[#311] services/control: Implement NetmapSnapshot method

Implement methods required for signatures. Receive network map from netmap
storage, convert it to Control service message and return in response.

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

pkg/services/control/server/netmap_snapshot.go

@@ -3,10 +3,87 @@ package control
 import (
 	"context"
 
+	netmapAPI "github.com/nspcc-dev/neofs-api-go/pkg/netmap"
 	"github.com/nspcc-dev/neofs-node/pkg/services/control"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/status"
 )
 
 // NetmapSnapshot reads network map snapshot from Netmap storage.
 func (s *Server) NetmapSnapshot(ctx context.Context, req *control.NetmapSnapshotRequest) (*control.NetmapSnapshotResponse, error) {
-	panic("implement me")
+	// verify request
+	if err := s.isValidRequest(req); err != nil {
+		return nil, status.Error(codes.PermissionDenied, err.Error())
+	}
+
+	// get current epoch
+	epoch, err := s.netMapSrc.Epoch()
+	if err != nil {
+		return nil, status.Error(codes.NotFound, err.Error())
+	}
+
+	apiNetMap, err := s.netMapSrc.GetNetMapByEpoch(epoch)
+	if err != nil {
+		return nil, status.Error(codes.NotFound, err.Error())
+	}
+
+	nm := new(control.Netmap)
+	nm.SetEpoch(epoch)
+	nm.SetNodes(nodesFromAPI(apiNetMap.Nodes))
+
+	// create and fill response
+	resp := new(control.NetmapSnapshotResponse)
+
+	body := new(control.NetmapSnapshotResponse_Body)
+	resp.SetBody(body)
+
+	body.SetNetmap(nm)
+
+	// sign the response
+	if err := SignMessage(s.key, resp); err != nil {
+		return nil, status.Error(codes.Internal, err.Error())
+	}
+
+	return resp, nil
+}
+
+func nodesFromAPI(apiNodes netmapAPI.Nodes) []*control.NodeInfo {
+	nodes := make([]*control.NodeInfo, 0, len(apiNodes))
+
+	for _, apiNode := range apiNodes {
+		node := new(control.NodeInfo)
+		node.SetPublicKey(apiNode.PublicKey())
+		node.SetAddress(apiNode.Address())
+		node.SetAttributes(attributesFromAPI(apiNode.Attributes()))
+		node.SetState(stateFromAPI(apiNode.State()))
+
+		nodes = append(nodes, node)
+	}
+
+	return nodes
+}
+
+func stateFromAPI(s netmapAPI.NodeState) control.HealthStatus {
+	switch s {
+	default:
+		return control.HealthStatus_STATUS_UNDEFINED
+	case netmapAPI.NodeStateOffline:
+		return control.HealthStatus_OFFLINE
+	case netmapAPI.NodeStateOnline:
+		return control.HealthStatus_ONLINE
+	}
+}
+
+func attributesFromAPI(apiAttrs []*netmapAPI.NodeAttribute) []*control.NodeInfo_Attribute {
+	attrs := make([]*control.NodeInfo_Attribute, 0, len(apiAttrs))
+
+	for _, apiAttr := range apiAttrs {
+		a := new(control.NodeInfo_Attribute)
+		a.SetKey(apiAttr.Key())
+		a.SetValue(apiAttr.Value())
+
+		attrs = append(attrs, a)
+	}
+
+	return attrs
 }