server+utxonursery: generate pkscript closures

This commit moves the newSweepPkScript function
previously in the nursery to be a helper function
within the server. Additionally, the function now
returns a closure that satisfies the configuration
interfaces of several other subsystems.

As a result, the configuration sites contain much
less boilerplate, as it's now encapsulated in
the newSweepPkScriptGen helper.

server.go

@@ -20,6 +20,7 @@ import (
 	"github.com/btcsuite/btcd/btcec"
 	"github.com/btcsuite/btcd/chaincfg/chainhash"
 	"github.com/btcsuite/btcd/connmgr"
+	"github.com/btcsuite/btcd/txscript"
 	"github.com/btcsuite/btcd/wire"
 	"github.com/btcsuite/btcutil"
 	"github.com/coreos/bbolt"
@@ -730,9 +731,7 @@ func newServer(listenAddrs []net.Addr, chanDB *channeldb.DB,
 
 	s.sweeper = sweep.New(&sweep.UtxoSweeperConfig{
 		FeeEstimator:       cc.feeEstimator,
-		GenSweepScript: func() ([]byte, error) {
+		GenSweepScript:     newSweepPkScriptGen(cc.wallet),
-			return newSweepPkScript(cc.wallet)
-		},
 		Signer:             cc.wallet.Cfg.Signer,
 		PublishTransaction: cc.wallet.PublishTransaction,
 		NewBatchTimer: func() <-chan time.Time {
@@ -775,9 +774,7 @@ func newServer(listenAddrs []net.Addr, chanDB *channeldb.DB,
 		ChainHash:              *activeNetParams.GenesisHash,
 		IncomingBroadcastDelta: DefaultIncomingBroadcastDelta,
 		OutgoingBroadcastDelta: DefaultOutgoingBroadcastDelta,
-		NewSweepAddr: func() ([]byte, error) {
+		NewSweepAddr:           newSweepPkScriptGen(cc.wallet),
-			return newSweepPkScript(cc.wallet)
-		},
 		PublishTx:              cc.wallet.PublishTransaction,
 		DeliverResolutionMsg: func(msgs ...contractcourt.ResolutionMsg) error {
 			for _, msg := range msgs {
@@ -854,9 +851,7 @@ func newServer(listenAddrs []net.Addr, chanDB *channeldb.DB,
 		CloseLink:          closeLink,
 		DB:                 chanDB,
 		Estimator:          s.cc.feeEstimator,
-		GenSweepScript: func() ([]byte, error) {
+		GenSweepScript:     newSweepPkScriptGen(cc.wallet),
-			return newSweepPkScript(cc.wallet)
-		},
 		Notifier:           cc.chainNotifier,
 		PublishTransaction: cc.wallet.PublishTransaction,
 		ContractBreaches:   contractBreaches,
@@ -1076,9 +1071,7 @@ func newServer(listenAddrs []net.Addr, chanDB *channeldb.DB,
 
 		s.towerClient, err = wtclient.New(&wtclient.Config{
 			Signer:         cc.wallet.Cfg.Signer,
-			NewAddress: func() ([]byte, error) {
+			NewAddress:     newSweepPkScriptGen(cc.wallet),
-				return newSweepPkScript(cc.wallet)
-			},
 			SecretKeyRing:  s.cc.keyRing,
 			Dial:           cfg.net.Dial,
 			AuthDial:       wtclient.AuthDial,
@@ -3233,3 +3226,20 @@ func (s *server) applyChannelUpdate(update *lnwire.ChannelUpdate) error {
 		return ErrServerShuttingDown
 	}
 }
+
+// newSweepPkScriptGen creates closure that generates a new public key script
+// which should be used to sweep any funds into the on-chain wallet.
+// Specifically, the script generated is a version 0, pay-to-witness-pubkey-hash
+// (p2wkh) output.
+func newSweepPkScriptGen(
+	wallet lnwallet.WalletController) func() ([]byte, error) {
+
+	return func() ([]byte, error) {
+		sweepAddr, err := wallet.NewAddress(lnwallet.WitnessPubKey, false)
+		if err != nil {
+			return nil, err
+		}
+
+		return txscript.PayToAddrScript(sweepAddr)
+	}
+}

utxonursery.go

@@ -8,7 +8,6 @@ import (
 	"sync"
 	"sync/atomic"
 
-	"github.com/btcsuite/btcd/txscript"
 	"github.com/btcsuite/btcd/wire"
 	"github.com/btcsuite/btcutil"
 	"github.com/davecgh/go-spew/spew"
@@ -1231,19 +1230,6 @@ func (u *utxoNursery) closeAndRemoveIfMature(chanPoint *wire.OutPoint) error {
 	return nil
 }
 
-// newSweepPkScript creates a new public key script which should be used to
-// sweep any time-locked, or contested channel funds into the wallet.
-// Specifically, the script generated is a version 0, pay-to-witness-pubkey-hash
-// (p2wkh) output.
-func newSweepPkScript(wallet lnwallet.WalletController) ([]byte, error) {
-	sweepAddr, err := wallet.NewAddress(lnwallet.WitnessPubKey, false)
-	if err != nil {
-		return nil, err
-	}
-
-	return txscript.PayToAddrScript(sweepAddr)
-}
-
 // babyOutput represents a two-stage CSV locked output, and is used to track
 // htlc outputs through incubation. The first stage requires broadcasting a
 // presigned timeout txn that spends from the CLTV locked output on the