[DURACOM-288] Provide a setting to use a different REST url during SSR execution

# Conflicts:
#	src/app/app.config.ts
#	src/app/core/services/server-hard-redirect.service.spec.ts
#	src/app/core/services/server-hard-redirect.service.ts
#	src/app/thumbnail/thumbnail.component.ts
#	src/modules/app/browser-init.service.ts
#	src/modules/app/server-init.service.ts

server.ts

@@ -79,6 +79,9 @@ let anonymousCache: LRU<string, any>;
 // extend environment with app config for server
 extendEnvironmentWithAppConfig(environment, appConfig);
 
+// The REST server base URL
+const REST_BASE_URL = environment.rest.ssrBaseUrl || environment.rest.baseUrl;
+
 // The Express app is exported so that it can be used by serverless Functions.
 export function app() {
 
@@ -176,7 +179,7 @@ export function app() {
    * Proxy the sitemaps
    */
   router.use('/sitemap**', createProxyMiddleware({
-    target: `${environment.rest.baseUrl}/sitemaps`,
+    target: `${REST_BASE_URL}/sitemaps`,
     pathRewrite: path => path.replace(environment.ui.nameSpace, '/'),
     changeOrigin: true
   }));
@@ -185,7 +188,7 @@ export function app() {
    * Proxy the linksets
    */
   router.use('/signposting**', createProxyMiddleware({
-    target: `${environment.rest.baseUrl}`,
+    target: `${REST_BASE_URL}`,
     pathRewrite: path => path.replace(environment.ui.nameSpace, '/'),
     changeOrigin: true
   }));
@@ -621,7 +624,7 @@ function start() {
  * The callback function to serve health check requests
  */
 function healthCheck(req, res) {
-  const baseUrl = `${environment.rest.baseUrl}${environment.actuators.endpointPath}`;
+  const baseUrl = `${REST_BASE_URL}${environment.actuators.endpointPath}`;
   axios.get(baseUrl)
     .then((response) => {
       res.status(response.status).send(response.data);

src/app/app.module.ts

@@ -30,6 +30,7 @@ import { EagerThemesModule } from '../themes/eager-themes.module';
 import { APP_CONFIG, AppConfig } from '../config/app-config.interface';
 import { StoreDevModules } from '../config/store/devtools';
 import { RootModule } from './root.module';
+import { DspaceRestInterceptor } from './core/dspace-rest/dspace-rest.interceptor';
 
 export function getConfig() {
   return environment;
@@ -103,6 +104,12 @@ const PROVIDERS = [
     useClass: LogInterceptor,
     multi: true
   },
+  // register DspaceRestInterceptor as HttpInterceptor
+  {
+    provide: HTTP_INTERCEPTORS,
+    useClass: DspaceRestInterceptor,
+    multi: true
+  },
   // register the dynamic matcher used by form. MUST be provided by the app module
   ...DYNAMIC_MATCHER_PROVIDERS,
 ];

