get google api auth tokens with client_id and client_secret

goolgeApiAuthTokens.js

const CLIENT_ID = <CLIENT_ID>;
const CLIENT_SECRET = <CLIENT_SECRET>;

// Hardcoded dummy redirect URI for non-web apps.
const REDIRECT_URI = 'urn:ietf:wg:oauth:2.0:oob';

// The URL root for accessing Google Accounts.
const GOOGLE_ACCOUNTS_BASE_URL = 'https://accounts.google.com';

const path = require('path');

const { URL, parse: parseURL } = require('url');

const https = require('https');

const readline = require('readline');

const querystring = require('querystring');

const OAUTH51SAFE = '~-._'; 

const specialEncoder = (safe) => (str) => str.split('').map(chr=>((!(safe.indexOf(chr)<0) || !/[^a-zA-Z0-9]/.test(chr)) ? chr : '%'+chr.charCodeAt(0).toString(16))).join('');

const encodeSpecialFormObj = (obj)=>querystring.stringify(obj, null, null,{ encodeURIComponent: specialEncoder(OAUTH51SAFE)  });

function postFormGetJson(formUrl, data) {

  const url = parseURL(formUrl.toString());

  const encodedData = encodeSpecialFormObj(data);

  const options = {
    hostname: url.host,
    port: 443,
    path: url.path,
    method: 'POST',
    headers: {
      'Content-Type': 'application/x-www-form-urlencoded',
      'Content-Length': encodedData.length
    }
  };

  return new Promise( (resolve,reject) => {
    let data = '';
    const request = https.request(options, resp => {
      if (resp.statusCode >= 400) {
        let err = new Error(`http error ${resp.statusCode}`);
        err.statusCode = resp.statusCode;
        reject(err);
      }
      resp.on('data', (chunk) => {
        data += chunk;
      });

      resp.on('end', ()=>{
        try {
          resolve(JSON.parse(data.toString()));
        } catch (e) {
          let err = new Error(`Unable to parse JSON from ${url}`);
          err.statusCode = resp.statusCode;
          reject(err);
        };
      });
    })
      .on('error', (e) => reject(e))
    request.write(encodedData);
  })



}

function paramifyURL({ url, params }) {
  const nurl = new URL(url.toString()); //clone url, because not mutate functions es bueno
  Object.entries(params).forEach(([key, value]) => nurl.searchParams.append(key, value));
  return nurl;
} 

function authTokens(clientId, clientSecret, authCode) {
  const url = new URL('o/oauth2/token', GOOGLE_ACCOUNTS_BASE_URL);

  const params = {
    client_id: clientId,
    client_secret: clientSecret,
    redirect_uri: REDIRECT_URI,
    code: authCode,
    grant_type: 'authorization_code',
  };

  return postFormGetJson(url, params);

}

function genPermitUrl(clientId, scope = 'https://mail.google.com/') {
  const url = new URL('o/oauth2/auth', GOOGLE_ACCOUNTS_BASE_URL);

  const params = {
    client_id: clientId,
    redirect_uri: REDIRECT_URI,
    scope,
    response_type: 'code',
  }

  return paramifyURL({ url, params }).href
}


function prompt(msg){
  const rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout

  });
  return new Promise( resolve => {
    rl.question(`${msg}:`, answer => {
      rl.close();
      resolve(answer.replace(/\n$/, ''));
    });
  })
}

if (require.main === module) {
  (async function main(){

    const permitUrl = genPermitUrl(CLIENT_ID);

    process.stdout.write(`* To authorize token, visit this url and follow the directions:\n\n-- ${permitUrl}\n\n`);

    const authCode = await prompt('Enter verification code');

    try {
      let codez = await authTokens(CLIENT_ID,CLIENT_SECRET, authCode);
      process.stdout.write(JSON.stringify(codez,null,4));
    } catch(e) {
      console.error('Could not retrieve tokens!',e);
    }
  })()
}

module.exports = { GeneratePermitUrl: genPermitUrl, FetchAuthTokens: authTokens }