import {tap} from 'rxjs/operators';
import { Injectable } from '@angular/core';
import { HttpEvent, HttpInterceptor, HttpHandler, HttpRequest, HttpResponse } from '@angular/common/http';
import { TransferState, makeStateKey } from '@angular/platform-browser';
import { Observable } from 'rxjs';

@Injectable()
export class ServerStateInterceptor implements HttpInterceptor {

  constructor(
    private _transferState: TransferState,
  ) {}

  intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    return next.handle(req).pipe(tap(event => {
      if (event instanceof HttpResponse) {
        this._transferState.set(makeStateKey(req.url), event.body);
      }
    }));
  }
}