Add payjoin sender

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 +151,8 @@ enum NodeError {
 	"InsufficientFunds",
 	"LiquiditySourceUnavailable",
 	"LiquidityFeeTooHigh",
+	"PayjoinSender",
+	"PayjoinRequestAmountMissing"
 };
 
 dictionary NodeStatus {

src/builder.rs

@@ -11,6 +11,7 @@ use crate::io::sqlite_store::SqliteStore;
 use crate::liquidity::LiquiditySource;
 use crate::logger::{log_error, log_info, FilesystemLogger, Logger};
 use crate::message_handler::NodeCustomMessageHandler;
+use crate::payjoin_sender::PayjoinSender;
 use crate::payment::store::PaymentStore;
 use crate::peer_store::PeerStore;
 use crate::tx_broadcaster::TransactionBroadcaster;
@@ -94,6 +95,11 @@ struct LiquiditySourceConfig {
 	lsps2_service: Option<(SocketAddress, PublicKey, Option<String>)>,
 }
 
+#[derive(Debug, Clone)]
+struct PayjoinSenderConfig {
+	payjoin_relay: payjoin::Url,
+}
+
 impl Default for LiquiditySourceConfig {
 	fn default() -> Self {
 		Self { lsps2_service: None }
@@ -173,6 +179,7 @@ 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 +195,14 @@ 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 +257,12 @@ impl NodeBuilder {
 		self
 	}
 
+	/// Configures the [`Node`] instance to enable sending payjoin transactions.
+	pub fn set_payjoin_sender_config(&mut self, payjoin_relay: payjoin::Url) -> &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.
@@ -369,6 +384,7 @@ impl NodeBuilder {
 			seed_bytes,
 			logger,
 			vss_store,
+			self.payjoin_sender_config.as_ref(),
 		)
 	}
 
@@ -390,6 +406,7 @@ impl NodeBuilder {
 			seed_bytes,
 			logger,
 			kv_store,
+			self.payjoin_sender_config.as_ref(),
 		)
 	}
 }
@@ -454,6 +471,11 @@ 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: payjoin::Url) {
+		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) {
@@ -524,6 +546,7 @@ fn build_with_store_internal(
 	gossip_source_config: Option<&GossipSourceConfig>,
 	liquidity_source_config: Option<&LiquiditySourceConfig>, seed_bytes: [u8; 64],
 	logger: Arc<FilesystemLogger>, kv_store: Arc<DynStore>,
+	payjoin_sender_config: Option<&PayjoinSenderConfig>,
 ) -> Result<Node, BuildError> {
 	// Initialize the on-chain wallet and chain access
 	let xprv = bitcoin::bip32::ExtendedPrivKey::new_master(config.network.into(), &seed_bytes)
@@ -973,6 +996,16 @@ fn build_with_store_internal(
 	};
 
 	let (stop_sender, _) = tokio::sync::watch::channel(());
+	let payjoin_sender = if let Some(payjoin_sender_config) = payjoin_sender_config {
+		let payjoin_sender = PayjoinSender::new(
+			Arc::clone(&logger),
+			Arc::clone(&wallet),
+			&payjoin_sender_config.payjoin_relay,
+		);
+		Some(Arc::new(payjoin_sender))
+	} else {
+		None
+	};
 
 	let is_listening = Arc::new(AtomicBool::new(false));
 	let latest_wallet_sync_timestamp = Arc::new(RwLock::new(None));
@@ -993,6 +1026,7 @@ fn build_with_store_internal(
 		channel_manager,
 		chain_monitor,
 		output_sweeper,
+		payjoin_sender,
 		peer_manager,
 		connection_manager,
 		keys_manager,

src/error.rs

@@ -71,6 +71,10 @@ pub enum Error {
 	LiquiditySourceUnavailable,
 	/// The given operation failed due to the LSP's required opening fee being too high.
 	LiquidityFeeTooHigh,
+	/// Amount is not prvoided and neither defined in the URI.
+	PayjoinRequestAmountMissing,
+	/// Payjoin errors
+	PayjoinSender,
 }
 
 impl fmt::Display for Error {
@@ -122,6 +126,10 @@ 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::PayjoinSender => write!(f, "Failed to send payjoin."),
+			Self::PayjoinRequestAmountMissing => {
+				write!(f, "Amount is not provided and neither defined in the URI.")
+			},
 		}
 	}
 }

