feat: expose lsps2 liquidity opening params

bindings/ldk_node.udl

@@ -1,6 +1,8 @@
 namespace ldk_node {
 	Mnemonic generate_entropy_mnemonic(WordCount? word_count);
 	Config default_config();
+	// Alby: compute LSPS2 opening fees for an LSP-provided offer.
+	u64? lsps2_compute_opening_fee_msat(u64 payment_size_msat, LSPS2OpeningFeeParams opening_fee_params);
 };
 
 dictionary Config {
@@ -145,6 +147,8 @@ interface Node {
 	OnchainPayment onchain_payment();
 	UnifiedQrPayment unified_qr_payment();
 	LSPS1Liquidity lsps1_liquidity();
+	// Alby: expose the LSPS2 opening fee menu so Hub can surface JIT limits to users.
+	LSPS2Liquidity lsps2_liquidity();
 	[Throws=NodeError]
 	void connect(PublicKey node_id, SocketAddress address, boolean persist);
 	[Throws=NodeError]
@@ -293,6 +297,28 @@ interface LSPS1Liquidity {
 	LSPS1OrderStatus check_order_status(LSPS1OrderId order_id);
 };
 
+interface LSPS2Liquidity {
+	[Throws=NodeError]
+	// Alby: fetch the LSP's LSPS2 opening fee menu.
+	LSPS2GetInfoResponse request_opening_fee_params();
+};
+
+dictionary LSPS2OpeningFeeParams {
+	u64 min_fee_msat;
+	u32 proportional;
+	LSPSDateTime valid_until;
+	u32 min_lifetime;
+	u32 max_client_to_self_delay;
+	u64 min_payment_size_msat;
+	u64 max_payment_size_msat;
+	string promise;
+};
+
+dictionary LSPS2GetInfoResponse {
+	// Alby: return the raw LSPS2 fee menu so clients can read min_payment_size_msat.
+	sequence<LSPS2OpeningFeeParams> opening_fee_params_menu;
+};
+
 [Error]
 enum NodeError {
 	"AlreadyRunning",

src/ffi/types.rs

@@ -38,6 +38,8 @@ pub use lightning_liquidity::lsps0::ser::LSPSDateTime;
 pub use lightning_liquidity::lsps1::msgs::{
 	LSPS1ChannelInfo, LSPS1OrderId, LSPS1OrderParams, LSPS1PaymentState,
 };
+// Alby: expose the LSPS2 opening fee menu item type over UniFFI.
+pub use lightning_liquidity::lsps2::msgs::LSPS2OpeningFeeParams;
 pub use lightning_types::payment::{PaymentHash, PaymentPreimage, PaymentSecret};
 pub use lightning_types::string::UntrustedString;
 pub use vss_client::headers::{VssHeaderProvider, VssHeaderProviderError};
@@ -49,7 +51,8 @@ pub use crate::config::{
 };
 use crate::error::Error;
 pub use crate::graph::{ChannelInfo, ChannelUpdateInfo, NodeAnnouncementInfo, NodeInfo};
-pub use crate::liquidity::{LSPS1OrderStatus, LSPS2ServiceConfig};
+// Alby: expose the LSPS2 get_info response over UniFFI.
+pub use crate::liquidity::{LSPS1OrderStatus, LSPS2GetInfoResponse, LSPS2ServiceConfig};
 pub use crate::logger::{LogLevel, LogRecord, LogWriter};
 pub use crate::payment::store::{
 	ConfirmationStatus, LSPFeeLimits, PaymentDirection, PaymentKind, PaymentStatus,

src/lib.rs

@@ -132,6 +132,8 @@ use ffi::*;
 use gossip::GossipSource;
 use graph::NetworkGraph;
 pub use io::utils::generate_entropy_mnemonic;
+// Alby: export LSPS2 opening fee computation for local fee estimation in Hub.
+pub use liquidity::lsps2_compute_opening_fee_msat;
 use io::utils::write_node_metrics;
 use lightning::chain::BestBlock;
 use lightning::events::bump_transaction::{Input, Wallet as LdkWallet};
@@ -144,7 +146,7 @@ use lightning::ln::msgs::SocketAddress;
 use lightning::routing::gossip::NodeAlias;
 use lightning::util::persist::KVStoreSync;
 use lightning_background_processor::process_events_async;
-use liquidity::{LSPS1Liquidity, LiquiditySource};
+use liquidity::{LSPS1Liquidity, LSPS2Liquidity, LiquiditySource};
 use logger::{log_debug, log_error, log_info, log_trace, LdkLogger, Logger};
 use payment::asynchronous::om_mailbox::OnionMessageMailbox;
 use payment::asynchronous::static_invoice_store::StaticInvoiceStore;
@@ -1045,6 +1047,34 @@ impl Node {
 		))
 	}
 
