Add ChannelMonitor::transaction_unconfirmed

Define an Electrum-friendly interface for ChannelMonitor where
transactions are unconfirmed independently from updating the latest
block.

Author: jkczyz

lightning/src/chain/channelmonitor.rs

@@ -1322,6 +1322,22 @@ impl<Signer: Sign> ChannelMonitor<Signer> {
 			header, txdata, height, broadcaster, fee_estimator, &logger)
 	}
 
+	/// TODO: Write docs
+	pub fn transaction_unconfirmed<B: Deref, F: Deref, L: Deref>(
+		&self,
+		txid: &Txid,
+		broadcaster: B,
+		fee_estimator: F,
+		logger: L,
+	) where
+		B::Target: BroadcasterInterface,
+		F::Target: FeeEstimator,
+		L::Target: Logger,
+	{
+		self.inner.lock().unwrap().transaction_unconfirmed(
+			txid, broadcaster, fee_estimator, logger);
+	}
+
 	/// Updates the monitor with the current best chain tip.
 	///
 	/// TODO: Expand docs.
@@ -2192,6 +2208,21 @@ impl<Signer: Sign> ChannelMonitorImpl<Signer> {
 		self.last_block_hash = header.prev_blockhash;
 	}
 
+	fn transaction_unconfirmed<B: Deref, F: Deref, L: Deref>(
+		&mut self,
+		txid: &Txid,
+		broadcaster: B,
+		fee_estimator: F,
+		logger: L,
+	) where
+		B::Target: BroadcasterInterface,
+		F::Target: FeeEstimator,
+		L::Target: Logger,
+	{
+		self.onchain_events_waiting_threshold_conf.retain(|ref entry| entry.txid != *txid);
+		self.onchain_tx_handler.transaction_unconfirmed(txid, broadcaster, fee_estimator, logger);
+	}
+
 	/// Filters a block's `txdata` for transactions spending watched outputs or for any child
 	/// transactions thereof.
 	fn filter_block<'a>(&self, txdata: &TransactionData<'a>) -> Vec<&'a Transaction> {

lightning/src/ln/onchaintx.rs

@@ -866,6 +866,30 @@ impl<ChannelSigner: Sign> OnchainTxHandler<ChannelSigner> {
 		}
 	}
 
+	pub(crate) fn transaction_unconfirmed<B: Deref, F: Deref, L: Deref>(
+		&mut self,
+		txid: &Txid,
+		broadcaster: B,
+		fee_estimator: F,
+		logger: L,
+	) where
+		B::Target: BroadcasterInterface,
+		F::Target: FeeEstimator,
+		L::Target: Logger,
+	{
+		let mut height = None;
+		for entry in self.onchain_events_waiting_threshold_conf.iter() {
+			if entry.txid == *txid {
+				height = Some(entry.height);
+				break;
+			}
+		}
+
+		if let Some(height) = height {
+			self.block_disconnected(height, broadcaster, fee_estimator, logger);
+		}
+	}
+
 	pub(crate) fn block_disconnected<B: Deref, F: Deref, L: Deref>(&mut self, height: u32, broadcaster: B, fee_estimator: F, logger: L)
 		where B::Target: BroadcasterInterface,
 		      F::Target: FeeEstimator,