uppy/examples/custom-provider/server/index.js

const express = require('express')
// the ../../../packages is just to use the local version
// instead of the npm version—in a real app use `require('@uppy/companion')`
const uppy = require('../../../packages/@uppy/companion')
const bodyParser = require('body-parser')
const session = require('express-session')

const app = express()

app.use(bodyParser.json())
app.use(session({
  secret: 'some-secret',
  resave: true,
  saveUninitialized: true
}))

app.use((req, res, next) => {
  res.setHeader('Access-Control-Allow-Origin', req.headers.origin || '*')
  res.setHeader(
    'Access-Control-Allow-Methods',
    'GET, POST, OPTIONS, PUT, PATCH, DELETE'
  )
  res.setHeader(
    'Access-Control-Allow-Headers',
    'Authorization, Origin, Content-Type, Accept'
  )
  next()
})

// Routes
app.get('/', (req, res) => {
  res.setHeader('Content-Type', 'text/plain')
  res.send('Welcome to my uppy companion service')
})

// initialize uppy
const uppyOptions = {
  providerOptions: {
    google: {
      key: 'your google key',
      secret: 'your google secret'
    }
  },
  customProviders: {
    mycustomprovider: {
      config: {
        // your oauth handlers
        authorize_url: 'http://localhost:3020/oauth/authorize',
        access_url: 'http://localhost:3020/oauth/token',
        oauth: 2,
        key: '***',
        secret: '**',
        scope: ['read', 'write']
      },
      // you provider module
      module: require('./customprovider')
    }
  },
  server: {
    host: 'localhost:3020',
    protocol: 'http'
  },
  filePath: './output',
  secret: 'some-secret',
  debug: true
}

app.get('/oauth/authorize', (req, res) => {
  // skips the default oauth process.
  // ideally this endpoint should handle the actual oauth process
  res.redirect(`http://localhost:3020/mycustomprovider/callback?state=${req.query.state}&access_token=randombytes`)
})

app.use(uppy.app(uppyOptions))

// handle 404
app.use((req, res, next) => {
  return res.status(404).json({ message: 'Not Found' })
})

// handle server errors
app.use((err, req, res, next) => {
  console.error('\x1b[31m', err.stack, '\x1b[0m')
  res.status(err.status || 500).json({ message: err.message, error: err })
})

uppy.socket(app.listen(3020), uppyOptions)

console.log('Welcome to Companion!')
console.log(`Listening on http://0.0.0.0:${3020}`)