+	/// Returns a liquidity handler allowing to query [bLIP-52 / LSPS2] JIT channel parameters.
+	///
+	/// Alby: expose the LSPS2 opening fee menu so Hub can surface min/max payment sizes.
+	/// [bLIP-52 / LSPS2]: https://github.com/lightning/blips/blob/master/blip-0052.md
+	#[cfg(not(feature = "uniffi"))]
+	pub fn lsps2_liquidity(&self) -> LSPS2Liquidity {
+		LSPS2Liquidity::new(
+			Arc::clone(&self.runtime),
+			Arc::clone(&self.connection_manager),
+			self.liquidity_source.clone(),
+			Arc::clone(&self.logger),
+		)
+	}
+
+	/// Returns a liquidity handler allowing to query [bLIP-52 / LSPS2] JIT channel parameters.
+	///
+	/// Alby: expose the LSPS2 opening fee menu so Hub can surface min/max payment sizes.
+	/// [bLIP-52 / LSPS2]: https://github.com/lightning/blips/blob/master/blip-0052.md
+	#[cfg(feature = "uniffi")]
+	pub fn lsps2_liquidity(&self) -> Arc<LSPS2Liquidity> {
+		Arc::new(LSPS2Liquidity::new(
+			Arc::clone(&self.runtime),
+			Arc::clone(&self.connection_manager),
+			self.liquidity_source.clone(),
+			Arc::clone(&self.logger),
+		))
+	}
+
 	/// Retrieve a list of known channels.
 	pub fn list_channels(&self) -> Vec<ChannelDetails> {
 		self.channel_manager.list_channels().into_iter().map(|c| c.into()).collect()

src/liquidity.rs

@@ -78,7 +78,7 @@ struct LSPS2Client {
 	lsp_address: SocketAddress,
 	token: Option<String>,
 	ldk_client_config: LdkLSPS2ClientConfig,
-	pending_fee_requests: Mutex<HashMap<LSPSRequestId, oneshot::Sender<LSPS2FeeResponse>>>,
+	pending_fee_requests: Mutex<HashMap<LSPSRequestId, oneshot::Sender<LSPS2GetInfoResponse>>>,
 	pending_buy_requests: Mutex<HashMap<LSPSRequestId, oneshot::Sender<LSPS2BuyResponse>>>,
 }
 
@@ -829,7 +829,7 @@ where
 					if let Some(sender) =
 						lsps2_client.pending_fee_requests.lock().unwrap().remove(&request_id)
 					{
-						let response = LSPS2FeeResponse { opening_fee_params_menu };
+						let response = LSPS2GetInfoResponse { opening_fee_params_menu };
 
 						match sender.send(response) {
 							Ok(()) => (),
@@ -1189,7 +1189,7 @@ where
 		Ok((invoice, min_prop_fee_ppm_msat))
 	}
 
-	async fn lsps2_request_opening_fee_params(&self) -> Result<LSPS2FeeResponse, Error> {
+	async fn lsps2_request_opening_fee_params(&self) -> Result<LSPS2GetInfoResponse, Error> {
 		let lsps2_client = self.lsps2_client.as_ref().ok_or(Error::LiquiditySourceUnavailable)?;
 
 		let client_handler = self.liquidity_manager.lsps2_client_handler().ok_or_else(|| {
@@ -1431,9 +1431,18 @@ type LSPS1PaymentInfo = lightning_liquidity::lsps1::msgs::LSPS1PaymentInfo;
 #[cfg(feature = "uniffi")]
 type LSPS1PaymentInfo = crate::ffi::LSPS1PaymentInfo;
 
+/// Response to an LSPS2 `get_info` request.
+///
+/// Alby: surfaced so Hub can read the LSP's min_payment_size_msat and other JIT limits.
+///
+/// See [bLIP-52 / LSPS2] for more information.
+///
+/// [bLIP-52 / LSPS2]: https://github.com/lightning/blips/blob/master/blip-0052.md
 #[derive(Debug, Clone)]
-pub(crate) struct LSPS2FeeResponse {
-	opening_fee_params_menu: Vec<LSPS2OpeningFeeParams>,
+pub struct LSPS2GetInfoResponse {
+	/// Alby: the raw LSPS2 fee menu returned by the LSP.
+	/// The set of opening fee parameters offered by the LSP.
+	pub opening_fee_params_menu: Vec<LSPS2OpeningFeeParams>,
 }
 
