lnwallet/chancloser: add aux chan closer, use in coop flow

lnwallet/channel.go

@@ -8814,7 +8814,7 @@ func CreateCooperativeCloseTx(fundingTxIn wire.TxIn,
 // LocalBalanceDust returns true if when creating a co-op close transaction,
 // the balance of the local party will be dust after accounting for any anchor
 // outputs.
-func (lc *LightningChannel) LocalBalanceDust() bool {
+func (lc *LightningChannel) LocalBalanceDust() (bool, btcutil.Amount) {
 	lc.RLock()
 	defer lc.RUnlock()
 
@@ -8828,13 +8828,15 @@ func (lc *LightningChannel) LocalBalanceDust() bool {
 		localBalance += 2 * AnchorSize
 	}
 
-	return localBalance <= chanState.LocalChanCfg.DustLimit
+	localDust := chanState.LocalChanCfg.DustLimit
+
+	return localBalance <= localDust, localDust
 }
 
 // RemoteBalanceDust returns true if when creating a co-op close transaction,
 // the balance of the remote party will be dust after accounting for any anchor
 // outputs.
-func (lc *LightningChannel) RemoteBalanceDust() bool {
+func (lc *LightningChannel) RemoteBalanceDust() (bool, btcutil.Amount) {
 	lc.RLock()
 	defer lc.RUnlock()
 
@@ -8848,7 +8850,40 @@ func (lc *LightningChannel) RemoteBalanceDust() bool {
 		remoteBalance += 2 * AnchorSize
 	}
 
-	return remoteBalance <= chanState.RemoteChanCfg.DustLimit
+	remoteDust := chanState.RemoteChanCfg.DustLimit
+
+	return remoteBalance <= remoteDust, remoteDust
+}
+
+// CommitBalances returns the local and remote balances in the current
+// commitment state.
+func (lc *LightningChannel) CommitBalances() (btcutil.Amount, btcutil.Amount) {
+	lc.RLock()
+	defer lc.RUnlock()
+
+	chanState := lc.channelState
+	localCommit := lc.channelState.LocalCommitment
+
+	localBalance := localCommit.LocalBalance.ToSatoshis()
+	remoteBalance := localCommit.RemoteBalance.ToSatoshis()
+
+	if chanState.ChanType.HasAnchors() {
+		if chanState.IsInitiator {
+			localBalance += 2 * AnchorSize
+		} else {
+			remoteBalance += 2 * AnchorSize
+		}
+	}
+
+	return localBalance, remoteBalance
+}
+
+// CommitFee returns the commitment fee for the current commitment state.
+func (lc *LightningChannel) CommitFee() btcutil.Amount {
+	lc.RLock()
+	defer lc.RUnlock()
+
+	return lc.channelState.LocalCommitment.CommitFee
 }
 
 // CalcFee returns the commitment fee to use for the given fee rate