js-libp2p-interfaces/src/topology/multicodec-topology.js

'use strict'

const withIs = require('class-is')

const Topology = require('./index')

class MulticodecTopology extends Topology {
  /**
   * @param {Object} props
   * @param {number} props.min minimum needed connections (default: 0)
   * @param {number} props.max maximum needed connections (default: Infinity)
   * @param {Array<string>} props.multicodecs protocol multicodecs
   * @param {Object} props.handlers
   * @param {function} props.handlers.onConnect protocol "onConnect" handler
   * @param {function} props.handlers.onDisconnect protocol "onDisconnect" handler
   * @constructor
   */
  constructor ({
    min,
    max,
    multicodecs,
    handlers
  }) {
    super({ min, max, handlers })

    if (!multicodecs) {
      throw new Error('one or more multicodec should be provided')
    }

    if (!handlers) {
      throw new Error('the handlers should be provided')
    }

    if (typeof handlers.onConnect !== 'function') {
      throw new Error('the \'onConnect\' handler must be provided')
    }

    if (typeof handlers.onDisconnect !== 'function') {
      throw new Error('the \'onDisconnect\' handler must be provided')
    }

    this.multicodecs = Array.isArray(multicodecs) ? multicodecs : [multicodecs]
    this._registrar = undefined

    this._onProtocolChange = this._onProtocolChange.bind(this)
  }

  set registrar (registrar) {
    this._registrar = registrar
    this._registrar.peerStore.on('change:protocols', this._onProtocolChange)

    // Update topology peers
    this._updatePeers(this._registrar.peerStore.peers.values())
  }

  /**
   * Update topology.
   * @param {Array<{id: PeerId, multiaddrs: Array<Multiaddr>, protocols: Array<string>}>} peerDataIterable
   * @returns {void}
   */
  _updatePeers (peerDataIterable) {
    for (const { id, protocols } of peerDataIterable) {
      if (this.multicodecs.filter(multicodec => protocols.includes(multicodec)).length) {
        // Add the peer regardless of whether or not there is currently a connection
        this.peers.add(id.toB58String())
        // If there is a connection, call _onConnect
        const connection = this._registrar.getConnection(id)
        connection && this._onConnect(id, connection)
      } else {
        // Remove any peers we might be tracking that are no longer of value to us
        this.peers.delete(id.toB58String())
      }
    }
  }

  /**
   * Check if a new peer support the multicodecs for this topology.
   * @param {Object} props
   * @param {PeerId} props.peerId
   * @param {Array<string>} props.protocols
   */
  _onProtocolChange ({ peerId, protocols }) {
    const hadPeer = this.peers.has(peerId.toB58String())
    const hasProtocol = protocols.filter(protocol => this.multicodecs.includes(protocol))

    // Not supporting the protocol anymore?
    if (hadPeer && hasProtocol.length === 0) {
      this._onDisconnect(peerId)
    }

    // New to protocol support
    for (const protocol of protocols) {
      if (this.multicodecs.includes(protocol)) {
        const peerData = this._registrar.peerStore.get(peerId)
        this._updatePeers([peerData])
        return
      }
    }
  }
}

module.exports = withIs(MulticodecTopology, { className: 'MulticodecTopology', symbolName: '@libp2p/js-interfaces/topology/multicodec-topology' })