public interface RxBilling {
  Observable<InventoryInApp> queryInAppPurchases(String... skuIds);

  Observable<InventorySubscription> querySubscriptions(String... skuIds);

  Completable isBillingForInAppSupported();

  Completable isBillingForSubscriptionsSupported();

  Single<PurchaseResponse> purchase(Inventory inventory, String developerPayload);

  Observable<PurchasedInApp> getPurchasedInApps();

  Observable<PurchasedSubscription> getPurchasedSubscriptions();

  Single<Integer> acknowledgePurchase(Purchased purchased);

  Single<Integer> consumePurchase(Purchased purchased);

  void destroy();

  @interface BillingResponse {
    int OK = 0;
    int USER_CANCELED = 1;
    int SERVICE_UNAVAILABLE = 2;
    int BILLING_UNAVAILABLE = 3;
    int ITEM_UNAVAILABLE = 4;
    int DEVELOPER_ERROR = 5;
    int ERROR = 6;
    int ITEM_ALREADY_OWNED = 7;
    int ITEM_NOT_OWNED = 8;
  }
}

class YourActivity extends Activity {
  private RxBilling rxBilling;

  @Override public void onCreate(Bundle savedInstanceState) {
    super.onCreate();
    rxBilling = new RxBillingGooglePlayLibraryV3(this);
  }

  @Override public void onDestroy() {
    super.onDestroy();
    rxBilling.destroy();
  }
}