65528: Renaming/Moving according to feedback; style and links added; chevrons fixed

src/app/community-list-page/community-list-datasource.ts

@@ -0,0 +1,33 @@
+import {CommunityListAdapter, FlatNode} from './community-list-adapter';
+import {CollectionViewer, DataSource} from '@angular/cdk/typings/collections';
+import {BehaviorSubject, Observable,} from 'rxjs';
+import {finalize, take,} from 'rxjs/operators';
+
+export class CommunityListDatasource implements DataSource<FlatNode> {
+
+    private communityList$ = new BehaviorSubject<FlatNode[]>([]);
+    private loading$ = new BehaviorSubject<boolean>(false);
+
+    constructor(private communityListService: CommunityListAdapter) {
+    }
+
+    connect(collectionViewer: CollectionViewer): Observable<FlatNode[]> {
+        this.loadCommunities(null);
+        return this.communityList$.asObservable();
+    }
+
+    loadCommunities(expandedNodes: FlatNode[]) {
+        this.loading$.next(true);
+
+        this.communityListService.loadCommunities(expandedNodes).pipe(
+            take(1),
+            finalize(() => this.loading$.next(false)),
+            ).subscribe((flatNodes: FlatNode[]) => this.communityList$.next(flatNodes));
+    }
+
+    disconnect(collectionViewer: CollectionViewer): void {
+        this.communityList$.complete();
+        this.loading$.complete();
+    }
+
+}