js-multiaddr-to-uri/index.js

const Multiaddr = require('multiaddr')

const reduceValue = (_, v) => v
const tcpUri = (str, port, parts, opts) => {
  // return tcp when explicitly requested
  if (opts && opts.assumeHttp === false) return `tcp://${str}:${port}`
  // check if tcp is the last protocol in multiaddr
  let protocol = 'tcp'
  let explicitPort = `:${port}`
  const last = parts[parts.length - 1]
  if (last.protocol === 'tcp') {
    // assume http and produce clean urls
    protocol = port === '443' ? 'https' : 'http'
    explicitPort = port === '443' || port === '80' ? '' : explicitPort
  }
  return `${protocol}://${str}${explicitPort}`
}

const Reducers = {
  ip4: reduceValue,
  ip6: (str, content, i, parts) => (
    parts.length === 1 && parts[0].protocol === 'ip6'
      ? content
      : `[${content}]`
  ),
  tcp: (str, content, i, parts, opts) => (
    parts.some(p => ['http', 'https', 'ws', 'wss'].includes(p.protocol))
      ? `${str}:${content}`
      : tcpUri(str, content, parts, opts)
  ),
  udp: (str, content) => `udp://${str}:${content}`,
  dnsaddr: reduceValue,
  dns4: reduceValue,
  dns6: reduceValue,
  ipfs: (str, content) => `${str}/ipfs/${content}`,
  p2p: (str, content) => `${str}/p2p/${content}`,
  http: str => `http://${str}`,
  https: str => `https://${str}`,
  ws: str => `ws://${str}`,
  wss: str => `wss://${str}`,
  'p2p-websocket-star': str => `${str}/p2p-websocket-star`,
  'p2p-webrtc-star': str => `${str}/p2p-webrtc-star`,
  'p2p-webrtc-direct': str => `${str}/p2p-webrtc-direct`
}

module.exports = (multiaddr, opts) => {
  const ma = new Multiaddr.Multiaddr(multiaddr)
  const parts = multiaddr.toString().split('/').slice(1)
  return ma
    .tuples()
    .map(tuple => ({
      protocol: parts.shift(),
      content: tuple[1] ? parts.shift() : null
    }))
    .reduce((str, part, i, parts) => {
      const reduce = Reducers[part.protocol]
      if (!reduce) throw new Error(`Unsupported protocol ${part.protocol}`)
      return reduce(str, part.content, i, parts, opts)
    }, '')
}