[#428] cmd/node: Implement iterator provider on local trust storage

Implement iterator provider on wrapper over the local trust storage.
Provided iterator passes normalized local trust values according to original
EigenTrust algorithm description. In the borderline case, normalized values
are set as 1/N, N - number of remote nodes in network map.

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

cmd/neofs-node/reputation.go

@@ -0,0 +1,90 @@
+package main
+
+import (
+	"bytes"
+
+	netmapcore "github.com/nspcc-dev/neofs-node/pkg/core/netmap"
+	"github.com/nspcc-dev/neofs-node/pkg/services/reputation"
+	trustcontroller "github.com/nspcc-dev/neofs-node/pkg/services/reputation/local/controller"
+	truststorage "github.com/nspcc-dev/neofs-node/pkg/services/reputation/local/storage"
+	"github.com/nspcc-dev/neofs-node/pkg/util/logger"
+	"github.com/pkg/errors"
+)
+
+type localTrustStorage struct {
+	log *logger.Logger
+
+	storage *truststorage.Storage
+
+	nmSrc netmapcore.Source
+
+	localKey []byte
+}
+
+type localTrustIterator struct {
+	ctx trustcontroller.Context
+
+	storage *localTrustStorage
+
+	epochStorage *truststorage.EpochTrustValueStorage
+}
+
+func (s *localTrustStorage) InitIterator(ctx trustcontroller.Context) (trustcontroller.Iterator, error) {
+	epochStorage, err := s.storage.DataForEpoch(ctx.Epoch())
+	if err != nil && !errors.Is(err, truststorage.ErrNoPositiveTrust) {
+		return nil, err
+	}
+
+	return &localTrustIterator{
+		ctx:          ctx,
+		storage:      s,
+		epochStorage: epochStorage,
+	}, nil
+}
+
+func (it *localTrustIterator) Iterate(h reputation.TrustHandler) error {
+	if it.epochStorage != nil {
+		err := it.epochStorage.Iterate(h)
+		if !errors.Is(err, truststorage.ErrNoPositiveTrust) {
+			return err
+		}
+	}
+
+	nm, err := it.storage.nmSrc.GetNetMapByEpoch(it.ctx.Epoch())
+	if err != nil {
+		return err
+	}
+
+	// find out if local node is presented in netmap
+	localIndex := -1
+
+	for i := range nm.Nodes {
+		if bytes.Equal(nm.Nodes[i].PublicKey(), it.storage.localKey) {
+			localIndex = i
+		}
+	}
+
+	ln := len(nm.Nodes)
+	if localIndex >= 0 && ln > 0 {
+		ln--
+	}
+
+	// calculate Pj http://ilpubs.stanford.edu:8090/562/1/2002-56.pdf Chapter 4.5.
+	p := reputation.TrustOne.Div(reputation.TrustValueFromInt(ln))
+
+	for i := range nm.Nodes {
+		if i == localIndex {
+			continue
+		}
+
+		trust := reputation.Trust{}
+		trust.SetPeer(reputation.PeerIDFromBytes(nm.Nodes[i].PublicKey()))
+		trust.SetValue(p)
+
+		if err := h(trust); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}