Merge pull request #1228 from atmire/w2p-79768_fix-issues-with-meta-tags

Fix issues with meta tags

src/app/+collection-page/collection-page.component.ts

@@ -1,6 +1,11 @@
 import { ChangeDetectionStrategy, Component, OnInit } from '@angular/core';
 import { ActivatedRoute, Router } from '@angular/router';
-import { BehaviorSubject, combineLatest as observableCombineLatest, Observable, Subject } from 'rxjs';
+import {
+  BehaviorSubject,
+  combineLatest as observableCombineLatest,
+  Observable,
+  Subject
+} from 'rxjs';
 import { filter, map, mergeMap, startWith, switchMap, take } from 'rxjs/operators';
 import { PaginatedSearchOptions } from '../shared/search/paginated-search-options.model';
 import { SearchService } from '../core/shared/search/search.service';
@@ -8,8 +13,6 @@ import { SortDirection, SortOptions } from '../core/cache/models/sort-options.mo
 import { CollectionDataService } from '../core/data/collection-data.service';
 import { PaginatedList } from '../core/data/paginated-list.model';
 import { RemoteData } from '../core/data/remote-data';
-
-import { MetadataService } from '../core/metadata/metadata.service';
 import { Bitstream } from '../core/shared/bitstream.model';
 
 import { Collection } from '../core/shared/collection.model';
@@ -65,7 +68,6 @@ export class CollectionPageComponent implements OnInit {
   constructor(
     private collectionDataService: CollectionDataService,
     private searchService: SearchService,
-    private metadata: MetadataService,
     private route: ActivatedRoute,
     private router: Router,
     private authService: AuthService,
@@ -122,10 +124,6 @@ export class CollectionPageComponent implements OnInit {
       getAllSucceededRemoteDataPayload(),
       map((collection) => getCollectionPageRoute(collection.id))
     );
-
-    this.route.queryParams.pipe(take(1)).subscribe((params) => {
-      this.metadata.processRemoteData(this.collectionRD$);
-    });
   }
 
   isNotEmpty(object: any) {

src/app/+item-page/full/full-item-page.component.ts

@@ -1,8 +1,8 @@
-import {filter, map} from 'rxjs/operators';
+import { filter, map } from 'rxjs/operators';
 import { ChangeDetectionStrategy, Component, OnInit } from '@angular/core';
 import { ActivatedRoute, Router } from '@angular/router';
 
-import { Observable ,  BehaviorSubject } from 'rxjs';
+import { Observable, BehaviorSubject } from 'rxjs';
 
 import { ItemPageComponent } from '../simple/item-page.component';
 import { MetadataMap } from '../../core/shared/metadata.models';
@@ -11,8 +11,6 @@ import { ItemDataService } from '../../core/data/item-data.service';
 import { RemoteData } from '../../core/data/remote-data';
 import { Item } from '../../core/shared/item.model';
 
-import { MetadataService } from '../../core/metadata/metadata.service';
-
 import { fadeInOut } from '../../shared/animations/fade';
 import { hasValue } from '../../shared/empty.util';
 import { AuthService } from '../../core/auth/auth.service';
@@ -35,8 +33,8 @@ export class FullItemPageComponent extends ItemPageComponent implements OnInit {
 
   metadata$: Observable<MetadataMap>;
 
-  constructor(route: ActivatedRoute, router: Router, items: ItemDataService, metadataService: MetadataService, authService: AuthService) {
+  constructor(route: ActivatedRoute, router: Router, items: ItemDataService, authService: AuthService) {
-    super(route, router, items, metadataService, authService);
+    super(route, router, items, authService);
   }
 
   /*** AoT inheritance fix, will hopefully be resolved in the near future **/

src/app/+item-page/simple/item-page.component.ts

@@ -8,8 +8,6 @@ import { RemoteData } from '../../core/data/remote-data';
 
 import { Item } from '../../core/shared/item.model';
 
-import { MetadataService } from '../../core/metadata/metadata.service';
-
 import { fadeInOut } from '../../shared/animations/fade';
 import { getAllSucceededRemoteDataPayload, redirectOn4xx } from '../../core/shared/operators';
 import { ViewMode } from '../../core/shared/view-mode.model';
@@ -54,7 +52,6 @@ export class ItemPageComponent implements OnInit {
     private route: ActivatedRoute,
     private router: Router,
     private items: ItemDataService,
-    private metadataService: MetadataService,
     private authService: AuthService,
   ) { }
 
@@ -66,7 +63,6 @@ export class ItemPageComponent implements OnInit {
       map((data) => data.dso as RemoteData<Item>),
       redirectOn4xx(this.router, this.authService)
     );
-    this.metadataService.processRemoteData(this.itemRD$);
     this.itemPageRoute$ = this.itemRD$.pipe(
       getAllSucceededRemoteDataPayload(),
       map((item) => getItemPageRoute(item))

src/app/core/core.reducers.ts

@@ -13,6 +13,7 @@ import {
   BitstreamFormatRegistryState
 } from '../+admin/admin-registries/bitstream-formats/bitstream-format.reducers';
 import { historyReducer, HistoryState } from './history/history.reducer';
+import { metaTagReducer, MetaTagState } from './metadata/meta-tag.reducer';
 
 export interface CoreState {
   'bitstreamFormats': BitstreamFormatRegistryState;
@@ -24,6 +25,7 @@ export interface CoreState {
   'index': MetaIndexState;
   'auth': AuthState;
   'json/patch': JsonPatchOperationsState;
+  'metaTag': MetaTagState;
   'route': RouteState;
 }
 
@@ -37,5 +39,6 @@ export const coreReducers: ActionReducerMap<CoreState> = {
   'index': indexReducer,
   'auth': authReducer,
   'json/patch': jsonPatchOperationsReducer,
+  'metaTag': metaTagReducer,
   'route': routeReducer
 };

src/app/core/metadata/meta-tag.actions.ts

@@ -0,0 +1,23 @@
+import { type } from '../../shared/ngrx/type';
+import { Action } from '@ngrx/store';
+
+// tslint:disable:max-classes-per-file
+export const MetaTagTypes = {
+  ADD: type('dspace/meta-tag/ADD'),
+  CLEAR: type('dspace/meta-tag/CLEAR')
+};
+
+export class AddMetaTagAction implements Action {
+  type = MetaTagTypes.ADD;
+  payload: string;
+
+  constructor(property: string) {
+    this.payload = property;
+  }
+}
+
+export class ClearMetaTagAction implements Action {
+  type = MetaTagTypes.CLEAR;
+}
+
+export type MetaTagAction = AddMetaTagAction | ClearMetaTagAction;

