spotify.js

const fastify = require('fastify')({ logger: true })
const oauthPlugin = require('fastify-oauth2')

fastify.register(oauthPlugin, {
  name: 'Spotify',
  scope: ['user-read-currently-playing'],
  credentials: {
    client: {
      id: process.env.CLIENT_ID,
      secret: process.env.CLIENT_SECRET
    },
    auth: oauthPlugin.SPOTIFY_CONFIGURATION
  },
  startRedirectPath: '/login/spotify',
  callbackUri: `http://localhost:${process.env.PORT}/login/spotify/callback`
})

fastify.get('/login/spotify/callback', async (req, reply) => {
  const token = await fastify.Spotify.getAccessTokenFromAuthorizationCodeFlow(req)

  req.log.info('The Spotify token is %o', token)
  reply.send({ access_token: token.access_token })
})

fastify.listen(process.env.PORT, (err) => {
  if (err) {
    fastify.log.error(err)
    process.exit(1)
  }
})