 #[derive(Debug, Clone)]
@@ -1446,13 +1455,13 @@ pub(crate) struct LSPS2BuyResponse {
 ///
 /// Should be retrieved by calling [`Node::lsps1_liquidity`].
 ///
-/// To open [bLIP-52 / LSPS2] JIT channels, please refer to
-/// [`Bolt11Payment::receive_via_jit_channel`].
+/// To query [bLIP-52 / LSPS2] JIT channel fees and limits, please refer to
+/// [`Node::lsps2_liquidity`].
 ///
 /// [bLIP-51 / LSPS1]: https://github.com/lightning/blips/blob/master/blip-0051.md
 /// [bLIP-52 / LSPS2]: https://github.com/lightning/blips/blob/master/blip-0052.md
 /// [`Node::lsps1_liquidity`]: crate::Node::lsps1_liquidity
-/// [`Bolt11Payment::receive_via_jit_channel`]: crate::payment::Bolt11Payment::receive_via_jit_channel
+/// [`Node::lsps2_liquidity`]: crate::Node::lsps2_liquidity
 #[derive(Clone)]
 pub struct LSPS1Liquidity {
 	runtime: Arc<Runtime>,
@@ -1540,3 +1549,82 @@ impl LSPS1Liquidity {
 		Ok(response)
 	}
 }
+
+/// A liquidity handler allowing to query [bLIP-52 / LSPS2] JIT channel parameters.
+///
+/// Should be retrieved by calling [`Node::lsps2_liquidity`].
+///
+/// Alby: this provides direct access to the LSP's opening fee menu without forcing invoice
+/// creation first.
+///
+/// To open [bLIP-52 / LSPS2] JIT channels, please refer to
+/// [`Bolt11Payment::receive_via_jit_channel`].
+///
+/// [bLIP-52 / LSPS2]: https://github.com/lightning/blips/blob/master/blip-0052.md
+/// [`Node::lsps2_liquidity`]: crate::Node::lsps2_liquidity
+/// [`Bolt11Payment::receive_via_jit_channel`]: crate::payment::Bolt11Payment::receive_via_jit_channel
+#[derive(Clone)]
+pub struct LSPS2Liquidity {
+	runtime: Arc<Runtime>,
+	connection_manager: Arc<ConnectionManager<Arc<Logger>>>,
+	liquidity_source: Option<Arc<LiquiditySource<Arc<Logger>>>>,
+	logger: Arc<Logger>,
+}
+
+impl LSPS2Liquidity {
+	pub(crate) fn new(
+		runtime: Arc<Runtime>,
+		connection_manager: Arc<ConnectionManager<Arc<Logger>>>,
+		liquidity_source: Option<Arc<LiquiditySource<Arc<Logger>>>>,
+		logger: Arc<Logger>,
+	) -> Self {
+		Self { runtime, connection_manager, liquidity_source, logger }
+	}
+
+	/// Connects to the configured LSP and requests its current JIT channel opening fee parameters.
+	///
+	/// Alby: Hub uses this to display the effective LSPS2 payment-size limits to users.
+	///
+	/// This issues an `lsps2.get_info` request and returns the LSP's `opening_fee_params_menu`.
+	pub fn request_opening_fee_params(&self) -> Result<LSPS2GetInfoResponse, Error> {
+		let liquidity_source =
+			self.liquidity_source.as_ref().ok_or(Error::LiquiditySourceUnavailable)?;
+
+		let (lsp_node_id, lsp_address) =
+			liquidity_source.get_lsps2_lsp_details().ok_or(Error::LiquiditySourceUnavailable)?;
+
+		let con_node_id = lsp_node_id;
+		let con_addr = lsp_address.clone();
+		let con_cm = Arc::clone(&self.connection_manager);
+
+		// We need to use our main runtime here as a local runtime might not be around to poll
+		// connection futures going forward.
+		self.runtime.block_on(async move {
+			con_cm.connect_peer_if_necessary(con_node_id, con_addr).await
+		})?;
+
+		log_info!(self.logger, "Connected to LSPS2 LSP {}@{}. ", lsp_node_id, lsp_address);
+
+		let liquidity_source = Arc::clone(&liquidity_source);
+		self.runtime.block_on(async move {
+			liquidity_source.lsps2_request_opening_fee_params().await
+		})
+	}
+}
+
+/// Computes the LSPS2 opening fee for a given payment size and fee parameters.
+///
+/// Alby: exported for clients that want to estimate the fee for a selected LSPS2 offer.
+///
+/// See [bLIP-52 / LSPS2] for more information.
+///
+/// [bLIP-52 / LSPS2]: https://github.com/lightning/blips/blob/master/blip-0052.md#computing-the-opening_fee
+pub fn lsps2_compute_opening_fee_msat(
+	payment_size_msat: u64, opening_fee_params: LSPS2OpeningFeeParams,
+) -> Option<u64> {
+	compute_opening_fee(
+		payment_size_msat,
+		opening_fee_params.min_fee_msat,
+		opening_fee_params.proportional as u64,
+	)
+}