replicate-mirror-strategy.js

const mirrorFolder = require('mirror-folder')
const { keyPair } = require('hypercore/lib/crypto')
const hyperdrive = require('hyperdrive')
const assert = require('assert')
const pify = require('pify')
const ram = require('random-access-memory')

const seed = Buffer(32).fill('hello')
const { publicKey, secretKey } = keyPair(seed)
const a = hyperdrive(ram, publicKey, {sparse: false, sparseMetadata: false, secretKey})
const b = hyperdrive(ram, publicKey, {sparse: false, sparseMetadata: false, secretKey})
const c = hyperdrive(ram, publicKey, {sparse: false, sparseMetadata: false, })

const replicate = (a, b) => pify((cb) => {
  const x = a.replicate()
  const y = b.replicate()
  x.pipe(y).pipe(x).on('end', cb)
})()

const readdir = (drive, ...args) => pify(drive.readdir.bind(drive))(...args)
const mirror = (a, b, ...args) => pify(mirrorFolder)(a, b, ...args)
const ready = (drive, ...args) => pify(drive.ready.bind(drive))(...args)
const mkdir = (drive, ...args) => pify(drive.mkdir.bind(drive))(...args)
const write = (drive, ...args) => pify(drive.writeFile.bind(drive))(...args)
const read = (drive, ...args) => pify(drive.readFile.bind(drive))(...args)

async function sync(x, y) {
  if (y.writable) return await mirror({name: '/', fs: x}, {name: '/', fs: y})
  else return await replicate(x, y)
}

async function check(a, b) {
  const invariant = await readdir(a, '/')
  const proof = await readdir(b, '/')
  for (const z of invariant) {
    const x = String(await read(a, '/'+z))
    const y = String(await read(b, '/'+z))
    assert(x == y)
  }
}

void async function main() {
  try {
    const writes = {
      '/a': Buffer('A'),
      '/b': Buffer('B'),
      '/c': Buffer('C'),

      '/1': Buffer('one'),
      '/2': Buffer('two'),
      '/3': Buffer('three'),
    }

    await ready(a)
    await ready(b)
    await ready(c)

    for (const filename in writes) {
      const buffer = writes[filename]
      await write(a, filename, buffer)
    }

    await sync(a, b)
    await sync(b, c)

    await check(a, b)
    await check(a, c)
    await check(b, c)

    console.log('ok!');
  } catch (err) {
    console.error('error:', err);
  }
}()