feat: add event bus

Adds an event emitter as a libp2p component that will echo every
emitted event on the main libp2p object.

Fixes #1574

src/components.ts

@@ -14,9 +14,12 @@ import type { PubSub } from '@libp2p/interface-pubsub'
 import type { DualDHT } from '@libp2p/interface-dht'
 import type { ConnectionManager } from '@libp2p/interface-connection-manager'
 import type { ConnectionGater } from '@libp2p/interface-connection-gater'
+import type { Libp2pEvents } from '@libp2p/interface-libp2p'
+import type { EventEmitter } from '@libp2p/interfaces/events'
 
 export interface Components {
   peerId: PeerId
+  events: EventEmitter<Libp2pEvents>
   addressManager: AddressManager
   peerStore: PeerStore
   upgrader: Upgrader
@@ -35,6 +38,7 @@ export interface Components {
 
 export interface ComponentsInit {
   peerId?: PeerId
+  events?: EventEmitter<Libp2pEvents>
   addressManager?: AddressManager
   peerStore?: PeerStore
   upgrader?: Upgrader
@@ -53,6 +57,7 @@ export interface ComponentsInit {
 
 export class DefaultComponents implements Components, Startable {
   private _peerId?: PeerId
+  private _events?: EventEmitter<Libp2pEvents>
   private _addressManager?: AddressManager
   private _peerStore?: PeerStore
   private _upgrader?: Upgrader
@@ -71,6 +76,7 @@ export class DefaultComponents implements Components, Startable {
 
   constructor (init: ComponentsInit = {}) {
     this._peerId = init.peerId
+    this._events = init.events
     this._addressManager = init.addressManager
     this._peerStore = init.peerStore
     this._upgrader = init.upgrader
@@ -163,6 +169,18 @@ export class DefaultComponents implements Components, Startable {
     this._peerId = peerId
   }
 
+  get events (): EventEmitter<Libp2pEvents> {
+    if (this._events == null) {
+      throw new CodeError('events not set', 'ERR_SERVICE_MISSING')
+    }
+
+    return this._events
+  }
+
+  set events (events: EventEmitter<Libp2pEvents>) {
+    this._events = events
+  }
+
   get addressManager (): AddressManager {
     if (this._addressManager == null) {
       throw new CodeError('addressManager not set', 'ERR_SERVICE_MISSING')

src/libp2p.ts

@@ -86,10 +86,24 @@ export class Libp2pNode extends EventEmitter<Libp2pEvents> implements Libp2p {
   constructor (init: Libp2pInit) {
     super()
 
+    // event bus - components can listen to this emitter to be notified of system events
+    // and also cause them to be emitted
+    const events = new EventEmitter<Libp2pEvents>()
+    const originalDispatch = events.dispatchEvent.bind(events)
+    events.dispatchEvent = (evt: any) => {
+      const internalResult = originalDispatch(evt)
+      const externalResult = this.dispatchEvent(
+        new CustomEvent(evt.type, { detail: evt.detail })
+      )
+
+      return internalResult || externalResult
+    }
+
     this.started = false
     this.peerId = init.peerId
     const components = this.components = new DefaultComponents({
       peerId: init.peerId,
+      events,
       datastore: init.datastore ?? new MemoryDatastore(),
       connectionGater: {
         denyDialPeer: async () => await Promise.resolve(false),

src/transport-manager.ts

@@ -11,6 +11,7 @@ import type { Startable } from '@libp2p/interfaces/startable'
 import { trackedMap } from '@libp2p/tracked-map'
 import type { Metrics } from '@libp2p/interface-metrics'
 import type { AddressManager } from '@libp2p/interface-address-manager'
+import type { Libp2pEvents } from '@libp2p/interface-libp2p'
 
 const log = logger('libp2p:transports')
 
@@ -22,6 +23,7 @@ export interface DefaultTransportManagerComponents {
   metrics?: Metrics
   addressManager: AddressManager
   upgrader: Upgrader
+  events: EventEmitter<Libp2pEvents>
 }
 
 export class DefaultTransportManager extends EventEmitter<TransportManagerEvents> implements TransportManager, Startable {
@@ -237,6 +239,8 @@ export class DefaultTransportManager extends EventEmitter<TransportManagerEvents
       }
       log(`libp2p in dial mode only: ${message}`)
     }
+
+    this.components.events.safeDispatchEvent('multiaddrs:change', { detail: this.getAddrs() })
   }
 
   /**