else {
    // Bad redirect
    return {};
  }
}