Implement and test Refund flow

bindings/ldk_node.udl

@@ -109,6 +109,10 @@ interface Bolt12Payment {
 	Offer receive(u64 amount_msat, [ByRef]string description);
 	[Throws=NodeError]
 	Offer receive_variable_amount([ByRef]string description);
+	[Throws=NodeError]
+	Bolt12Invoice request_refund([ByRef]Refund refund);
+	[Throws=NodeError]
+	Refund create_refund(u64 amount_msat, u32 expiry_secs);
 };
 
 interface SpontaneousPayment {
@@ -136,6 +140,7 @@ enum NodeError {
 	"InvoiceCreationFailed",
 	"InvoiceRequestCreationFailed",
 	"OfferCreationFailed",
+	"RefundCreationFailed",
 	"PaymentSendingFailed",
 	"ProbeSendingFailed",
 	"ChannelCreationFailed",
@@ -161,6 +166,7 @@ enum NodeError {
 	"InvalidAmount",
 	"InvalidInvoice",
 	"InvalidOffer",
+	"InvalidRefund",
 	"InvalidChannelId",
 	"InvalidNetwork",
 	"DuplicatePayment",
@@ -393,6 +399,12 @@ typedef string Bolt11Invoice;
 [Custom]
 typedef string Offer;
 
+[Custom]
+typedef string Refund;
+
+[Custom]
+typedef string Bolt12Invoice;
+
 [Custom]
 typedef string OfferId;
 

src/error.rs

@@ -17,6 +17,8 @@ pub enum Error {
 	InvoiceRequestCreationFailed,
 	/// Offer creation failed.
 	OfferCreationFailed,
+	/// Refund creation failed.
+	RefundCreationFailed,
 	/// Sending a payment has failed.
 	PaymentSendingFailed,
 	/// Sending a payment probe has failed.
@@ -67,6 +69,8 @@ pub enum Error {
 	InvalidInvoice,
 	/// The given offer is invalid.
 	InvalidOffer,
+	/// The given refund is invalid.
+	InvalidRefund,
 	/// The given channel ID is invalid.
 	InvalidChannelId,
 	/// The given network is invalid.
@@ -95,6 +99,7 @@ impl fmt::Display for Error {
 			Self::InvoiceCreationFailed => write!(f, "Failed to create invoice."),
 			Self::InvoiceRequestCreationFailed => write!(f, "Failed to create invoice request."),
 			Self::OfferCreationFailed => write!(f, "Failed to create offer."),
+			Self::RefundCreationFailed => write!(f, "Failed to create refund."),
 			Self::PaymentSendingFailed => write!(f, "Failed to send the given payment."),
 			Self::ProbeSendingFailed => write!(f, "Failed to send the given payment probe."),
 			Self::ChannelCreationFailed => write!(f, "Failed to create channel."),
@@ -122,6 +127,7 @@ impl fmt::Display for Error {
 			Self::InvalidAmount => write!(f, "The given amount is invalid."),
 			Self::InvalidInvoice => write!(f, "The given invoice is invalid."),
 			Self::InvalidOffer => write!(f, "The given offer is invalid."),
+			Self::InvalidRefund => write!(f, "The given refund is invalid."),
 			Self::InvalidChannelId => write!(f, "The given channel ID is invalid."),
 			Self::InvalidNetwork => write!(f, "The given network is invalid."),
 			Self::DuplicatePayment => {

src/payment/bolt12.rs

@@ -11,12 +11,15 @@ use crate::payment::store::{
 use crate::types::ChannelManager;
 
 use lightning::ln::channelmanager::{PaymentId, Retry};
+use lightning::offers::invoice::Bolt12Invoice;
 use lightning::offers::offer::{Amount, Offer};
 use lightning::offers::parse::Bolt12SemanticError;
+use lightning::offers::refund::Refund;
 
 use rand::RngCore;
 
 use std::sync::{Arc, RwLock};
+use std::time::{Duration, SystemTime, UNIX_EPOCH};
 
