export class AuthInterceptor implements HttpInterceptor {

    authService;
    refreshTokenInProgress = false;

    tokenRefreshedSource = new Subject();
    tokenRefreshed$ = this.tokenRefreshedSource.asObservable();

    constructor(private injector: Injector, private router: Router, private snackBar: MdSnackBar) {}

    addAuthHeader(request) {
        const authHeader = this.authService.getAuthorizationHeader();
        if (authHeader) {
            return request.clone({
                setHeaders: {
                    "Authorization": authHeader
                }
            });
        }
        return request;
    }

    refreshToken() {
        if (this.refreshTokenInProgress) {
            return new Observable(observer => {
                this.tokenRefreshed$.subscribe(() => {
                    observer.next();
                    observer.complete();
                });
            });
        } else {
            this.refreshTokenInProgress = true;

            return this.authService.refreshToken()
               .do(() => {
                    this.refreshTokenInProgress = false;
                    this.tokenRefreshedSource.next();
                });
        }
    }

    logout() {
        this.authService.logout();
        this.router.navigate(["login"]);
    }

    intercept(request: HttpRequest<any>, next: HttpHandler): Observable<any> {
        this.authService = this.injector.get(AuthService);

        // Handle request
        request = this.addAuthHeader(request);

        // Handle response
        return next.handle(request).catch(error => {

            if (error.status === 401) {
                return this.refreshToken()
                    .switchMap(() => {
                        request = this.addAuthHeader(request);
                        return next.handle(request);
                    })
                    .catch(() => {
                        this.logout();
                        return Observable.empty();
                    });
            }

            return Observable.throw(error);
        });
    }
}