chanfunding: make coin selection generic

Before this commit the coin selection logic in the chanfunding package
would always assume that there is a P2WSH funding output and potentially
a P2TR change output. But because we want to re-use the coin selection
for things other than just channel funding, we make the logic more
generic by allowing us to specify both the existing weight of the
transaction (the already known, static parts of the TX) as well as the
type of the potential change output we would use.

lnwallet/chanfunding/coin_select_test.go

@@ -25,6 +25,8 @@ var (
 	p2khScript, _ = hex.DecodeString(
 		"76a91411034bdcb6ccb7744fdfdeea958a6fb0b415a03288ac",
 	)
+
+	defaultChanFundingChangeType = P2TRChangeAddress
 )
 
 // fundingFee is a helper method that returns the fee estimate used for a tx
@@ -117,11 +119,15 @@ func TestCalculateFees(t *testing.T) {
 		},
 	}
 
+	fundingOutputEstimate := input.TxWeightEstimator{}
+	fundingOutputEstimate.AddP2WSHOutput()
+
 	for _, test := range testCases {
 		test := test
 		t.Run(test.name, func(t *testing.T) {
 			feeNoChange, feeWithChange, err := calculateFees(
-				test.utxos, feeRate,
+				test.utxos, feeRate, fundingOutputEstimate,
+				defaultChanFundingChangeType,
 			)
 			require.Equal(t, test.expectedErr, err)
 
@@ -259,6 +265,9 @@ func TestCoinSelect(t *testing.T) {
 		},
 	}
 
+	fundingOutputEstimate := input.TxWeightEstimator{}
+	fundingOutputEstimate.AddP2WSHOutput()
+
 	for _, test := range testCases {
 		test := test
 		t.Run(test.name, func(t *testing.T) {
@@ -267,6 +276,8 @@ func TestCoinSelect(t *testing.T) {
 			selected, changeAmt, err := CoinSelect(
 				feeRate, test.outputValue, dustLimit, test.coins,
 				wallet.CoinSelectionLargest,
+				fundingOutputEstimate,
+				defaultChanFundingChangeType,
 			)
 			if !test.expectErr && err != nil {
 				t.Fatalf(err.Error())
@@ -472,6 +483,9 @@ func TestCoinSelectSubtractFees(t *testing.T) {
 		},
 	}
 
+	fundingOutputEstimate := input.TxWeightEstimator{}
+	fundingOutputEstimate.AddP2WSHOutput()
+
 	for _, test := range testCases {
 		test := test
 
@@ -484,6 +498,8 @@ func TestCoinSelectSubtractFees(t *testing.T) {
 			selected, localFundingAmt, changeAmt, err := CoinSelectSubtractFees(
 				feeRate, test.spendValue, dustLimit, test.coins,
 				wallet.CoinSelectionLargest,
+				fundingOutputEstimate,
+				defaultChanFundingChangeType,
 			)
 			if err != nil {
 				switch {
@@ -714,6 +730,9 @@ func TestCoinSelectUpToAmount(t *testing.T) {
 		expectedChange: 10000,
 	}}
 
+	fundingOutputEstimate := input.TxWeightEstimator{}
+	fundingOutputEstimate.AddP2WSHOutput()
+
 	for _, test := range testCases {
 		test := test
 
@@ -724,6 +743,8 @@ func TestCoinSelectUpToAmount(t *testing.T) {
 				feeRate, test.minValue, test.maxValue,
 				test.reserved, dustLimit, test.coins,
 				wallet.CoinSelectionLargest,
+				fundingOutputEstimate,
+				defaultChanFundingChangeType,
 			)
 			if len(test.expectErr) == 0 && err != nil {
 				t.Fatalf(err.Error())