Finished refactoring, guards, docs, tests

src/app/+collection-page/create-collection-page/create-collection-page.guard.ts

@@ -0,0 +1,46 @@
+import { Injectable } from '@angular/core';
+import { ActivatedRouteSnapshot, CanActivate, Router, RouterStateSnapshot } from '@angular/router';
+
+import { hasNoValue, hasValue } from '../../shared/empty.util';
+import { CommunityDataService } from '../../core/data/community-data.service';
+import { RemoteData } from '../../core/data/remote-data';
+import { Community } from '../../core/shared/community.model';
+import { getFinishedRemoteData } from '../../core/shared/operators';
+import { map, tap } from 'rxjs/operators';
+import { Observable, of as observableOf } from 'rxjs';
+
+/**
+ * Prevent creation of a collection without a parent community provided
+ * @class CreateCollectionPageGuard
+ */
+@Injectable()
+export class CreateCollectionPageGuard implements CanActivate {
+  public constructor(private router: Router, private communityService: CommunityDataService) {
+  }
+
+  /**
+   * True when either a parent ID query parameter has been provided and the parent ID resolves to a valid parent community
+   * Reroutes to a 404 page when the page cannot be activated
+   * @method canActivate
+   */
+  canActivate(route: ActivatedRouteSnapshot, state: RouterStateSnapshot): Observable<boolean> {
+    const parentID = route.queryParams.parent;
+    if (hasNoValue(parentID)) {
+      this.router.navigate(['/404']);
+      return observableOf(false);
+    }
+    const parent: Observable<RemoteData<Community>> = this.communityService.findById(parentID)
+      .pipe(
+        getFinishedRemoteData(),
+      );
+
+    return parent.pipe(
+      map((communityRD: RemoteData<Community>) => hasValue(communityRD) && communityRD.hasSucceeded && hasValue(communityRD.payload)),
+      tap((isValid: boolean) => {
+        if (!isValid) {
+          this.router.navigate(['/404']);
+        }
+      })
+    );
+  }
+}