feat: Add Bolt12Invoice wrapper for FFI bindings

Implement Bolt12Invoice struct in uniffi_types to provide a wrapper around LDK's Bolt12Invoice for cross-language bindings.

Modified payment handling in bolt12.rs to:
- Support both native and FFI-compatible types via type aliasing
- Implement conditional compilation for transparent FFI support
- Update payment functions to handle wrapped types

Added testing to verify that properties are preserved when wrapping/unwrapping between native and FFI types.

Author: alexanderwiederin

bindings/ldk_node.udl

@@ -767,6 +767,31 @@ interface Refund {
 	string? payer_note();
 };
 
+interface Bolt12Invoice {
+	[Throws=NodeError, Name=from_str]
+	constructor([ByRef] string invoice_str);
+	PaymentHash payment_hash();
+	u64 amount_msats();
+	Amount? amount();
+	PublicKey signing_pubkey();
+	u64 created_at();
+	u64? absolute_expiry_seconds();
+	u64 relative_expiry();
+	boolean is_expired();
+	string? description();
+	string? issuer();
+	string? payer_note();
+	sequence<u8>? metadata();
+	u64? quantity();
+	sequence<u8> signable_hash();
+	PublicKey payer_signing_pubkey();
+	PublicKey? issuer_signing_pubkey();
+	sequence<u8> chain();
+	sequence<sequence<u8>>? offer_chains();
+	sequence<Address> fallback_addresses();
+	sequence<u8> encode();
+};
+
 [Custom]
 typedef string Txid;
 
@@ -785,9 +810,6 @@ typedef string NodeId;
 [Custom]
 typedef string Address;
 
-[Custom]
-typedef string Bolt12Invoice;
-
 [Custom]
 typedef string OfferId;
 

src/payment/bolt12.rs

@@ -16,7 +16,7 @@ use crate::payment::store::{PaymentDetails, PaymentDirection, PaymentKind, Payme
 use crate::types::{ChannelManager, PaymentStore};
 
 use lightning::ln::channelmanager::{PaymentId, Retry};
-use lightning::offers::invoice::Bolt12Invoice;
+use lightning::offers::invoice::Bolt12Invoice as LdkBolt12Invoice;
 use lightning::offers::offer::{Amount, Offer as LdkOffer, Quantity};
 use lightning::offers::parse::Bolt12SemanticError;
 use lightning::offers::refund::Refund as LdkRefund;
@@ -28,6 +28,20 @@ use std::num::NonZeroU64;
 use std::sync::{Arc, RwLock};
 use std::time::{Duration, SystemTime, UNIX_EPOCH};
 
+#[cfg(not(feature = "uniffi"))]
+type Bolt12Invoice = LdkBolt12Invoice;
+#[cfg(feature = "uniffi")]
+type Bolt12Invoice = Arc<crate::uniffi_types::Bolt12Invoice>;
+
+#[cfg(not(feature = "uniffi"))]
+fn maybe_wrap_bolt12_invoice(invoice: LdkBolt12Invoice) -> Bolt12Invoice {
+	invoice
+}
+#[cfg(feature = "uniffi")]
+fn maybe_wrap_bolt12_invoice(invoice: LdkBolt12Invoice) -> Bolt12Invoice {
+	Arc::new(invoice.into())
+}
+
 #[cfg(not(feature = "uniffi"))]
 type Offer = LdkOffer;
 #[cfg(feature = "uniffi")]
@@ -376,6 +390,7 @@ impl Bolt12Payment {
 	/// retrieve the refund).
 	///
 	/// [`Refund`]: lightning::offers::refund::Refund
+	/// [`Bolt12Invoice`]: lightning::offers::invoice::Bolt12Invoice
 	pub fn request_refund_payment(&self, refund: &Refund) -> Result<Bolt12Invoice, Error> {
 		let refund = maybe_convert_refund(refund);
 		let invoice = self.channel_manager.request_refund_payment(refund).map_err(|e| {
@@ -405,7 +420,7 @@ impl Bolt12Payment {
 
 		self.payment_store.insert(payment)?;
 
-		Ok(invoice)
+		Ok(maybe_wrap_bolt12_invoice(invoice))
 	}
 
 	/// Returns a [`Refund`] object that can be used to offer a refund payment of the amount given.