[#488] reputation/remoteProvider: Implement intermediate remote

Move common remoteProvider code to cmd/reputation/common.
Hide WriterProvider initialization behind interface and
add implementation of that interface to local and
intermediate packages in cmd/reputation directory.

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

cmd/neofs-node/reputation/common/remote.go

@@ -0,0 +1,90 @@
+package common
+
+import (
+	apiClient "github.com/nspcc-dev/neofs-api-go/pkg/client"
+	"github.com/nspcc-dev/neofs-node/pkg/network"
+	reputationcommon "github.com/nspcc-dev/neofs-node/pkg/services/reputation/common"
+	reputationrouter "github.com/nspcc-dev/neofs-node/pkg/services/reputation/common/router"
+	trustcontroller "github.com/nspcc-dev/neofs-node/pkg/services/reputation/local/controller"
+	"github.com/pkg/errors"
+)
+
+type clientCache interface {
+	Get(string) (apiClient.Client, error)
+}
+
+// clientKeyRemoteProvider must provide remote writer and take into account
+// that requests must be sent via passed api client and must be signed with
+// passed private key.
+type clientKeyRemoteProvider interface {
+	WithClient(apiClient.Client) reputationcommon.WriterProvider
+}
+
+// remoteTrustProvider is implementation of reputation RemoteWriterProvider interface.
+// It caches clients, checks if it is the end of the route and checks either current
+// node is remote target or not.
+//
+// remoteTrustProvider requires to be provided with clientKeyRemoteProvider.
+type remoteTrustProvider struct {
+	localAddrSrc    network.LocalAddressSource
+	deadEndProvider reputationcommon.WriterProvider
+	clientCache     clientCache
+	remoteProvider  clientKeyRemoteProvider
+}
+
+// RemoteProviderPrm groups the required parameters of the remoteTrustProvider's constructor.
+//
+// All values must comply with the requirements imposed on them.
+// Passing incorrect parameter values will result in constructor
+// failure (error or panic depending on the implementation).
+type RemoteProviderPrm struct {
+	LocalAddrSrc    network.LocalAddressSource
+	DeadEndProvider reputationcommon.WriterProvider
+	ClientCache     clientCache
+	WriterProvider  clientKeyRemoteProvider
+}
+
+func NewRemoteTrustProvider(prm RemoteProviderPrm) reputationrouter.RemoteWriterProvider {
+	switch {
+	case prm.LocalAddrSrc == nil:
+		PanicOnPrmValue("LocalAddrSrc", prm.LocalAddrSrc)
+	case prm.DeadEndProvider == nil:
+		PanicOnPrmValue("DeadEndProvider", prm.DeadEndProvider)
+	case prm.ClientCache == nil:
+		PanicOnPrmValue("ClientCache", prm.ClientCache)
+	case prm.WriterProvider == nil:
+		PanicOnPrmValue("WriterProvider", prm.WriterProvider)
+	}
+
+	return &remoteTrustProvider{
+		localAddrSrc:    prm.LocalAddrSrc,
+		deadEndProvider: prm.DeadEndProvider,
+		clientCache:     prm.ClientCache,
+		remoteProvider:  prm.WriterProvider,
+	}
+}
+
+func (rtp *remoteTrustProvider) InitRemote(srv reputationcommon.ServerInfo) (reputationcommon.WriterProvider, error) {
+	if srv == nil {
+		return rtp.deadEndProvider, nil
+	}
+
+	addr := srv.Address()
+
+	if rtp.localAddrSrc.LocalAddress().String() == srv.Address() {
+		// if local => return no-op writer
+		return trustcontroller.SimpleWriterProvider(new(NopReputationWriter)), nil
+	}
+
+	ipAddr, err := network.IPAddrFromMultiaddr(addr)
+	if err != nil {
+		return nil, errors.Wrap(err, "could not convert address to IP format")
+	}
+
+	c, err := rtp.clientCache.Get(ipAddr)
+	if err != nil {
+		return nil, errors.Wrap(err, "could not initialize API client")
+	}
+
+	return rtp.remoteProvider.WithClient(c), nil
+}