Add ability to send payjoin transactions.

Implements the payjoin sender part as describe in BIP77.

This would allow the on chain wallet linked to LDK node to send payjoin
transactions.

Cargo.toml

@@ -68,6 +68,7 @@ tokio = { version = "1", default-features = false, features = [ "rt-multi-thread
 esplora-client = { version = "0.6", default-features = false }
 libc = "0.2"
 uniffi = { version = "0.26.0", features = ["build"], optional = true }
+payjoin = { version = "0.15.0", features = ["send", "receive", "v2"] }
 
 [target.'cfg(vss)'.dependencies]
 vss-client = "0.2"

bindings/ldk_node.udl

@@ -151,6 +151,12 @@ enum NodeError {
 	"InsufficientFunds",
 	"LiquiditySourceUnavailable",
 	"LiquidityFeeTooHigh",
+	"PayjoinSenderUnavailable",
+	"PayjoinUriNetworkMismatch",
+	"PayjoinRequestMissingAmount",
+	"PayjoinRequestCreationFailed",
+	"PayjoinResponseProcessingFailed",
+	"PayjoinRequestTimeout",
 };
 
 dictionary NodeStatus {

src/builder.rs

@@ -16,7 +16,7 @@ use crate::peer_store::PeerStore;
 use crate::tx_broadcaster::TransactionBroadcaster;
 use crate::types::{
 	ChainMonitor, ChannelManager, DynStore, GossipSync, KeysManager, MessageRouter, NetworkGraph,
-	OnionMessenger, PeerManager,
+	OnionMessenger, PayjoinSender, PeerManager,
 };
 use crate::wallet::Wallet;
 use crate::{LogLevel, Node};
@@ -94,6 +94,11 @@ struct LiquiditySourceConfig {
 	lsps2_service: Option<(SocketAddress, PublicKey, Option<String>)>,
 }
 
+#[derive(Debug, Clone)]
+struct PayjoinSenderConfig {
+	payjoin_relay: String,
+}
+
 impl Default for LiquiditySourceConfig {
 	fn default() -> Self {
 		Self { lsps2_service: None }
@@ -173,6 +178,7 @@ pub struct NodeBuilder {
 	chain_data_source_config: Option<ChainDataSourceConfig>,
 	gossip_source_config: Option<GossipSourceConfig>,
 	liquidity_source_config: Option<LiquiditySourceConfig>,
+	payjoin_sender_config: Option<PayjoinSenderConfig>,
 }
 
 impl NodeBuilder {
@@ -188,12 +194,14 @@ impl NodeBuilder {
 		let chain_data_source_config = None;
 		let gossip_source_config = None;
 		let liquidity_source_config = None;
+		let payjoin_sender_config = None;
 		Self {
 			config,
 			entropy_source_config,
 			chain_data_source_config,
 			gossip_source_config,
 			liquidity_source_config,
+			payjoin_sender_config,
 		}
 	}
 
@@ -248,6 +256,12 @@ impl NodeBuilder {
 		self
 	}
 
+	/// Configures the [`Node`] instance to enable sending payjoin transactions.
+	pub fn set_payjoin_sender_config(&mut self, payjoin_relay: String) -> &mut Self {
+		self.payjoin_sender_config = Some(PayjoinSenderConfig { payjoin_relay });
+		self
+	}
+
 	/// Configures the [`Node`] instance to source its inbound liquidity from the given
 	/// [LSPS2](https://github.com/BitcoinAndLightningLayerSpecs/lsp/blob/main/LSPS2/README.md)
 	/// service.
@@ -366,6 +380,7 @@ impl NodeBuilder {
 			self.chain_data_source_config.as_ref(),
 			self.gossip_source_config.as_ref(),
 			self.liquidity_source_config.as_ref(),
+			self.payjoin_sender_config.as_ref(),
 			seed_bytes,
 			logger,
 			vss_store,
@@ -387,6 +402,7 @@ impl NodeBuilder {
 			self.chain_data_source_config.as_ref(),
 			self.gossip_source_config.as_ref(),
 			self.liquidity_source_config.as_ref(),
+			self.payjoin_sender_config.as_ref(),
 			seed_bytes,
 			logger,
 			kv_store,
@@ -454,6 +470,11 @@ impl ArcedNodeBuilder {
 		self.inner.write().unwrap().set_gossip_source_p2p();
 	}
 