src/app/core/dspace-rest/dspace-rest.interceptor.spec.ts

@@ -0,0 +1,194 @@
+import {
+  HTTP_INTERCEPTORS,
+  HttpClient,
+} from '@angular/common/http';
+import {
+  HttpClientTestingModule,
+  HttpTestingController,
+} from '@angular/common/http/testing';
+import { PLATFORM_ID } from '@angular/core';
+import { TestBed } from '@angular/core/testing';
+
+import {
+  APP_CONFIG,
+  AppConfig,
+} from '../../../config/app-config.interface';
+import { DspaceRestInterceptor } from './dspace-rest.interceptor';
+import { DspaceRestService } from './dspace-rest.service';
+
+describe('DspaceRestInterceptor', () => {
+  let httpMock: HttpTestingController;
+  let httpClient: HttpClient;
+  const appConfig: Partial<AppConfig> = {
+    rest: {
+      ssl: false,
+      host: 'localhost',
+      port: 8080,
+      nameSpace: '/server',
+      baseUrl: 'http://api.example.com/server',
+    },
+  };
+  const appConfigWithSSR: Partial<AppConfig> = {
+    rest: {
+      ssl: false,
+      host: 'localhost',
+      port: 8080,
+      nameSpace: '/server',
+      baseUrl: 'http://api.example.com/server',
+      ssrBaseUrl: 'http://ssr.example.com/server',
+    },
+  };
+
+  describe('When SSR base URL is not set ', () => {
+    describe('and it\'s in the browser', () => {
+      beforeEach(() => {
+        TestBed.configureTestingModule({
+          imports: [HttpClientTestingModule],
+          providers: [
+            DspaceRestService,
+            {
+              provide: HTTP_INTERCEPTORS,
+              useClass: DspaceRestInterceptor,
+              multi: true,
+            },
+            { provide: APP_CONFIG, useValue: appConfig },
+            { provide: PLATFORM_ID, useValue: 'browser' },
+          ],
+        });
+
+        httpMock = TestBed.inject(HttpTestingController);
+        httpClient = TestBed.inject(HttpClient);
+      });
+
+      it('should not modify the request', () => {
+        const url = 'http://api.example.com/server/items';
+        httpClient.get(url).subscribe((response) => {
+          expect(response).toBeTruthy();
+        });
+
+        const req = httpMock.expectOne(url);
+        expect(req.request.url).toBe(url);
+        req.flush({});
+        httpMock.verify();
+      });
+    });
+
+    describe('and it\'s in SSR mode', () => {
+      beforeEach(() => {
+        TestBed.configureTestingModule({
+          imports: [HttpClientTestingModule],
+          providers: [
+            DspaceRestService,
+            {
+              provide: HTTP_INTERCEPTORS,
+              useClass: DspaceRestInterceptor,
+              multi: true,
+            },
+            { provide: APP_CONFIG, useValue: appConfig },
+            { provide: PLATFORM_ID, useValue: 'server' },
+          ],
+        });
+
+        httpMock = TestBed.inject(HttpTestingController);
+        httpClient = TestBed.inject(HttpClient);
+      });
+
+      it('should not replace the base URL', () => {
+        const url = 'http://api.example.com/server/items';
+
+        httpClient.get(url).subscribe((response) => {
+          expect(response).toBeTruthy();
+        });
+
+        const req = httpMock.expectOne(url);
+        expect(req.request.url).toBe(url);
+        req.flush({});
+        httpMock.verify();
+      });
+    });
+  });
+
+  describe('When SSR base URL is set ', () => {
+    describe('and it\'s in the browser', () => {
+      beforeEach(() => {
+        TestBed.configureTestingModule({
+          imports: [HttpClientTestingModule],
+          providers: [
+            DspaceRestService,
+            {
+              provide: HTTP_INTERCEPTORS,
+              useClass: DspaceRestInterceptor,
+              multi: true,
+            },
+            { provide: APP_CONFIG, useValue: appConfigWithSSR },
+            { provide: PLATFORM_ID, useValue: 'browser' },
+          ],
+        });
+
+        httpMock = TestBed.inject(HttpTestingController);
+        httpClient = TestBed.inject(HttpClient);
+      });
+
+      it('should not modify the request', () => {
+        const url = 'http://api.example.com/server/items';
+        httpClient.get(url).subscribe((response) => {
+          expect(response).toBeTruthy();
+        });
+
+        const req = httpMock.expectOne(url);
+        expect(req.request.url).toBe(url);
+        req.flush({});
+        httpMock.verify();
+      });
+    });
+
+    describe('and it\'s in SSR mode', () => {
+      beforeEach(() => {
+        TestBed.configureTestingModule({
+          imports: [HttpClientTestingModule],
+          providers: [
+            DspaceRestService,
+            {
+              provide: HTTP_INTERCEPTORS,
+              useClass: DspaceRestInterceptor,
+              multi: true,
+            },
+            { provide: APP_CONFIG, useValue: appConfigWithSSR },
+            { provide: PLATFORM_ID, useValue: 'server' },
+          ],
+        });
+
+        httpMock = TestBed.inject(HttpTestingController);
+        httpClient = TestBed.inject(HttpClient);
+      });
+
+      it('should replace the base URL', () => {
+        const url = 'http://api.example.com/server/items';
+        const ssrBaseUrl = appConfigWithSSR.rest.ssrBaseUrl;
+
+        httpClient.get(url).subscribe((response) => {
+          expect(response).toBeTruthy();
+        });
+
+        const req = httpMock.expectOne(ssrBaseUrl + '/items');
+        expect(req.request.url).toBe(ssrBaseUrl + '/items');
+        req.flush({});
+        httpMock.verify();
+      });
+
+      it('should not replace any query param containing the base URL', () => {
+        const url = 'http://api.example.com/server/items?url=http://api.example.com/server/item/1';
+        const ssrBaseUrl = appConfigWithSSR.rest.ssrBaseUrl;
+
+        httpClient.get(url).subscribe((response) => {
+          expect(response).toBeTruthy();
+        });
+
+        const req = httpMock.expectOne(ssrBaseUrl + '/items?url=http://api.example.com/server/item/1');
+        expect(req.request.url).toBe(ssrBaseUrl + '/items?url=http://api.example.com/server/item/1');
+        req.flush({});
+        httpMock.verify();
+      });
+    });
+  });
+});

