staticaddr: unit test CalculateWithdrawalTxValues

staticaddr/withdraw/manager_test.go

@@ -4,11 +4,19 @@ import (
 	"context"
 	"testing"
 
+	"github.com/btcsuite/btcd/btcutil"
+	"github.com/btcsuite/btcd/chaincfg"
+	"github.com/btcsuite/btcd/chaincfg/chainhash"
 	"github.com/btcsuite/btcd/txscript"
 	"github.com/btcsuite/btcd/wire"
+	"github.com/lightninglabs/loop/staticaddr/deposit"
 	"github.com/lightninglabs/loop/swapserverrpc"
 	"github.com/lightninglabs/loop/test"
+	"github.com/lightningnetwork/lnd/funding"
 	"github.com/lightningnetwork/lnd/input"
+	"github.com/lightningnetwork/lnd/lnrpc"
+	"github.com/lightningnetwork/lnd/lnwallet"
+	"github.com/lightningnetwork/lnd/lnwallet/chainfee"
 	"github.com/stretchr/testify/require"
 )
 
@@ -368,3 +376,233 @@ func TestSignMusig2Tx_MissingOutpointInDepositMap(t *testing.T) {
 	// Expect an error indicating the missing outpoint.
 	require.ErrorContains(t, err, "tx outpoint not in deposit index map")
 }
+
+// TestCalculateWithdrawalTxValues tests various edge cases in withdrawal
+// transaction value calculations.
+func TestCalculateWithdrawalTxValues(t *testing.T) {
+	t.Parallel()
+
+	// Create a taproot address for withdrawal.
+	taprootAddr, err := btcutil.NewAddressTaproot(
+		make([]byte, 32), &chaincfg.RegressionNetParams,
+	)
+	require.NoError(t, err)
+
+	// Standard fee rate for testing.
+	feeRate := chainfee.SatPerKWeight(1000)
+
+	// Helper to create deposits.
+	createDeposit := func(value btcutil.Amount, idx uint32) *deposit.Deposit {
+		hash := chainhash.Hash{}
+		hash[0] = byte(idx)
+		return &deposit.Deposit{
+			OutPoint: wire.OutPoint{
+				Hash:  hash,
+				Index: idx,
+			},
+			Value: value,
+		}
+	}
+
+	tests := []struct {
+		name           string
+		deposits       []*deposit.Deposit
+		localAmount    btcutil.Amount
+		feeRate        chainfee.SatPerKWeight
+		withdrawAddr   btcutil.Address
+		commitmentType lnrpc.CommitmentType
+		expectedErr    string
+		expectDustFee  bool // change is dust, given to miners
+	}{
+		{
+			name: "neither address nor commitment type specified",
+			deposits: []*deposit.Deposit{
+				createDeposit(100000, 0),
+			},
+			localAmount:    0,
+			feeRate:        feeRate,
+			withdrawAddr:   nil,
+			commitmentType: lnrpc.CommitmentType_UNKNOWN_COMMITMENT_TYPE,
+			expectedErr:    "either address or commitment type must be specified",
+		},
+		{
+			name: "change is dust - given to miners",
+			deposits: []*deposit.Deposit{
+				createDeposit(100000, 0),
+			},
+			// Set localAmount such that change after feeWithChange
+			// would be dust, but change after feeWithoutChange >= 0.
+			// This triggers case: change-feeWithoutChange >= 0
+			localAmount:    99300, // Leaves ~700 sats which is dust
+			feeRate:        feeRate,
+			withdrawAddr:   taprootAddr,
+			commitmentType: lnrpc.CommitmentType_UNKNOWN_COMMITMENT_TYPE,
+			expectedErr:    "",
+			expectDustFee:  true,
+		},
+		{
+			name: "insufficient funds after dust and fee",
+			deposits: []*deposit.Deposit{
+				createDeposit(1000, 0),
+			},
+			localAmount:    900,
+			feeRate:        feeRate,
+			withdrawAddr:   taprootAddr,
+			commitmentType: lnrpc.CommitmentType_UNKNOWN_COMMITMENT_TYPE,
+			expectedErr:    "doesn't cover for fees",
+		},
+		{
+			name: "negative change after fees",
+			deposits: []*deposit.Deposit{
+				createDeposit(10000, 0),
+			},
+			localAmount:    15000,
+			feeRate:        feeRate,
+			withdrawAddr:   taprootAddr,
+			commitmentType: lnrpc.CommitmentType_UNKNOWN_COMMITMENT_TYPE,
+			expectedErr:    "doesn't cover for fees",
+		},
+		{
+			name: "min channel size guard - below minimum",
+			deposits: []*deposit.Deposit{
+				createDeposit(funding.MinChanFundingSize-10, 0),
+			},
+			localAmount:    0,
+			feeRate:        feeRate,
+			withdrawAddr:   nil,
+			commitmentType: lnrpc.CommitmentType_SIMPLE_TAPROOT,
+			expectedErr: "is lower than the minimum channel " +
+				"funding size",