 /// A payment handler allowing to create and pay [BOLT 12] offers and refunds.
 ///
@@ -264,4 +267,82 @@ impl Bolt12Payment {
 
 		Ok(offer)
 	}
+
+	/// Requests a refund payment for the given [`Refund`].
+	///
+	/// The returned [`Bolt12Invoice`] is for informational purposes only (i.e., isn't needed to
+	/// retrieve the refund).
+	pub fn request_refund(&self, refund: &Refund) -> Result<Bolt12Invoice, Error> {
+		let invoice = self.channel_manager.request_refund_payment(refund).map_err(|e| {
+			log_error!(self.logger, "Failed to request refund payment: {:?}", e);
+			Error::InvoiceRequestCreationFailed
+		})?;
+
+		let payment_hash = invoice.payment_hash();
+		let payment_id = PaymentId(payment_hash.0);
+
+		let payment = PaymentDetails {
+			id: payment_id,
+			kind: PaymentKind::Bolt12Refund {
+				hash: Some(payment_hash),
+				preimage: None,
+				secret: None,
+			},
+			amount_msat: Some(refund.amount_msats()),
+			direction: PaymentDirection::Inbound,
+			status: PaymentStatus::Pending,
+		};
+
+		self.payment_store.insert(payment)?;
+
+		Ok(invoice)
+	}
+
+	/// Returns a [`Refund`] object that can be used to offer a refund payment of the amount given.
+	pub fn create_refund(&self, amount_msat: u64, expiry_secs: u32) -> Result<Refund, Error> {
+		let mut random_bytes = [0u8; 32];
+		rand::thread_rng().fill_bytes(&mut random_bytes);
+		let payment_id = PaymentId(random_bytes);
+
+		let expiration = (SystemTime::now() + Duration::from_secs(expiry_secs as u64))
+			.duration_since(UNIX_EPOCH)
+			.unwrap();
+		let retry_strategy = Retry::Timeout(LDK_PAYMENT_RETRY_TIMEOUT);
+		let max_total_routing_fee_msat = None;
+
+		let refund = self
+			.channel_manager
+			.create_refund_builder(
+				amount_msat,
+				expiration,
+				payment_id,
+				retry_strategy,
+				max_total_routing_fee_msat,
+			)
+			.map_err(|e| {
+				log_error!(self.logger, "Failed to create refund builder: {:?}", e);
+				Error::RefundCreationFailed
+			})?
+			.build()
+			.map_err(|e| {
+				log_error!(self.logger, "Failed to create refund: {:?}", e);
+				Error::RefundCreationFailed
+			})?;
+
+		log_info!(self.logger, "Offering refund of {}msat", amount_msat);
+
+		let kind = PaymentKind::Bolt12Refund { hash: None, preimage: None, secret: None };
+
+		let payment = PaymentDetails {
+			id: payment_id,
+			kind,
+			amount_msat: Some(amount_msat),
+			direction: PaymentDirection::Outbound,
+			status: PaymentStatus::Pending,
+		};
+
+		self.payment_store.insert(payment)?;
+
+		Ok(refund)
+	}
 }

src/uniffi_types.rs

@@ -2,7 +2,9 @@ pub use crate::payment::store::{LSPFeeLimits, PaymentDirection, PaymentKind, Pay
 
 pub use lightning::events::{ClosureReason, PaymentFailureReason};
 pub use lightning::ln::{ChannelId, PaymentHash, PaymentPreimage, PaymentSecret};
+pub use lightning::offers::invoice::Bolt12Invoice;
 pub use lightning::offers::offer::{Offer, OfferId};
+pub use lightning::offers::refund::Refund;
 pub use lightning::util::string::UntrustedString;
 
 pub use lightning_invoice::Bolt11Invoice;
@@ -21,6 +23,7 @@ use bitcoin::hashes::sha256::Hash as Sha256;
 use bitcoin::hashes::Hash;
 use bitcoin::secp256k1::PublicKey;
 use lightning::ln::channelmanager::PaymentId;
+use lightning::util::ser::Writeable;
 use lightning_invoice::SignedRawBolt11Invoice;
 
 use std::convert::TryInto;
@@ -88,6 +91,35 @@ impl UniffiCustomTypeConverter for Offer {
 	}
 }
 
