refactor followlinks to use a single object for all params and add an isOptional param. Also add support for embedding links to search service

src/app/core/shared/search/search.service.ts

@@ -41,6 +41,43 @@ import { SearchConfig } from './search-filters/search-config.model';
 import { PaginationService } from '../../pagination/pagination.service';
 import { SearchConfigurationService } from './search-configuration.service';
 import { PaginationComponentOptions } from '../../../shared/pagination/pagination-component-options.model';
+import { DataService } from '../../data/data.service';
+import { Store } from '@ngrx/store';
+import { CoreState } from '../../core.reducers';
+import { ObjectCacheService } from '../../cache/object-cache.service';
+import { NotificationsService } from '../../../shared/notifications/notifications.service';
+import { HttpClient } from '@angular/common/http';
+import { DSOChangeAnalyzer } from '../../data/dso-change-analyzer.service';
+
+/* tslint:disable:max-classes-per-file */
+/**
+ * A class that lets us delegate some methods to DataService
+ */
+class DataServiceImpl extends DataService<any> {
+  protected linkPath = 'discover';
+
+  constructor(
+    protected requestService: RequestService,
+    protected rdbService: RemoteDataBuildService,
+    protected store: Store<CoreState>,
+    protected objectCache: ObjectCacheService,
+    protected halService: HALEndpointService,
+    protected notificationsService: NotificationsService,
+    protected http: HttpClient,
+    protected comparator: DSOChangeAnalyzer<any>) {
+    super();
+  }
+
+  /**
+   * Adds the embed options to the link for the request
+   * @param href            The href the params are to be added to
+   * @param args            params for the query string
+   * @param linksToFollow   links we want to embed in query string if shouldEmbed is true
+   */
+  public addEmbedParams(href: string, args: string[], ...linksToFollow: FollowLinkConfig<any>[]) {
+    return super.addEmbedParams(href, args, ...linksToFollow);
+  }
+}
 
 /**
  * Service that performs all general actions that have to do with the search page
@@ -78,6 +115,11 @@ export class SearchService implements OnDestroy {
    */
   private sub;
 
+  /**
+   * Instance of DataServiceImpl that lets us delegate some methods to DataService
+   */
+  private searchDataService: DataServiceImpl;
+
   constructor(private router: Router,
               private routeService: RouteService,
               protected requestService: RequestService,
@@ -89,6 +131,16 @@ export class SearchService implements OnDestroy {
               private paginationService: PaginationService,
               private searchConfigurationService: SearchConfigurationService
   ) {
+    this.searchDataService = new DataServiceImpl(
+      undefined,
+      undefined,
+      undefined,
+      undefined,
+      undefined,
+      undefined,
+      undefined,
+      undefined
+    );
   }
 
   /**
@@ -131,7 +183,17 @@ export class SearchService implements OnDestroy {
   search<T extends DSpaceObject>(searchOptions?: PaginatedSearchOptions, responseMsToLive?: number, useCachedVersionIfAvailable = true, reRequestOnStale = true, ...linksToFollow: FollowLinkConfig<T>[]): Observable<RemoteData<SearchObjects<T>>> {
     const href$ = this.getEndpoint(searchOptions);
 
-    href$.pipe(take(1)).subscribe((url: string) => {
+    href$.pipe(
+      take(1),
+      map((href: string) => {
+        const args = this.searchDataService.addEmbedParams(href, [], ...linksToFollow);
+        if (isNotEmpty(args)) {
+          return new URLCombiner(href, `?${args.join('&')}`).toString();
+        } else {
+          return href;
+        }
+      })
+    ).subscribe((url: string) => {
       const request = new this.request(this.requestService.generateRequestId(), url);
 
       const getResponseParserFn: () => GenericConstructor<ResponseParsingService> = () => {
@@ -152,7 +214,7 @@ export class SearchService implements OnDestroy {
     );
 
     return this.directlyAttachIndexableObjects(sqr$, useCachedVersionIfAvailable, reRequestOnStale, ...linksToFollow);
- }
+  }
 
   /**
    * Method to retrieve request entries for search results from the server
@@ -399,9 +461,9 @@ export class SearchService implements OnDestroy {
         let pageParams = { page: 1 };
         const queryParams = { view: viewMode };
         if (viewMode === ViewMode.DetailedListElement) {
-          pageParams = Object.assign(pageParams, {pageSize: 1});
+          pageParams = Object.assign(pageParams, { pageSize: 1 });
         } else if (config.pageSize === 1) {
-          pageParams = Object.assign(pageParams, {pageSize: 10});
+          pageParams = Object.assign(pageParams, { pageSize: 10 });
         }
         this.paginationService.updateRouteWithUrl(this.searchConfigurationService.paginationID, hasValue(searchLinkParts) ? searchLinkParts : [this.getSearchLink()], pageParams, queryParams);
       });
@@ -413,7 +475,7 @@ export class SearchService implements OnDestroy {
    * @param {string} configurationName the name of the configuration
    * @returns {Observable<RemoteData<SearchConfig[]>>} The found configuration
    */
-  getSearchConfigurationFor(scope?: string, configurationName?: string ): Observable<RemoteData<SearchConfig>> {
+  getSearchConfigurationFor(scope?: string, configurationName?: string): Observable<RemoteData<SearchConfig>> {
     const href$ = this.halService.getEndpoint(this.configurationLinkPath).pipe(
       map((url: string) => this.getConfigUrl(url, scope, configurationName)),
     );