msal.js angular 6 SPA callback and errors handling

I m using msal.js on a angular 6 SPA to handle authentication, I have a few problems: First, I couldn t find a clear example on how to handle errors with the lib, so I picked things left and right, and I arrived to the next result:

@Injectable()
export class AuthenticationService {
_clientApplication: Msal.UserAgentApplication;
_clientApplicationPR: Msal.UserAgentApplication;
private _authority: string;

constructor(private apiService: ApiService, private backendRoutes: BackendRoutes) {
    this._authority = `https://login.microsoftonline.com/tfp/${environment.tenant}/${environment.signUpSignInPolicy}`;

    this._clientApplication =
        new Msal.UserAgentApplication(
            environment.clientID,
            this._authority,
            this._authCallback,
            {
                cacheLocation: 'localStorage',
                redirectUri: window.location.origin
            });
}

private _authCallback(errorDesc: any, token: any, error: any, tokenType: 
any) {
    console.log("in call back");
    if (token) {
        this.addUser();
    } else {
        // console.log(`${error} - ${errorDesc}`);
         if (errorDesc.indexOf("AADB2C90118") > -1) {
            //Forgotten password
            this._clientApplicationPR = new Msal.UserAgentApplication(
                environment.clientID,
                `https://login.microsoftonline.com/tfp/${environment.tenant}/${environment.passResetPolicy}`,
                this._authCallback,
                {
                    cacheLocation: 'localStorage',
                    redirectUri: window.location.origin
                });
            this._clientApplicationPR.loginRedirect(environment.b2cScopes);
        } else if (errorDesc.indexOf("AADB2C90077") > -1) {
            //Expired Token    
   this._clientApplication.acquireTokenRedirect(environment.b2cScopes);
        }
    }
}

getAuthenticationToken(): Promise<string> {
    return 
 this._clientApplication.acquireTokenSilent(environment.b2cScopes)
        .then(token => token)
        .catch(error => {
            return Promise.reject(error);
        });
    }
}

The getAuthenticationToken function is used into my httpinterceptor to set the bearer token. This is working fine, except when my token expires emitting the next error:

main.c20e047e67b91051727f.js:1 AADB2C90077: User does not have an existing session and request prompt parameter has a value of 'None'. Correlation ID: 3a627592-5ab0-4e54-b01d-e4296e4d4002 Timestamp: 2018-11-27 08:30:32Z |interaction_required

In my attempt to handle this case, you can see the callback checking the error code content. The problem is, my callback is never called after a acquireTokenSilent failure...I wonder why and if I am doing something wrong? For the acquireTokenSilent, I m guessing you can handle the error into the promise rejection. Although not ideal.

Secondly, the context in the callback is not the same as my service one, I don t have access to "this", from what I ve read, it is overwritten by the library. My temporary hack for "AADB2C90118 forgotten password error", is to dirtily create a new userAgentAplication with the appropriate authority, is there any way to have access to my service context in the callback and avoid doing that?

Edit I managed to make things work out fine: "this" references the userAgentApplication itself in the callback so instead of creating a new one you can do something like this:

      constructor(private apiService: ApiService, private backendRoutes: BackendRoutes) {
            this._authority = `https://login.microsoftonline.com/tfp/${environment.tenant}/${environment.signUpSignInPolicy}`;

            this._clientApplication =
                new Msal.UserAgentApplication(
                    environment.clientID,
                    this._authority,
                    this.msalHandler,
                    {
                        cacheLocation: 'localStorage',
                        redirectUri: window.location.origin
                    });
        }

        msalHandler(errorDesc: any, token: any, error: any, tokenType: any) {
            let userAgent: Msal.UserAgentApplication = <any>(this);
            if (errorDesc.indexOf("AADB2C90118") > -1) {
                //Forgotten password
                userAgent.authority = `https://login.microsoftonline.com/tfp/${environment.tenant}/${environment.passResetPolicy}`;
                userAgent.loginRedirect(environment.b2cScopes);

            } else if (errorDesc.indexOf("AADB2C90077") > -1) {
                //Expired Token
                this.logout();
            }
        }

OR bind this to your callBack:

   this._clientApplication =
            new Msal.UserAgentApplication(
                environment.clientID,
                this._authority,
                this.msalHandler.bind(this),
                {
                    cacheLocation: 'localStorage',
                    redirectUri: window.location.origin
                });

and my interceptor:

 intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
        return from(this.authenticationService.getAuthenticationToken()
            .then(token => {
                return req.clone({
                    setHeaders: {
                        Authorization: `Bearer ${token}`
                    }
                });
            })
            .catch(err => {
                this.authenticationService.msalHandler(err,null,null,null);
                return req;
            }))
            .switchMap(req => {
                return next.handle(req);
            });
    }

For infos, I m using the latest "msal": "^0.2.3", "typescript": "~2.7.2", "@angular/core": "^6.0.3".