rpc/client: add TransferNEP5 method to easily transfer tokens

We have TransferAsset for regular tokens, so it'd be nice to have TransferNEP5
for NEP5 ones. Relates to #599.

cli/wallet/nep5.go

@@ -5,15 +5,9 @@ import (
 	"fmt"
 
 	"github.com/nspcc-dev/neo-go/cli/flags"
-	"github.com/nspcc-dev/neo-go/pkg/core"
-	"github.com/nspcc-dev/neo-go/pkg/core/transaction"
 	"github.com/nspcc-dev/neo-go/pkg/encoding/address"
-	"github.com/nspcc-dev/neo-go/pkg/io"
 	"github.com/nspcc-dev/neo-go/pkg/rpc/client"
-	"github.com/nspcc-dev/neo-go/pkg/rpc/request"
 	"github.com/nspcc-dev/neo-go/pkg/util"
-	"github.com/nspcc-dev/neo-go/pkg/vm/emit"
-	"github.com/nspcc-dev/neo-go/pkg/vm/opcode"
 	"github.com/nspcc-dev/neo-go/pkg/wallet"
 	"github.com/urfave/cli"
 )
@@ -339,38 +333,19 @@ func transferNEP5(ctx *cli.Context) error {
 		return cli.NewExitError(fmt.Errorf("invalid amount: %v", err), 1)
 	}
 
-	// Note: we don't use invoke function here because it requires
-	// 2 round trips instead of one.
-	w := io.NewBufBinWriter()
-	emit.Int(w.BinWriter, amount)
-	emit.Bytes(w.BinWriter, to.BytesBE())
-	emit.Bytes(w.BinWriter, from.BytesBE())
-	emit.Int(w.BinWriter, 3)
-	emit.Opcode(w.BinWriter, opcode.PACK)
-	emit.String(w.BinWriter, "transfer")
-	emit.AppCall(w.BinWriter, token.Hash, false)
-	emit.Opcode(w.BinWriter, opcode.THROWIFNOT)
-
 	gas := flags.Fixed8FromContext(ctx, "gas")
-	tx := transaction.NewInvocationTX(w.Bytes(), gas)
-	tx.AddVerificationHash(from)
-
-	if err := request.AddInputsAndUnspentsToTx(tx, fromFlag.String(), core.UtilityTokenID(), gas, c); err != nil {
-		return cli.NewExitError(fmt.Errorf("can't add GAS to a tx: %v", err), 1)
-	}
 
 	if pass, err := readPassword("Password > "); err != nil {
 		return cli.NewExitError(err, 1)
 	} else if err := acc.Decrypt(pass); err != nil {
 		return cli.NewExitError(err, 1)
-	} else if err := acc.SignTx(tx); err != nil {
-		return cli.NewExitError(fmt.Errorf("can't sign tx: %v", err), 1)
 	}
 
-	if err := c.SendRawTransaction(tx); err != nil {
+	hash, err := c.TransferNEP5(acc, to, token, amount, gas)
+	if err != nil {
 		return cli.NewExitError(err, 1)
 	}
 
-	fmt.Println(tx.Hash())
+	fmt.Println(hash.StringLE())
 	return nil
 }

pkg/rpc/client/nep5.go

@@ -4,9 +4,15 @@ import (
 	"errors"
 	"fmt"
 
+	"github.com/nspcc-dev/neo-go/pkg/core"
+	"github.com/nspcc-dev/neo-go/pkg/core/transaction"
+	"github.com/nspcc-dev/neo-go/pkg/encoding/address"
+	"github.com/nspcc-dev/neo-go/pkg/io"
+	"github.com/nspcc-dev/neo-go/pkg/rpc/request"
 	"github.com/nspcc-dev/neo-go/pkg/smartcontract"
 	"github.com/nspcc-dev/neo-go/pkg/util"
 	"github.com/nspcc-dev/neo-go/pkg/vm/emit"
+	"github.com/nspcc-dev/neo-go/pkg/vm/opcode"
 	"github.com/nspcc-dev/neo-go/pkg/wallet"
 )
 
@@ -87,6 +93,47 @@ func (c *Client) NEP5TokenInfo(tokenHash util.Uint160) (*wallet.Token, error) {
 	return wallet.NewToken(tokenHash, name, symbol, decimals), nil
 }
 
+// TransferNEP5 creates an invocation transaction that invokes 'transfer' method
+// on a given token to move specified amount of NEP5 assets (in FixedN format
+// using contract's number of decimals) to given account.
+func (c *Client) TransferNEP5(acc *wallet.Account, to util.Uint160, token *wallet.Token, amount int64, gas util.Fixed8) (util.Uint256, error) {
+	from, err := address.StringToUint160(acc.Address)
+	if err != nil {
+		return util.Uint256{}, fmt.Errorf("bad account address: %v", err)
+	}
+	// Note: we don't use invoke function here because it requires
+	// 2 round trips instead of one.
+	w := io.NewBufBinWriter()
+	emit.Int(w.BinWriter, amount)
+	emit.Bytes(w.BinWriter, to.BytesBE())
+	emit.Bytes(w.BinWriter, from.BytesBE())
+	emit.Int(w.BinWriter, 3)
+	emit.Opcode(w.BinWriter, opcode.PACK)
+	emit.String(w.BinWriter, "transfer")
+	emit.AppCall(w.BinWriter, token.Hash, false)
+	emit.Opcode(w.BinWriter, opcode.THROWIFNOT)
+
+	tx := transaction.NewInvocationTX(w.Bytes(), gas)
+	tx.Attributes = append(tx.Attributes, transaction.Attribute{
+		Usage: transaction.Script,
+		Data:  from.BytesBE(),
+	})
+
+	if err := request.AddInputsAndUnspentsToTx(tx, acc.Address, core.UtilityTokenID(), gas, c); err != nil {
+		return util.Uint256{}, fmt.Errorf("can't add GAS to transaction: %v", err)
+	}
+
+	if err := acc.SignTx(tx); err != nil {
+		return util.Uint256{}, fmt.Errorf("can't sign tx: %v", err)
+	}
+
+	if err := c.SendRawTransaction(tx); err != nil {
+		return util.Uint256{}, err
+	}
+
+	return tx.Hash(), nil
+}
+
 func topIntFromStack(st []smartcontract.Parameter) (int64, error) {
 	index := len(st) - 1 // top stack element is last in the array
 	var decimals int64