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

// @flow
import { setDefaultProtocol } from 'insomnia-url';
import * as c from './constants';
import { responseToObject } from './misc';
import { sendWithSettings } from '../network';
import * as models from '../../models/index';
import { getBasicAuthHeader } from '../basic-auth/get-header';

export default async function(
  requestId: string,
  accessTokenUrl: string,
  credentialsInBody: boolean,
  clientId: string,
  clientSecret: string,
  scope: string = '',
  audience: string = '',
  resource: string = '',
): Promise<Object> {
  const params = [{ name: c.P_GRANT_TYPE, value: c.GRANT_TYPE_CLIENT_CREDENTIALS }];

  // Add optional params
  scope && params.push({ name: c.P_SCOPE, value: scope });
  audience && params.push({ name: c.P_AUDIENCE, value: audience });
  resource && params.push({ name: c.P_RESOURCE, value: resource });

  const headers = [
    { name: 'Content-Type', value: 'application/x-www-form-urlencoded' },
    {
      name: 'Accept',
      value: 'application/x-www-form-urlencoded, application/json',
    },
  ];

  if (credentialsInBody) {
    params.push({ name: c.P_CLIENT_ID, value: clientId });
    params.push({ name: c.P_CLIENT_SECRET, value: clientSecret });
  } else {
    headers.push(getBasicAuthHeader(clientId, clientSecret));
  }

  const url = setDefaultProtocol(accessTokenUrl);

  const responsePatch = await sendWithSettings(requestId, {
    headers,
    url,
    method: 'POST',
    body: models.request.newBodyFormUrlEncoded(params),
  });

  const response = await models.response.create(responsePatch);

  const bodyBuffer = models.response.getBodyBuffer(response);
  if (!bodyBuffer) {
    return {
      [c.X_ERROR]: `No body returned from ${url}`,
      [c.X_RESPONSE_ID]: response._id,
    };
  }

  const statusCode = response.statusCode || 0;
  if (statusCode < 200 || statusCode >= 300) {
    return {
      [c.X_ERROR]: `Failed to fetch token url=${url} status=${statusCode}`,
      [c.X_RESPONSE_ID]: response._id,
    };
  }

  const results = responseToObject(bodyBuffer.toString('utf8'), [
    c.P_ACCESS_TOKEN,
    c.P_TOKEN_TYPE,
    c.P_EXPIRES_IN,
    c.P_SCOPE,
    c.P_AUDIENCE,
    c.P_RESOURCE,
    c.P_ERROR,
    c.P_ERROR_URI,
    c.P_ERROR_DESCRIPTION,
  ]);

  results[c.X_RESPONSE_ID] = response._id;

  return results;
}