From 296a13ce2b3df7ab99427cbaed9b5d28fdaf0cc3 Mon Sep 17 00:00:00 2001
From: Elias Rohrer <dev@tnull.de>
Date: Mon, 8 Jan 2024 08:30:04 +0100
Subject: [PATCH] Implement LSPS2 API methods

---
 src/lib.rs       | 69 ++++++++++++++++++++++++++++++++++++++++++++++++
 src/liquidity.rs |  7 +++++
 2 files changed, 76 insertions(+)

diff --git a/src/lib.rs b/src/lib.rs
index 5d2f90215..245a41585 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1574,6 +1574,75 @@ impl<K: KVStore + Sync + Send + 'static> Node<K> {
 		Ok(invoice)
 	}
 
+	/// Returns a payable invoice that can be used to request a payment of the amount given and
+	/// receive it via a newly created just-in-time (JIT) channel.
+	///
+	/// When the returned invoice is paid, the configured [LSPS2]-compliant LSP will open a channel
+	/// to us, supplying just-in-time inbound liquidity.
+	///
+	/// [LSPS2]: https://github.com/BitcoinAndLightningLayerSpecs/lsp/blob/main/LSPS2/README.md
+	pub fn receive_payment_via_jit_channel(
+		&self, amount_msat: u64, description: &str, expiry_secs: u32,
+	) -> Result<Bolt11Invoice, Error> {
+		self.receive_payment_via_jit_channel_inner(Some(amount_msat), description, expiry_secs)
+	}
+
+	/// Returns a payable invoice that can be used to request a variable amount payment (also known
+	/// as "zero-amount" invoice) and receive it via a newly created just-in-time (JIT) channel.
+	///
+	/// When the returned invoice is paid, the configured [LSPS2]-compliant LSP will open a channel
+	/// to us, supplying just-in-time inbound liquidity.
+	///
+	/// [LSPS2]: https://github.com/BitcoinAndLightningLayerSpecs/lsp/blob/main/LSPS2/README.md
+	pub fn receive_variable_amount_payment_via_jit_channel(
+		&self, description: &str, expiry_secs: u32,
+	) -> Result<Bolt11Invoice, Error> {
+		self.receive_payment_via_jit_channel_inner(None, description, expiry_secs)
+	}
+
+	fn receive_payment_via_jit_channel_inner(
+		&self, amount_msat: Option<u64>, description: &str, expiry_secs: u32,
+	) -> Result<Bolt11Invoice, Error> {
+		let (node_id, address) = self
+			.liquidity_source
+			.get_liquidity_source_details()
+			.ok_or(Error::LiquiditySourceUnavailable)?;
+
+		let rt_lock = self.runtime.read().unwrap();
+		let runtime = rt_lock.as_ref().unwrap();
+
+		let peer_info = PeerInfo { node_id, address };
+
+		let con_node_id = peer_info.node_id;
+		let con_addr = peer_info.address.clone();
+		let con_logger = Arc::clone(&self.logger);
+		let con_pm = Arc::clone(&self.peer_manager);
+
+		// We need to use our main runtime here as a local runtime might not be around to poll
+		// connection futures going forward.
+		tokio::task::block_in_place(move || {
+			runtime.block_on(async move {
+				connect_peer_if_necessary(con_node_id, con_addr, con_pm, con_logger).await
+			})
+		})?;
+
+		log_info!(self.logger, "Connected to LSP {}@{}. ", peer_info.node_id, peer_info.address);
+
+		let liquidity_source = Arc::clone(&self.liquidity_source);
+		let invoice = tokio::task::block_in_place(move || {
+			runtime.block_on(async move {
+				liquidity_source
+					.lsps2_receive_to_jit_channel(amount_msat, description, expiry_secs)
+					.await
+			})
+		})?;
+
+		// Persist LSP peer to make sure we reconnect on restart.
+		self.peer_store.add_peer(peer_info)?;
+
+		Ok(invoice)
+	}
+
 	/// Retrieve the details of a specific payment with the given hash.
 	///
 	/// Returns `Some` if the payment was known and `None` otherwise.
diff --git a/src/liquidity.rs b/src/liquidity.rs
index 73479768a..76796967a 100644
--- a/src/liquidity.rs
+++ b/src/liquidity.rs
@@ -86,6 +86,13 @@ where
 		}
 	}
 
+	pub(crate) fn get_liquidity_source_details(&self) -> Option<(PublicKey, SocketAddress)> {
+		match self {
+			Self::None => None,
+			Self::LSPS2 { node_id, address, .. } => Some((*node_id, address.clone())),
+		}
+	}
+
 	pub(crate) async fn handle_next_event(&self) {
 		match self {
 			Self::None => {}