next.js/examples/with-firebase-authentication/server.js

const express = require('express')
const bodyParser = require('body-parser')
const session = require('express-session')
const FileStore = require('session-file-store')(session)
const next = require('next')
const admin = require('firebase-admin')

const dev = process.env.NODE_ENV !== 'production'
const app = next({ dev })
const handle = app.getRequestHandler()

const firebase = admin.initializeApp({
  credential: admin.credential.cert(require('./credentials/server')),
  databaseURL: '' // TODO database URL goes here
}, 'server')

app.prepare()
.then(() => {
  const server = express()

  server.use(bodyParser.json())
  server.use(session({
    secret: 'geheimnis',
    saveUninitialized: true,
    store: new FileStore({path: '/tmp/sessions', secret: 'geheimnis'}),
    resave: false,
    rolling: true,
    httpOnly: true,
    cookie: { maxAge: 604800000 } // week
  }))

  server.use((req, res, next) => {
    req.firebaseServer = firebase
    next()
  })

  server.post('/api/login', (req, res) => {
    if (!req.body) return res.sendStatus(400)

    const token = req.body.token
    firebase.auth().verifyIdToken(token)
      .then((decodedToken) => {
        req.session.decodedToken = decodedToken
        return decodedToken
      })
      .then((decodedToken) => res.json({ status: true, decodedToken }))
      .catch((error) => res.json({ error }))
  })

  server.post('/api/logout', (req, res) => {
    req.session.decodedToken = null
    res.json({ status: true })
  })

  server.get('*', (req, res) => {
    return handle(req, res)
  })

  server.listen(3000, (err) => {
    if (err) throw err
    console.log('> Ready on http://localhost:3000')
  })
})