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;
@@ -99,6 +100,7 @@ mod wallet;
 
 pub use bip39;
 pub use bitcoin;
+use bitcoin::address::NetworkChecked;
 pub use lightning;
 pub use lightning_invoice;
 
@@ -108,6 +110,7 @@ pub use error::Error as NodeError;
 use error::Error;
 
 pub use event::Event;
+use payjoin_sender::PayjoinSender;
 pub use types::ChannelConfig;
 
 pub use io::utils::generate_entropy_mnemonic;
@@ -181,6 +184,7 @@ pub struct Node {
 	output_sweeper: Arc<Sweeper>,
 	peer_manager: Arc<PeerManager>,
 	connection_manager: Arc<ConnectionManager<Arc<FilesystemLogger>>>,
+	payjoin_sender: Option<Arc<PayjoinSender<Arc<FilesystemLogger>>>>,
 	keys_manager: Arc<KeysManager>,
 	network_graph: Arc<NetworkGraph>,
 	gossip_source: Arc<GossipSource>,
@@ -697,6 +701,65 @@ impl Node {
 		Ok(())
 	}
 
+	/// This method can be used to send a payjoin transaction as defined
+	/// in BIP77.
+	///
+	/// The method will construct an `Original PSBT` from the data
+	/// provided in the `payjoin_uri` and `amount` parameters. The
+	/// amount must be set either in the `payjoin_uri` or in the
+	/// `amount` parameter. If the amount is set in both, the paramter
+	/// amount parameter will be used.
+	///
+	/// After constructing the `Original PSBT`, the method will
+	/// extract the payjoin request data from the `Original PSBT`
+	/// utilising the `payjoin` crate.
+	///
+	/// Then we start a background process to that will run for 1
+	/// hour, polling the payjoin endpoint every 10 seconds. If an `OK` (ie status code == 200)
+	/// is received, polling will stop and we will try to process the
+	/// response from the payjoin receiver. If the response(or `Payjoin Proposal`) is valid, we will finalise the
+	/// transaction and broadcast it to the network.
+	///
+	/// Notice that the `Txid` returned from this method is the
+	/// `Original PSBT` transaction id, but the `Payjoin Proposal`
+	/// transaction id could be different if the receiver changed the
+	/// transaction.
+	pub async fn send_payjoin_transaction(
+		&self, payjoin_uri: payjoin::Uri<'static, NetworkChecked>, amount: Option<bitcoin::Amount>,
+	) -> Result<Option<bitcoin::Txid>, Error> {
+		let rt_lock = self.runtime.read().unwrap();
+		if rt_lock.is_none() {
+			return Err(Error::NotRunning);
+		}
+		let payjoin_sender = Arc::clone(self.payjoin_sender.as_ref().ok_or(Error::PayjoinSender)?);
+		let original_psbt = payjoin_sender.create_payjoin_request(payjoin_uri.clone(), amount)?;
+		let txid = original_psbt.clone().unsigned_tx.txid();
+		let (request, context) =
+			payjoin_sender.extract_request_data(payjoin_uri, original_psbt.clone())?;
+
+		let time = std::time::Instant::now();
+		let runtime = rt_lock.as_ref().unwrap();
+		runtime.spawn(async move {
+			let response = payjoin_sender.poll(&request, time).await;
+			if let Some(response) = response {
+				let psbt = context.process_response(&mut response.as_slice());
+				match psbt {
+					Ok(Some(psbt)) => {
+						let finalized =
+							payjoin_sender.finalise_payjoin_tx(psbt, original_psbt.clone());
+						if let Ok(txid) = finalized {
+							let txid: bitcoin::Txid = txid.into();
+							return Some(txid);
+						}
+					},
+					_ => return None,
+				}
+			}
+			None
+		});
+		Ok(Some(txid))
+	}
+
 	/// Disconnects all peers, stops all running background tasks, and shuts down [`Node`].
 	///
 	/// After this returns most API methods will return [`Error::NotRunning`].