Split channelmonitor's broadcast_by_holder_state

Now callers will separately retrieve the claim requests/
holder revokable script and the new watched holder outputs.
This will be used in the next commit for times when we
need to get holder claim requests, but don't have access to
the holder commitment transaction.

Author: valentinewallace

lightning/src/chain/channelmonitor.rs

@@ -1525,9 +1525,11 @@ impl<ChanSigner: ChannelKeys> ChannelMonitor<ChanSigner> {
 		(claimable_outpoints, Some((htlc_txid, outputs)))
 	}
 
-	fn broadcast_by_holder_state(&self, commitment_tx: &Transaction, holder_tx: &HolderSignedTx) -> (Vec<ClaimRequest>, Vec<(u32, TxOut)>, Option<(Script, PublicKey, PublicKey)>) {
+	// Returns (1) `ClaimRequest`s that can be given to the OnChainTxHandler, so that the handler can
+	// broadcast transactions claiming holder HTLC commitment outputs and (2) a holder revokable
+	// script so we can detect whether a holder transaction has been seen on-chain.
+	fn get_broadcasted_holder_claims(&self, holder_tx: &HolderSignedTx) -> (Vec<ClaimRequest>, Option<(Script, PublicKey, PublicKey)>) {
 		let mut claim_requests = Vec::with_capacity(holder_tx.htlc_outputs.len());
-		let mut watch_outputs = Vec::with_capacity(holder_tx.htlc_outputs.len());
 
 		let redeemscript = chan_utils::get_revokeable_redeemscript(&holder_tx.revocation_key, self.on_holder_tx_csv, &holder_tx.delayed_payment_key);
 		let broadcasted_holder_revokable_script = Some((redeemscript.to_v0_p2wsh(), holder_tx.per_commitment_point.clone(), holder_tx.revocation_key.clone()));
@@ -1546,11 +1548,21 @@ impl<ChanSigner: ChannelKeys> ChannelMonitor<ChanSigner> {
 							} else { None },
 						amount: htlc.amount_msat,
 				}});
-				watch_outputs.push((transaction_output_index, commitment_tx.output[transaction_output_index as usize].clone()));
 			}
 		}
 
-		(claim_requests, watch_outputs, broadcasted_holder_revokable_script)
+		(claim_requests, broadcasted_holder_revokable_script)
+	}
+
+	// Returns holder HTLC outputs to watch and react to in case of spending.
+	fn get_broadcasted_holder_watch_outputs(&self, holder_tx: &HolderSignedTx, commitment_tx: &Transaction) -> Vec<(u32, TxOut)> {
+		let mut watch_outputs = Vec::with_capacity(holder_tx.htlc_outputs.len());
+		for &(ref htlc, _, _) in holder_tx.htlc_outputs.iter() {
+			if let Some(transaction_output_index) = htlc.transaction_output_index {
+				watch_outputs.push((transaction_output_index, commitment_tx.output[transaction_output_index as usize].clone()));
+			}
+		}
+		watch_outputs
 	}
 
 	/// Attempts to claim any claimable HTLCs in a commitment transaction which was not (yet)
@@ -1585,10 +1597,10 @@ impl<ChanSigner: ChannelKeys> ChannelMonitor<ChanSigner> {
 		}
 
 		macro_rules! append_onchain_update {
-			($updates: expr) => {
+			($updates: expr, $to_watch: expr) => {
 				claim_requests = $updates.0;
-				watch_outputs.append(&mut $updates.1);
-				self.broadcasted_holder_revokable_script = $updates.2;
+				self.broadcasted_holder_revokable_script = $updates.1;
+				watch_outputs.append(&mut $to_watch);
 			}
 		}
 
@@ -1598,14 +1610,16 @@ impl<ChanSigner: ChannelKeys> ChannelMonitor<ChanSigner> {
 		if self.current_holder_commitment_tx.txid == commitment_txid {
 			is_holder_tx = true;
 			log_trace!(logger, "Got latest holder commitment tx broadcast, searching for available HTLCs to claim");
-			let mut res = self.broadcast_by_holder_state(tx, &self.current_holder_commitment_tx);
-			append_onchain_update!(res);
+			let res = self.get_broadcasted_holder_claims(&self.current_holder_commitment_tx);
+			let mut to_watch = self.get_broadcasted_holder_watch_outputs(&self.current_holder_commitment_tx, tx);
+			append_onchain_update!(res, to_watch);
 		} else if let &Some(ref holder_tx) = &self.prev_holder_signed_commitment_tx {
 			if holder_tx.txid == commitment_txid {
 				is_holder_tx = true;
 				log_trace!(logger, "Got previous holder commitment tx broadcast, searching for available HTLCs to claim");
-				let mut res = self.broadcast_by_holder_state(tx, holder_tx);
-				append_onchain_update!(res);
+				let res = self.get_broadcasted_holder_claims(holder_tx);
+				let mut to_watch = self.get_broadcasted_holder_watch_outputs(holder_tx, tx);
+				append_onchain_update!(res, to_watch);
 			}
 		}
 
@@ -1773,7 +1787,8 @@ impl<ChanSigner: ChannelKeys> ChannelMonitor<ChanSigner> {
 			self.pending_monitor_events.push(MonitorEvent::CommitmentTxBroadcasted(self.funding_info.0));
 			if let Some(commitment_tx) = self.onchain_tx_handler.get_fully_signed_holder_tx(&self.funding_redeemscript) {
 				self.holder_tx_signed = true;
-				let (mut new_outpoints, new_outputs, _) = self.broadcast_by_holder_state(&commitment_tx, &self.current_holder_commitment_tx);
+				let (mut new_outpoints, _) = self.get_broadcasted_holder_claims(&self.current_holder_commitment_tx);
+				let new_outputs = self.get_broadcasted_holder_watch_outputs(&self.current_holder_commitment_tx, &commitment_tx);
 				if !new_outputs.is_empty() {
 					watch_outputs.push((self.current_holder_commitment_tx.txid.clone(), new_outputs));
 				}