65528: ComCol Tree with full FlatList that gets generated at page-load

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

@@ -0,0 +1,74 @@
+import {CommunityForList, CommunityListService} from './CommunityListService';
+import {CollectionViewer, DataSource} from '@angular/cdk/typings/collections';
+import {BehaviorSubject, Observable, of} from 'rxjs';
+import {catchError, finalize, map} from 'rxjs/operators';
+
+export interface CommunityFlatNode {
+    expandable: boolean;
+    name: string;
+    level: number;
+    isExpanded?: boolean;
+    parent?: CommunityFlatNode;
+    community: CommunityForList;
+}
+
+export class CommunityListDataSource implements DataSource<CommunityFlatNode> {
+
+    private communityListSubject = new BehaviorSubject<CommunityFlatNode[]>([]);
+    private loadingSubject = new BehaviorSubject<boolean>(false);
+
+    public loading$ = this.loadingSubject.asObservable();
+
+    constructor(private communityListService: CommunityListService) {}
+
+    connect(collectionViewer: CollectionViewer): Observable<CommunityFlatNode[]> {
+        return this.communityListSubject.asObservable();
+    }
+
+    disconnect(collectionViewer: CollectionViewer): void {
+        this.communityListSubject.complete();
+        this.loadingSubject.complete();
+    }
+
+    loadCommunities() {
+        this.loadingSubject.next(true);
+
+        this.communityListService.getCommunityList()
+            .pipe(
+                catchError(() => of([])),
+                finalize(() => this.loadingSubject.next(false)),
+                map((result: CommunityForList[]) => {
+                    const communityFlatNodes: CommunityFlatNode[] = [];
+                    const level = 0;
+                    return this.transformListOfCommunities(result, level, communityFlatNodes, null);
+                })
+            )
+            .subscribe((communityFlatNode) => {
+                this.communityListSubject.next(communityFlatNode)
+            });
+    };
+
+    transformListOfCommunities(listOfCommunities: CommunityForList[],
+                               level: number,
+                               communityFlatNodes: CommunityFlatNode[],
+                               parent: CommunityFlatNode): CommunityFlatNode[] {
+        level++;
+        for (const community of listOfCommunities) {
+            const hasSubComs = ((!!community.subcoms && community.subcoms.length > 0));
+            const communityFlatNode: CommunityFlatNode = {
+                expandable: hasSubComs,
+                name: community.name,
+                level: level,
+                isExpanded: false,
+                community: community,
+                parent: parent
+            }
+            communityFlatNodes.push(communityFlatNode);
+            if (hasSubComs) {
+                this.transformListOfCommunities(community.subcoms, level, communityFlatNodes, communityFlatNode);
+            }
+        }
+        return communityFlatNodes;
+    }
+
+}