src/app/core/metadata/meta-tag.reducer.spec.ts

@@ -0,0 +1,50 @@
+/**
+ * The contents of this file are subject to the license and copyright
+ * detailed in the LICENSE and NOTICE files at the root of the source
+ * tree and available online at
+ *
+ * http://www.dspace.org/license/
+ */
+
+import { metaTagReducer } from './meta-tag.reducer';
+import { AddMetaTagAction, ClearMetaTagAction } from './meta-tag.actions';
+
+const nullAction = { type: null };
+
+describe('metaTagReducer', () => {
+  it('should start with an empty array', () => {
+    const state0 = metaTagReducer(undefined, nullAction);
+    expect(state0.tagsInUse).toEqual([]);
+  });
+
+  it('should return the current state on invalid action', () => {
+    const state0 = {
+      tagsInUse: ['foo', 'bar'],
+    };
+
+    const state1 = metaTagReducer(state0, nullAction);
+    expect(state1).toEqual(state0);
+  });
+
+  it('should add tags on AddMetaTagAction', () => {
+    const state0 = {
+      tagsInUse: ['foo'],
+    };
+
+    const state1 = metaTagReducer(state0, new AddMetaTagAction('bar'));
+    const state2 = metaTagReducer(state1, new AddMetaTagAction('baz'));
+
+    expect(state1.tagsInUse).toEqual(['foo', 'bar']);
+    expect(state2.tagsInUse).toEqual(['foo', 'bar', 'baz']);
+  });
+
+  it('should clear tags on ClearMetaTagAction', () => {
+    const state0 = {
+      tagsInUse: ['foo', 'bar'],
+    };
+
+    const state1 = metaTagReducer(state0, new ClearMetaTagAction());
+
+    expect(state1.tagsInUse).toEqual([]);
+  });
+});

src/app/core/metadata/meta-tag.reducer.ts

@@ -0,0 +1,38 @@
+import {
+  MetaTagAction,
+  MetaTagTypes,
+  AddMetaTagAction,
+  ClearMetaTagAction,
+} from './meta-tag.actions';
+
+export interface MetaTagState {
+  tagsInUse: string[];
+}
+
+const initialstate: MetaTagState = {
+  tagsInUse: []
+};
+
+export const metaTagReducer = (state: MetaTagState = initialstate, action: MetaTagAction): MetaTagState => {
+  switch (action.type) {
+    case MetaTagTypes.ADD: {
+      return addMetaTag(state, action as AddMetaTagAction);
+    }
+    case MetaTagTypes.CLEAR: {
+      return clearMetaTags(state, action as ClearMetaTagAction);
+    }
+    default: {
+      return state;
+    }
+  }
+};
+
+const addMetaTag = (state: MetaTagState, action: AddMetaTagAction): MetaTagState => {
+  return {
+    tagsInUse: [...state.tagsInUse, action.payload]
+  };
+};
+
+const clearMetaTags = (state: MetaTagState, action: ClearMetaTagAction): MetaTagState => {
+  return Object.assign({}, initialstate);
+};

src/app/core/metadata/metadata.service.spec.ts

@@ -1,82 +1,28 @@
-import { CommonModule, Location } from '@angular/common';
+import { fakeAsync, tick } from '@angular/core/testing';
-import { HttpClient } from '@angular/common/http';
+import { Meta, Title } from '@angular/platform-browser';
-import { Component, CUSTOM_ELEMENTS_SCHEMA } from '@angular/core';
+import { NavigationEnd, Router } from '@angular/router';
-import { ComponentFixture, fakeAsync, TestBed, tick } from '@angular/core/testing';
-import { Meta, MetaDefinition, Title } from '@angular/platform-browser';
-import { ActivatedRoute, Router } from '@angular/router';
-import { RouterTestingModule } from '@angular/router/testing';
 
-import { Store, StoreModule } from '@ngrx/store';
+import { TranslateService } from '@ngx-translate/core';
-
+import { Observable, of } from 'rxjs';
-import { TranslateLoader, TranslateModule, TranslateService } from '@ngx-translate/core';
-import { EmptyError, Observable, of } from 'rxjs';
 
 import { RemoteData } from '../data/remote-data';
 import { Item } from '../shared/item.model';
 
-import {
+import { ItemMock, MockBitstream1, MockBitstream3 } from '../../shared/mocks/item.mock';
-  ItemMock,
+import { createSuccessfulRemoteDataObject, createSuccessfulRemoteDataObject$ } from '../../shared/remote-data.utils';
-  MockBitstream1,
+import { PaginatedList } from '../data/paginated-list.model';
-  MockBitstream2,
-  MockBitstreamFormat1,
-  MockBitstreamFormat2
-} from '../../shared/mocks/item.mock';
-import { TranslateLoaderMock } from '../../shared/mocks/translate-loader.mock';
-import { NotificationsService } from '../../shared/notifications/notifications.service';
-import { createSuccessfulRemoteDataObject$ } from '../../shared/remote-data.utils';
-import { FollowLinkConfig } from '../../shared/utils/follow-link-config.model';
-import { AuthService } from '../auth/auth.service';
-import { BrowseService } from '../browse/browse.service';
-import { RemoteDataBuildService } from '../cache/builders/remote-data-build.service';
-import { ObjectCacheService } from '../cache/object-cache.service';
-
-import { CoreState } from '../core.reducers';
-import { BitstreamDataService } from '../data/bitstream-data.service';
-import { BitstreamFormatDataService } from '../data/bitstream-format-data.service';
-import { CommunityDataService } from '../data/community-data.service';
-import { DefaultChangeAnalyzer } from '../data/default-change-analyzer.service';
-import { DSOChangeAnalyzer } from '../data/dso-change-analyzer.service';
-
-import { ItemDataService } from '../data/item-data.service';
-import { buildPaginatedList, PaginatedList } from '../data/paginated-list.model';
-import { FindListOptions } from '../data/request.models';
-import { RequestService } from '../data/request.service';
-import { BitstreamFormat } from '../shared/bitstream-format.model';
 import { Bitstream } from '../shared/bitstream.model';
-import { HALEndpointService } from '../shared/hal-endpoint.service';
 import { MetadataValue } from '../shared/metadata.models';
-import { PageInfo } from '../shared/page-info.model';
-import { UUIDService } from '../shared/uuid.service';
 
 import { MetadataService } from './metadata.service';
-import { environment } from '../../../environments/environment';
-import { storeModuleConfig } from '../../app.reducer';
-import { HardRedirectService } from '../services/hard-redirect.service';
-import { URLCombiner } from '../url-combiner/url-combiner';
 import { RootDataService } from '../data/root-data.service';
-import { Root } from '../data/root.model';
+import { Bundle } from '../shared/bundle.model';
-
+import { createPaginatedList } from '../../shared/testing/utils.test';
-/* tslint:disable:max-classes-per-file */
+import { getMockTranslateService } from '../../shared/mocks/translate.service.mock';
-@Component({
+import { DSONameService } from '../breadcrumbs/dso-name.service';
-  template: `
+import { HardRedirectService } from '../services/hard-redirect.service';
-    <router-outlet></router-outlet>`
+import { getMockStore } from '@ngrx/store/testing';
-})
+import { AddMetaTagAction, ClearMetaTagAction } from './meta-tag.actions';
-class TestComponent {
-  constructor(private metadata: MetadataService) {
-    metadata.listenForRouteChange();
-  }
-}
-
-@Component({ template: '' })
-class DummyItemComponent {
-  constructor(private route: ActivatedRoute, private items: ItemDataService, private metadata: MetadataService) {
-    this.route.params.subscribe((params) => {
-      this.metadata.processRemoteData(this.items.findById(params.id));
-    });
-  }
-}
-
-/* tslint:enable:max-classes-per-file */
 
 describe('MetadataService', () => {
   let metadataService: MetadataService;
@@ -85,188 +31,339 @@ describe('MetadataService', () => {
 
   let title: Title;
 
-  let store: Store<CoreState>;
+  let dsoNameService: DSONameService;
 
-  let objectCacheService: ObjectCacheService;
+  let bundleDataService;
-  let requestService: RequestService;
+  let bitstreamDataService;
-  let uuidService: UUIDService;
-  let remoteDataBuildService: RemoteDataBuildService;
-  let itemDataService: ItemDataService;
-  let authService: AuthService;
   let rootService: RootDataService;
   let translateService: TranslateService;
+  let hardRedirectService: HardRedirectService;
 