+	/// Configures the [`Node`] instance to enable sending payjoin transactions.
+	pub fn set_payjoin_sender_config(&self, payjoin_relay: String) {
+		self.inner.write().unwrap().set_payjoin_sender_config(payjoin_relay);
+	}
+
 	/// Configures the [`Node`] instance to source its gossip data from the given RapidGossipSync
 	/// server.
 	pub fn set_gossip_source_rgs(&self, rgs_server_url: String) {
@@ -522,7 +543,8 @@ impl ArcedNodeBuilder {
 fn build_with_store_internal(
 	config: Arc<Config>, chain_data_source_config: Option<&ChainDataSourceConfig>,
 	gossip_source_config: Option<&GossipSourceConfig>,
-	liquidity_source_config: Option<&LiquiditySourceConfig>, seed_bytes: [u8; 64],
+	liquidity_source_config: Option<&LiquiditySourceConfig>,
+	payjoin_sender_config: Option<&PayjoinSenderConfig>, seed_bytes: [u8; 64],
 	logger: Arc<FilesystemLogger>, kv_store: Arc<DynStore>,
 ) -> Result<Node, BuildError> {
 	// Initialize the on-chain wallet and chain access
@@ -974,6 +996,20 @@ fn build_with_store_internal(
 
 	let (stop_sender, _) = tokio::sync::watch::channel(());
 
+	let payjoin_sender = payjoin_sender_config.as_ref().and_then(|psc| {
+		if let Ok(payjoin_relay) = payjoin::Url::parse(&psc.payjoin_relay) {
+			Some(Arc::new(PayjoinSender::new(
+				Arc::clone(&logger),
+				Arc::clone(&wallet),
+				Arc::clone(&tx_broadcaster),
+				payjoin_relay,
+			)))
+		} else {
+			log_info!(logger, "The provided payjoin relay URL is invalid.");
+			None
+		}
+	});
+
 	let is_listening = Arc::new(AtomicBool::new(false));
 	let latest_wallet_sync_timestamp = Arc::new(RwLock::new(None));
 	let latest_onchain_wallet_sync_timestamp = Arc::new(RwLock::new(None));
@@ -993,6 +1029,7 @@ fn build_with_store_internal(
 		channel_manager,
 		chain_monitor,
 		output_sweeper,
+		payjoin_sender,
 		peer_manager,
 		connection_manager,
 		keys_manager,

src/error.rs

@@ -71,6 +71,18 @@ pub enum Error {
 	LiquiditySourceUnavailable,
 	/// The given operation failed due to the LSP's required opening fee being too high.
 	LiquidityFeeTooHigh,
+	/// Failed to access payjoin sender object.
+	PayjoinSenderUnavailable,
+	/// Payjoin URI network mismatch.
+	PayjoinUriNetworkMismatch,
+	/// Amount is neither user-provided nor defined in the URI.
+	PayjoinRequestMissingAmount,
+	/// Failed to build a payjoin request.
+	PayjoinRequestCreationFailed,
+	/// Payjoin response processing failed.
+	PayjoinResponseProcessingFailed,
+	/// Payjoin request timed out.
+	PayjoinRequestTimeout,
 }
 
