Add Event::ChannelClosed::last_local_balance_msats

Users commonly want to know what their balance was when a channel
was closed, which this provides in a somewhat simplified manner.

It does not consider pending HTLCs and will always overstate our
balance by transaction fees.

Author: Mirebella

lightning/src/events/mod.rs

@@ -1276,6 +1276,15 @@ pub enum Event {
 		/// status of the closing tx.
 		/// Note that for instances serialized in v0.0.119 or prior this will be missing (None).
 		channel_funding_txo: Option<transaction::OutPoint>,
+		/// An upper bound on the our last local balance in msats before the channel was closed.
+		///
+		/// Will overstate our balance as it ignores pending outbound HTLCs and transaction fees.
+		///
+		/// For more accurate balances including fee information see
+		/// [`ChainMonitor::get_claimable_balances`].
+		///
+		/// This field will be `None` only for objects serialized prior to LDK 0.1.
+		last_local_balance_msats: Option<u64>,
 	},
 	/// Used to indicate to the user that they can abandon the funding transaction and recycle the
 	/// inputs for another purpose.
@@ -1555,7 +1564,8 @@ impl Writeable for Event {
 				});
 			},
 			&Event::ChannelClosed { ref channel_id, ref user_channel_id, ref reason,
-				ref counterparty_node_id, ref channel_capacity_sats, ref channel_funding_txo
+				ref counterparty_node_id, ref channel_capacity_sats, ref channel_funding_txo,
+				ref last_local_balance_msats,
 			} => {
 				9u8.write(writer)?;
 				// `user_channel_id` used to be a single u64 value. In order to remain backwards
@@ -1571,6 +1581,7 @@ impl Writeable for Event {
 					(5, counterparty_node_id, option),
 					(7, channel_capacity_sats, option),
 					(9, channel_funding_txo, option),
+					(11, last_local_balance_msats, option)
 				});
 			},
 			&Event::DiscardFunding { ref channel_id, ref funding_info } => {
@@ -1939,6 +1950,7 @@ impl MaybeReadable for Event {
 					let mut counterparty_node_id = None;
 					let mut channel_capacity_sats = None;
 					let mut channel_funding_txo = None;
+					let mut last_local_balance_msats = None;
 					read_tlv_fields!(reader, {
 						(0, channel_id, required),
 						(1, user_channel_id_low_opt, option),
@@ -1947,6 +1959,7 @@ impl MaybeReadable for Event {
 						(5, counterparty_node_id, option),
 						(7, channel_capacity_sats, option),
 						(9, channel_funding_txo, option),
+						(11, last_local_balance_msats, option)
 					});
 
 					// `user_channel_id` used to be a single u64 value. In order to remain
@@ -1956,7 +1969,7 @@ impl MaybeReadable for Event {
 						((user_channel_id_high_opt.unwrap_or(0) as u128) << 64);
 
 					Ok(Some(Event::ChannelClosed { channel_id, user_channel_id, reason: _init_tlv_based_struct_field!(reason, upgradable_required),
-						counterparty_node_id, channel_capacity_sats, channel_funding_txo }))
+						counterparty_node_id, channel_capacity_sats, channel_funding_txo, last_local_balance_msats}))
 				};
 				f()
 			},

lightning/src/ln/channel.rs

@@ -937,6 +937,7 @@ pub(crate) struct ShutdownResult {
 	pub(crate) is_manual_broadcast: bool,
 	pub(crate) unbroadcasted_funding_tx: Option<Transaction>,
 	pub(crate) channel_funding_txo: Option<OutPoint>,
+	pub(crate) last_local_balance_msats: u64,
 }
 
 /// Tracks the transaction number, along with current and next commitment points.
@@ -2066,6 +2067,8 @@ impl<SP: Deref> ChannelContext<SP> where SP::Target: SignerProvider  {
 		})
 	}
 
+	pub(crate) fn get_value_to_self_msat(&self) -> u64 {self.value_to_self_msat}
+
 	/// Allowed in any state (including after shutdown)
 	pub fn get_update_time_counter(&self) -> u32 {
 		self.update_time_counter
@@ -3532,6 +3535,7 @@ impl<SP: Deref> ChannelContext<SP> where SP::Target: SignerProvider  {
 			unbroadcasted_funding_tx,
 			is_manual_broadcast: self.is_manual_broadcast,
 			channel_funding_txo: self.get_funding_txo(),
+			last_local_balance_msats: self.value_to_self_msat,
 		}
 	}
 
@@ -6180,6 +6184,7 @@ impl<SP: Deref> Channel<SP> where
 			unbroadcasted_funding_tx: self.context.unbroadcasted_funding(),
 			is_manual_broadcast: self.context.is_manual_broadcast,
 			channel_funding_txo: self.context.get_funding_txo(),
+			last_local_balance_msats: self.context.value_to_self_msat,
 		}
 	}
 

lightning/src/ln/channelmanager.rs

@@ -3574,6 +3574,7 @@ where
 				counterparty_node_id: Some(shutdown_res.counterparty_node_id),
 				channel_capacity_sats: Some(shutdown_res.channel_capacity_satoshis),
 				channel_funding_txo: shutdown_res.channel_funding_txo,
+				last_local_balance_msats: Some(shutdown_res.last_local_balance_msats),
 			}, None));
 
 			if let Some(transaction) = shutdown_res.unbroadcasted_funding_tx {
@@ -12039,6 +12040,7 @@ where
 						counterparty_node_id: Some(channel.context.get_counterparty_node_id()),
 						channel_capacity_sats: Some(channel.context.get_value_satoshis()),
 						channel_funding_txo: channel.context.get_funding_txo(),
+						last_local_balance_msats: Some(channel.context.get_value_to_self_msat()),
 					}, None));
 					for (channel_htlc_source, payment_hash) in channel.inflight_htlc_sources() {
 						let mut found_htlc = false;
@@ -12095,6 +12097,7 @@ where
 					counterparty_node_id: Some(channel.context.get_counterparty_node_id()),
 					channel_capacity_sats: Some(channel.context.get_value_satoshis()),
 					channel_funding_txo: channel.context.get_funding_txo(),
+					last_local_balance_msats: Some(channel.context.get_value_to_self_msat()),
 				}, None));
 			} else {
 				log_error!(logger, "Missing ChannelMonitor for channel {} needed by ChannelManager.", &channel.context.channel_id());