-  let location: Location;
   let router: Router;
-  let fixture: ComponentFixture<TestComponent>;
+  let store;
+
+  const initialState = { 'core': { metaTag: { tagsInUse: ['title', 'description'] }}};
 
-  let tagStore: Map<string, MetaDefinition[]>;
 
   beforeEach(() => {
+    rootService = jasmine.createSpyObj({
+      findRoot: createSuccessfulRemoteDataObject$({ dspaceVersion: 'mock-dspace-version' })
+    });
+    bitstreamDataService = jasmine.createSpyObj({
+      findAllByHref: createSuccessfulRemoteDataObject$(createPaginatedList([MockBitstream3]))
+    });
+    bundleDataService = jasmine.createSpyObj({
+      findByItemAndName: mockBundleRD$([MockBitstream3])
+    });
+    translateService = getMockTranslateService();
+    meta = jasmine.createSpyObj('meta', {
+      addTag: {},
+      removeTag: {}
+    });
+    title = jasmine.createSpyObj({
+      setTitle: {}
+    });
+    dsoNameService = jasmine.createSpyObj({
+      getName: ItemMock.firstMetadataValue('dc.title')
+    });
+    router = {
+      url: '/items/0ec7ff22-f211-40ab-a69e-c819b0b1f357',
+      events: of(new NavigationEnd(1, '', '')),
+      routerState: {
+        root: {}
+      }
+    } as any as Router;
+    hardRedirectService = jasmine.createSpyObj( {
+      getRequestOrigin: 'https://request.org',
+    });
 
-    store = new Store<CoreState>(undefined, undefined, undefined);
+    // @ts-ignore
+    store = getMockStore({ initialState });
     spyOn(store, 'dispatch');
 
-    objectCacheService = new ObjectCacheService(store, undefined);
+    metadataService = new MetadataService(
-    uuidService = new UUIDService();
+      router,
-    requestService = new RequestService(objectCacheService, uuidService, store, undefined);
+      translateService,
-    remoteDataBuildService = new RemoteDataBuildService(objectCacheService, undefined, requestService);
+      meta,
-    const mockBitstreamDataService = {
+      title,
-      findAllByItemAndBundleName(item: Item, bundleName: string, options?: FindListOptions, ...linksToFollow: FollowLinkConfig<Bitstream>[]): Observable<RemoteData<PaginatedList<Bitstream>>> {
+      dsoNameService,
-        if (item.equals(ItemMock)) {
+      bundleDataService,
-          return createSuccessfulRemoteDataObject$(buildPaginatedList(new PageInfo(), [MockBitstream1, MockBitstream2]));
+      bitstreamDataService,
-        } else {
+      undefined,
-          return createSuccessfulRemoteDataObject$(buildPaginatedList(new PageInfo(), []));
+      rootService,
-        }
+      store,
-      },
+      hardRedirectService
-    };
+    );
-    const mockBitstreamFormatDataService = {
-      findByBitstream(bitstream: Bitstream): Observable<RemoteData<BitstreamFormat>> {
-        switch (bitstream) {
-          case MockBitstream1:
-            return createSuccessfulRemoteDataObject$(MockBitstreamFormat1);
-            break;
-          case MockBitstream2:
-            return createSuccessfulRemoteDataObject$(MockBitstreamFormat2);
-            break;
-          default:
-            return createSuccessfulRemoteDataObject$(new BitstreamFormat());
-        }
-      }
-    };
-    rootService = jasmine.createSpyObj('rootService', {
-      findRoot: createSuccessfulRemoteDataObject$(Object.assign(new Root(), {
-        dspaceVersion: 'mock-dspace-version'
-      }))
-    });
-
-    TestBed.configureTestingModule({
-      imports: [
-        CommonModule,
-        StoreModule.forRoot({}, storeModuleConfig),
-        TranslateModule.forRoot({
-          loader: {
-            provide: TranslateLoader,
-            useClass: TranslateLoaderMock
-          }
-        }),
-        RouterTestingModule.withRoutes([
-          { path: 'items/:id', component: DummyItemComponent, pathMatch: 'full' },
-          {
-            path: 'other',
-            component: DummyItemComponent,
-            pathMatch: 'full',
-            data: { title: 'Dummy Title', description: 'This is a dummy item component for testing!' }
-          }
-        ])
-      ],
-      declarations: [
-        TestComponent,
-        DummyItemComponent
-      ],
-      providers: [
-        { provide: ObjectCacheService, useValue: objectCacheService },
-        { provide: RequestService, useValue: requestService },
-        { provide: RemoteDataBuildService, useValue: remoteDataBuildService },
-        { provide: HALEndpointService, useValue: {} },
-        { provide: AuthService, useValue: {} },
-        { provide: NotificationsService, useValue: {} },
-        { provide: HttpClient, useValue: {} },
-        { provide: DSOChangeAnalyzer, useValue: {} },
-        { provide: CommunityDataService, useValue: {} },
-        { provide: DefaultChangeAnalyzer, useValue: {} },
-        { provide: BitstreamFormatDataService, useValue: mockBitstreamFormatDataService },
-        { provide: BitstreamDataService, useValue: mockBitstreamDataService },
-        { provide: RootDataService, useValue: rootService },
-        Meta,
-        Title,
-        // tslint:disable-next-line:no-empty
-        { provide: ItemDataService, useValue: { findById: () => {} } },
-        BrowseService,
-        MetadataService
-      ],
-      schemas: [CUSTOM_ELEMENTS_SCHEMA]
-    });
-    meta = TestBed.inject(Meta);
-    title = TestBed.inject(Title);
-    itemDataService = TestBed.inject(ItemDataService);
-    metadataService = TestBed.inject(MetadataService);
-    authService = TestBed.inject(AuthService);
-    translateService = TestBed.inject(TranslateService);
-
-    router = TestBed.inject(Router);
-    location = TestBed.inject(Location);
-
-    fixture = TestBed.createComponent(TestComponent);
-
-    tagStore = metadataService.getTagStore();
   });
 
   it('items page should set meta tags', fakeAsync(() => {
-    spyOn(itemDataService, 'findById').and.returnValue(mockRemoteData(ItemMock));
+    (metadataService as any).processRouteChange({
-    router.navigate(['/items/0ec7ff22-f211-40ab-a69e-c819b0b1f357']);
+      data: {
+        value: {
+          dso: createSuccessfulRemoteDataObject(ItemMock),
+        }
+      }
+    });
     tick();
-    expect(title.getTitle()).toEqual('Test PowerPoint Document');
+    expect(title.setTitle).toHaveBeenCalledWith('Test PowerPoint Document');
-    expect(tagStore.get('citation_title')[0].content).toEqual('Test PowerPoint Document');
+    expect(meta.addTag).toHaveBeenCalledWith({
-    expect(tagStore.get('citation_author')[0].content).toEqual('Doe, Jane');
+      property: 'citation_title',
-    expect(tagStore.get('citation_date')[0].content).toEqual('1650-06-26');
+      content: 'Test PowerPoint Document'
-    expect(tagStore.get('citation_issn')[0].content).toEqual('123456789');
+    });
-    expect(tagStore.get('citation_language')[0].content).toEqual('en');
+    expect(meta.addTag).toHaveBeenCalledWith({ property: 'citation_author', content: 'Doe, Jane' });
-    expect(tagStore.get('citation_keywords')[0].content).toEqual('keyword1; keyword2; keyword3');
+    expect(meta.addTag).toHaveBeenCalledWith({
+      property: 'citation_publication_date',
+      content: '1650-06-26'
+    });
+    expect(meta.addTag).toHaveBeenCalledWith({ property: 'citation_issn', content: '123456789' });
+    expect(meta.addTag).toHaveBeenCalledWith({ property: 'citation_language', content: 'en' });
+    expect(meta.addTag).toHaveBeenCalledWith({
+      property: 'citation_keywords',
+      content: 'keyword1; keyword2; keyword3'
+    });
   }));
 
