[#60] morph/netmap: Implement Epoch method on Client

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

pkg/morph/client/netmap/client.go

@@ -36,7 +36,8 @@ type cfg struct {
 	netMapMethod, // get network map method name
 	snapshotMethod, // get network map snapshot method name
 	updateStateMethod, // update state method name for invocation
-	innerRingListMethod string // IR list method name for invocation
+	innerRingListMethod, // IR list method name for invocation
+	epochMethod string // get epoch number method name
 }
 
 const (
@@ -46,6 +47,7 @@ const (
 	defaultSnapshotMethod      = "snapshot"      // default get network map snapshot method name
 	defaultUpdateStateMethod   = "updateState"   // default update state method name
 	defaultInnerRIngListMethod = "innerRingList" // default IR list method name
+	defaultEpochMethod         = "epoch"         // default get epoch number method name
 )
 
 func defaultConfig() *cfg {
@@ -56,6 +58,7 @@ func defaultConfig() *cfg {
 		snapshotMethod:      defaultSnapshotMethod,
 		updateStateMethod:   defaultUpdateStateMethod,
 		innerRingListMethod: defaultInnerRIngListMethod,
+		epochMethod:         defaultEpochMethod,
 	}
 }
 
@@ -160,3 +163,17 @@ func WithInnerRingListMethod(n string) Option {
 		}
 	}
 }
+
+// WithEpochMethod returns a client constructor option that
+// specifies the method name of epoch number receiving operation.
+//
+// Ignores empty value.
+//
+// If option not provided, "epoch" is used.
+func WithEpochMethod(n string) Option {
+	return func(c *cfg) {
+		if n != "" {
+			c.epochMethod = n
+		}
+	}
+}

pkg/morph/client/netmap/epoch.go

@@ -0,0 +1,49 @@
+package netmap
+
+import (
+	"github.com/nspcc-dev/neofs-node/pkg/morph/client"
+	"github.com/pkg/errors"
+)
+
+// EpochArgs groups the arguments
+// of get epoch number test invoke call.
+type EpochArgs struct {
+}
+
+// EpochValues groups the stack parameters
+// returned by get epoch number test invoke.
+type EpochValues struct {
+	num int64
+}
+
+// Number return the number of NeoFS epoch.
+func (e EpochValues) Number() int64 {
+	return e.num
+}
+
+// Epoch performs the test invoke of get epoch number
+// method of NeoFS Netmap contract.
+func (c *Client) Epoch(_ EpochArgs) (*EpochValues, error) {
+	items, err := c.client.TestInvoke(
+		c.epochMethod,
+	)
+	if err != nil {
+		return nil, errors.Wrapf(err,
+			"could not perform test invocation (%s)",
+			c.epochMethod)
+	}
+
+	if ln := len(items); ln != 1 {
+		return nil, errors.Errorf("unexpected stack item count (%s): %d",
+			c.epochMethod, ln)
+	}
+
+	num, err := client.IntFromStackItem(items[0])
+	if err != nil {
+		return nil, errors.Wrapf(err, "could not get number from stack item (%s)", c.epochMethod)
+	}
+
+	return &EpochValues{
+		num: num,
+	}, nil
+}