add set mode option

pkg/econet/econetgrpc/econet.go

@@ -70,3 +70,49 @@ func (s *EconetGRPCServer) GetDevice(ctx context.Context, req *pb.GetDeviceReque
 	span.SetStatus(codes.Ok, "")
 	return &pb.GetDeviceResponse{Device: deviceToProto(d)}, nil
 }
+
+// modeSlugs maps the settable proto Mode enum to the normalized slugs the
+// client (and Device.mode) use. MODE_UNSPECIFIED is intentionally absent;
+// protovalidate rejects it before we get here.
+var modeSlugs = map[pb.Mode]string{
+	pb.Mode_MODE_OFF:           "off",
+	pb.Mode_MODE_ELECTRIC:      "electric",
+	pb.Mode_MODE_ENERGY_SAVING: "energy-saving",
+	pb.Mode_MODE_HEAT_PUMP:     "heat-pump",
+	pb.Mode_MODE_HIGH_DEMAND:   "high-demand",
+	pb.Mode_MODE_GAS:           "gas",
+	pb.Mode_MODE_PERFORMANCE:   "performance",
+	pb.Mode_MODE_VACATION:      "vacation",
+}
+
+func (s *EconetGRPCServer) SetMode(ctx context.Context, req *pb.SetModeRequest) (
+	*pb.SetModeResponse, error,
+) {
+	ctx, span := s.tracer.Start(ctx, "setMode", trace.WithAttributes(
+		attribute.String("serialNumber", req.GetSerialNumber()),
+		attribute.String("mode", req.GetMode().String()),
+	))
+	defer span.End()
+
+	slug, ok := modeSlugs[req.GetMode()]
+	if !ok {
+		err := status.Errorf(grpccodes.InvalidArgument, "unsupported mode %q", req.GetMode())
+		span.SetStatus(codes.Error, err.Error())
+		return nil, err
+	}
+
+	if err := s.client.SetMode(ctx, req.GetSerialNumber(), slug); err != nil {
+		err := status.Error(grpccodes.FailedPrecondition, err.Error())
+		span.SetStatus(codes.Error, err.Error())
+		return nil, err
+	}
+
+	span.SetStatus(codes.Ok, "")
+	// State applies asynchronously; return the last-known snapshot. Guard against
+	// a concurrent refresh evicting the device between publish and lookup.
+	resp := &pb.SetModeResponse{}
+	if d := s.client.Device(req.GetSerialNumber()); d != nil {
+		resp.Device = deviceToProto(d)
+	}
+	return resp, nil
+}