src/app/core/dspace-rest/dspace-rest.interceptor.ts

@@ -0,0 +1,52 @@
+import { isPlatformBrowser } from '@angular/common';
+import {
+  HttpEvent,
+  HttpHandler,
+  HttpInterceptor,
+  HttpRequest,
+} from '@angular/common/http';
+import {
+  Inject,
+  Injectable,
+  PLATFORM_ID,
+} from '@angular/core';
+import { Observable } from 'rxjs';
+
+import {
+  APP_CONFIG,
+  AppConfig,
+} from '../../../config/app-config.interface';
+import { isEmpty } from '../../shared/empty.util';
+
+@Injectable()
+/**
+ * This Interceptor is used to use the configured base URL for the request made during SSR execution
+ */
+export class DspaceRestInterceptor implements HttpInterceptor {
+
+  /**
+   * Contains the configured application base URL
+   * @protected
+   */
+  protected baseUrl: string;
+  protected ssrBaseUrl: string;
+
+  constructor(
+    @Inject(APP_CONFIG) protected appConfig: AppConfig,
+    @Inject(PLATFORM_ID) private platformId: string,
+  ) {
+    this.baseUrl = this.appConfig.rest.baseUrl;
+    this.ssrBaseUrl = this.appConfig.rest.ssrBaseUrl;
+  }
+
+  intercept(request: HttpRequest<unknown>, next: HttpHandler): Observable<HttpEvent<unknown>> {
+    if (isPlatformBrowser(this.platformId) || isEmpty(this.ssrBaseUrl) || this.baseUrl === this.ssrBaseUrl) {
+      return next.handle(request);
+    }
+
+    // Different SSR Base URL specified so replace it in the current request url
+    const url = request.url.replace(this.baseUrl, this.ssrBaseUrl);
+    const newRequest: HttpRequest<any> = request.clone({ url });
+    return next.handle(newRequest);
+  }
+}

src/app/core/services/server-hard-redirect.service.spec.ts

@@ -1,4 +1,6 @@
 import { TestBed } from '@angular/core/testing';
+
+import { environment } from '../../../environments/environment.test';
 import { ServerHardRedirectService } from './server-hard-redirect.service';
 
 describe('ServerHardRedirectService', () => {
@@ -6,7 +8,7 @@ describe('ServerHardRedirectService', () => {
   const mockRequest = jasmine.createSpyObj(['get']);
   const mockResponse = jasmine.createSpyObj(['redirect', 'end']);
 