+		},
+		{
+			name: "min channel size guard - exactly minimum",
+			deposits: []*deposit.Deposit{
+				createDeposit(funding.MinChanFundingSize+1000, 0),
+			},
+			localAmount:    0,
+			feeRate:        feeRate,
+			withdrawAddr:   nil,
+			commitmentType: lnrpc.CommitmentType_SIMPLE_TAPROOT,
+			expectedErr:    "",
+		},
+		{
+			name: "withdrawal amount below dust limit",
+			deposits: []*deposit.Deposit{
+				createDeposit(400, 0),
+			},
+			localAmount:    0,
+			feeRate:        feeRate,
+			withdrawAddr:   taprootAddr,
+			commitmentType: lnrpc.CommitmentType_UNKNOWN_COMMITMENT_TYPE,
+			expectedErr:    "below dust limit",
+		},
+		{
+			name: "change higher than input value",
+			deposits: []*deposit.Deposit{
+				createDeposit(10000, 0),
+				createDeposit(5000, 1),
+			},
+			localAmount:    5000,
+			feeRate:        chainfee.SatPerKWeight(100),
+			withdrawAddr:   taprootAddr,
+			commitmentType: lnrpc.CommitmentType_UNKNOWN_COMMITMENT_TYPE,
+			expectedErr:    "change amount",
+		},
+		{
+			name: "successful withdrawal with change",
+			deposits: []*deposit.Deposit{
+				createDeposit(100000, 0),
+			},
+			localAmount:    50000,
+			feeRate:        feeRate,
+			withdrawAddr:   taprootAddr,
+			commitmentType: lnrpc.CommitmentType_UNKNOWN_COMMITMENT_TYPE,
+			expectedErr:    "",
+		},
+		{
+			name: "successful withdrawal no change",
+			deposits: []*deposit.Deposit{
+				createDeposit(100000, 0),
+			},
+			localAmount:    0,
+			feeRate:        feeRate,
+			withdrawAddr:   taprootAddr,
+			commitmentType: lnrpc.CommitmentType_UNKNOWN_COMMITMENT_TYPE,
+			expectedErr:    "",
+		},
+		{
+			name: "successful channel open above min size",
+			deposits: []*deposit.Deposit{
+				createDeposit(funding.MinChanFundingSize*2, 0),
+			},
+			localAmount:    0,
+			feeRate:        feeRate,
+			withdrawAddr:   nil,
+			commitmentType: lnrpc.CommitmentType_SIMPLE_TAPROOT,
+			expectedErr:    "",
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			withdrawAmt, changeAmt, err := CalculateWithdrawalTxValues(
+				tc.deposits, tc.localAmount, tc.feeRate,
+				tc.withdrawAddr, tc.commitmentType,
+			)
+
+			if tc.expectedErr != "" {
+				require.Error(t, err)
+				require.ErrorContains(t, err, tc.expectedErr)
+				return
+			}
+
+			require.NoError(t, err)
+			require.Greater(t, withdrawAmt, btcutil.Amount(0))
+			require.GreaterOrEqual(t, changeAmt, btcutil.Amount(0))
+
+			// Verify that withdrawal amount meets dust threshold.
+			dustLimit := lnwallet.DustLimitForSize(input.P2TRSize)
+			require.GreaterOrEqual(t, withdrawAmt, dustLimit)
+
+			// If this is a channel open, verify min channel size.
+			if tc.commitmentType != lnrpc.CommitmentType_UNKNOWN_COMMITMENT_TYPE {
+				require.GreaterOrEqual(
+					t, withdrawAmt, funding.MinChanFundingSize,
+				)
+			}
+
+			// If expecting dust to be given to miners, verify
+			// changeAmt is 0.
+			if tc.expectDustFee {
+				require.Equal(t, btcutil.Amount(0), changeAmt,
+					"change should be 0 when dust is given to miners")
+			}
+
+			// Verify total accounting: inputs = withdrawal + change + fees.
+			totalInputs := btcutil.Amount(0)
+			for _, d := range tc.deposits {
+				totalInputs += d.Value
+			}
+
+			hasChange := changeAmt > 0
+			weight, err := WithdrawalTxWeight(
+				len(tc.deposits), tc.withdrawAddr,
+				tc.commitmentType, hasChange,
+			)
+			require.NoError(t, err)
+
+			fee := tc.feeRate.FeeForWeight(weight)
+
+			// When dust is given to miners, the "fee" includes both
+			// the transaction fee and the dust amount.
+			if tc.expectDustFee {
+				// Total should equal withdrawal + implicit fee (including dust)
+				implicitFee := totalInputs - withdrawAmt - changeAmt
+				require.Greater(t, implicitFee, fee,
+					"implicit fee should be greater than tx fee when dust is given to miners")
+			} else {
+				require.Equal(t, totalInputs, withdrawAmt+changeAmt+fee)
+			}
+		})
+	}
+}