refact: step 2 - break down old membership local transport logic

src/state/CallViewModel/localMember/LocalTransport.ts

@@ -12,13 +12,14 @@ import {
 } from "matrix-js-sdk/lib/matrixrtc";
 import { type MatrixClient } from "matrix-js-sdk";
 import {
+  catchError,
   combineLatest,
   distinctUntilChanged,
   first,
   from,
   map,
   merge,
-  Observable,
+  type Observable,
   of,
   startWith,
   switchMap,
@@ -184,7 +185,7 @@ export const createLocalTransport$ = ({
     switchMap(async ([transport, delayId]) => {
       try {
         return await doOpenIdAndJWTFromUrl(
-          transport.livekit_service_url,
+          transport,
           forceJwtEndpoint,
           ownMembershipIdentity,
           roomId,
@@ -192,18 +193,11 @@ export const createLocalTransport$ = ({
           delayId ?? undefined,
         );
       } catch (e) {
-        if (
-          e instanceof FailToGetOpenIdToken ||
-          e instanceof NoMatrix2AuthorizationService
-        ) {
-          // rethrow as is
-          throw e;
-        }
-        // Catch others and rethrow as FailToGetOpenIdToken that has user friendly message.
-        logger.error("Failed to get JWT from preferred transport", e);
-        throw new FailToGetOpenIdToken(
-          e instanceof Error ? e : new Error(String(e)),
+        logger.error(
+          `Failed to authenticate to transport ${transport.livekit_service_url}`,
+          e,
         );
+        throw mapAuthErrorToUserFriendlyError(e);
       }
     }),
   );
@@ -283,7 +277,7 @@ function observerOldestMembership$(
 // If the OpenID request were to fail, then it's acceptable for us to fail
 // this function early, as we assume the homeserver has got some problems.
 async function doOpenIdAndJWTFromUrl(
-  url: string,
+  transport: LivekitTransportConfig,
   forceJwtEndpoint: JwtEndpointVersion,
   membership: CallMembershipIdentityParts,
   roomId: string,
@@ -297,7 +291,7 @@ async function doOpenIdAndJWTFromUrl(
   const sfuConfig = await getSFUConfigWithOpenID(
     client,
     membership,
-    url,
+    transport.livekit_service_url,
     roomId,
     {
       forceJwtEndpoint: forceJwtEndpoint,
@@ -307,10 +301,7 @@ async function doOpenIdAndJWTFromUrl(
     logger,
   );
   return {
-    transport: {
-      type: "livekit",
-      livekit_service_url: url,
-    },
+    transport,
     sfuConfig,
   };
 }
@@ -327,6 +318,37 @@ function observeLocalTransportForOldestMembership(
   ownMembershipIdentity: CallMembershipIdentityParts,
   roomId: string,
 ): LocalTransport {
+  // Ensure we can authenticate with the SFU.
+  const authenticatedOldestMemberTransport$ = oldestMemberTransport$.pipe(
+    switchMap((transport) => {
+      // Oldest member not available -we are first- (or invalid SFU config).
+      if (transport === null) return of(null);
+
+      // Whenever there is transport change we want to revert
+      // to no transport while we do the authentication.
+      // So do a from(promise) here to be able to startWith(null)
+      return from(
+        doOpenIdAndJWTFromUrl(
+          transport,
+          JwtEndpointVersion.Legacy,
+          ownMembershipIdentity,
+          roomId,
+          client,
+          undefined,
+        ),
+      ).pipe(
+        catchError((e: unknown) => {
+          logger.error(
+            `Failed to authenticate to transport ${transport.livekit_service_url}`,
+            e,
+          );
+          throw mapAuthErrorToUserFriendlyError(e);
+        }),
+        startWith(null),
+      );
+    }),
+  );
+
   // --- Oldest member mode ---
   return {
     // Never update the transport that we advertise in our membership. Just
@@ -335,7 +357,9 @@ function observeLocalTransportForOldestMembership(
     // state changes.
     advertised$: scope.behavior(
       merge(
-        oldestMemberTransport$,
+        authenticatedOldestMemberTransport$.pipe(
+          map((t) => t?.transport ?? null),
+        ),
         preferredTransport$.pipe(map((t) => t.transport)),
       ).pipe(
         first((t) => t !== null),
@@ -347,25 +371,7 @@ function observeLocalTransportForOldestMembership(
     ),
     // Publish on the transport used by the oldest member.
     active$: scope.behavior(
-      oldestMemberTransport$.pipe(
-        switchMap((transport) => {
-          // Oldest member not available (or invalid SFU config).
-          if (transport === null) return of(null);
-          // Oldest member available: fetch the SFU config.
-          const fetchOldestMemberTransport =
-            async (): Promise<LocalTransportWithSFUConfig> => ({
-              transport,
-              sfuConfig: await getSFUConfigWithOpenID(
-                client,
-                ownMembershipIdentity,
-                transport.livekit_service_url,
-                roomId,
-                { forceJwtEndpoint: JwtEndpointVersion.Legacy },
-                logger,
-              ),
-            });
-          return from(fetchOldestMemberTransport()).pipe(startWith(null));
-        }),
+      authenticatedOldestMemberTransport$.pipe(
         tap((t) =>
           logger.info(
             `Publish on transport: ${t?.transport.livekit_service_url}`,
@@ -376,3 +382,17 @@ function observeLocalTransportForOldestMembership(
     ),
   };
 }
+
+function mapAuthErrorToUserFriendlyError(e: unknown): Error {
+  if (
+    e instanceof FailToGetOpenIdToken ||
+    e instanceof NoMatrix2AuthorizationService
+  ) {
+    // rethrow as is
+    return e;
+  }
+  // Catch others and rethrow as FailToGetOpenIdToken that has user friendly message.
+  return new FailToGetOpenIdToken(
+    e instanceof Error ? e : new Error(String(e)),
+  );
+}