index.js

const hyperdrive = require('hyperdrive')
const level = require('level-party')

const raf = require('random-access-file')
const path = require('path')
const chokidar = require('chokidar')

const swarm = require('discovery-swarm')()
const archiveSwarm = require('hyperdrive-archive-swarm')
const lpm = require('length-prefixed-message')

const createArchive = require('./load-or-create-archive.js')

const db = level('./hyperdrive.db')
const drive = hyperdrive(db)

const boxLink = new Buffer('137cdd378ddbfc57a0f14819c24a0123c41c8aa4')

createArchive(drive, db, 'my-peers', {
  live: true,
  file: name => raf(path.resolve('.', name))
}, function (err, localArchive) {
  if (err) throw err

  chokidar
    .watch('./send')
    .on('add', file => localArchive.append(file))
    .on('change', file => localArchive.append(file))

  archiveSwarm(localArchive)

  swarm.listen()
  swarm.join(boxLink)
  swarm.on('connection', function (peer) {
    lpm.write(peer, localArchive.key)
    lpm.read(peer, function (link) {
      archiveSwarm(drive.createArchive(link, {
        live: true,
        file: name => raf(path.resolve('./receive/', name))
      }))
    })
  })
})

load-or-create-archive.js

'use strict'
const sub = require('subleveldown')

module.exports = function (drive, db, name, opts, cb) {
  if (name == null) {
    name = 'default'
  }

  const archives = sub(sub(db, 'simple-dropbox'), 'archives')
  archives.get(name, function (err, link) {
    if (link != null) {
      return cb(null, drive.createArchive(new Buffer(link, 'hex'), opts))
    }

    if (err.notFound) {
      var archive = drive.createArchive(opts)

      return archives.put(name, archive.key.toString('hex'), function (err) {
        if (err) return cb(err)

        return cb(null, archive)
      })
    }

    return cb(err)
  })
}

start.sh

mkdir -p peer-{1,2}/send
(cd peer-1 && node ../index.js) &
(cd peer-2 && node ../index.js) &

sleep 2;

touch peer-{1,2}/send/test.js
cat >> peer-{1,2}/send/test.js <<EOF
Hello world
Multi-line string
May remove lines
Bye!
EOF;

# Try editing either of test.js and remove/add lines. random-access-file doesn't fit this usecase, but what does?