   it('items page should set meta tags as published Thesis', fakeAsync(() => {
-    spyOn(itemDataService, 'findById').and.returnValue(mockRemoteData(mockPublisher(mockType(ItemMock, 'Thesis'))));
+    (metadataService as any).processRouteChange({
-    router.navigate(['/items/0ec7ff22-f211-40ab-a69e-c819b0b1f357']);
+      data: {
+        value: {
+          dso: createSuccessfulRemoteDataObject(mockPublisher(mockType(ItemMock, 'Thesis'))),
+        }
+      }
+    });
     tick();
-    expect(tagStore.get('citation_dissertation_name')[0].content).toEqual('Test PowerPoint Document');
+    expect(meta.addTag).toHaveBeenCalledWith({
-    expect(tagStore.get('citation_dissertation_institution')[0].content).toEqual('Mock Publisher');
+      property: 'citation_dissertation_name',
-    expect(tagStore.get('citation_abstract_html_url')[0].content).toEqual([environment.ui.baseUrl, router.url].join(''));
+      content: 'Test PowerPoint Document'
-    expect(tagStore.get('citation_pdf_url')[0].content).toEqual('/bitstreams/99b00f3c-1cc6-4689-8158-91965bee6b28/download');
+    });
+    expect(meta.addTag).toHaveBeenCalledWith({
+      property: 'citation_pdf_url',
+      content: 'https://request.org/bitstreams/4db100c1-e1f5-4055-9404-9bc3e2d15f29/download'
+    });
   }));
 
   it('items page should set meta tags as published Technical Report', fakeAsync(() => {
-    spyOn(itemDataService, 'findById').and.returnValue(mockRemoteData(mockPublisher(mockType(ItemMock, 'Technical Report'))));
+    (metadataService as any).processRouteChange({
-    router.navigate(['/items/0ec7ff22-f211-40ab-a69e-c819b0b1f357']);
+      data: {
+        value: {
+          dso: createSuccessfulRemoteDataObject(mockPublisher(mockType(ItemMock, 'Technical Report'))),
+        }
+      }
+    });
     tick();
-    expect(tagStore.get('citation_technical_report_institution')[0].content).toEqual('Mock Publisher');
+    expect(meta.addTag).toHaveBeenCalledWith({
+      property: 'citation_technical_report_institution',
+      content: 'Mock Publisher'
+    });
   }));
 
-  it('other navigation should add title, description and Generator', fakeAsync(() => {
+  it('other navigation should add title and description', fakeAsync(() => {
-    spyOn(itemDataService, 'findById').and.returnValue(mockRemoteData(ItemMock));
+    (translateService.get as jasmine.Spy).and.returnValues(of('DSpace :: '), of('Dummy Title'), of('This is a dummy item component for testing!'));
-    spyOn(translateService, 'get').and.returnValues(of('DSpace :: '), of('Dummy Title'), of('This is a dummy item component for testing!'));
+    (metadataService as any).processRouteChange({
-    router.navigate(['/items/0ec7ff22-f211-40ab-a69e-c819b0b1f357']);
+      data: {
+        value: {
+          title: 'Dummy Title',
+          description: 'This is a dummy item component for testing!'
+        }
+      }
+    });
     tick();
-    expect(tagStore.size).toBeGreaterThan(0);
+    expect(title.setTitle).toHaveBeenCalledWith('DSpace :: Dummy Title');
-    router.navigate(['/other']);
+    expect(meta.addTag).toHaveBeenCalledWith({
-    tick();
+      property: 'title',
-    expect(tagStore.size).toEqual(3);
+      content: 'DSpace :: Dummy Title'
-    expect(title.getTitle()).toEqual('DSpace :: Dummy Title');
+    });
-    expect(tagStore.get('title')[0].content).toEqual('DSpace :: Dummy Title');
+    expect(meta.addTag).toHaveBeenCalledWith({
-    expect(tagStore.get('description')[0].content).toEqual('This is a dummy item component for testing!');
+      property: 'description',
-    expect(tagStore.get('Generator')[0].content).toEqual('mock-dspace-version');
+      content: 'This is a dummy item component for testing!'
+    });
   }));
 
-  describe('when the item has no bitstreams', () => {
+  describe(`listenForRouteChange`, () => {
-
+    it(`should call processRouteChange`, fakeAsync(() => {
-    beforeEach(() => {
+      spyOn(metadataService as any, 'processRouteChange').and.callFake(() => undefined);
-      // this.bitstreamDataService.findAllByItemAndBundleName(this.item, 'ORIGINAL')
+      metadataService.listenForRouteChange();
-      // spyOn(MockItem, 'getFiles').and.returnValue(observableOf([]));
+      tick();
+      expect((metadataService as any).processRouteChange).toHaveBeenCalled();
+    }));
+    it(`should add Generator`, fakeAsync(() => {
+      spyOn(metadataService as any, 'processRouteChange').and.callFake(() => undefined);
+      metadataService.listenForRouteChange();
+      tick();
+      expect(meta.addTag).toHaveBeenCalledWith({
+        property: 'Generator',
+        content: 'mock-dspace-version'
+      });
+    }));
   });
 
-    it('processRemoteData should not produce an EmptyError', fakeAsync(() => {
+  describe('citation_abstract_html_url', () => {
-      spyOn(itemDataService, 'findById').and.returnValue(mockRemoteData(ItemMock));
+    it('should use dc.identifier.uri if available', fakeAsync(() => {
-      spyOn(metadataService, 'processRemoteData').and.callThrough();
+      (metadataService as any).processRouteChange({
-      router.navigate(['/items/0ec7ff22-f211-40ab-a69e-c819b0b1f357']);
+        data: {
+          value: {
+            dso: createSuccessfulRemoteDataObject(mockUri(ItemMock, 'https://ddg.gg')),
+          }
+        }
+      });
       tick();
-      expect(metadataService.processRemoteData).not.toThrow(new EmptyError());
+      expect(meta.addTag).toHaveBeenCalledWith({
+        property: 'citation_abstract_html_url',
+        content: 'https://ddg.gg'
+      });
     }));
 
+    it('should use current route as fallback', fakeAsync(() => {
+      (metadataService as any).processRouteChange({
+        data: {
+          value: {
+            dso: createSuccessfulRemoteDataObject(mockUri(ItemMock)),
+          }
+        }
+      });
+      tick();
+      expect(meta.addTag).toHaveBeenCalledWith({
+        property: 'citation_abstract_html_url',
+        content: 'https://request.org/items/0ec7ff22-f211-40ab-a69e-c819b0b1f357'
+      });
+    }));
   });
 
