[#40] morph/client: Implement read config method

Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>

pkg/morph/client/netmap/config.go

@@ -0,0 +1,61 @@
+package netmap
+
+import (
+	"github.com/nspcc-dev/neo-go/pkg/vm/stackitem"
+	"github.com/nspcc-dev/neofs-node/pkg/morph/client"
+	"github.com/pkg/errors"
+)
+
+// ConfigArgs groups the arguments
+// of get config value test invoke call.
+type ConfigArgs struct {
+	key []byte
+}
+
+// EpochValues groups the stack parameters
+// returned by get epoch number test invoke.
+type ConfigValues struct {
+	val interface{}
+}
+
+// SetKey sets binary key to configuration parameter.
+func (c *ConfigArgs) SetKey(v []byte) {
+	c.key = v
+}
+
+// Value returns configuration value.
+func (c ConfigValues) Value() interface{} {
+	return c.val
+}
+
+// Config performs the test invoke of get config value
+// method of NeoFS Netmap contract.
+func (c *Client) Config(args ConfigArgs, assert func(stackitem.Item) (interface{}, error)) (*ConfigValues, error) {
+	items, err := c.client.TestInvoke(
+		c.configMethod,
+		args.key,
+	)
+	if err != nil {
+		return nil, errors.Wrapf(err,
+			"could not perform test invocation (%s)",
+			c.configMethod)
+	}
+
+	if ln := len(items); ln != 1 {
+		return nil, errors.Errorf("unexpected stack item count (%s): %d",
+			c.configMethod, ln)
+	}
+
+	val, err := assert(items[0])
+	if err != nil {
+		return nil, errors.Wrap(err, "value type assertion failed")
+	}
+
+	return &ConfigValues{
+		val: val,
+	}, nil
+}
+
+func IntegerAssert(item stackitem.Item) (interface{}, error) {
+	return client.IntFromStackItem(item)
+}