rpc: add (*Client).GetDesignatedByRole method

pkg/rpc/client/native.go

@@ -3,9 +3,14 @@ package client
 // Various non-policy things from native contracts.
 
 import (
+	"crypto/elliptic"
 	"fmt"
 
 	"github.com/nspcc-dev/neo-go/pkg/core/native/nativenames"
+	"github.com/nspcc-dev/neo-go/pkg/core/native/noderoles"
+	"github.com/nspcc-dev/neo-go/pkg/crypto/keys"
+	"github.com/nspcc-dev/neo-go/pkg/smartcontract"
+	"github.com/nspcc-dev/neo-go/pkg/vm/stackitem"
 )
 
 // GetOraclePrice invokes `getPrice` method on a native Oracle contract.
@@ -34,3 +39,54 @@ func (c *Client) GetGasPerBlock() (int64, error) {
 	}
 	return c.invokeNativeGetMethod(neoHash, "getGasPerBlock")
 }
+
+// GetDesignatedByRole invokes `getDesignatedByRole` method on a native RoleManagement contract.
+func (c *Client) GetDesignatedByRole(role noderoles.Role, index uint32) (keys.PublicKeys, error) {
+	rmHash, err := c.GetNativeContractHash(nativenames.Designation)
+	if err != nil {
+		return nil, fmt.Errorf("failed to get native RoleManagement hash: %w", err)
+	}
+	result, err := c.InvokeFunction(rmHash, "getDesignatedByRole", []smartcontract.Parameter{
+		{
+			Type:  smartcontract.IntegerType,
+			Value: int64(role),
+		},
+		{
+			Type:  smartcontract.IntegerType,
+			Value: int64(index),
+		},
+	}, nil)
+	if err != nil {
+		return nil, err
+	}
+	err = getInvocationError(result)
+	if err != nil {
+		return nil, fmt.Errorf("`getDesignatedByRole`: %w", err)
+	}
+	return topPublicKeysFromStack(result.Stack)
+}
+
+// topPublicKeysFromStack returns the top array of public keys from stack.
+func topPublicKeysFromStack(st []stackitem.Item) (keys.PublicKeys, error) {
+	index := len(st) - 1 // top stack element is last in the array
+	var (
+		pks keys.PublicKeys
+		err error
+	)
+	items, ok := st[index].Value().([]stackitem.Item)
+	if !ok {
+		return nil, fmt.Errorf("invalid stack item type: %s", st[index].Type())
+	}
+	pks = make(keys.PublicKeys, len(items))
+	for i, item := range items {
+		val, ok := item.Value().([]byte)
+		if !ok {
+			return nil, fmt.Errorf("invalid array element #%d: %s", i, item.Type())
+		}
+		pks[i], err = keys.NewPublicKeyFromBytes(val, elliptic.P256())
+		if err != nil {
+			return nil, err
+		}
+	}
+	return pks, nil
+}