Kaspawallet: implement fee calcs, centralize constant and logic

cmd/kaspawallet/daemon/server/create_unsigned_transaction.go

@@ -12,9 +12,6 @@ import (
 	"time"
 )
 
-// TODO: Implement a better fee estimation mechanism
-const feePerInput = 10000
-
 func (s *server) CreateUnsignedTransactions(_ context.Context, request *pb.CreateUnsignedTransactionsRequest) (
 	*pb.CreateUnsignedTransactionsResponse, error) {
 	s.lock.Lock()
@@ -52,7 +49,7 @@ func (s *server) createUnsignedTransactions(address string, amount uint64, fromA
 		fromAddresses = append(fromAddresses, fromAddress)
 	}
 
-	selectedUTXOs, changeSompi, err := s.selectUTXOs(amount, feePerInput, fromAddresses)
+	selectedUTXOs, changeSompi, err := s.selectUTXOs(amount, libkaspawallet.FeePerInput, fromAddresses)
 	if err != nil {
 		return nil, err
 	}

cmd/kaspawallet/daemon/server/external_spendable_utxos.go

@@ -55,7 +55,7 @@ func (s *server) selectExternalSpendableUTXOs(externalUTXOs *appmessage.GetUTXOs
 func isExternalUTXOSpendable(entry *appmessage.UTXOsByAddressesEntry, virtualDAAScore uint64, coinbaseMaturity uint64) bool {
 	if !entry.UTXOEntry.IsCoinbase {
 		return true
-	} else if entry.UTXOEntry.Amount <= feePerInput {
+	} else if entry.UTXOEntry.Amount <= libkaspawallet.FeePerInput {
 		return false
 	}
 	return entry.UTXOEntry.BlockDAAScore+coinbaseMaturity < virtualDAAScore

cmd/kaspawallet/daemon/server/split_transaction.go

@@ -79,7 +79,7 @@ func (s *server) mergeTransaction(
 			DerivationPath: s.walletAddressPath(changeWalletAddress),
 		}
 		totalValue += output.Value
-		totalValue -= feePerInput
+		totalValue -= libkaspawallet.FeePerInput
 	}
 
 	if totalValue < sentValue {
@@ -200,7 +200,7 @@ func (s *server) createSplitTransaction(transaction *serialization.PartiallySign
 		})
 
 		totalSompi += selectedUTXOs[i-startIndex].UTXOEntry.Amount()
-		totalSompi -= feePerInput
+		totalSompi -= libkaspawallet.FeePerInput
 	}
 	unsignedTransactionBytes, err := libkaspawallet.CreateUnsignedTransaction(s.keysFile.ExtendedPublicKeys,
 		s.keysFile.MinimumSignatures,
@@ -265,7 +265,7 @@ func (s *server) moreUTXOsForMergeTransaction(alreadySelectedUTXOs []*libkaspawa
 			Outpoint:       utxo.Outpoint,
 			UTXOEntry:      utxo.UTXOEntry,
 			DerivationPath: s.walletAddressPath(utxo.address)})
-		totalValueAdded += utxo.UTXOEntry.Amount() - feePerInput
+		totalValueAdded += utxo.UTXOEntry.Amount() - libkaspawallet.FeePerInput
 		if totalValueAdded >= requiredAmount {
 			break
 		}

cmd/kaspawallet/libkaspawallet/fees.go

@@ -0,0 +1,54 @@
+package libkaspawallet
+
+import (
+	"github.com/pkg/errors"
+
+	"github.com/kaspanet/kaspad/domain/consensus/model/externalapi"
+)
+
+// TODO: Implement a better fee construction and estimation mechanism.
+
+//FeePerInput is the current constant per input to pay for transactions.
+const FeePerInput uint64 = 10000
+
+//CalculateFees calculates the totalFee for a slice of transactions
+func CalculateFees(transactions []*externalapi.DomainTransaction) (uint64, error) {
+
+	var totalFee uint64
+
+	for _, tx := range transactions {
+		fee, err := CalculateFee(tx)
+		if err != nil {
+			return 0, err
+		}
+		totalFee += fee
+	}
+
+	return totalFee, nil
+}
+
+//CalculateFee calculates fee for a transaction
+func CalculateFee(transaction *externalapi.DomainTransaction) (uint64, error) {
+
+	var totalInputAmount uint64
+	var totalOutputAmount uint64
+
+	for _, input := range transaction.Inputs {
+		totalInputAmount += input.UTXOEntry.Amount()
+	}
+	for _, output := range transaction.Outputs {
+		totalOutputAmount += output.Value
+	}
+
+	return CalculateFeeFromInputAndOutputTotalAmounts(totalInputAmount, totalOutputAmount)
+}
+
+//CalculateFeeFromInputAndOutputTotalAmounts calculates tx fee form total input and output amounts
+//this func is more performant then CalculateFee if total input and output amounts are knowen.
+func CalculateFeeFromInputAndOutputTotalAmounts(totalInputAmount uint64, totalOutputAmount uint64) (uint64, error) {
+	if totalInputAmount > totalOutputAmount {
+		return 0, errors.Errorf("The input amount may not exceed the output amount, Cannot Calculate negative fees")
+	}
+
+	return totalInputAmount - totalOutputAmount, nil
+}