 impl fmt::Display for Error {
@@ -122,6 +134,24 @@ impl fmt::Display for Error {
 			Self::LiquidityFeeTooHigh => {
 				write!(f, "The given operation failed due to the LSP's required opening fee being too high.")
 			},
+			Self::PayjoinSenderUnavailable => {
+				write!(f, "Failed to access payjoin sender object. Make sure you have enabled Payjoin sending support.")
+			},
+			Self::PayjoinRequestMissingAmount => {
+				write!(f, "Amount is neither user-provided nor defined in the URI.")
+			},
+			Self::PayjoinRequestCreationFailed => {
+				write!(f, "Failed construct a payjoin request. Make sure the provided URI is valid and the configured Payjoin relay is available.")
+			},
+			Self::PayjoinUriNetworkMismatch => {
+				write!(f, "The Provided Payjoin URI does not match the node network.")
+			},
+			Self::PayjoinResponseProcessingFailed => {
+				write!(f, "Payjoin receiver responded to our request with an invalid response that was ignored. Notice they can still broadcast the original PSBT we shared with them")
+			},
+			Self::PayjoinRequestTimeout => {
+				write!(f, "Payjoin receiver did not respond to our request within the timeout period. Notice they can still broadcast the original PSBT we shared with them")
+			},
 		}
 	}
 }

src/lib.rs

@@ -88,6 +88,7 @@ pub mod io;
 mod liquidity;
 mod logger;
 mod message_handler;
+mod payjoin_sender;
 pub mod payment;
 mod peer_store;
 mod sweep;
@@ -101,6 +102,7 @@ pub use bip39;
 pub use bitcoin;
 pub use lightning;
 pub use lightning_invoice;
+pub use payjoin::Uri;
 
 pub use balance::{BalanceDetails, LightningBalance, PendingSweepBalance};
 pub use config::{default_config, Config};
@@ -130,11 +132,11 @@ use event::{EventHandler, EventQueue};
 use gossip::GossipSource;
 use liquidity::LiquiditySource;
 use payment::store::PaymentStore;
-use payment::{Bolt11Payment, OnchainPayment, PaymentDetails, SpontaneousPayment};
+use payment::{Bolt11Payment, OnchainPayment, PayjoinPayment, PaymentDetails, SpontaneousPayment};
 use peer_store::{PeerInfo, PeerStore};
 use types::{
 	Broadcaster, ChainMonitor, ChannelManager, DynStore, FeeEstimator, KeysManager, NetworkGraph,
-	PeerManager, Router, Scorer, Sweeper, Wallet,
+	PayjoinSender, PeerManager, Router, Scorer, Sweeper, Wallet,
 };
 pub use types::{ChannelDetails, PeerDetails, UserChannelId};
 
@@ -181,6 +183,7 @@ pub struct Node {
 	output_sweeper: Arc<Sweeper>,
 	peer_manager: Arc<PeerManager>,
 	connection_manager: Arc<ConnectionManager<Arc<FilesystemLogger>>>,
+	payjoin_sender: Option<Arc<PayjoinSender>>,
 	keys_manager: Arc<KeysManager>,
 	network_graph: Arc<NetworkGraph>,
 	gossip_source: Arc<GossipSource>,
@@ -891,6 +894,36 @@ impl Node {
 		))
 	}
 
+	/// Returns a payment handler allowing to send and receive on-chain payments.
+	#[cfg(not(feature = "uniffi"))]
+	pub fn payjoin_payment(&self) -> Result<PayjoinPayment, Error> {
+		self.payjoin_sender.as_ref().map_or_else(
+			|| Err(Error::PayjoinSenderUnavailable),
+			|ps| {
+				Ok(PayjoinPayment::new(
+					Arc::clone(&self.runtime),
+					ps.clone(),
+					Arc::clone(&self.config),
+				))
+			},
+		)
+	}
+
+	/// Returns a payment handler allowing to send and receive on-chain payments.
+	#[cfg(feature = "uniffi")]
+	pub fn payjoin_payment(&self) -> Result<PayjoinPayment, Error> {
+		self.payjoin_sender.as_ref().map_or_else(
+			|| Err(Error::PayjoinSenderUnavailable),
+			|ps| {
+				Ok(PayjoinPayment::new(
+					Arc::clone(&self.runtime),
+					ps.clone(),
+					Arc::clone(&self.config),
+				))
+			},
+		)
+	}
+
 	/// 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()