Add list of active peers to repo

packages/automerge-repo/src/Repo.ts

@@ -37,6 +37,8 @@ export class Repo extends EventEmitter<RepoEvents> {
 
   #handleCache: Record<DocumentId, DocHandle<any>> = {}
 
+  #synchronizer: CollectionSynchronizer
+
   /** By default, we share generously with all peers. */
   /** @hidden */
   sharePolicy: SharePolicy = async () => true
@@ -98,7 +100,7 @@ export class Repo extends EventEmitter<RepoEvents> {
       }
 
       // Register the document with the synchronizer. This advertises our interest in the document.
-      synchronizer.addDocument(handle.documentId)
+      this.#synchronizer.addDocument(handle.documentId)
     })
 
     this.on("delete-document", ({ documentId }) => {
@@ -114,10 +116,10 @@ export class Repo extends EventEmitter<RepoEvents> {
 
     // SYNCHRONIZER
     // The synchronizer uses the network subsystem to keep documents in sync with peers.
-    const synchronizer = new CollectionSynchronizer(this)
+    this.#synchronizer = new CollectionSynchronizer(this)
 
     // When the synchronizer emits messages, send them to peers
-    synchronizer.on("message", message => {
+    this.#synchronizer.on("message", message => {
       this.#log(`sending ${message.type} message to ${message.targetId}`)
       networkSubsystem.send(message)
     })
@@ -135,24 +137,27 @@ export class Repo extends EventEmitter<RepoEvents> {
     // When we get a new peer, register it with the synchronizer
     networkSubsystem.on("peer", async ({ peerId }) => {
       this.#log("peer connected", { peerId })
-      synchronizer.addPeer(peerId)
+      this.#synchronizer.addPeer(peerId)
     })
 
     // When a peer disconnects, remove it from the synchronizer
     networkSubsystem.on("peer-disconnected", ({ peerId }) => {
-      synchronizer.removePeer(peerId)
+      this.#synchronizer.removePeer(peerId)
     })
 
     // Handle incoming messages
     networkSubsystem.on("message", async msg => {
-      await synchronizer.receiveMessage(msg)
+      await this.#synchronizer.receiveMessage(msg)
     })
 
     if (storageSubsystem) {
       // todo: debounce
-      synchronizer.on("sync-state", ({ documentId, peerId, syncState }) => {
-        storageSubsystem.saveSyncState(documentId, peerId, syncState)
-      })
+      this.#synchronizer.on(
+        "sync-state",
+        ({ documentId, peerId, syncState }) => {
+          storageSubsystem.saveSyncState(documentId, peerId, syncState)
+        }
+      )
     }
   }
 
@@ -179,6 +184,11 @@ export class Repo extends EventEmitter<RepoEvents> {
     return this.#handleCache
   }
 
+  /** Returns a list of all connected peer ids */
+  get peers(): PeerId[] {
+    return this.#synchronizer.peers
+  }
+
   /**
    * Creates a new document and returns a handle to it. The initial value of the document is
    * an empty object `{}`. Its documentId is generated by the system. we emit a `document` event

packages/automerge-repo/src/synchronizer/CollectionSynchronizer.ts

@@ -140,4 +140,9 @@ export class CollectionSynchronizer extends Synchronizer {
       docSynchronizer.endSync(peerId)
     }
   }
+
+  /** Returns a list of all connected peer ids */
+  get peers(): PeerId[] {
+    return Array.from(this.#peers)
+  }
 }

packages/automerge-repo/test/Repo.test.ts

@@ -825,6 +825,15 @@ describe("Repo", () => {
         A.getHeads(charlieHandle.docSync())
       )
     })
+
+    it("can report the connected peers", async () => {
+      const { bobRepo, charlieRepo, teardown } = await setup()
+
+      assert.deepStrictEqual(bobRepo.peers, ["alice", "charlie"])
+      assert.deepStrictEqual(charlieRepo.peers, ["bob"])
+
+      teardown()
+    })
   })
 
   describe("with peers (mesh network)", () => {