[#326] morph/balance: Provide interface to "transferX" method's invocations

Implement TransferX method on Balance contract client. Implement TransferX
method on Balance client's wrapper that encapsulates it's TransferX call.

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

pkg/morph/client/balance/client.go

@@ -28,17 +28,20 @@ var ErrNilClient = errors.New("balance contract client is nil")
 type Option func(*cfg)
 
 type cfg struct {
+	transferXMethod, // transferX method name for invocation
 	balanceOfMethod, // balanceOf method name for invocation
 	decimalsMethod string // decimals method name for invocation
 }
 
 const (
+	defaultTransferXMethod = "transferX" // default "transferX" method name
 	defaultBalanceOfMethod = "balanceOf" // default "balance of" method name
 	defaultDecimalsMethod  = "decimals"  // default decimals method name
 )
 
 func defaultConfig() *cfg {
 	return &cfg{
+		transferXMethod: defaultTransferXMethod,
 		balanceOfMethod: defaultBalanceOfMethod,
 		decimalsMethod:  defaultDecimalsMethod,
 	}
@@ -100,3 +103,17 @@ func WithDecimalsMethod(n string) Option {
 		}
 	}
 }
+
+// WithTransferXMethod returns a client constructor option that
+// specifies the "transferX" method name.
+//
+// Ignores empty value.
+//
+// If option not provided, "transferX" is used.
+func WithTransferXMethod(n string) Option {
+	return func(c *cfg) {
+		if n != "" {
+			c.transferXMethod = n
+		}
+	}
+}

pkg/morph/client/balance/transfer.go

@@ -0,0 +1,53 @@
+package balance
+
+import (
+	"github.com/pkg/errors"
+)
+
+// TransferXArgs groups the arguments
+// of "transferX" invocation call.
+type TransferXArgs struct {
+	amount int64 // amount in GASe-12
+
+	sender []byte // sender's wallet script hash
+
+	recipient []byte // recipient's wallet script hash
+
+	details []byte // transfer details
+}
+
+// SetAmount sets amount of funds to transfer
+// in GASe-12.
+func (t *TransferXArgs) SetAmount(v int64) {
+	t.amount = v
+}
+
+// SetSender sets wallet script hash
+// of the sender of funds in a binary format.
+func (t *TransferXArgs) SetSender(v []byte) {
+	t.sender = v
+}
+
+// SetRecipient sets wallet script hash
+// of the recipient of funds in a binary format.
+func (t *TransferXArgs) SetRecipient(v []byte) {
+	t.recipient = v
+}
+
+// SetDetails sets details of the money transaction
+// in a binary format.
+func (t *TransferXArgs) SetDetails(v []byte) {
+	t.details = v
+}
+
+// TransferX invokes the call of "transferX" method
+// of NeoFS Balance contract.
+func (c *Client) TransferX(args TransferXArgs) error {
+	return errors.Wrapf(c.client.Invoke(
+		c.transferXMethod,
+		args.sender,
+		args.recipient,
+		args.amount,
+		args.details,
+	), "could not invoke method (%s)", c.transferXMethod)
+}

pkg/morph/client/balance/wrapper/transfer.go

@@ -0,0 +1,40 @@
+package wrapper
+
+import (
+	"github.com/nspcc-dev/neofs-api-go/pkg/owner"
+	"github.com/nspcc-dev/neofs-node/pkg/morph/client/balance"
+	"github.com/pkg/errors"
+)
+
+// TransferPrm groups parameters of TransferX method.
+type TransferPrm struct {
+	Amount int64
+
+	From, To *owner.ID
+
+	Details []byte
+}
+
+// TransferX transfers Amound of GASe-12 from p.From to p.To
+// with details p.Details through smart contract call.
+func (w *Wrapper) TransferX(p TransferPrm) error {
+	from, err := owner.ScriptHashBE(p.From)
+	if err != nil {
+		return errors.Wrap(err, "invalid sender")
+	}
+
+	to, err := owner.ScriptHashBE(p.To)
+	if err != nil {
+		return errors.Wrap(err, "invalid recipient")
+	}
+
+	// prepare invocation arguments
+	args := balance.TransferXArgs{}
+	args.SetSender(from)
+	args.SetRecipient(to)
+	args.SetAmount(p.Amount)
+	args.SetDetails(p.Details)
+
+	// invoke smart contract call
+	return w.client.TransferX(args)
+}