-  const mockRemoteData = (mockItem: Item): Observable<RemoteData<Item>> => {
+  describe('citation_*_institution / citation_publisher', () => {
-    return createSuccessfulRemoteDataObject$(ItemMock);
+    it('should use citation_dissertation_institution tag for dissertations', fakeAsync(() => {
-  };
+      (metadataService as any).processRouteChange({
+        data: {
+          value: {
+            dso: createSuccessfulRemoteDataObject(mockPublisher(mockType(ItemMock, 'Thesis'))),
+          }
+        }
+      });
+      tick();
+      expect(meta.addTag).toHaveBeenCalledWith({
+        property: 'citation_dissertation_institution',
+        content: 'Mock Publisher'
+      });
+      expect(meta.addTag).not.toHaveBeenCalledWith(jasmine.objectContaining({ property: 'citation_technical_report_institution' }));
+      expect(meta.addTag).not.toHaveBeenCalledWith(jasmine.objectContaining({ property: 'citation_publisher' }));
+    }));
+
+    it('should use citation_tech_report_institution tag for tech reports', fakeAsync(() => {
+      (metadataService as any).processRouteChange({
+        data: {
+          value: {
+            dso: createSuccessfulRemoteDataObject(mockPublisher(mockType(ItemMock, 'Technical Report'))),
+          }
+        }
+      });
+      tick();
+      expect(meta.addTag).not.toHaveBeenCalledWith(jasmine.objectContaining({ property: 'citation_dissertation_institution' }));
+      expect(meta.addTag).toHaveBeenCalledWith({
+        property: 'citation_technical_report_institution',
+        content: 'Mock Publisher'
+      });
+      expect(meta.addTag).not.toHaveBeenCalledWith(jasmine.objectContaining({ property: 'citation_publisher' }));
+    }));
+
+    it('should use citation_publisher for other item types', fakeAsync(() => {
+      (metadataService as any).processRouteChange({
+        data: {
+          value: {
+            dso: createSuccessfulRemoteDataObject(mockPublisher(mockType(ItemMock, 'Some Other Type'))),
+          }
+        }
+      });
+      tick();
+      expect(meta.addTag).not.toHaveBeenCalledWith(jasmine.objectContaining({ property: 'citation_dissertation_institution' }));
+      expect(meta.addTag).not.toHaveBeenCalledWith(jasmine.objectContaining({ property: 'citation_technical_report_institution' }));
+      expect(meta.addTag).toHaveBeenCalledWith({
+        property: 'citation_publisher',
+        content: 'Mock Publisher'
+      });
+    }));
+  });
+
+  describe('citation_pdf_url', () => {
+    it('should link to primary Bitstream URL regardless of format', fakeAsync(() => {
+      (bundleDataService.findByItemAndName as jasmine.Spy).and.returnValue(mockBundleRD$([], MockBitstream3));
+
+      (metadataService as any).processRouteChange({
+        data: {
+          value: {
+            dso: createSuccessfulRemoteDataObject(ItemMock),
+          }
+        }
+      });
+      tick();
+      expect(meta.addTag).toHaveBeenCalledWith({
+        property: 'citation_pdf_url',
+        content: 'https://request.org/bitstreams/4db100c1-e1f5-4055-9404-9bc3e2d15f29/download'
+      });
+    }));
+
+    describe('no primary Bitstream', () => {
+      it('should link to first and only Bitstream regardless of format', fakeAsync(() => {
+        (bundleDataService.findByItemAndName as jasmine.Spy).and.returnValue(mockBundleRD$([MockBitstream3]));
+
+        (metadataService as any).processRouteChange({
+          data: {
+            value: {
+              dso: createSuccessfulRemoteDataObject(ItemMock),
+            }
+          }
+        });
+        tick();
+        expect(meta.addTag).toHaveBeenCalledWith({
+          property: 'citation_pdf_url',
+          content: 'https://request.org/bitstreams/4db100c1-e1f5-4055-9404-9bc3e2d15f29/download'
+        });
+      }));
+
+      it('should link to first Bitstream with allowed format', fakeAsync(() => {
+        const bitstreams = [MockBitstream3, MockBitstream3, MockBitstream1];
+        (bundleDataService.findByItemAndName as jasmine.Spy).and.returnValue(mockBundleRD$(bitstreams));
+        (bitstreamDataService.findAllByHref as jasmine.Spy).and.returnValues(
+          ...mockBitstreamPages$(bitstreams).map(bp => createSuccessfulRemoteDataObject$(bp)),
+        );
+
+        (metadataService as any).processRouteChange({
+          data: {
+            value: {
+              dso: createSuccessfulRemoteDataObject(ItemMock),
+            }
+          }
+        });
+        tick();
+        expect(meta.addTag).toHaveBeenCalledWith({
+          property: 'citation_pdf_url',
+          content: 'https://request.org/bitstreams/cf9b0c8e-a1eb-4b65-afd0-567366448713/download'
+        });
+      }));
+    });
+  });
+
+  describe('tagstore', () => {
+    beforeEach(fakeAsync(() => {
+      (metadataService as any).processRouteChange({
+        data: {
+          value: {
+            dso: createSuccessfulRemoteDataObject(ItemMock),
+          }
+        }
+      });
+      tick();
+    }));
+
+    it('should remove previous tags on route change', fakeAsync(() => {
+      expect(meta.removeTag).toHaveBeenCalledWith('property=\'title\'');
+      expect(meta.removeTag).toHaveBeenCalledWith('property=\'description\'');
+    }));
+
+    it('should clear all tags and add new ones on route change', () => {
+      expect(store.dispatch.calls.argsFor(0)).toEqual([new ClearMetaTagAction()]);
+      expect(store.dispatch.calls.argsFor(1)).toEqual([new AddMetaTagAction('title')]);
+      expect(store.dispatch.calls.argsFor(2)).toEqual([new AddMetaTagAction('description')]);
+    });
+  });
 
   const mockType = (mockItem: Item, type: string): Item => {
     const typedMockItem = Object.assign(new Item(), mockItem) as Item;
@@ -285,4 +382,30 @@ describe('MetadataService', () => {
     return publishedMockItem;
   };
 
+  const mockUri = (mockItem: Item, uri?: string): Item => {
+    const publishedMockItem = Object.assign(new Item(), mockItem) as Item;
+    publishedMockItem.metadata['dc.identifier.uri'] = [{ value: uri }] as MetadataValue[];
+    return publishedMockItem;
+  };
+
+  const mockBundleRD$ = (bitstreams: Bitstream[], primary?: Bitstream): Observable<RemoteData<Bundle>> => {
+    return createSuccessfulRemoteDataObject$(
+      Object.assign(new Bundle(), {
+        name: 'ORIGINAL',
+        bitstreams: createSuccessfulRemoteDataObject$(mockBitstreamPages$(bitstreams)[0]),
+        primaryBitstream: createSuccessfulRemoteDataObject$(primary),
+      })
+    );
+  };
+
+  const mockBitstreamPages$ = (bitstreams: Bitstream[]): PaginatedList<Bitstream>[] => {
+    return bitstreams.map((bitstream, index) => Object.assign(createPaginatedList([bitstream]), {
+      pageInfo: {
+        totalElements: bitstreams.length,       // announce multiple elements/pages
+      },
+      _links: index < bitstreams.length - 1
+        ? { next: { href: 'not empty' }}        // fake link to the next bitstream page
+        : { next: { href: undefined }},         // last page has no link
+    }));
+  };
 });

src/app/core/metadata/metadata.service.ts

@@ -5,12 +5,11 @@ import { ActivatedRoute, NavigationEnd, Router } from '@angular/router';
 
 import { TranslateService } from '@ngx-translate/core';
 
