[#786] morph/client: Add NNS contract address getter

Signed-off-by: Alex Vanin <alexey@nspcc.ru>

pkg/morph/client/nns.go

@@ -0,0 +1,62 @@
+package client
+
+import (
+	"fmt"
+	"strconv"
+
+	nns "github.com/nspcc-dev/neo-go/examples/nft-nd-nns"
+	"github.com/nspcc-dev/neo-go/pkg/util"
+)
+
+const (
+	nnsContractID = 1 // NNS contract must be deployed first in side chain
+
+	// NNSAuditContractName is a name of the audit contract in NNS.
+	NNSAuditContractName = "audit.neofs"
+	// NNSBalanceContractName is a name of the balance contract in NNS.
+	NNSBalanceContractName = "balance.neofs"
+	// NNSContainerContractName is a name of the container contract in NNS.
+	NNSContainerContractName = "container.neofs"
+	// NNSNeoFSIDContractName is a name of the neofsid contract in NNS.
+	NNSNeoFSIDContractName = "neofsid.neofs"
+	// NNSNetmapContractName is a name of the netmap contract in NNS.
+	NNSNetmapContractName = "netmap.neofs"
+	// NNSProxyContractName is a name of the proxy contract in NNS.
+	NNSProxyContractName = "proxy.neofs"
+	// NNSReputationContractName is a name of the reputation contract in NNS.
+	NNSReputationContractName = "reputation.neofs"
+)
+
+// NNSAlphabetContractName returns contract name of the alphabet contract in NNS
+// based on alphabet index.
+func NNSAlphabetContractName(index int) string {
+	return "alphabet" + strconv.Itoa(index) + ".neofs"
+}
+
+// NNSContractAddress returns contract address script hash based on its name
+// in NNS contract.
+func (c *Client) NNSContractAddress(name string) (sh util.Uint160, err error) {
+	if c.multiClient != nil {
+		return sh, c.multiClient.iterateClients(func(c *Client) error {
+			sh, err = c.NNSContractAddress(name)
+			return err
+		})
+	}
+
+	cs, err := c.client.GetContractStateByID(nnsContractID) // cache it?
+	if err != nil {
+		return sh, fmt.Errorf("NNS contract state: %w", err)
+	}
+
+	s, err := c.client.NNSResolve(cs.Hash, name, nns.TXT)
+	if err != nil {
+		return sh, fmt.Errorf("NNS.resolve: %w", err)
+	}
+
+	sh, err = util.Uint160DecodeStringLE(s)
+	if err != nil {
+		return sh, fmt.Errorf("NNS u160 decode: %w", err)
+	}
+
+	return sh, nil
+}