cmd/kaspawallet/parse.go

@@ -3,13 +3,15 @@ package main
 import (
 	"encoding/hex"
 	"fmt"
+	"io/ioutil"
+	"strings"
+
+	"github.com/kaspanet/kaspad/cmd/kaspawallet/libkaspawallet"
 	"github.com/kaspanet/kaspad/cmd/kaspawallet/libkaspawallet/serialization"
 	"github.com/kaspanet/kaspad/domain/consensus/utils/consensushashing"
 	"github.com/kaspanet/kaspad/domain/consensus/utils/constants"
 	"github.com/kaspanet/kaspad/domain/consensus/utils/txscript"
 	"github.com/pkg/errors"
-	"io/ioutil"
-	"strings"
 )
 
 func parse(conf *parseConfig) error {
@@ -42,7 +44,6 @@ func parse(conf *parseConfig) error {
 
 		fmt.Printf("Transaction #%d ID: \t%s\n", i+1, consensushashing.TransactionID(partiallySignedTransaction.Tx))
 		fmt.Println()
-
 		allInputSompi := uint64(0)
 		for index, input := range partiallySignedTransaction.Tx.Inputs {
 			partiallySignedInput := partiallySignedTransaction.PartiallySignedInputs[index]
@@ -51,7 +52,6 @@ func parse(conf *parseConfig) error {
 				fmt.Printf("Input %d: \tOutpoint: %s:%d \tAmount: %.2f Kaspa\n", index, input.PreviousOutpoint.TransactionID,
 					input.PreviousOutpoint.Index, float64(partiallySignedInput.PrevOutput.Value)/float64(constants.SompiPerKaspa))
 			}
-
 			allInputSompi += partiallySignedInput.PrevOutput.Value
 		}
 		if conf.Verbose {
@@ -73,12 +73,18 @@ func parse(conf *parseConfig) error {
 
 			fmt.Printf("Output %d: \tRecipient: %s \tAmount: %.2f Kaspa\n",
 				index, addressString, float64(output.Value)/float64(constants.SompiPerKaspa))
-
 			allOutputSompi += output.Value
+
 		}
 		fmt.Println()
 
-		fmt.Printf("Fee:\t%d Sompi\n\n", allInputSompi-allOutputSompi)
+		fee, err := libkaspawallet.CalculateFeeFromInputAndOutputTotalAmounts(allInputSompi, allOutputSompi)
+		if err != nil {
+			return err
+		}
+
+		fmt.Printf("Fee:\t%d Sompi\n\n", fee)
+
 	}
 
 	return nil

cmd/kaspawallet/sweep.go

@@ -24,8 +24,6 @@ import (
 	"github.com/pkg/errors"
 )
 
-const feePerInput = 10000
-
 func sweep(conf *sweepConfig) error {
 
 	privateKeyBytes, err := hex.DecodeString(conf.PrivateKey)
@@ -89,7 +87,7 @@ func sweep(conf *sweepConfig) error {
 		return err
 	}
 
-	splitTransactions, err := createSplitTransactionsWithSchnorrPrivteKey(conf.NetParams(), UTXOs, toAddress, feePerInput)
+	splitTransactions, err := createSplitTransactionsWithSchnorrPrivteKey(conf.NetParams(), UTXOs, toAddress)
 	if err != nil {
 		return err
 	}
@@ -141,8 +139,7 @@ func newDummyTransaction() *externalapi.DomainTransaction {
 func createSplitTransactionsWithSchnorrPrivteKey(
 	params *dagconfig.Params,
 	selectedUTXOs []*libkaspawallet.UTXO,
-	toAddress util.Address,
-	feePerInput int) ([]*externalapi.DomainTransaction, error) {
+	toAddress util.Address) ([]*externalapi.DomainTransaction, error) {
 
 	var splitTransactions []*externalapi.DomainTransaction
 
@@ -180,7 +177,7 @@ func createSplitTransactionsWithSchnorrPrivteKey(
 		)
 
 		currentTx.Outputs[0] = &externalapi.DomainTransactionOutput{
-			Value:           totalSplitAmount - uint64(len(currentTx.Inputs)*feePerInput),
+			Value:           totalSplitAmount - uint64(len(currentTx.Inputs)*int(libkaspawallet.FeePerInput)),
 			ScriptPublicKey: scriptPublicKey,
 		}