optimize show filter

src/app/modules/shows/services/show-data.service.ts

@@ -3,6 +3,8 @@ import {Observable} from 'rxjs';
 import {DbService} from '../../../services/db.service';
 import {Show} from './show';
 import {map, shareReplay} from 'rxjs/operators';
+import {QueryFn} from '@angular/fire/compat/firestore/interfaces';
+import firebase from 'firebase/compat/app';
 
 @Injectable({
   providedIn: 'root',
@@ -22,6 +24,23 @@ export class ShowDataService {
 
   public listRaw$ = () => this.dbService.col$<Show>(this.collection);
 
+  public listPublicSince$(lastMonths: number): Observable<Show[]> {
+    const startDate = new Date();
+    startDate.setHours(0, 0, 0, 0);
+    startDate.setDate(startDate.getDate() - lastMonths * 30);
+    const startTimestamp = firebase.firestore.Timestamp.fromDate(startDate);
+
+    const queryFn: QueryFn = ref => ref.where('published', '==', true).where('date', '>=', startTimestamp).orderBy('date', 'desc');
+
+    return this.dbService.col$<Show>(this.collection, queryFn).pipe(
+      map(shows => shows.filter(show => !show.archived)),
+      shareReplay({
+        bufferSize: 1,
+        refCount: true,
+      })
+    );
+  }
+
   public read$ = (showId: string): Observable<Show | null> => this.dbService.doc$(`${this.collection}/${showId}`);
 
   public update = async (showId: string, data: Partial<Show>): Promise<void> => await this.dbService.doc(`${this.collection}/${showId}`).update(data);