adding changeToAddress

libsv · May 6, 2021 · cb887e0 · cb887e0
1 parent c3986f1
commit cb887e0
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Showing 3 changed files with 190 additions and 14 deletions.
diff --git a/bscript/address.go b/bscript/address.go
@@ -77,7 +77,7 @@ func NewAddressFromPublicKeyHash(hash []byte, mainnet bool) (*Address, error) {
 	if !mainnet {
 		bb[0] = 111
 	}
-
+	// nolint:makezero // stop complaining
 	bb = append(bb, hash...)
 
 	return &Address{
@@ -99,7 +99,7 @@ func NewAddressFromPublicKey(pubKey *bsvec.PublicKey, mainnet bool) (*Address, e
 	if !mainnet {
 		bb[0] = 111
 	}
-
+	// nolint:makezero // stop complaining
 	bb = append(bb, hash...)
 
 	return &Address{

diff --git a/txchange.go b/txchange.go
@@ -18,45 +18,83 @@ func (tx *Tx) ChangeToAddress(addr string, f []*Fee) error {
 }
 
 // Change calculates the amount of fees needed to cover the transaction
-// and adds the left over change in a new output using the script provided.
+//  and adds the left over change in a new output using the script provided.
 func (tx *Tx) Change(s *bscript.Script, f []*Fee) error {
+	available, hasChange, err := tx.change(s, f, true)
+	if err != nil {
+		return err
+	}
+	if hasChange {
+		// add rest of available sats to the change output
+		tx.Outputs[len(tx.Outputs)-1].Satoshis = available
+	}
+	return nil
+}
+
+// ChangeToOutput will calculate fees and add them to an output at the index specified (0 based).
+// If an invalid index is supplied and error is returned.
+func (tx *Tx) ChangeToOutput(index uint, f []*Fee) error {
+	if int(index) > len(tx.Outputs)-1 {
+		return errors.New("index is greater than number of inputs in transaction")
+	}
+	available, hasChange, err := tx.change(tx.Outputs[index].LockingScript, f, false)
+	if err != nil {
+		return err
+	}
+	if hasChange {
+		tx.Outputs[index].Satoshis += available
+	}
+	return nil
+}
 
+// CalculateFee will return the amount of fees the current transaction will
+// require.
+func (tx *Tx) CalculateFee(f []*Fee) (uint64, error) {
+	total := tx.TotalInputSatoshis() - tx.TotalOutputSatoshis()
+	sats, _, err := tx.change(nil, f, false)
+	if err != nil {
+		return 0, err
+	}
+	return total - sats, nil
+}
+
+// change will return the amount of satoshis to add to an input after fees are removed.
+// True will be returned if change has been added.
+func (tx *Tx) change(s *bscript.Script, f []*Fee, newOutput bool) (uint64, bool, error) {
 	inputAmount := tx.TotalInputSatoshis()
 	outputAmount := tx.TotalOutputSatoshis()
 
 	if inputAmount < outputAmount {
-		return errors.New("satoshis inputted to the tx are less than the outputted satoshis")
+		return 0, false, errors.New("satoshis inputted to the tx are less than the outputted satoshis")
 	}
 
 	available := inputAmount - outputAmount
 
 	standardFees, err := ExtractStandardFee(f)
 	if err != nil {
-		return err
+		return 0, false, err
 	}
 
 	if !tx.canAddChange(available, standardFees) {
-		return nil
+		return 0, false, err
+	}
+	if newOutput {
+		tx.AddOutput(&Output{Satoshis: 0, LockingScript: s})
 	}
-
-	tx.AddOutput(&Output{Satoshis: 0, LockingScript: s})
 
 	var preSignedFeeRequired uint64
 	if preSignedFeeRequired, err = tx.getPreSignedFeeRequired(f); err != nil {
-		return err
+		return 0, false, err
 	}
 
 	var expectedUnlockingScriptFees uint64
 	if expectedUnlockingScriptFees, err = tx.getExpectedUnlockingScriptFees(f); err != nil {
-		return err
+		return 0, false, err
 	}
 
 	available -= preSignedFeeRequired + expectedUnlockingScriptFees
 
-	// add rest of available sats to the change output
-	tx.Outputs[len(tx.Outputs)-1].Satoshis = available
-
-	return nil
+	return available, true, nil
 }
 
 func (tx *Tx) canAddChange(available uint64, standardFees *Fee) bool {

diff --git a/txchange_test.go b/txchange_test.go
@@ -1,6 +1,7 @@
 package bt_test
 
 import (
+	"errors"
 	"testing"
 