-  const service: ServerHardRedirectService = new ServerHardRedirectService(mockRequest, mockResponse);
+  const service: ServerHardRedirectService = new ServerHardRedirectService(environment, mockRequest, mockResponse);
   const origin = 'https://test-host.com:4000';
 
   beforeEach(() => {

src/app/core/services/server-hard-redirect.service.ts

@@ -2,6 +2,8 @@ import { Inject, Injectable } from '@angular/core';
 import { Request, Response } from 'express';
 import { REQUEST, RESPONSE } from '@nguniversal/express-engine/tokens';
 import { HardRedirectService } from './hard-redirect.service';
+import { APP_CONFIG, AppConfig } from '../../../config/app-config.interface';
+import { isNotEmpty } from '../../shared/empty.util';
 
 /**
  * Service for performing hard redirects within the server app module
@@ -10,6 +12,7 @@ import { HardRedirectService } from './hard-redirect.service';
 export class ServerHardRedirectService extends HardRedirectService {
 
   constructor(
+    @Inject(APP_CONFIG) protected appConfig: AppConfig,
     @Inject(REQUEST) protected req: Request,
     @Inject(RESPONSE) protected res: Response,
   ) {
@@ -25,17 +28,22 @@ export class ServerHardRedirectService extends HardRedirectService {
    *    optional HTTP status code to use for redirect (default = 302, which is a temporary redirect)
    */
   redirect(url: string, statusCode?: number) {
-
     if (url === this.req.url) {
       return;
     }
 
+    let redirectUrl = url;
+    // If redirect url contains SSR base url then replace with public base url
+    if (isNotEmpty(this.appConfig.rest.ssrBaseUrl) && this.appConfig.rest.baseUrl !== this.appConfig.rest.ssrBaseUrl) {
+      redirectUrl = url.replace(this.appConfig.rest.ssrBaseUrl, this.appConfig.rest.baseUrl);
+    }
+
     if (this.res.finished) {
       const req: any = this.req;
       req._r_count = (req._r_count || 0) + 1;
 
       console.warn('Attempted to redirect on a finished response. From',
-        this.req.url, 'to', url);
+        this.req.url, 'to', redirectUrl);
 
       if (req._r_count > 10) {
         console.error('Detected a redirection loop. killing the nodejs process');
@@ -49,9 +57,9 @@ export class ServerHardRedirectService extends HardRedirectService {
         status = 302;
       }
 
-      console.log(`Redirecting from ${this.req.url} to ${url} with ${status}`);
+      console.info(`Redirecting from ${this.req.url} to ${redirectUrl} with ${status}`);
 
-      this.res.redirect(status, url);
+      this.res.redirect(status, redirectUrl);
       this.res.end();
       // I haven't found a way to correctly stop Angular rendering.
       // So we just let it end its work, though we have already closed

src/app/thumbnail/thumbnail.component.ts

@@ -1,4 +1,4 @@
-import { Component, Input, OnChanges, SimpleChanges } from '@angular/core';
+import { Component, Inject, Input, OnChanges, PLATFORM_ID, SimpleChanges } from '@angular/core';
 import { Bitstream } from '../core/shared/bitstream.model';
 import { hasNoValue, hasValue } from '../shared/empty.util';
 import { RemoteData } from '../core/data/remote-data';
@@ -8,6 +8,7 @@ import { FeatureID } from '../core/data/feature-authorization/feature-id';
 import { AuthorizationDataService } from '../core/data/feature-authorization/authorization-data.service';
 import { AuthService } from '../core/auth/auth.service';
 import { FileService } from '../core/shared/file.service';
+import { isPlatformBrowser } from '@angular/common';
 