+impl UniffiCustomTypeConverter for Refund {
+	type Builtin = String;
+
+	fn into_custom(val: Self::Builtin) -> uniffi::Result<Self> {
+		Refund::from_str(&val).map_err(|_| Error::InvalidRefund.into())
+	}
+
+	fn from_custom(obj: Self) -> Self::Builtin {
+		obj.to_string()
+	}
+}
+
+impl UniffiCustomTypeConverter for Bolt12Invoice {
+	type Builtin = String;
+
+	fn into_custom(val: Self::Builtin) -> uniffi::Result<Self> {
+		if let Some(bytes_vec) = hex_utils::to_vec(&val) {
+			if let Ok(invoice) = Bolt12Invoice::try_from(bytes_vec) {
+				return Ok(invoice);
+			}
+		}
+		Err(Error::InvalidInvoice.into())
+	}
+
+	fn from_custom(obj: Self) -> Self::Builtin {
+		hex_utils::to_string(&obj.encode())
+	}
+}
+
 impl UniffiCustomTypeConverter for OfferId {
 	type Builtin = String;
 

tests/integration_tests_rust.rs

@@ -487,4 +487,47 @@ fn simple_bolt12_send_receive() {
 		},
 	}
 	assert_eq!(node_b_payments.first().unwrap().amount_msat, Some(expected_amount_msat));
+
+	// Now node_b refunds the amount node_a just overpaid.
+	let overpaid_amount = expected_amount_msat - offer_amount_msat;
+	let refund = node_b.bolt12_payment().create_refund(overpaid_amount, 3600).unwrap();
+	let invoice = node_a.bolt12_payment().request_refund(&refund).unwrap();
+	expect_payment_received_event!(node_a, overpaid_amount);
+
+	let node_b_payment_id = node_b
+		.list_payments_with_filter(|p| p.amount_msat == Some(overpaid_amount))
+		.first()
+		.unwrap()
+		.id;
+	expect_payment_successful_event!(node_b, Some(node_b_payment_id), None);
+
+	let node_b_payments = node_b.list_payments_with_filter(|p| p.id == node_b_payment_id);
+	assert_eq!(node_b_payments.len(), 1);
+	match node_b_payments.first().unwrap().kind {
+		PaymentKind::Bolt12Refund { hash, preimage, secret: _ } => {
+			assert!(hash.is_some());
+			assert!(preimage.is_some());
+			//TODO: We should eventually set and assert the secret sender-side, too, but the BOLT12
+			//API currently doesn't allow to do that.
+		},
+		_ => {
+			panic!("Unexpected payment kind");
+		},
+	}
+	assert_eq!(node_b_payments.first().unwrap().amount_msat, Some(overpaid_amount));
+
+	let node_a_payment_id = PaymentId(invoice.payment_hash().0);
+	let node_a_payments = node_a.list_payments_with_filter(|p| p.id == node_a_payment_id);
+	assert_eq!(node_a_payments.len(), 1);
+	match node_a_payments.first().unwrap().kind {
+		PaymentKind::Bolt12Refund { hash, preimage, secret } => {
+			assert!(hash.is_some());
+			assert!(preimage.is_some());
+			assert!(secret.is_some());
+		},
+		_ => {
+			panic!("Unexpected payment kind");
+		},
+	}
+	assert_eq!(node_a_payments.first().unwrap().amount_msat, Some(overpaid_amount));
 }