How do I make intercept function in Interceptor waits a Promise

Question

I'm trying to make intercept function waits for Promise to be resolved before each API call to check user if still active or not , if he is active I'll perform his request other wise I'll return EMPTY;(Prevent him from editing and logout) like this

@Injectable()
export class AuthInterceptor implements HttpInterceptor {
  constructor(
    private userChecker: UserChecker
  ) {}

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

// custom code for headers 

let x = this.userChecker.getUserStatus(); // this function call API and will return a promise that resolve boolean true if he is still active and false if not 

/* try 1
x.then((resolve) => {
   if (!resolve) {
     // logut 
   }else return next.handle(request);
});
*/

/*try 2
if(userChecker.shouldLogout){
// logout
}else return next.handle(request);
*/

//this is the normal state without any try of above
return next.handle(request);


}

At Try1 : will continue execution without returning anything either if it resolve true or false

At Try2 : will continue before shouldLogout modified in API subscription

How do I prevent intercept from continue execution until I receive the flag from the API to continue or logout

Answer 1

You should convert your promise to an Observable instead with from. Then use filter to prevent the request from happening unless the shouldLogout flag is set to false:

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

return from(this.userChecker.getUserStatus()).pipe(
  filter(() => !this.userChecker.shouldLogout),
  mergeMap(() => next.handle(request))
);