streamer

type Client interface {
	// AddListener registers a new streaming updates listener for the
	// listener.GetName() stream.
	// The stream name must be unique and AddListener will error out if a listener
	// for the same stream is already registered.
	AddListener(l Listener) error
	// Stream starts streaming loop for a registered by AddListener listener
	// If successful, Stream never return and should be called in it's own go routine or main()
	// If the provided Listener is not registered, Stream will try to register it prior to starting streaming
	Stream(l Listener) error
	// RemoveListener removes currently registered listener. It returns true is the
	// listener with provided l.Name() exists and was unregistered successfully
	// RemoveListener is the only way to terminate streaming loop
	RemoveListener(l Listener) bool
}

type Listener interface {
	// GetName() returns name of the stream, the listener is getting updates on
	GetName() string
	// ReportError is going to be called by the streamer on every error.
	// If ReportError() will return nil, streamer will try to continue streaming
	// If ReportError() will return error != nil - streaming on the stream will be terminated
	ReportError(e error) error
	// Update will be called for every new update received from the stream
	// u is guaranteed to be of a type returned by New(), so - myUpdate := u.(MyDataType) should never panic
	// Update() returns bool indicating whether to continue streaming:
	//   true - continue streaming; false - stop streaming
	//   If Update() returns false -> ReportError() will be called with io.EOF,
	//   in this case, if ReportError() returns nil, streaming will continue with the new connection & stream
	Update(u *protos.DataUpdateBatch) bool
	// GetExtraArgs will be called prior to each stream request and its returned value will be used to initialize
	// ExtraArgs field in GetUpdates request payload. Most listeners may just return nil
	GetExtraArgs() *any.Any
}