D-Net

import { Injectable, Inject, PLATFORM_ID } from '@angular/core';

import { HttpInterceptor, HttpRequest, HttpHandler, HttpEvent, HttpResponse } from '@angular/common/http';

import { Observable, of } from 'rxjs';

import { tap } from 'rxjs/operators';

import { TransferState, makeStateKey, StateKey } from '@angular/platform-browser';

import { isPlatformServer } from '@angular/common';

@Injectable({

  providedIn: 'root'

})

export class HttpInterceptorService implements HttpInterceptor {

  constructor(private transferState: TransferState, @Inject(PLATFORM_ID) private platformId: any) {}

  public intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {

    //console.info("intercept transferstate");

    if (request.method !== 'GET') {

      return next.handle(request);

    }

    const key: StateKey<string> = makeStateKey<string>(request.url);

    const storedResponse = this.transferState.get<any>(key, null);

    //console.info(key, storedResponse);

    if (storedResponse) {

      const response = new HttpResponse({body: storedResponse, status: 200});

      if (!isPlatformServer(this.platformId)) {

        //console.info("browser remove: ", key);

        this.transferState.remove(key);

      }

      return of(response);

    } else {

      if (isPlatformServer(this.platformId)) {

        return next.handle(request).pipe(tap((event) => {

          //console.info("server add: ", key);

          this.transferState.set(key, (<HttpResponse<any>>event).body);

        }));

      } else {

        return next.handle(request);

      }

    }

  }

}