[#488] reputation: Initial Trusts using netMap

Make initial trust values depend on NetMap:
initial trust equals 1 / (`amount of storage nodes`).

Signed-off-by: Pavel Karpy <carpawell@nspcc.ru>

cmd/neofs-node/reputation.go

@@ -38,7 +38,6 @@ import (
 )
 
 const EigenTrustAlpha = 0.1
-const EigenTrustInitialTrust = 0.5
 
 func initReputationService(c *cfg) {
 	staticClient, err := client.NewStatic(
@@ -154,7 +153,7 @@ func initReputationService(c *cfg) {
 				Alpha: EigenTrustAlpha,
 			},
 			InitialTrustSource: intermediatereputation.InitialTrustSource{
-				Trust: reputation.TrustValueFromFloat64(EigenTrustInitialTrust),
+				NetMap: nmSrc,
 			},
 			IntermediateValueTarget: intermediateTrustRouter,
 			WorkerPool:              c.cfgReputation.workerPool,

cmd/neofs-node/reputation/intermediate/calculator.go

@@ -1,6 +1,10 @@
 package intermediate
 
 import (
+	"errors"
+	"fmt"
+
+	"github.com/nspcc-dev/neofs-node/pkg/core/netmap"
 	"github.com/nspcc-dev/neofs-node/pkg/services/reputation"
 	"github.com/nspcc-dev/neofs-node/pkg/services/reputation/eigentrust"
 	eigencalc "github.com/nspcc-dev/neofs-node/pkg/services/reputation/eigentrust/calculator"
@@ -10,12 +14,24 @@ import (
 // InitialTrustSource is implementation of the
 // reputation/eigentrust/calculator's InitialTrustSource interface.
 type InitialTrustSource struct {
-	Trust reputation.TrustValue
+	NetMap netmap.Source
 }
 
+var ErrEmptyNetMap = errors.New("empty NepMap")
+
 // InitialTrust returns `initialTrust` as initial trust value.
 func (i InitialTrustSource) InitialTrust(reputation.PeerID) (reputation.TrustValue, error) {
-	return i.Trust, nil
+	nm, err := i.NetMap.GetNetMap(1)
+	if err != nil {
+		return reputation.TrustZero, fmt.Errorf("failed to get NetMap: %w", err)
+	}
+
+	nodeCount := reputation.TrustValueFromFloat64(float64(len(nm.Nodes)))
+	if nodeCount == 0 {
+		return reputation.TrustZero, ErrEmptyNetMap
+	}
+
+	return reputation.TrustOne.Div(nodeCount), nil
 }
 
 // DaughtersTrustCalculator wraps EigenTrust calculator and implements