From 7c0a03c7c87e0bab1705177c117b78e72cc101cf Mon Sep 17 00:00:00 2001
From: Conner Fromknecht <conner@lightning.engineering>
Date: Thu, 13 Jun 2019 17:30:22 -0700
Subject: [PATCH] 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      | 46 ++++++++++++++++++++++++++++------------------
 utxonursery.go | 14 --------------
 2 files changed, 28 insertions(+), 32 deletions(-)

diff --git a/server.go b/server.go
index ee6998ae..73a0ef6e 100644
--- a/server.go
+++ b/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"
@@ -729,10 +730,8 @@ func newServer(listenAddrs []net.Addr, chanDB *channeldb.DB,
 	}
 
 	s.sweeper = sweep.New(&sweep.UtxoSweeperConfig{
-		FeeEstimator: cc.feeEstimator,
-		GenSweepScript: func() ([]byte, error) {
-			return newSweepPkScript(cc.wallet)
-		},
+		FeeEstimator:       cc.feeEstimator,
+		GenSweepScript:     newSweepPkScriptGen(cc.wallet),
 		Signer:             cc.wallet.Cfg.Signer,
 		PublishTransaction: cc.wallet.PublishTransaction,
 		NewBatchTimer: func() <-chan time.Time {
@@ -775,10 +774,8 @@ func newServer(listenAddrs []net.Addr, chanDB *channeldb.DB,
 		ChainHash:              *activeNetParams.GenesisHash,
 		IncomingBroadcastDelta: DefaultIncomingBroadcastDelta,
 		OutgoingBroadcastDelta: DefaultOutgoingBroadcastDelta,
-		NewSweepAddr: func() ([]byte, error) {
-			return newSweepPkScript(cc.wallet)
-		},
-		PublishTx: cc.wallet.PublishTransaction,
+		NewSweepAddr:           newSweepPkScriptGen(cc.wallet),
+		PublishTx:              cc.wallet.PublishTransaction,
 		DeliverResolutionMsg: func(msgs ...contractcourt.ResolutionMsg) error {
 			for _, msg := range msgs {
 				err := s.htlcSwitch.ProcessContractResolution(msg)
@@ -851,12 +848,10 @@ func newServer(listenAddrs []net.Addr, chanDB *channeldb.DB,
 	}, chanDB)
 
 	s.breachArbiter = newBreachArbiter(&BreachConfig{
-		CloseLink: closeLink,
-		DB:        chanDB,
-		Estimator: s.cc.feeEstimator,
-		GenSweepScript: func() ([]byte, error) {
-			return newSweepPkScript(cc.wallet)
-		},
+		CloseLink:          closeLink,
+		DB:                 chanDB,
+		Estimator:          s.cc.feeEstimator,
+		GenSweepScript:     newSweepPkScriptGen(cc.wallet),
 		Notifier:           cc.chainNotifier,
 		PublishTransaction: cc.wallet.PublishTransaction,
 		ContractBreaches:   contractBreaches,
@@ -1075,10 +1070,8 @@ func newServer(listenAddrs []net.Addr, chanDB *channeldb.DB,
 		}
 
 		s.towerClient, err = wtclient.New(&wtclient.Config{
-			Signer: cc.wallet.Cfg.Signer,
-			NewAddress: func() ([]byte, error) {
-				return newSweepPkScript(cc.wallet)
-			},
+			Signer:         cc.wallet.Cfg.Signer,
+			NewAddress:     newSweepPkScriptGen(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)
+	}
+}
diff --git a/utxonursery.go b/utxonursery.go
index bfdc075a..0e4501b6 100644
--- a/utxonursery.go
+++ b/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