Add a maxconfirms argument to ListUnspentWitness

This change was inspired by lightningnetwork#1984 - the underlying call to
ListUnspent supports a (min, max) range so it makes sense that
the WalletController interface can also support this; a
default no-maximum can be expressed using a MaxInt32 value.

lnwallet/btcwallet/btcwallet.go

@@ -217,7 +217,7 @@ func (b *BtcWallet) Stop() error {
 func (b *BtcWallet) ConfirmedBalance(confs int32) (btcutil.Amount, error) {
 	var balance btcutil.Amount
 
-	witnessOutputs, err := b.ListUnspentWitness(confs)
+	witnessOutputs, err := b.ListUnspentWitness(confs, math.MaxInt32)
 	if err != nil {
 		return 0, err
 	}
@@ -299,9 +299,9 @@ func (b *BtcWallet) UnlockOutpoint(o wire.OutPoint) {
 // controls which pay to witness programs either directly or indirectly.
 //
 // This is a part of the WalletController interface.
-func (b *BtcWallet) ListUnspentWitness(minConfs int32) ([]*lnwallet.Utxo, error) {
+func (b *BtcWallet) ListUnspentWitness(minConfs, maxConfs int32) (
+	[]*lnwallet.Utxo, error) {
 	// First, grab all the unfiltered currently unspent outputs.
-	maxConfs := int32(math.MaxInt32)
 	unspentOutputs, err := b.wallet.ListUnspent(minConfs, maxConfs, nil)
 	if err != nil {
 		return nil, err

lnwallet/interface.go

@@ -160,11 +160,13 @@ type WalletController interface {
 		feeRate SatPerKWeight) (*chainhash.Hash, error)
 
 	// ListUnspentWitness returns all unspent outputs which are version 0
-	// witness programs. The 'confirms' parameter indicates the minimum
-	// number of confirmations an output needs in order to be returned by
-	// this method. Passing -1 as 'confirms' indicates that even
-	// unconfirmed outputs should be returned.
-	ListUnspentWitness(confirms int32) ([]*Utxo, error)
+	// witness programs. The 'minconfirms' and 'maxconfirms' parameters
+	// indicate the minimum and maximum number of confirmations an output
+	// needs in order to be returned by this method. Passing -1 as
+	// 'minconfirms' indicates that even unconfirmed outputs should be
+	// returned. Using MaxInt32 as 'maxconfirms' implies returning all
+	// outputs with at least 'minconfirms'.
+	ListUnspentWitness(minconfirms, maxconfirms int32) ([]*Utxo, error)
 
 	// ListTransactionDetails returns a list of all transactions which are
 	// relevant to the wallet.

lnwallet/wallet.go

@@ -5,6 +5,7 @@ import (
 	"crypto/sha256"
 	"errors"
 	"fmt"
+	"math"
 	"net"
 	"sync"
 	"sync/atomic"
@@ -1276,7 +1277,7 @@ func (l *LightningWallet) selectCoinsAndChange(feeRate SatPerKWeight,
 
 	// Find all unlocked unspent witness outputs that satisfy the minimum
 	// number of confirmations required.
-	coins, err := l.ListUnspentWitness(minConfs)
+	coins, err := l.ListUnspentWitness(minConfs, math.MaxInt32)
 	if err != nil {
 		return err
 	}

mock.go

@@ -234,7 +234,8 @@ func (*mockWalletController) SendOutputs(outputs []*wire.TxOut,
 
 // ListUnspentWitness is called by the wallet when doing coin selection. We just
 // need one unspent for the funding transaction.
-func (m *mockWalletController) ListUnspentWitness(confirms int32) ([]*lnwallet.Utxo, error) {
+func (m *mockWalletController) ListUnspentWitness(minconfirms,
+	maxconfirms int32) ([]*lnwallet.Utxo, error) {
 	utxo := &lnwallet.Utxo{
 		AddressType: lnwallet.WitnessPubKey,
 		Value:       btcutil.Amount(10 * btcutil.SatoshiPerBitcoin),