 	"github.com/bitcoinsv/bsvutil"
@@ -299,3 +300,140 @@ func TestTx_Change(t *testing.T) {
 		assert.Equal(t, "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", tx.ToString())
 	})
 }
+
+func TestTx_ChangeToOutput(t *testing.T) {
+	tests := map[string]struct {
+		tx              *bt.Tx
+		index           uint
+		fees            []*bt.Fee
+		expOutputTotal  uint64
+		expChangeOutput uint64
+		err             error
+	}{
+		"no change to add should return no change output": {
+			tx: func() *bt.Tx {
+				tx := bt.NewTx()
+				assert.NoError(t, tx.From(
+					"07912972e42095fe58daaf09161c5a5da57be47c2054dc2aaa52b30fefa1940b",
+					0,
+					"76a914af2590a45ae401651fdbdf59a76ad43d1862534088ac",
+					1000))
+				assert.NoError(t, tx.PayTo("mxAoAyZFXX6LZBWhoam3vjm6xt9NxPQ15f", 1000))
+				return tx
+			}(),
+			index:           0,
+			fees:            bt.DefaultFees(),
+			expOutputTotal:  1000,
+			expChangeOutput: 1000,
+			err:             nil,
+		}, "change to add should add change to output": {
+			tx: func() *bt.Tx {
+				tx := bt.NewTx()
+				assert.NoError(t, tx.From(
+					"07912972e42095fe58daaf09161c5a5da57be47c2054dc2aaa52b30fefa1940b",
+					0,
+					"76a914af2590a45ae401651fdbdf59a76ad43d1862534088ac",
+					1000))
+				assert.NoError(t, tx.PayTo("mxAoAyZFXX6LZBWhoam3vjm6xt9NxPQ15f", 500))
+				return tx
+			}(),
+			index:           0,
+			fees:            bt.DefaultFees(),
+			expOutputTotal:  904,
+			expChangeOutput: 904,
+			err:             nil,
+		}, "change to add should add change to specified output": {
+			tx: func() *bt.Tx {
+				tx := bt.NewTx()
+				assert.NoError(t, tx.From(
+					"07912972e42095fe58daaf09161c5a5da57be47c2054dc2aaa52b30fefa1940b",
+					0,
+					"76a914af2590a45ae401651fdbdf59a76ad43d1862534088ac",
+					2500))
+				assert.NoError(t, tx.PayTo("mxAoAyZFXX6LZBWhoam3vjm6xt9NxPQ15f", 500))
+				assert.NoError(t, tx.PayTo("mxAoAyZFXX6LZBWhoam3vjm6xt9NxPQ15f", 500))
+				assert.NoError(t, tx.PayTo("mxAoAyZFXX6LZBWhoam3vjm6xt9NxPQ15f", 500))
+				assert.NoError(t, tx.PayTo("mxAoAyZFXX6LZBWhoam3vjm6xt9NxPQ15f", 500))
+				return tx
+			}(),
+			index:           3,
+			fees:            bt.DefaultFees(),
+			expOutputTotal:  2353,
+			expChangeOutput: 853,
+			err:             nil,
+		}, "index out of range should return error": {
+			tx: func() *bt.Tx {
+				tx := bt.NewTx()
+				assert.NoError(t, tx.From(
+					"07912972e42095fe58daaf09161c5a5da57be47c2054dc2aaa52b30fefa1940b",
+					0,
+					"76a914af2590a45ae401651fdbdf59a76ad43d1862534088ac",
+					1000))
+				assert.NoError(t, tx.PayTo("mxAoAyZFXX6LZBWhoam3vjm6xt9NxPQ15f", 500))
+				return tx
+			}(),
+			index: 1,
+			fees:  bt.DefaultFees(),
+			err:   errors.New("index is greater than number of inputs in transaction"),
+		},
+	}
+	for name, test := range tests {
+		t.Run(name, func(t *testing.T) {
+			err := test.tx.ChangeToOutput(test.index, test.fees)
+			if test.err != nil {
+				assert.Error(t, err)
+				assert.Equal(t, test.err, err)
+				return
+			}
+			assert.Equal(t, test.expOutputTotal, test.tx.TotalOutputSatoshis())
+			assert.Equal(t, test.expChangeOutput, test.tx.Outputs[test.index].Satoshis)
+		})
+	}
+}
+
+func TestTx_CalculateChange(t *testing.T) {
+	tests := map[string]struct {
+		tx      *bt.Tx
+		fees    []*bt.Fee
+		expFees uint64
+		err     error
+	}{
+		"Transaction with one input one output should return 96": {
+			tx: func() *bt.Tx {
+				tx := bt.NewTx()
+				assert.NoError(t, tx.From(
+					"07912972e42095fe58daaf09161c5a5da57be47c2054dc2aaa52b30fefa1940b",
+					0,
+					"76a914af2590a45ae401651fdbdf59a76ad43d1862534088ac",
+					1000))
+				assert.NoError(t, tx.PayTo("mxAoAyZFXX6LZBWhoam3vjm6xt9NxPQ15f", 500))
+				return tx
+			}(),
+			fees:    bt.DefaultFees(),
+			expFees: 96,
+		}, "Transaction with one input 4 outputs should return 147": {
+			tx: func() *bt.Tx {
+				tx := bt.NewTx()
+				assert.NoError(t, tx.From(
+					"07912972e42095fe58daaf09161c5a5da57be47c2054dc2aaa52b30fefa1940b",
+					0,
+					"76a914af2590a45ae401651fdbdf59a76ad43d1862534088ac",
+					2500))
+				assert.NoError(t, tx.PayTo("mxAoAyZFXX6LZBWhoam3vjm6xt9NxPQ15f", 500))
+				assert.NoError(t, tx.PayTo("mxAoAyZFXX6LZBWhoam3vjm6xt9NxPQ15f", 500))
+				assert.NoError(t, tx.PayTo("mxAoAyZFXX6LZBWhoam3vjm6xt9NxPQ15f", 500))
+				assert.NoError(t, tx.PayTo("mxAoAyZFXX6LZBWhoam3vjm6xt9NxPQ15f", 500))
+				return tx
+			}(),
+			fees:    bt.DefaultFees(),
+			expFees: 147,
+		},
+	}
+	for name, test := range tests {
+		t.Run(name, func(t *testing.T) {
+			fee, err := test.tx.CalculateFee(test.fees)
+			assert.Equal(t, test.err, err)
+			assert.Equal(t, test.expFees, fee)
+		})
+	}
+}