auth-interceptor.ts

import { Injectable } from '@angular/core';
import { HttpEvent, HttpHandler, HttpInterceptor, HttpRequest } from '@angular/common/http';
import { Router } from '@angular/router';

import { Observable, throwError } from 'rxjs';
import { catchError, switchMap } from 'rxjs/operators';

import { AuthService } from '@auth/services/auth.service';
import { TokenService } from '@auth/services/token.service';

@Injectable()
export class AuthInterceptor implements HttpInterceptor {

  constructor(
    private tokenService: TokenService,
    private authService: AuthService,
    private router: Router
  ) { }

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

    if (request.url.includes('refresh-token')) {
      return next.handle(this.addRefreshToken(request));
    }
    request = this.addToken(request);
    return next.handle(request)
      .pipe(
        catchError(response => {
          if (response.status === 401) {
            return this.authService.refreshToken()
              .pipe(
                switchMap(() => next.handle(this.addToken(request))),
                catchError(msg => {
                  if (msg === 'Token has expired' || msg === 'Missing Authorization Header') {
                    this.authService.logout();
                    this.router.navigate(['/login'])
                  }
                  return throwError(msg);
                })
              );
          }
          return throwError(response);
        })
      );
  }

  addRefreshToken(request: HttpRequest<any>) {
    const token = this.tokenService.getRefreshToken();
    if (token) {
      request = request.clone({
        setHeaders: {
          Authorization: `Bearer ${token}`
        }
      });
    }
    return request;
  }


  addToken(request: HttpRequest<any>) {
    const token = this.tokenService.getToken();
    if (token) {
      request = request.clone({
        setHeaders: {
          Authorization: `Bearer ${token}`
        }
      });
    }
    return request;
  }

}