Simplify HolderHTLCOutput constructor and track CLTV expiry

This allows us to interrogate a PackageTemplate for the CLTV
timelock of the resulting transaction.

Author: TheBlueMatt

lightning/src/chain/channelmonitor.rs

@@ -1786,14 +1786,17 @@ impl<Signer: Sign> ChannelMonitorImpl<Signer> {
 
 		for &(ref htlc, _, _) in holder_tx.htlc_outputs.iter() {
 			if let Some(transaction_output_index) = htlc.transaction_output_index {
-				let htlc_output = HolderHTLCOutput::build(if !htlc.offered {
-					if let Some(preimage) = self.payment_preimages.get(&htlc.payment_hash) {
-						Some(preimage.clone())
+				let htlc_output = if htlc.offered {
+						HolderHTLCOutput::build_offered(htlc.amount_msat, htlc.cltv_expiry)
 					} else {
-						// We can't build an HTLC-Success transaction without the preimage
-						continue;
-					}
-				} else { None }, htlc.amount_msat);
+						let payment_preimage = if let Some(preimage) = self.payment_preimages.get(&htlc.payment_hash) {
+							preimage.clone()
+						} else {
+							// We can't build an HTLC-Success transaction without the preimage
+							continue;
+						};
+						HolderHTLCOutput::build_accepted(payment_preimage, htlc.amount_msat)
+					};
 				let htlc_package = PackageTemplate::build_package(holder_tx.txid, transaction_output_index, PackageSolvingData::HolderHTLCOutput(htlc_output), height, false, height);
 				claim_requests.push(htlc_package);
 			}

lightning/src/chain/package.rs

@@ -213,21 +213,33 @@ impl_writeable_tlv_based!(CounterpartyReceivedHTLCOutput, {
 pub(crate) struct HolderHTLCOutput {
 	preimage: Option<PaymentPreimage>,
 	amount: u64,
+	/// Defaults to 0 for HTLC-Success transactions, which have no expiry
+	cltv_expiry: u32,
 }
 
 impl HolderHTLCOutput {
-	pub(crate) fn build(preimage: Option<PaymentPreimage>, amount: u64) -> Self {
+	pub(crate) fn build_offered(amount: u64, cltv_expiry: u32) -> Self {
 		HolderHTLCOutput {
-			preimage,
-			amount
+			preimage: None,
+			amount,
+			cltv_expiry,
+		}
+	}
+
+	pub(crate) fn build_accepted(preimage: PaymentPreimage, amount: u64) -> Self {
+		HolderHTLCOutput {
+			preimage: Some(preimage),
+			amount,
+			cltv_expiry: 0,
 		}
 	}
 }
 
 impl_writeable_tlv_based!(HolderHTLCOutput, {
 	(0, amount),
+	(2, cltv_expiry),
 }, {
-	(2, preimage),
+	(4, preimage),
 }, {});
 
 /// A struct to describe the channel output on the funding transaction.
@@ -879,7 +891,7 @@ mod tests {
 		() => {
 			{
 				let preimage = PaymentPreimage([2;32]);
-				PackageSolvingData::HolderHTLCOutput(HolderHTLCOutput::build(Some(preimage), 0))
+				PackageSolvingData::HolderHTLCOutput(HolderHTLCOutput::build_accepted(preimage, 0))
 			}
 		}
 	}