From 5a54218e659f02f9aba8e46adfb10e860010f101 Mon Sep 17 00:00:00 2001
From: Valentine Wallace <vwallace@protonmail.com>
Date: Thu, 23 May 2024 10:53:53 -0400
Subject: [PATCH] WIP: Static invoice building tests

---
 lightning/src/offers/offer.rs          |  7 +++
 lightning/src/offers/static_invoice.rs | 80 ++++++++++++++++++++++++++
 2 files changed, 87 insertions(+)

diff --git a/lightning/src/offers/offer.rs b/lightning/src/offers/offer.rs
index eb9385a14d4..70149232a68 100644
--- a/lightning/src/offers/offer.rs
+++ b/lightning/src/offers/offer.rs
@@ -664,6 +664,13 @@ impl Offer {
 	pub fn expects_quantity(&self) -> bool {
 		self.contents.expects_quantity()
 	}
+
+	#[cfg(test)]
+	pub(crate) fn verify<T: secp256k1::Signing>(
+		&self, key: &ExpandedKey, secp_ctx: &Secp256k1<T>
+	) -> Result<(OfferId, Option<KeyPair>), ()> {
+		self.contents.verify(&self.bytes, key, secp_ctx)
+	}
 }
 
 macro_rules! request_invoice_derived_payer_id { ($self: ident, $builder: ty) => {
diff --git a/lightning/src/offers/static_invoice.rs b/lightning/src/offers/static_invoice.rs
index 9d0d3d83a8d..e02fbfb6425 100644
--- a/lightning/src/offers/static_invoice.rs
+++ b/lightning/src/offers/static_invoice.rs
@@ -509,3 +509,83 @@ impl TryFrom<(OfferTlvStream, InvoiceTlvStream)> for InvoiceContents {
 		})
 	}
 }
+
+#[cfg(test)]
+mod tests {
+	use super::{StaticInvoiceBuilder, DEFAULT_RELATIVE_EXPIRY};
+
+	use crate::blinded_path::{BlindedHop, BlindedPath, IntroductionNode};
+	use crate::ln::features::{Bolt12InvoiceFeatures, OfferFeatures};
+	use crate::ln::inbound_payment::ExpandedKey;
+	use crate::offers::invoice::SIGNATURE_TAG;
+	use crate::offers::merkle;
+	use crate::offers::merkle::TaggedHash;
+	use crate::offers::offer::{OfferBuilder, Quantity};
+	use crate::offers::test_utils::*;
+	use crate::sign::KeyMaterial;
+	use crate::util::ser::Writeable;
+	use bitcoin::blockdata::constants::ChainHash;
+	use bitcoin::network::constants::Network;
+	use bitcoin::secp256k1::Secp256k1;
+
+	#[test]
+	fn builds_invoice_for_offer_with_defaults() {
+		let node_id = recipient_pubkey();
+		let payment_paths = payment_paths();
+		let now = now();
+		let expanded_key = ExpandedKey::new(&KeyMaterial([42; 32]));
+		let entropy = FixedEntropy {};
+		let secp_ctx = Secp256k1::new();
+
+		let blinded_path = BlindedPath {
+			introduction_node: IntroductionNode::NodeId(pubkey(40)),
+			blinding_point: pubkey(41),
+			blinded_hops: vec![
+				BlindedHop { blinded_node_id: pubkey(42), encrypted_payload: vec![0; 43] },
+				BlindedHop { blinded_node_id: node_id, encrypted_payload: vec![0; 44] },
+			],
+		};
+
+		let offer =
+			OfferBuilder::deriving_signing_pubkey(node_id, &expanded_key, &entropy, &secp_ctx)
+				.path(blinded_path.clone())
+				.build()
+				.unwrap();
+
+		let (_offer_id, keys_opt) = offer.verify(&expanded_key, &secp_ctx).unwrap();
+		let invoice = StaticInvoiceBuilder::for_offer_using_keys(
+			&offer,
+			payment_paths.clone(),
+			now,
+			keys_opt.unwrap(),
+		)
+		.unwrap()
+		.build_and_sign(&secp_ctx)
+		.unwrap();
+
+		let mut buffer = Vec::new();
+		invoice.write(&mut buffer).unwrap();
+
+		assert_eq!(invoice.bytes, buffer.as_slice());
+		assert!(invoice.metadata().is_some());
+		assert_eq!(invoice.amount(), None);
+		assert_eq!(invoice.description(), None);
+		assert_eq!(invoice.offer_features(), &OfferFeatures::empty());
+		assert_eq!(invoice.absolute_expiry(), None);
+		assert_eq!(invoice.message_paths(), &[blinded_path]);
+		assert_eq!(invoice.issuer(), None);
+		assert_eq!(invoice.supported_quantity(), Quantity::One);
+		assert_ne!(invoice.signing_pubkey(), recipient_pubkey());
+		assert_eq!(invoice.chain(), ChainHash::using_genesis_block(Network::Bitcoin));
+		assert_eq!(invoice.payment_paths(), payment_paths.as_slice());
+		assert_eq!(invoice.created_at(), now);
+		assert_eq!(invoice.relative_expiry(), DEFAULT_RELATIVE_EXPIRY);
+		#[cfg(feature = "std")]
+		assert!(!invoice.is_expired());
+		assert_eq!(invoice.fallbacks(), vec![]);
+		assert_eq!(invoice.invoice_features(), &Bolt12InvoiceFeatures::empty());
+
+		let message = TaggedHash::from_valid_tlv_stream_bytes(SIGNATURE_TAG, &invoice.bytes);
+		assert!(merkle::verify_signature(&invoice.signature, &message, keys_opt.unwrap().public_key()).is_ok());
+	}
+}