-import { BehaviorSubject, combineLatest, Observable } from 'rxjs';
+import { BehaviorSubject, combineLatest, EMPTY, Observable, of as observableOf } from 'rxjs';
-import { catchError, distinctUntilKeyChanged, filter, first, map, take } from 'rxjs/operators';
+import { expand, filter, map, switchMap, take } from 'rxjs/operators';
 
-import { hasValue, isNotEmpty } from '../../shared/empty.util';
+import { hasNoValue, hasValue } from '../../shared/empty.util';
 import { DSONameService } from '../breadcrumbs/dso-name.service';
-import { CacheableObject } from '../cache/object-cache.reducer';
 import { BitstreamDataService } from '../data/bitstream-data.service';
 import { BitstreamFormatDataService } from '../data/bitstream-format-data.service';
 
@@ -19,22 +18,57 @@ import { BitstreamFormat } from '../shared/bitstream-format.model';
 import { Bitstream } from '../shared/bitstream.model';
 import { DSpaceObject } from '../shared/dspace-object.model';
 import { Item } from '../shared/item.model';
-import {
+import { getFirstCompletedRemoteData, getFirstSucceededRemoteDataPayload } from '../shared/operators';
-  getFirstSucceededRemoteDataPayload,
-  getFirstSucceededRemoteListPayload
-} from '../shared/operators';
-import { environment } from '../../../environments/environment';
 import { RootDataService } from '../data/root-data.service';
 import { getBitstreamDownloadRoute } from '../../app-routing-paths';
+import { BundleDataService } from '../data/bundle-data.service';
+import { followLink } from '../../shared/utils/follow-link-config.model';
+import { Bundle } from '../shared/bundle.model';
+import { PaginatedList } from '../data/paginated-list.model';
+import { URLCombiner } from '../url-combiner/url-combiner';
+import { HardRedirectService } from '../services/hard-redirect.service';
+import { MetaTagState } from './meta-tag.reducer';
+import { createSelector, select, Store } from '@ngrx/store';
+import { AddMetaTagAction, ClearMetaTagAction } from './meta-tag.actions';
+import { coreSelector } from '../core.selectors';
+import { CoreState } from '../core.reducers';
+
+/**
+ * The base selector function to select the metaTag section in the store
+ */
+const metaTagSelector = createSelector(
+  coreSelector,
+  (state: CoreState) => state.metaTag
+);
+
+/**
+ * Selector function to select the tags in use from the MetaTagState
+ */
+const tagsInUseSelector =
+  createSelector(
+    metaTagSelector,
+    (state: MetaTagState) => state.tagsInUse,
+  );
 
 @Injectable()
 export class MetadataService {
 
-  private initialized: boolean;
+  private currentObject: BehaviorSubject<DSpaceObject> = new BehaviorSubject<DSpaceObject>(undefined);
 
-  private tagStore: Map<string, MetaDefinition[]>;
+  /**
-
+   * When generating the citation_pdf_url meta tag for Items with more than one Bitstream (and no primary Bitstream),
-  private currentObject: BehaviorSubject<DSpaceObject>;
+   * the first Bitstream to match one of the following MIME types is selected.
+   * See {@linkcode getFirstAllowedFormatBitstreamLink}
+   * @private
+   */
+  private readonly CITATION_PDF_URL_MIMETYPES = [
+    'application/pdf',                                                          // .pdf
+    'application/postscript',                                                   // .ps
+    'application/msword',                                                       // .doc
+    'application/vnd.openxmlformats-officedocument.wordprocessingml.document',  // .docx
+    'application/rtf',                                                          // .rtf
+    'application/epub+zip',                                                     // .epub
+  ];
 
   constructor(
     private router: Router,
@@ -42,21 +76,19 @@ export class MetadataService {
     private meta: Meta,
     private title: Title,
     private dsoNameService: DSONameService,
+    private bundleDataService: BundleDataService,
     private bitstreamDataService: BitstreamDataService,
     private bitstreamFormatDataService: BitstreamFormatDataService,
-    private rootService: RootDataService
+    private rootService: RootDataService,
+    private store: Store<CoreState>,
+    private hardRedirectService: HardRedirectService,
   ) {
-    // TODO: determine what open graph meta tags are needed and whether
-    // the differ per route. potentially add image based on DSpaceObject
-    this.meta.addTags([
-      { property: 'og:title', content: 'DSpace Angular Universal' },
-      { property: 'og:description', content: 'The modern front-end for DSpace 7.' }
-    ]);
-    this.initialized = false;
-    this.tagStore = new Map<string, MetaDefinition[]>();
   }
 
   public listenForRouteChange(): void {
+    // This never changes, set it only once
+    this.setGenerator();
+
     this.router.events.pipe(
       filter((event) => event instanceof NavigationEnd),
       map(() => this.router.routerState.root),
@@ -68,22 +100,9 @@ export class MetadataService {
     });
   }
 
-  public processRemoteData(remoteData: Observable<RemoteData<CacheableObject>>): void {
-    remoteData.pipe(map((rd: RemoteData<CacheableObject>) => rd.payload),
-      filter((co: CacheableObject) => hasValue(co)),
-      take(1))
-      .subscribe((dspaceObject: DSpaceObject) => {
-        if (!this.initialized) {
-          this.initialize(dspaceObject);
-        }
-        this.currentObject.next(dspaceObject);
-      });
-  }
-
   private processRouteChange(routeInfo: any): void {
-    if (routeInfo.params.value.id === undefined) {
     this.clearMetaTags();
-    }
+
     if (routeInfo.data.value.title) {
       const titlePrefix = this.translate.get('repository.title.prefix');
       const title = this.translate.get(routeInfo.data.value.title, routeInfo.data.value);
@@ -98,15 +117,10 @@ export class MetadataService {
       });
     }
 
-    this.setGenerator();
+    if (hasValue(routeInfo.data.value.dso) && hasValue(routeInfo.data.value.dso.payload)) {
+      this.currentObject.next(routeInfo.data.value.dso.payload);
+      this.setDSOMetaTags();
     }
-
-  private initialize(dspaceObject: DSpaceObject): void {
-    this.currentObject = new BehaviorSubject<DSpaceObject>(dspaceObject);
-    this.currentObject.asObservable().pipe(distinctUntilKeyChanged('uuid')).subscribe(() => {
-      this.setMetaTags();
-    });
-    this.initialized = true;
   }
 
   private getCurrentRoute(route: ActivatedRoute): ActivatedRoute {
@@ -116,16 +130,14 @@ export class MetadataService {
     return route;
   }
 
-  private setMetaTags(): void {
+  private setDSOMetaTags(): void {
-
-    this.clearMetaTags();
 
     this.setTitleTag();
     this.setDescriptionTag();
 
     this.setCitationTitleTag();
     this.setCitationAuthorTags();
-    this.setCitationDateTag();
+    this.setCitationPublicationDateTag();
     this.setCitationISSNTag();
     this.setCitationISBNTag();
 
@@ -134,14 +146,10 @@ export class MetadataService {
 
     this.setCitationAbstractUrlTag();
     this.setCitationPdfUrlTag();
+    this.setCitationPublisherTag();
 
     if (this.isDissertation()) {
       this.setCitationDissertationNameTag();
-      this.setCitationDissertationInstitutionTag();
-    }
-
-    if (this.isTechReport()) {
-      this.setCitationTechReportInstitutionTag();
     }
 
