index.js

const express = require('express')
const app = express()
const port = 3000 // get this from config
const host = 'localhost' // get this from config
const startUpMsg = `proxy listening on port ${port}!`
const serveIndex = require('serve-index')
const Dat = require('dat-node')
const path = require('path')

// this dats folder could also be configurable
app.use(express.static(__dirname + '/dats'))
app.use('/', serveIndex(__dirname + '/dats'))

app.use(function (req, res, next) {
  const orig = req.url
  const { referer, host } = req.headers
  if (referer && /^(\/)/.test(req.url)) {
    const folder = referer.replace(`http://${host}/`, '')
    res.redirect(`/${folder.replace('/', '')}${req.url}`)
  }

  next()
})

app.get('/dat/:key', (req, res) => {
  const { key } = req.params
  Dat(`./dats/${key}`, {
    key: key
  }, function (err, dat) {
    if (err) throw err
    dat.joinNetwork({}, _ => {
      res.json({
        url: `http://${host}:${port}/${key}`
      })
    })
  })
})

app.listen(port, _ => console.log(startUpMsg))