Allow for on-config updated pushes to services

This is an inversion of control for low-level services that cannot depend on ConfigService. Instead, they can register with a subscription to be notified when the server config updates and set their own feature flag states from that.

libs/common/src/platform/abstractions/config/config.service.ts

@@ -1,6 +1,6 @@
 // FIXME: Update this file to be type safe and remove this and next line
 // @ts-strict-ignore
-import { Observable } from "rxjs";
+import { Observable, Subscription } from "rxjs";
 import { SemVer } from "semver";
 
 import { FeatureFlag, FeatureFlagValueType } from "../../../enums/feature-flag.enum";
@@ -10,6 +10,8 @@ import { Region } from "../environment.service";
 
 import { ServerConfig } from "./server-config";
 
+export type ConfigCallback = (serverConfig: ServerConfig) => void;
+
 export abstract class ConfigService {
   /** The server config of the currently active user */
   serverConfig$: Observable<ServerConfig | null>;
@@ -54,4 +56,10 @@ export abstract class ConfigService {
    * Triggers a check that the config for the currently active user is up-to-date. If it is not, it will be fetched from the server and stored.
    */
   abstract ensureConfigFetched(): Promise<void>;
+
+  abstract broadcastConfigChangesTo(...listeners: OnServerConfigChange[]): Subscription;
+}
+
+export interface OnServerConfigChange {
+  onServerConfigChange(newConfig: ServerConfig): void;
 }

libs/common/src/platform/services/config/default-config.service.ts

@@ -10,6 +10,7 @@ import {
   of,
   shareReplay,
   Subject,
+  Subscription,
   switchMap,
   tap,
 } from "rxjs";
@@ -20,7 +21,11 @@ import { AuthenticationStatus } from "../../../auth/enums/authentication-status"
 import { FeatureFlag, getFeatureFlagValue } from "../../../enums/feature-flag.enum";
 import { UserId } from "../../../types/guid";
 import { ConfigApiServiceAbstraction } from "../../abstractions/config/config-api.service.abstraction";
-import { ConfigService } from "../../abstractions/config/config.service";
+import {
+  ConfigCallback,
+  ConfigService,
+  OnServerConfigChange,
+} from "../../abstractions/config/config.service";
 import { ServerConfig } from "../../abstractions/config/server-config";
 import { Environment, EnvironmentService, Region } from "../../abstractions/environment.service";
 import { LogService } from "../../abstractions/log.service";
@@ -53,6 +58,7 @@ export const GLOBAL_SERVER_CONFIGURATIONS = KeyDefinition.record<ServerConfig, A
 // FIXME: currently we are limited to api requests for active users. Update to accept a UserId and APIUrl once ApiService supports it.
 export class DefaultConfigService implements ConfigService {
   private failedFetchFallbackSubject = new Subject<ServerConfig>();
+  private callbacks: ConfigCallback[] = [];
 
   serverConfig$: Observable<ServerConfig>;
 
@@ -149,6 +155,12 @@ export class DefaultConfigService implements ConfigService {
     await firstValueFrom(this.serverConfig$);
   }
 
+  broadcastConfigChangesTo(...listeners: OnServerConfigChange[]): Subscription {
+    return this.serverConfig$.subscribe((config) =>
+      listeners.forEach((listener) => listener.onServerConfigChange(config)),
+    );
+  }
+
   private olderThanRetrievalInterval(date: Date) {
     return new Date().getTime() - date.getTime() > RETRIEVAL_INTERVAL;
   }