SendToAddress RPC call (#114)

* func to get private key from raw bytes

* added function to create raw transfer tx

* fixes

* more fixes

* prettify code and comments; neoscan interaction put in dedicated files

pkg/rpc/txBuilder.go

@@ -0,0 +1,86 @@
+package rpc
+
+import (
+	"bytes"
+
+	"github.com/CityOfZion/neo-go/pkg/core/transaction"
+	"github.com/CityOfZion/neo-go/pkg/crypto"
+	"github.com/CityOfZion/neo-go/pkg/util"
+	"github.com/CityOfZion/neo-go/pkg/wallet"
+	errs "github.com/pkg/errors"
+)
+
+func CreateRawContractTransaction(params ContractTxParams) (*transaction.Transaction, error) {
+	var (
+		err                            error
+		tx                             = transaction.NewContractTX()
+		toAddressHash, fromAddressHash util.Uint160
+		fromAddress                    string
+		senderOutput, receiverOutput   *transaction.Output
+		inputs                         []transaction.Input
+		spent                          util.Fixed8
+		witness                        transaction.Witness
+
+		wif, assetID, address, amount, balancer = params.wif, params.assetId, params.address, params.value, params.balancer
+	)
+
+	if fromAddress, err = wif.PrivateKey.Address(); err != nil {
+		return nil, errs.Wrapf(err, "Failed to take address from WIF: %v", wif.S)
+	}
+
+	if fromAddressHash, err = crypto.Uint160DecodeAddress(fromAddress); err != nil {
+		return nil, errs.Wrapf(err, "Failed to take script hash from address: %v", fromAddress)
+	}
+
+	if toAddressHash, err = crypto.Uint160DecodeAddress(address); err != nil {
+		return nil, errs.Wrapf(err, "Failed to take script hash from address: %v", address)
+	}
+	tx.Attributes = append(tx.Attributes,
+		&transaction.Attribute{
+			Usage: transaction.Script,
+			Data:  fromAddressHash.Bytes(),
+		})
+
+	if inputs, spent, err = balancer.CalculateInputs(fromAddress, assetID, amount); err != nil {
+		return nil, errs.Wrap(err, "Failed to get inputs for transaction")
+	}
+	for _, input := range inputs {
+		tx.AddInput(&input)
+	}
+
+	senderOutput = transaction.NewOutput(assetID, spent-amount, fromAddressHash)
+	tx.AddOutput(senderOutput)
+	receiverOutput = transaction.NewOutput(assetID, amount, toAddressHash)
+	tx.AddOutput(receiverOutput)
+
+	if witness.InvocationScript, err = getInvocationScript(tx, wif); err != nil {
+		return nil, errs.Wrap(err, "Failed to create invocation script")
+	}
+	if witness.VerificationScript, err = wif.GetVerificationScript(); err != nil {
+		return nil, errs.Wrap(err, "Failed to create verification script")
+	}
+	tx.Scripts = append(tx.Scripts, &witness)
+	tx.Hash()
+
+	return tx, nil
+}
+
+func getInvocationScript(tx *transaction.Transaction, wif wallet.WIF) ([]byte, error) {
+	const (
+		pushbytes64 = 0x40
+	)
+	var (
+		err       error
+		buf       = new(bytes.Buffer)
+		signature []byte
+	)
+	if err = tx.EncodeBinary(buf); err != nil {
+		return nil, errs.Wrap(err, "Failed to encode transaction to binary")
+	}
+	bytes := buf.Bytes()
+	signature, err = wif.PrivateKey.Sign(bytes[:(len(bytes) - 1)])
+	if err != nil {
+		return nil, errs.Wrap(err, "Failed ti sign transaction with private key")
+	}
+	return append([]byte{pushbytes64}, signature...), nil
+}