server-state.interceptor.ts

import {Inject, Injectable, Optional} from '@angular/core';
import {HttpHandler, HttpInterceptor, HttpRequest, HttpResponse} from '@angular/common/http';
import {tap} from 'rxjs/operators';
import {makeStateKey, TransferState} from '@angular/platform-browser';
import {REQUEST} from '@nguniversal/express-engine/tokens';
import {Request} from 'express';

@Injectable()
export class ServerStateInterceptor implements HttpInterceptor {
 constructor(@Optional() @Inject(REQUEST) private request: Request, private transferState: TransferState) {}

 intercept(request: HttpRequest<unknown>, next: HttpHandler) {
  const clonedRequest = request.clone({
   headers: request.headers
    .set('X-Forwarded-For', this.request?.headers['x-forwarded-for'] || '')
    .set('X-Referer', this.request?.headers.referer || '')
    .set('User-Agent', this.request?.headers['user-agent'] || ''),
  });

  return next.handle(clonedRequest).pipe(
   tap((event) => {
    if (event instanceof HttpResponse && (event.status === 200 || event.status === 202)) {
     this.transferState.set(makeStateKey(request.url), event.body);
    }
   }),
  );
 }
}