Move DefaultMessageRouter::create_blinded_paths

An upcoming change to the MessageRouter trait will require reusing
DefaultMessageRouter::create_blinded_paths. Move the code to a utility
function so facilitate this.

Author: jkczyz

lightning/src/onion_message/messenger.rs

@@ -449,50 +449,12 @@ where
 	pub fn new(network_graph: G, entropy_source: ES) -> Self {
 		Self { network_graph, entropy_source }
 	}
-}
-
-impl<G: Deref<Target=NetworkGraph<L>>, L: Deref, ES: Deref> MessageRouter for DefaultMessageRouter<G, L, ES>
-where
-	L::Target: Logger,
-	ES::Target: EntropySource,
-{
-	fn find_path(
-		&self, sender: PublicKey, peers: Vec<PublicKey>, mut destination: Destination
-	) -> Result<OnionMessagePath, ()> {
-		let network_graph = self.network_graph.deref().read_only();
-		destination.resolve(&network_graph);
-
-		let first_node = match destination.first_node() {
-			Some(first_node) => first_node,
-			None => return Err(()),
-		};
-
-		if peers.contains(&first_node) || sender == first_node {
-			Ok(OnionMessagePath {
-				intermediate_nodes: vec![], destination, first_node_addresses: None
-			})
-		} else {
-			let node_details = network_graph
-				.node(&NodeId::from_pubkey(&first_node))
-				.and_then(|node_info| node_info.announcement_info.as_ref())
-				.map(|announcement_info| (announcement_info.features(), announcement_info.addresses()));
-
-			match node_details {
-				Some((features, addresses)) if features.supports_onion_messages() && addresses.len() > 0 => {
-					let first_node_addresses = Some(addresses.clone());
-					Ok(OnionMessagePath {
-						intermediate_nodes: vec![], destination, first_node_addresses
-					})
-				},
-				_ => Err(()),
-			}
-		}
-	}
 
-	fn create_blinded_paths<
+	fn create_blinded_paths_from_iter<
+		I: Iterator<Item = ForwardNode>,
 		T: secp256k1::Signing + secp256k1::Verification
 	>(
-		&self, recipient: PublicKey, peers: Vec<ForwardNode>, secp_ctx: &Secp256k1<T>,
+		&self, recipient: PublicKey, peers: I, secp_ctx: &Secp256k1<T>,
 	) -> Result<Vec<BlindedPath>, ()> {
 		// Limit the number of blinded paths that are computed.
 		const MAX_PATHS: usize = 3;
@@ -505,7 +467,7 @@ where
 		let is_recipient_announced =
 			network_graph.nodes().contains_key(&NodeId::from_pubkey(&recipient));
 
-		let mut peer_info = peers.into_iter()
+		let mut peer_info = peers
 			// Limit to peers with announced channels
 			.filter_map(|peer|
 				network_graph
@@ -548,6 +510,53 @@ where
 	}
 }
 
+impl<G: Deref<Target=NetworkGraph<L>>, L: Deref, ES: Deref> MessageRouter for DefaultMessageRouter<G, L, ES>
+where
+	L::Target: Logger,
+	ES::Target: EntropySource,
+{
+	fn find_path(
+		&self, sender: PublicKey, peers: Vec<PublicKey>, mut destination: Destination
+	) -> Result<OnionMessagePath, ()> {
+		let network_graph = self.network_graph.deref().read_only();
+		destination.resolve(&network_graph);
+
+		let first_node = match destination.first_node() {
+			Some(first_node) => first_node,
+			None => return Err(()),
+		};
+
+		if peers.contains(&first_node) || sender == first_node {
+			Ok(OnionMessagePath {
+				intermediate_nodes: vec![], destination, first_node_addresses: None
+			})
+		} else {
+			let node_details = network_graph
+				.node(&NodeId::from_pubkey(&first_node))
+				.and_then(|node_info| node_info.announcement_info.as_ref())
+				.map(|announcement_info| (announcement_info.features(), announcement_info.addresses()));
+
+			match node_details {
+				Some((features, addresses)) if features.supports_onion_messages() && addresses.len() > 0 => {
+					let first_node_addresses = Some(addresses.clone());
+					Ok(OnionMessagePath {
+						intermediate_nodes: vec![], destination, first_node_addresses
+					})
+				},
+				_ => Err(()),
+			}
+		}
+	}
+
+	fn create_blinded_paths<
+		T: secp256k1::Signing + secp256k1::Verification
+	>(
+		&self, recipient: PublicKey, peers: Vec<ForwardNode>, secp_ctx: &Secp256k1<T>,
+	) -> Result<Vec<BlindedPath>, ()> {
+		self.create_blinded_paths_from_iter(recipient, peers.into_iter(), secp_ctx)
+	}
+}
+
 /// A path for sending an [`OnionMessage`].
 #[derive(Clone)]
 pub struct OnionMessagePath {