Add fabric binary transport loop

agents/rap-node-agent/internal/fabricproto/transport.go

@@ -0,0 +1,73 @@
+package fabricproto
+
+import (
+	"context"
+	"errors"
+	"io"
+)
+
+type EventHandler func(SessionEvent) ([]Frame, error)
+
+type TransportLoop struct {
+	Session    *Session
+	MaxPayload int
+	OnEvent    EventHandler
+}
+
+func (l TransportLoop) Run(ctx context.Context, r io.Reader, w io.Writer) error {
+	if l.Session == nil {
+		return ErrSessionNotConfigured
+	}
+	maxPayload := l.MaxPayload
+	if maxPayload <= 0 {
+		maxPayload = DefaultMaxPayload
+	}
+	for {
+		select {
+		case <-ctx.Done():
+			return ctx.Err()
+		default:
+		}
+
+		frame, err := ReadFrame(r, maxPayload)
+		if errors.Is(err, io.EOF) {
+			return nil
+		}
+		if err != nil {
+			return err
+		}
+		if err := l.Handle(ctx, frame, w); err != nil {
+			return err
+		}
+	}
+}
+
+func (l TransportLoop) Handle(ctx context.Context, frame Frame, w io.Writer) error {
+	if l.Session == nil {
+		return ErrSessionNotConfigured
+	}
+	event, responses, err := l.Session.HandleFrame(frame)
+	if err != nil {
+		return err
+	}
+	if l.OnEvent != nil && event.Type != SessionEventNone {
+		extra, err := l.OnEvent(event)
+		if err != nil {
+			return err
+		}
+		responses = append(responses, extra...)
+	}
+	for _, response := range responses {
+		select {
+		case <-ctx.Done():
+			return ctx.Err()
+		default:
+		}
+		if err := WriteFrame(w, response); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+var ErrSessionNotConfigured = errors.New("fabric transport loop session is not configured")