Added signposting for preprints

src/app/features/preprints/pages/preprint-details/preprint-details.component.ts

@@ -35,6 +35,7 @@ import { FixSpecialCharPipe } from '@osf/shared/pipes/fix-special-char.pipe';
 import { CustomDialogService } from '@osf/shared/services/custom-dialog.service';
 import { DataciteService } from '@osf/shared/services/datacite/datacite.service';
 import { MetaTagsService } from '@osf/shared/services/meta-tags.service';
+import { SignpostingService } from '@osf/shared/services/signposting.service';
 import { ToastService } from '@osf/shared/services/toast.service';
 import { ContributorsSelectors } from '@osf/shared/stores/contributors';
 
@@ -104,6 +105,7 @@ export class PreprintDetailsComponent implements OnInit, OnDestroy {
   private readonly prerenderReady = inject(PrerenderReadyService);
   private readonly platformId = inject(PLATFORM_ID);
   private readonly isBrowser = isPlatformBrowser(this.platformId);
+  private readonly signpostingService = inject(SignpostingService);
 
   private readonly environment = inject(ENVIRONMENT);
 
@@ -304,6 +306,8 @@ export class PreprintDetailsComponent implements OnInit, OnDestroy {
     this.actions.getPreprintProviderById(this.providerId());
     this.fetchPreprint(this.preprintId());
 
+    this.signpostingService.addSignpostingHeaders();
+
     this.dataciteService.logIdentifiableView(this.preprint$).pipe(takeUntilDestroyed(this.destroyRef)).subscribe();
   }
 
@@ -413,6 +417,7 @@ export class PreprintDetailsComponent implements OnInit, OnDestroy {
           givenName: contributor.givenName,
           familyName: contributor.familyName,
         })),
+        signpostingLinks: this.signpostingService.mockSignpostingLinks,
       },
       this.destroyRef
     );

src/app/shared/models/meta-tags/meta-tags-data.model.ts

@@ -2,6 +2,13 @@ import { MetaTagAuthor } from './meta-tag-author.model';
 
 export type Content = string | number | null | undefined | MetaTagAuthor;
 
+export interface SignpostingLink {
+  rel: string;
+  href: string;
+  type?: string;
+  title?: string;
+}
+
 export type DataContent = Content | Content[];
 
 export interface MetaTagsData {
@@ -28,4 +35,5 @@ export interface MetaTagsData {
   twitterCreator?: DataContent;
   contributors?: DataContent;
   keywords?: DataContent;
+  signpostingLinks?: SignpostingLink[];
 }

src/app/shared/services/meta-tags.service.ts

@@ -11,7 +11,7 @@ import { replaceBadEncodedChars } from '@osf/shared/helpers/format-bad-encoding.
 import { MetadataRecordFormat } from '../enums/metadata-record-format.enum';
 import { HeadTagDef } from '../models/meta-tags/head-tag-def.model';
 import { MetaTagAuthor } from '../models/meta-tags/meta-tag-author.model';
-import { Content, DataContent, MetaTagsData } from '../models/meta-tags/meta-tags-data.model';
+import { Content, DataContent, MetaTagsData, SignpostingLink } from '../models/meta-tags/meta-tags-data.model';
 
 import { MetadataRecordsService } from './metadata-records.service';
 
@@ -123,6 +123,11 @@ export class MetaTagsService {
     this.prerenderReady.setNotReady();
     const combinedData = { ...this.defaultMetaTags, ...metaTagsData };
     const headTags = this.getHeadTags(combinedData);
+
+    if (metaTagsData.signpostingLinks) {
+      headTags.push(...this.getSignpostingLinkTags(metaTagsData.signpostingLinks));
+    }
+
     of(metaTagsData.osfGuid)
       .pipe(
         switchMap((osfid) =>
@@ -231,6 +236,19 @@ export class MetaTagsService {
       .filter((tag) => tag.attrs.content);
   }
 
+  private getSignpostingLinkTags(signpostingLinks: SignpostingLink[]): HeadTagDef[] {
+    return signpostingLinks.map((link) => ({
+      type: 'link' as const,
+      attrs: {
+        rel: link.rel,
+        href: link.href,
+        ...(link.type && { type: link.type }),
+        ...(link.title && { title: link.title }),
+        class: this.metaTagClass,
+      },
+    }));
+  }
+
   private buildMetaTagContent(name: string, content: Content): Content {
     if (['citation_author', 'dc.creator'].includes(name) && typeof content === 'object') {
       const author = content as MetaTagAuthor;

src/app/shared/services/signposting.service.ts

@@ -0,0 +1,68 @@
+import { of } from 'rxjs';
+
+import { inject, Injectable, RESPONSE_INIT } from '@angular/core';
+
+import { SignpostingLink } from '../models/meta-tags/meta-tags-data.model';
+
+@Injectable({
+  providedIn: 'root',
+})
+export class SignpostingService {
+  private readonly responseInit = inject(RESPONSE_INIT, { optional: true });
+
+  mockSignpostingLinks: SignpostingLink[] = [
+    {
+      rel: 'describedby',
+      href: '/api/descriptions/project-123',
+      type: 'application/json',
+    },
+    {
+      rel: 'cite-as',
+      href: 'https://doi.org/10.1234/example',
+      type: 'text/html',
+    },
+    {
+      rel: 'item',
+      href: '/project/123/files/',
+      type: 'text/html',
+      title: 'Project Files',
+    },
+    {
+      rel: 'collection',
+      href: '/user/projects/',
+      type: 'text/html',
+      title: 'User Projects',
+    },
+  ];
+
+  addSignpostingHeaders(): void {
+    of(this.mockSignpostingLinks).subscribe({
+      next: (links) => {
+        if (!this.responseInit || !this.responseInit.headers) {
+          return;
+        }
+
+        const headers =
+          this.responseInit?.headers instanceof Headers
+            ? this.responseInit.headers
+            : new Headers(this.responseInit?.headers);
+
+        const linkHeader = this.formatLinkHeader(links);
+        headers.set('Link', linkHeader);
+
+        this.responseInit.headers = headers;
+      },
+    });
+  }
+
+  formatLinkHeader(links: SignpostingLink[]): string {
+    return links
+      .map((link) => {
+        const parts = [`<${link.href}>`, `rel="${link.rel}"`];
+        if (link.type) parts.push(`type="${link.type}"`);
+        if (link.title) parts.push(`title="${link.title}"`);
+        return parts.join('; ');
+      })
+      .join(', ');
+  }
+}