func Invoke(this *ole.IDispatch, dispid int, riid *ole.GUID, lcid int, flags int16, dispparams *ole.DISPPARAMS, result *ole.VARIANT, pexcepinfo *ole.EXCEPINFO, nerr *uint) uintptr {
	switch dispid {
	case 0:
		log.Println("DataArrival")
		winsock := (*EventReceiver)(unsafe.Pointer(this)).host
		var data ole.VARIANT
		ole.VariantInit(&data)
		oleutil.CallMethod(winsock, "GetData", &data)
		s := string(data.ToArray().ToByteArray())
		println()
		println(s)
		println()
	case 1:
		log.Println("Connected")
		winsock := (*EventReceiver)(unsafe.Pointer(this)).host
		oleutil.CallMethod(winsock, "SendData", "GET / HTTP/1.0\r\n\r\n")
	case 3:
		log.Println("SendProgress")
	case 4:
		log.Println("SendComplete")
	case 5:
		log.Println("Close")
		this.Release()
	case 6:
		log.Fatal("Error")
	default:
		log.Println(dispid)
	}
	return ole.E_NOTIMPL
}

func showMethodsAndProperties(i *ole.IDispatch) {
	n, err := i.GetTypeInfoCount()
	if err != nil {
		log.Fatalln(err)
	}
	tinfo, err := i.GetTypeInfo()
	if err != nil {
		log.Fatalln(err)
	}

	fmt.Println("n=", n, "tinfo=", tinfo)
}

// ConnectObject creates a connection point between two services for communication.
func ConnectObject(disp *ole.IDispatch, iid *ole.GUID, idisp interface{}) (cookie uint32, err error) {
	unknown, err := disp.QueryInterface(ole.IID_IConnectionPointContainer)
	if err != nil {
		return
	}

	container := (*ole.IConnectionPointContainer)(unsafe.Pointer(unknown))
	var point *ole.IConnectionPoint
	err = container.FindConnectionPoint(iid, &point)
	if err != nil {
		return
	}
	if edisp, ok := idisp.(*ole.IUnknown); ok {
		cookie, err = point.Advise(edisp)
		container.Release()
		if err != nil {
			return
		}
	}
	rv := reflect.ValueOf(disp).Elem()
	if rv.Type().Kind() == reflect.Struct {
		dest := &stdDispatch{}
		dest.lpVtbl = &stdDispatchVtbl{}
		dest.lpVtbl.pQueryInterface = syscall.NewCallback(dispQueryInterface)
		dest.lpVtbl.pAddRef = syscall.NewCallback(dispAddRef)
		dest.lpVtbl.pRelease = syscall.NewCallback(dispRelease)
		dest.lpVtbl.pGetTypeInfoCount = syscall.NewCallback(dispGetTypeInfoCount)
		dest.lpVtbl.pGetTypeInfo = syscall.NewCallback(dispGetTypeInfo)
		dest.lpVtbl.pGetIDsOfNames = syscall.NewCallback(dispGetIDsOfNames)
		dest.lpVtbl.pInvoke = syscall.NewCallback(dispInvoke)
		dest.iface = disp
		dest.iid = iid
		cookie, err = point.Advise((*ole.IUnknown)(unsafe.Pointer(dest)))
		container.Release()
		if err != nil {
			point.Release()
			return
		}
		return
	}

	container.Release()

	return 0, ole.NewError(ole.E_INVALIDARG)
}

// GetProperty retrieves property from IDispatch.
func GetProperty(disp *ole.IDispatch, name string, params ...interface{}) (result *ole.VARIANT, err error) {
	var dispid []int32
	dispid, err = disp.GetIDsOfName([]string{name})
	if err != nil {
		return
	}

	if len(params) < 1 {
		result, err = disp.Invoke(dispid[0], ole.DISPATCH_PROPERTYGET)
	} else {
		result, err = disp.Invoke(dispid[0], ole.DISPATCH_PROPERTYGET, params...)
	}

	return
}

// CallMethod calls method on IDispatch with parameters.
func CallMethod(disp *ole.IDispatch, name string, params ...interface{}) (result *ole.VARIANT, err error) {
	var dispid []int32
	dispid, err = disp.GetIDsOfName([]string{name})
	if err != nil {
		return
	}

	if len(params) < 1 {
		result, err = disp.Invoke(dispid[0], ole.DISPATCH_METHOD)
	} else {
		result, err = disp.Invoke(dispid[0], ole.DISPATCH_METHOD, params...)
	}

	return
}

// PutProperty mutates property.
func PutProperty(disp *ole.IDispatch, name string, params ...interface{}) (result *ole.VARIANT, err error) {
	return disp.InvokeWithOptionalArgs(name, ole.DISPATCH_PROPERTYPUT, params)
}

// CallMethod calls method on IDispatch with parameters.
func CallMethod(disp *ole.IDispatch, name string, params ...interface{}) (result *ole.VARIANT, err error) {
	return disp.InvokeWithOptionalArgs(name, ole.DISPATCH_METHOD, params)
}