export interface NgGapiClientConfig extends ClientConfig {
    discoveryDocs: string[];
}


//And the extended ClientConfig
interface ClientConfig {
    /**
     * The app's client ID, found and created in the Google Developers Console.
     */
    client_id?: string;

    /**
     * The domains for which to create sign-in cookies. Either a URI, single_host_origin, or none.
     * Defaults to single_host_origin if unspecified.
     */
    cookie_policy?: string;

    /**
     * The scopes to request, as a space-delimited string. Optional if fetch_basic_profile is not set to false.
     */
    scope?: string;

    /**
     * Fetch users' basic profile information when they sign in. Adds 'profile' and 'email' to the requested scopes. True if unspecified.
     */
    fetch_basic_profile?: boolean;

    /**
     * The Google Apps domain to which users must belong to sign in. This is susceptible to modification by clients,
     * so be sure to verify the hosted domain property of the returned user. Use GoogleUser.getHostedDomain() on the client,
     * and the hd claim in the ID Token on the server to verify the domain is what you expected.
     */
    hosted_domain?: string;

    /**
     * Used only for OpenID 2.0 client migration. Set to the value of the realm that you are currently using for OpenID 2.0,
     * as described in <a href="https://developers.google.com/accounts/docs/OpenID#openid-connect">OpenID 2.0 (Migration)</a>.
     */
    openid_realm?: string;

    /**
     * The UX mode to use for the sign-in flow.
     * By default, it will open the consent flow in a popup.
     */
    ux_mode?: "popup" | "redirect";

    /**
     * If using ux_mode='redirect', this parameter allows you to override the default redirect_uri that will be used at the end of the consent flow.
     * The default redirect_uri is the current URL stripped of query parameters and hash fragment.
     */
    redirect_uri?: string;
  }

import {
    GoogleApiModule, 
    GoogleApiService, 
    GoogleAuthService, 
    NgGapiClientConfig, 
    NG_GAPI_CONFIG,
    GoogleApiConfig
} from "ng-gapi";

let gapiClientConfig: NgGapiClientConfig = {
    client_id: "CLIENT_ID",
    discoveryDocs: ["https://analyticsreporting.googleapis.com/$discovery/rest?version=v4"],
    scope: [
        "https://www.googleapis.com/auth/analytics.readonly",
        "https://www.googleapis.com/auth/analytics"
    ].join(" ")
};

@NgModule({
    imports: [
        //...
          GoogleApiModule.forRoot({
            provide: NG_GAPI_CONFIG,
            useValue: gapiClientConfig
          }),
        //...
    ]
})
export MyModule {}

export class FooService {
    constructor(gapiService: GoogleApiService) {
        gapiService.onLoad().subscribe(()=> {
           // Here we can use gapi
           
        });
    }
}

//Example of a UserService 

@Injectable()
export class UserService {
    public static SESSION_STORAGE_KEY: string = 'accessToken';
    private user: GoogleUser;
    
    constructor(private googleAuth: GoogleAuthService){ 
    }
    
    public getToken(): string {
        let token: string = sessionStorage.getItem(UserService.SESSION_STORAGE_KEY);
        if (!token) {
            throw new Error("no token set , authentication required");
        }
        return sessionStorage.getItem(UserService.SESSION_STORAGE_KEY);
    }
    
    public signIn(): void {
        this.googleAuth.getAuth()
            .subscribe((auth) => {
                auth.signIn().then(res => this.signInSuccessHandler(res));
            });
    }
    
    private signInSuccessHandler(res: GoogleUser) {
            this.user = res;
            sessionStorage.setItem(
                UserService.SESSION_STORAGE_KEY, res.getAuthResponse().access_token
            );
        }
}

export class FooService {
    constructor(gapiService: GoogleApiService) {
        gapiService.onLoad().subscribe(()=> {
           const myBatch: HttpBatch = new HttpBatch();
           myBatch.add(
               // your request
           );
        });
    }
}

 {
   client_id: "your client id",
   discoveryDocs: ["url to discovery docs", "another url"],
   scope: "space separated scopes"
}