[#83] services/util: Implement response service

Create response package. Implement response Service that sets values of
response meta header.

Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>

pkg/services/util/response/client_stream.go

@@ -0,0 +1,45 @@
+package response
+
+import (
+	"github.com/nspcc-dev/neofs-node/pkg/services/util"
+	"github.com/pkg/errors"
+)
+
+// ClientMessageStreamer represents client-side message streamer
+// that sets meta values to the response.
+type ClientMessageStreamer struct {
+	cfg *cfg
+
+	send util.RequestMessageWriter
+
+	close util.ClientStreamCloser
+}
+
+// Recv calls send method of internal streamer.
+func (s *ClientMessageStreamer) Send(req interface{}) error {
+	return errors.Wrapf(
+		s.send(req),
+		"(%T) could not send the request", s)
+}
+
+// CloseAndRecv closes internal stream, receivers the response,
+// sets meta values and returns the result.
+func (s *ClientMessageStreamer) CloseAndRecv() (util.ResponseMessage, error) {
+	resp, err := s.close()
+	if err != nil {
+		return nil, errors.Wrapf(err, "(%T) could not close stream and receive response", s)
+	}
+
+	setMeta(resp, s.cfg)
+
+	return resp, nil
+}
+
+// CreateRequestStreamer wraps stream methods and returns ClientMessageStreamer instance.
+func (s *Service) CreateRequestStreamer(sender util.RequestMessageWriter, closer util.ClientStreamCloser) *ClientMessageStreamer {
+	return &ClientMessageStreamer{
+		cfg:   s.cfg,
+		send:  sender,
+		close: closer,
+	}
+}

pkg/services/util/response/server_stream.go

@@ -0,0 +1,42 @@
+package response
+
+import (
+	"context"
+
+	"github.com/nspcc-dev/neofs-node/pkg/services/util"
+	"github.com/pkg/errors"
+)
+
+// ServerMessageStreamer represents server-side message streamer
+// that sets meta values to all response messages.
+type ServerMessageStreamer struct {
+	cfg *cfg
+
+	recv util.ResponseMessageReader
+}
+
+// Recv calls Recv method of internal streamer, sets response meta
+// values and returns the response.
+func (s *ServerMessageStreamer) Recv() (util.ResponseMessage, error) {
+	m, err := s.recv()
+	if err != nil {
+		return nil, errors.Wrap(err, "could not receive response message for signing")
+	}
+
+	setMeta(m, s.cfg)
+
+	return m, nil
+}
+
+// HandleServerStreamRequest builds internal streamer via handlers, wraps it to ServerMessageStreamer and returns the result.
+func (s *Service) HandleServerStreamRequest(ctx context.Context, req interface{}, handler util.ServerStreamHandler) (*ServerMessageStreamer, error) {
+	msgRdr, err := handler(ctx, req)
+	if err != nil {
+		return nil, errors.Wrap(err, "could not create message reader")
+	}
+
+	return &ServerMessageStreamer{
+		cfg:  s.cfg,
+		recv: msgRdr,
+	}, nil
+}

pkg/services/util/response/service.go

@@ -0,0 +1,58 @@
+package response
+
+import (
+	"github.com/nspcc-dev/neofs-api-go/pkg"
+	"github.com/nspcc-dev/neofs-api-go/v2/refs"
+	"github.com/nspcc-dev/neofs-api-go/v2/session"
+	"github.com/nspcc-dev/neofs-node/pkg/services/util"
+)
+
+// Service represents universal v2 service
+// that sets response meta header values.
+type Service struct {
+	cfg *cfg
+}
+
+// Option is an option of Service constructor.
+type Option func(*cfg)
+
+type cfg struct {
+	version *refs.Version
+
+	// TODO: neofs-node#83 add network state
+}
+
+func defaultCfg() *cfg {
+	return &cfg{
+		version: pkg.SDKVersion().ToV2(),
+	}
+}
+
+// NewService creates, initializes and returns Service instance.
+func NewService(opts ...Option) *Service {
+	c := defaultCfg()
+
+	for i := range opts {
+		opts[i](c)
+	}
+
+	return &Service{
+		cfg: c,
+	}
+}
+
+func setMeta(resp util.ResponseMessage, cfg *cfg) {
+	meta := new(session.ResponseMetaHeader)
+	meta.SetVersion(cfg.version)
+	meta.SetTTL(1) // FIXME: TTL must be calculated
+
+	// TODO: neofs-node#83
+	// meta.SetEpoch()
+
+	if origin := resp.GetMetaHeader(); origin != nil {
+		// FIXME: what if origin is set by local server?
+		meta.SetOrigin(origin)
+	}
+
+	resp.SetMetaHeader(meta)
+}

pkg/services/util/response/unary.go

@@ -0,0 +1,21 @@
+package response
+
+import (
+	"context"
+
+	"github.com/nspcc-dev/neofs-node/pkg/services/util"
+	"github.com/pkg/errors"
+)
+
+// HandleUnaryRequest call passes request to handler, sets response meta header values and returns it.
+func (s *Service) HandleUnaryRequest(ctx context.Context, req interface{}, handler util.UnaryHandler) (util.ResponseMessage, error) {
+	// process request
+	resp, err := handler(ctx, req)
+	if err != nil {
+		return nil, errors.Wrap(err, "could not handle request")
+	}
+
+	setMeta(resp, s.cfg)
+
+	return resp, nil
+}