 /**
  * This component renders a given Bitstream as a thumbnail.
@@ -60,6 +61,7 @@ export class ThumbnailComponent implements OnChanges {
   isLoading = true;
 
   constructor(
+    @Inject(PLATFORM_ID) private platformID: any,
     protected auth: AuthService,
     protected authorizationService: AuthorizationDataService,
     protected fileService: FileService,
@@ -71,6 +73,7 @@ export class ThumbnailComponent implements OnChanges {
    * Use a default image if no actual image is available.
    */
   ngOnChanges(changes: SimpleChanges): void {
+    if (isPlatformBrowser(this.platformID)) {
       if (hasNoValue(this.thumbnail)) {
         this.setSrc(this.defaultImage);
         return;
@@ -83,6 +86,7 @@ export class ThumbnailComponent implements OnChanges {
         this.setSrc(this.defaultImage);
       }
     }
+  }
 
   /**
    * The current thumbnail Bitstream

src/config/server-config.interface.ts

@@ -6,4 +6,6 @@ export class ServerConfig implements Config {
   public port: number;
   public nameSpace: string;
   public baseUrl?: string;
+  public ssrBaseUrl?: string;
+  public hasSsrBaseUrl?: boolean;
 }

src/modules/app/browser-init.service.ts

@@ -32,7 +32,7 @@ import { logStartupMessage } from '../../../startup-message';
 import { MenuService } from '../../app/shared/menu/menu.service';
 import { RequestService } from '../../app/core/data/request.service';
 import { RootDataService } from '../../app/core/data/root-data.service';
-import { firstValueFrom, Subscription } from 'rxjs';
+import { firstValueFrom, lastValueFrom, Subscription } from 'rxjs';
 import { ServerCheckGuard } from '../../app/core/server-check/server-check.guard';
 import { HALEndpointService } from '../../app/core/shared/hal-endpoint.service';
 
@@ -121,13 +121,20 @@ export class BrowserInitService extends InitService {
    * @private
    */
   private async loadAppState(): Promise<boolean> {
+    // The app state can be transferred only when SSR and CSR are using the same base url for the REST API
+    if (!this.appConfig.rest.hasSsrBaseUrl) {
       const state = this.transferState.get<any>(InitService.NGRX_STATE, null);
       this.transferState.remove(InitService.NGRX_STATE);
       this.store.dispatch(new StoreAction(StoreActionTypes.REHYDRATE, state));
-    return this.store.select(coreSelector).pipe(
+      return lastValueFrom(
+        this.store.select(coreSelector).pipe(
           find((core: any) => isNotEmpty(core)),
-      map(() => true)
-    ).toPromise();
+          map(() => true),
+        ),
+      );
+    } else {
+      return Promise.resolve(true);
+    }
   }
 
   private trackAuthTokenExpiration(): void {

src/modules/app/server-init.service.ts

@@ -21,6 +21,7 @@ import { BreadcrumbsService } from '../../app/breadcrumbs/breadcrumbs.service';
 import { ThemeService } from '../../app/shared/theme-support/theme.service';
 import { take } from 'rxjs/operators';
 import { MenuService } from '../../app/shared/menu/menu.service';
+import { isNotEmpty } from '../../app/shared/empty.util';
 
 /**
  * Performs server-side initialization.
@@ -91,6 +92,14 @@ export class ServerInitService extends InitService {
   }
 
   private saveAppConfigForCSR(): void {
+    if (isNotEmpty(environment.rest.ssrBaseUrl) && environment.rest.baseUrl !== environment.rest.ssrBaseUrl) {
+      // Avoid to transfer ssrBaseUrl in order to prevent security issues
+      const config: AppConfig = Object.assign({}, environment as AppConfig, {
+        rest: Object.assign({}, environment.rest, { ssrBaseUrl: '', hasSsrBaseUrl: true }),
+      });
+      this.transferState.set<AppConfig>(APP_CONFIG_STATE, config);
+    } else {
       this.transferState.set<AppConfig>(APP_CONFIG_STATE, environment as AppConfig);
     }
+  }
 }