     // this.setCitationJournalTitleTag();
@@ -176,7 +184,7 @@ export class MetadataService {
   private setDescriptionTag(): void {
     // TODO: truncate abstract
     const value = this.getMetaTagValue('dc.description.abstract');
-    this.addMetaTag('desciption', value);
+    this.addMetaTag('description', value);
   }
 
   /**
@@ -196,11 +204,11 @@ export class MetadataService {
   }
 
   /**
-   * Add <meta name="citation_date" ... >  to the <head>
+   * Add <meta name="citation_publication_date" ... >  to the <head>
    */
-  private setCitationDateTag(): void {
+  private setCitationPublicationDateTag(): void {
     const value = this.getFirstMetaTagValue(['dc.date.copyright', 'dc.date.issued', 'dc.date.available', 'dc.date.accessioned']);
-    this.addMetaTag('citation_date', value);
+    this.addMetaTag('citation_publication_date', value);
   }
 
   /**
@@ -236,19 +244,17 @@ export class MetadataService {
   }
 
   /**
-   * Add <meta name="citation_dissertation_institution" ... >  to the <head>
+   * Add dc.publisher to the <head>. The tag name depends on the item type.
    */
-  private setCitationDissertationInstitutionTag(): void {
+  private setCitationPublisherTag(): void {
     const value = this.getMetaTagValue('dc.publisher');
+    if (this.isDissertation()) {
       this.addMetaTag('citation_dissertation_institution', value);
-  }
+    } else if (this.isTechReport()) {
-
-  /**
-   * Add <meta name="citation_technical_report_institution" ... >  to the <head>
-   */
-  private setCitationTechReportInstitutionTag(): void {
-    const value = this.getMetaTagValue('dc.publisher');
       this.addMetaTag('citation_technical_report_institution', value);
+    } else {
+      this.addMetaTag('citation_publisher', value);
+    }
   }
 
   /**
@@ -264,8 +270,11 @@ export class MetadataService {
    */
   private setCitationAbstractUrlTag(): void {
     if (this.currentObject.value instanceof Item) {
-      const value = [environment.ui.baseUrl, this.router.url].join('');
+      let url = this.getMetaTagValue('dc.identifier.uri');
-      this.addMetaTag('citation_abstract_html_url', value);
+      if (hasNoValue(url)) {
+        url = new URLCombiner(this.hardRedirectService.getRequestOrigin(), this.router.url).toString();
+      }
+      this.addMetaTag('citation_abstract_html_url', url);
     }
   }
 
@@ -275,27 +284,118 @@ export class MetadataService {
   private setCitationPdfUrlTag(): void {
     if (this.currentObject.value instanceof Item) {
       const item = this.currentObject.value as Item;
-      this.bitstreamDataService.findAllByItemAndBundleName(item, 'ORIGINAL')
+
-        .pipe(
+      // Retrieve the ORIGINAL bundle for the item
-          getFirstSucceededRemoteListPayload(),
+      this.bundleDataService.findByItemAndName(
-          first((files) => isNotEmpty(files)),
+        item,
-          catchError((error) => {
+        'ORIGINAL',
-            console.debug(error.message);
+        true,
-            return [];
+        true,
-          }))
+        followLink('primaryBitstream'),
-        .subscribe((bitstreams: Bitstream[]) => {
+        followLink('bitstreams', {}, followLink('format')),
-          for (const bitstream of bitstreams) {
+      ).pipe(
-            this.bitstreamFormatDataService.findByBitstream(bitstream).pipe(
+        getFirstSucceededRemoteDataPayload(),
-              getFirstSucceededRemoteDataPayload()
+        switchMap((bundle: Bundle) =>
-            ).subscribe((format: BitstreamFormat) => {
+
-              if (format.mimetype === 'application/pdf') {
+          // First try the primary bitstream
-                const bitstreamLink =  getBitstreamDownloadRoute(bitstream);
+          bundle.primaryBitstream.pipe(
-                this.addMetaTag('citation_pdf_url', bitstreamLink);
+            getFirstCompletedRemoteData(),
+            map((rd: RemoteData<Bitstream>) => {
+              if (hasValue(rd.payload)) {
+                return rd.payload;
+              } else {
+                return null;
               }
+            }),
+            // return the bundle as well so we can use it again if there's no primary bitstream
+            map((bitstream: Bitstream) => [bundle, bitstream])
+          )
+        ),
+        switchMap(([bundle, primaryBitstream]: [Bundle, Bitstream]) => {
+          if (hasValue(primaryBitstream)) {
+            // If there was a primary bitstream, emit its link
+            return [getBitstreamDownloadRoute(primaryBitstream)];
+          } else {
+            // Otherwise consider the regular bitstreams in the bundle
+            return bundle.bitstreams.pipe(
+              getFirstCompletedRemoteData(),
+              switchMap((bitstreamRd: RemoteData<PaginatedList<Bitstream>>) => {
+                if (hasValue(bitstreamRd.payload) && bitstreamRd.payload.totalElements === 1) {
+                  // If there's only one bitstream in the bundle, emit its link
+                  return [getBitstreamDownloadRoute(bitstreamRd.payload.page[0])];
+                } else {
+                  // Otherwise check all bitstreams to see if one matches the format whitelist
+                  return this.getFirstAllowedFormatBitstreamLink(bitstreamRd);
+                }
+              })
+            );
+          }
+        }),
+        take(1)
+      ).subscribe((link: string) => {
+        // Use the found link to set the <meta> tag
+        this.addMetaTag(
+          'citation_pdf_url',
+          new URLCombiner(this.hardRedirectService.getRequestOrigin(), link).toString()
+        );
       });
     }
-        });
   }
+
+  /**
+   * For Items with more than one Bitstream (and no primary Bitstream), link to the first Bitstream with a MIME type
+   * included in {@linkcode CITATION_PDF_URL_MIMETYPES}
+   * @param bitstreamRd
+   * @private
+   */
+  private getFirstAllowedFormatBitstreamLink(bitstreamRd: RemoteData<PaginatedList<Bitstream>>): Observable<string> {
+    return observableOf(bitstreamRd.payload).pipe(
+      // Because there can be more than one page of bitstreams, this expand operator
+      // will retrieve them in turn. Due to the take(1) at the bottom, it will only
+      // retrieve pages until a match is found
+      expand((paginatedList: PaginatedList<Bitstream>) => {
+        if (hasNoValue(paginatedList.next)) {
+          // If there's no next page, stop.
+          return EMPTY;
+        } else {
+          // Otherwise retrieve the next page
+          return this.bitstreamDataService.findAllByHref(
+            paginatedList.next,
+            undefined,
+            true,
+            true,
+            followLink('format')
+          ).pipe(
+            getFirstCompletedRemoteData(),
+            map((next: RemoteData<PaginatedList<Bitstream>>) => {
+              if (hasValue(next.payload)) {
+                return next.payload;
+              } else {
+                return EMPTY;
+              }
+            })
+          );
+        }
+      }),
+      // Return the array of bitstreams inside each paginated list
+      map((paginatedList: PaginatedList<Bitstream>) => paginatedList.page),
+      // Emit the bitstreams in the list one at a time
+      switchMap((bitstreams: Bitstream[]) => bitstreams),
+      // Retrieve the format for each bitstream
+      switchMap((bitstream: Bitstream) => bitstream.format.pipe(
+        getFirstSucceededRemoteDataPayload(),
+        // Keep the original bitstream, because it, not the format, is what we'll need
+        // for the link at the end
+        map((format: BitstreamFormat) => [bitstream, format])
+      )),
+      // Filter out only pairs with whitelisted formats
+      filter(([, format]: [Bitstream, BitstreamFormat]) =>
+        hasValue(format) && this.CITATION_PDF_URL_MIMETYPES.includes(format.mimetype)),
+      // We only need 1
+      take(1),
+      // Emit the link of the match
+      map(([bitstream, ]: [Bitstream, BitstreamFormat]) => getBitstreamDownloadRoute(bitstream))
+    );
   }
 
