js-libp2p/src/circuit/listener.js

'use strict'

const { EventEmitter } = require('events')
const multiaddr = require('multiaddr')

/**
 * @typedef {import('multiaddr')} Multiaddr
 * @typedef {import('libp2p-interfaces/src/transport/types').Listener} Listener
 */

/**
 * @param {import('../')} libp2p
 * @returns {Listener} a transport listener
 */
module.exports = (libp2p) => {
  const listeningAddrs = new Map()

  /**
   * Add swarm handler and listen for incoming connections
   *
   * @param {Multiaddr} addr
   * @returns {Promise<void>}
   */
  async function listen (addr) {
    const addrString = String(addr).split('/p2p-circuit').find(a => a !== '')

    const relayConn = await libp2p.dial(multiaddr(addrString))
    const relayedAddr = relayConn.remoteAddr.encapsulate('/p2p-circuit')

    listeningAddrs.set(relayConn.remotePeer.toB58String(), relayedAddr)
    listener.emit('listening')
  }

  /**
   * Get fixed up multiaddrs
   *
   * NOTE: This method will grab the peers multiaddrs and expand them such that:
   *
   * a) If it's an existing /p2p-circuit address for a specific relay i.e.
   * `/ip4/0.0.0.0/tcp/0/ipfs/QmRelay/p2p-circuit` this method will expand the
   * address to `/ip4/0.0.0.0/tcp/0/ipfs/QmRelay/p2p-circuit/ipfs/QmPeer` where
   * `QmPeer` is this peers id
   * b) If it's not a /p2p-circuit address, it will encapsulate the address as a /p2p-circuit
   * addr, such when dialing over a relay with this address, it will create the circuit using
   * the encapsulated transport address. This is useful when for example, a peer should only
   * be dialed over TCP rather than any other transport
   *
   * @returns {Multiaddr[]}
   */
  function getAddrs () {
    const addrs = []
    for (const addr of listeningAddrs.values()) {
      addrs.push(addr)
    }
    return addrs
  }

  /** @type Listener */
  const listener = Object.assign(new EventEmitter(), {
    close: () => Promise.resolve(),
    listen,
    getAddrs
  })

  // Remove listeningAddrs when a peer disconnects
  libp2p.connectionManager.on('peer:disconnect', (connection) => {
    const deleted = listeningAddrs.delete(connection.remotePeer.toB58String())

    if (deleted) {
      // Announce listen addresses change
      listener.emit('close')
    }
  })

  return listener
}