auth.js

const fs = require('fs')
const readline = require('readline')
const { google } = require('googleapis')

const credentials = require('./credentials.json')

const OAuthClient = new google.auth.OAuth2({
   clientId: credentials.client_id,
   clientSecret: credentials.client_secret,
   redirectUri: credentials.redirect_uris[0],
})

async function load() {
   try {
      const stored = JSON.parse(await fs.promises.readFile('./tokens.json'))
      if (stored.access_token) {
         OAuthClient.credentials = stored
         return true
      }
      return false
   } catch (e) {
      return false
   }
}

async function save(data) {
   await fs.promises.writeFile('./tokens.json', JSON.stringify(data))
}

async function auth() {
   const isLoaded = await load()
   if (isLoaded) return

   await new Promise(function (resolve, reject) {
      const uri = OAuthClient.generateAuthUrl({
         access_type: 'offline',
         scope: 'https://www.googleapis.com/auth/youtube',
      })
      console.log(decodeURIComponent(uri))

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

      rl.question('code: ', async function (code) {
         rl.close()
         try {
            const { res } = await OAuthClient.getToken(decodeURIComponent(code))
            await save(res.data)
            await load()
            resolve()
         } catch (error) {
            console.log(error)
            reject(error)
         }
      })
   })
}

async function refresh() {
   const { res } = await OAuthClient.refreshAccessToken()
   await save(res.data)
}

module.exports.OAuthClient = OAuthClient
module.exports.auth = auth
module.exports.refresh = refresh