[#58] common: Add getters for alphabet and IR nodes from chain

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

common/ir.go

@@ -3,6 +3,9 @@ package common
 import (
 	"github.com/nspcc-dev/neo-go/pkg/interop"
 	"github.com/nspcc-dev/neo-go/pkg/interop/contract"
+	"github.com/nspcc-dev/neo-go/pkg/interop/native/ledger"
+	"github.com/nspcc-dev/neo-go/pkg/interop/native/neo"
+	"github.com/nspcc-dev/neo-go/pkg/interop/native/roles"
 	"github.com/nspcc-dev/neo-go/pkg/interop/runtime"
 	"github.com/nspcc-dev/neo-go/pkg/interop/storage"
 )
@@ -71,3 +74,51 @@ func CommitteeMultiAddressViaStorage(ctx storage.Context, key interface{}) []byt
 func CommitteeMultiAddress(sc interop.Hash160) []byte {
 	return contract.Call(sc, committeeMethod, contract.ReadOnly).([]byte)
 }
+
+// InnerRingNodes return list of inner ring nodes from state validator role
+// in side chain.
+func InnerRingNodes() []IRNode {
+	blockHeight := ledger.CurrentIndex()
+	list := roles.GetDesignatedByRole(roles.NeoFSAlphabet, uint32(blockHeight))
+	return keysToNodes(list)
+}
+
+// AlphabetNodes return list of alphabet nodes from committee in side chain.
+func AlphabetNodes() []IRNode {
+	list := neo.GetCommittee()
+	return keysToNodes(list)
+}
+
+// AlphabetAddress returns multi address of alphabet public keys.
+func AlphabetAddress() []byte {
+	alphabet := neo.GetCommittee()
+	return Multiaddress(alphabet, false)
+}
+
+// Multiaddress returns default multi signature account address for N keys.
+// If committee set to true, then it is `M = N/2+1` committee account.
+func Multiaddress(n []interop.PublicKey, committee bool) []byte {
+	threshold := len(n)/3*2 + 1
+	if committee {
+		threshold = len(n)/2 + 1
+	}
+
+	keys := []interop.PublicKey{}
+	for _, key := range n {
+		keys = append(keys, key)
+	}
+
+	return contract.CreateMultisigAccount(threshold, keys)
+}
+
+func keysToNodes(list []interop.PublicKey) []IRNode {
+	result := []IRNode{}
+
+	for i := range list {
+		result = append(result, IRNode{
+			PublicKey: list[i],
+		})
+	}
+
+	return result
+}