sse für live collab eingebaut

listify-api/src/lists/list-realtime.service.ts

@@ -0,0 +1,97 @@
+import { Injectable, MessageEvent } from '@nestjs/common';
+import { Observable, Observer } from 'rxjs';
+import { UserList } from '../list-templates/list-template.types';
+
+export type ListRealtimeEvent =
+  | {
+      type: 'list.snapshot';
+      data: UserList;
+    }
+  | {
+      type: 'list.deleted';
+      data: { listId: string };
+    }
+  | {
+      type: 'heartbeat';
+      data: { at: string };
+    };
+
+@Injectable()
+export class ListRealtimeService {
+  // In-memory SSE fanout for one API process. If the API is scaled horizontally,
+  // replace this map with a shared pub/sub backend while keeping the event shape.
+  private readonly channels = new Map<string, Set<Observer<ListRealtimeEvent>>>();
+
+  /**
+   * Opens an owner-scoped stream. The controller authenticates the request before
+   * calling this method, so subscribers only receive their own list events.
+   */
+  eventsFor(ownerId: string): Observable<MessageEvent> {
+    return new Observable<ListRealtimeEvent>((observer) => {
+      this.addObserver(ownerId, observer);
+
+      // Keep proxies and browsers from treating an otherwise quiet stream as idle.
+      const heartbeatInterval = setInterval(() => {
+        observer.next({
+          type: 'heartbeat',
+          data: { at: new Date().toISOString() },
+        });
+      }, 25_000);
+
+      return () => {
+        clearInterval(heartbeatInterval);
+        this.removeObserver(ownerId, observer);
+      };
+    });
+  }
+
+  publishSnapshot(ownerId: string, list: UserList): void {
+    this.publish(ownerId, {
+      type: 'list.snapshot',
+      data: list,
+    });
+  }
+
+  publishDeleted(ownerId: string, listId: string): void {
+    this.publish(ownerId, {
+      type: 'list.deleted',
+      data: { listId },
+    });
+  }
+
+  private publish(ownerId: string, event: ListRealtimeEvent): void {
+    const observers = this.channels.get(ownerId);
+
+    if (!observers) {
+      return;
+    }
+
+    observers.forEach((observer) => observer.next(event));
+  }
+
+  private addObserver(
+    ownerId: string,
+    observer: Observer<ListRealtimeEvent>,
+  ): void {
+    const observers = this.channels.get(ownerId) ?? new Set();
+    observers.add(observer);
+    this.channels.set(ownerId, observers);
+  }
+
+  private removeObserver(
+    ownerId: string,
+    observer: Observer<ListRealtimeEvent>,
+  ): void {
+    const observers = this.channels.get(ownerId);
+
+    if (!observers) {
+      return;
+    }
+
+    observers.delete(observer);
+
+    if (observers.size === 0) {
+      this.channels.delete(ownerId);
+    }
+  }
+}