   /**
@@ -303,7 +403,7 @@ export class MetadataService {
    */
   private setGenerator(): void {
     this.rootService.findRoot().pipe(getFirstSucceededRemoteDataPayload()).subscribe((root) => {
-      this.addMetaTag('Generator', root.dspaceVersion);
+      this.meta.addTag({ property: 'Generator', content: root.dspaceVersion });
     });
   }
 
@@ -351,7 +451,7 @@ export class MetadataService {
     if (content) {
       const tag = { property, content } as MetaDefinition;
       this.meta.addTag(tag);
-      this.storeTag(property, tag);
+      this.storeTag(property);
     }
   }
 
@@ -361,33 +461,21 @@ export class MetadataService {
     }
   }
 
-  private storeTag(key: string, tag: MetaDefinition): void {
+  private storeTag(key: string): void {
-    const tags: MetaDefinition[] = this.getTags(key);
+    this.store.dispatch(new AddMetaTagAction(key));
-    tags.push(tag);
-    this.setTags(key, tags);
-  }
-
-  private getTags(key: string): MetaDefinition[] {
-    let tags: MetaDefinition[] = this.tagStore.get(key);
-    if (tags === undefined) {
-      tags = [];
-    }
-    return tags;
-  }
-
-  private setTags(key: string, tags: MetaDefinition[]): void {
-    this.tagStore.set(key, tags);
   }
 
   public clearMetaTags() {
-    this.tagStore.forEach((tags: MetaDefinition[], property: string) => {
+    this.store.pipe(
+      select(tagsInUseSelector),
+      take(1)
+    ).subscribe((tagsInUse: string[]) => {
+      for (const property of tagsInUse) {
         this.meta.removeTag('property=\'' + property + '\'');
+      }
+      this.store.dispatch(new ClearMetaTagAction());
     });
-    this.tagStore.clear();
   }
 
-  public getTagStore(): Map<string, MetaDefinition[]> {
-    return this.tagStore;
-  }
 
 }

src/app/shared/mocks/item.mock.ts

@@ -5,6 +5,7 @@ import { Bitstream } from '../../core/shared/bitstream.model';
 import { Item } from '../../core/shared/item.model';
 import { createSuccessfulRemoteDataObject$ } from '../remote-data.utils';
 import { createPaginatedList } from '../testing/utils.test';
+import { Bundle } from '../../core/shared/bundle.model';
 
 export const MockBitstreamFormat1: BitstreamFormat = Object.assign(new BitstreamFormat(), {
   shortDescription: 'Microsoft Word XML',
@@ -34,11 +35,25 @@ export const MockBitstreamFormat2: BitstreamFormat = Object.assign(new Bitstream
     }
 });
 
+export const MockBitstreamFormat3: BitstreamFormat = Object.assign(new BitstreamFormat(), {
+  shortDescription: 'Binary',
+  description: 'Some scary unknown binary file',
+  mimetype: 'application/octet-stream',
+  supportLevel: 0,
+  internal: false,
+  extensions: null,
+  _links:{
+    self: {
+      href: 'https://dspace7.4science.it/dspace-spring-rest/api/core/bitstreamformats/17'
+    }
+  }
+});
+
 export const MockBitstream1: Bitstream = Object.assign(new Bitstream(),
   {
     sizeBytes: 10201,
     content: 'https://dspace7.4science.it/dspace-spring-rest/api/core/bitstreams/cf9b0c8e-a1eb-4b65-afd0-567366448713/content',
-    format: observableOf(MockBitstreamFormat1),
+    format: createSuccessfulRemoteDataObject$(MockBitstreamFormat1),
     bundleName: 'ORIGINAL',
     _links:{
       self: {
@@ -61,7 +76,7 @@ export const MockBitstream1: Bitstream = Object.assign(new Bitstream(),
 export const MockBitstream2: Bitstream = Object.assign(new Bitstream(), {
   sizeBytes: 31302,
   content: 'https://dspace7.4science.it/dspace-spring-rest/api/core/bitstreams/99b00f3c-1cc6-4689-8158-91965bee6b28/content',
-  format: observableOf(MockBitstreamFormat2),
+  format: createSuccessfulRemoteDataObject$(MockBitstreamFormat2),
   bundleName: 'ORIGINAL',
   id: '99b00f3c-1cc6-4689-8158-91965bee6b28',
   uuid: '99b00f3c-1cc6-4689-8158-91965bee6b28',
@@ -82,16 +97,33 @@ export const MockBitstream2: Bitstream = Object.assign(new Bitstream(), {
   }
 });
 
-/* tslint:disable:no-shadowed-variable */
+export const MockBitstream3: Bitstream = Object.assign(new Bitstream(), {
-export const ItemMock: Item = Object.assign(new Item(), {
+  sizeBytes: 4975123,
-  handle: '10673/6',
+  content: 'https://dspace7.4science.it/dspace-spring-rest/api/core/bitstreams/4db100c1-e1f5-4055-9404-9bc3e2d15f29/content',
-  lastModified: '2017-04-24T19:44:08.178+0000',
+  format: createSuccessfulRemoteDataObject$(MockBitstreamFormat3),
-  isArchived: true,
+  bundleName: 'ORIGINAL',
-  isDiscoverable: true,
+  id: '4db100c1-e1f5-4055-9404-9bc3e2d15f29',
-  isWithdrawn: false,
+  uuid: '4db100c1-e1f5-4055-9404-9bc3e2d15f29',
-  bundles: createSuccessfulRemoteDataObject$(createPaginatedList([
+  type: 'bitstream',
+  _links: {
+    self: { href: 'https://dspace7.4science.it/dspace-spring-rest/api/core/bitstreams/4db100c1-e1f5-4055-9404-9bc3e2d15f29' },
+    content: { href: 'https://dspace7.4science.it/dspace-spring-rest/api/core/bitstreams/4db100c1-e1f5-4055-9404-9bc3e2d15f29/content' },
+    format: { href: 'https://dspace7.4science.it/dspace-spring-rest/api/core/bitstreamformats/17' },
+    bundle: { href: '' }
+  },
+  metadata: {
+    'dc.title': [
       {
+        language: null,
+        value: 'scary'
+      }
+    ]
+  }
+});
+
+export const MockOriginalBundle: Bundle = Object.assign(new Bundle(), {
   name: 'ORIGINAL',
+  primaryBitstream: createSuccessfulRemoteDataObject$(MockBitstream2),
   bitstreams: observableOf(Object.assign({
     _links: {
       self: {
@@ -124,7 +156,18 @@ export const ItemMock: Item = Object.assign(new Item(), {
       ]
     }
   }))
-    }
+});
+
+
+/* tslint:disable:no-shadowed-variable */
+export const ItemMock: Item = Object.assign(new Item(), {
+  handle: '10673/6',
+  lastModified: '2017-04-24T19:44:08.178+0000',
+  isArchived: true,
+  isDiscoverable: true,
+  isWithdrawn: false,
+  bundles: createSuccessfulRemoteDataObject$(createPaginatedList([
+    MockOriginalBundle,
   ])),
   _links:{
     self: {