app.js

const Koa = require('koa')
const app = new Koa()

// trust proxy
app.proxy = true

// sessions
const convert = require('koa-convert')
const session = require('koa-generic-session')
app.keys = ['your-session-secret']
app.use(convert(session()))

// body parser
const bodyParser = require('koa-bodyparser')
app.use(bodyParser())

// authentication
require('./authn')
const passport = require('koa-passport')
app.use(passport.initialize())
app.use(passport.session())

// routes
const fs    = require('fs')
const route = require('koa-route')

app.use(route.get('/logout', function(ctx) {
  ctx.logout()
  ctx.redirect('/login')
}))

app.use(route.get('/login',
  passport.authenticate('oauth2')
))

app.use(route.get('/oauth/callback',
  passport.authenticate('oauth2', {
    failureRedirect: '/login',
    successRedirect: '/'
  })
))

// Require authentication for now
app.use(function(ctx, next) {
  if (ctx.isAuthenticated()) {
    return next()
  } else {
    ctx.redirect('/login')
  }
})

app.use(route.get('/api/token', function(ctx) {
  const user = ctx.req.user
  ctx.body = { token: user.accessToken }
}))

// start server
const port = process.env.PORT || 3000
app.listen(port, () => console.log('Server listening on', port))