feat(nbstore): add doc sync state (#9131)

packages/common/nbstore/src/sync/doc/index.ts

@@ -1,16 +1,55 @@
+import type { Observable } from 'rxjs';
+import { combineLatest, map } from 'rxjs';
+
 import type { DocStorage, SyncStorage } from '../../storage';
 import { DocSyncPeer } from './peer';
 
+export interface DocSyncState {
+  total: number;
+  syncing: number;
+  retrying: boolean;
+  errorMessage: string | null;
+}
+
+export interface DocSyncDocState {
+  syncing: boolean;
+  retrying: boolean;
+  errorMessage: string | null;
+}
+
 export class DocSync {
-  private readonly peers: DocSyncPeer[];
+  private readonly peers: DocSyncPeer[] = this.remotes.map(
+    remote => new DocSyncPeer(this.local, this.sync, remote)
+  );
   private abort: AbortController | null = null;
 
+  readonly state$: Observable<DocSyncState> = combineLatest(
+    this.peers.map(peer => peer.peerState$)
+  ).pipe(
+    map(allPeers => ({
+      total: allPeers.reduce((acc, peer) => acc + peer.total, 0),
+      syncing: allPeers.reduce((acc, peer) => acc + peer.syncing, 0),
+      retrying: allPeers.some(peer => peer.retrying),
+      errorMessage:
+        allPeers.find(peer => peer.errorMessage)?.errorMessage ?? null,
+    }))
+  );
+
   constructor(
     readonly local: DocStorage,
     readonly sync: SyncStorage,
     readonly remotes: DocStorage[]
-  ) {
-    this.peers = remotes.map(remote => new DocSyncPeer(local, sync, remote));
+  ) {}
+
+  docState$(docId: string): Observable<DocSyncDocState> {
+    return combineLatest(this.peers.map(peer => peer.docState$(docId))).pipe(
+      map(allPeers => ({
+        errorMessage:
+          allPeers.find(peer => peer.errorMessage)?.errorMessage ?? null,
+        retrying: allPeers.some(peer => peer.retrying),
+        syncing: allPeers.some(peer => peer.syncing),
+      }))
+    );
   }
 
   start() {