From 22018014cac2cdb5f57ffdb22d86f86d5dbd1900 Mon Sep 17 00:00:00 2001
From: Jesse de Wit <witdejesse@hotmail.com>
Date: Tue, 8 Apr 2025 16:30:11 +0200
Subject: [PATCH] put route hints in email

---
 src/email.rs        | 28 +++++++++++++++++++++++++++-
 src/htlc_manager.rs |  1 +
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/src/email.rs b/src/email.rs
index 0c61cc6..088758a 100644
--- a/src/email.rs
+++ b/src/email.rs
@@ -4,6 +4,7 @@ use aws_sdk_sesv2::{
     types::{Body, Content, Destination, EmailContent, Message},
     Client,
 };
+use lightning_invoice::RouteHint;
 #[cfg(test)]
 use mockall::automock;
 use secp256k1::{hashes::sha256, PublicKey};
@@ -12,21 +13,37 @@ use tracing::{debug, error, warn};
 pub struct NotifyPaymentFailedRequest {
     pub destination: PublicKey,
     pub error: anyhow::Error,
+    pub hints: Vec<RouteHint>,
     pub payment_hash: sha256::Hash,
     pub invoice: String,
 }
 
 impl NotifyPaymentFailedRequest {
     pub fn to_html(&self) -> impl Into<String> {
+        let hints: Vec<_> = self
+            .hints
+            .iter()
+            .filter_map(|r| r.0.last())
+            .enumerate()
+            .map(|(i, hint)| {
+                format!(
+                    "<tr><td>Route hint {}: {}, {}</td></tr>",
+                    i,
+                    hint.src_node_id,
+                    scid_to_string(hint.short_channel_id),
+                )
+            })
+            .collect();
         format!(
             "
             <table>
-                <tr><td>Destination: {}</td></tr>
+                <tr><td>Destination: {}</td></tr>{}
                 <tr><td>Error: {}</td></tr>
                 <tr><td>Payment hash: {}</td></tr>
                 <tr><td>Invoice: {}</td></tr>
             </table>",
             self.destination,
+            hints.join(""),
             self.error
                 .to_string()
                 .replace("&", "&amp;")
@@ -41,6 +58,15 @@ impl NotifyPaymentFailedRequest {
     }
 }
 
+fn scid_to_string(scid: u64) -> String {
+    format!(
+        "{}x{}x{}",
+        scid >> 40,
+        (scid >> 16) & 0xFFFFFF,
+        scid & 0xFFFF
+    )
+}
+
 #[cfg_attr(test, automock)]
 #[async_trait::async_trait]
 pub trait NotificationService {
diff --git a/src/htlc_manager.rs b/src/htlc_manager.rs
index d98cd21..0590019 100644
--- a/src/htlc_manager.rs
+++ b/src/htlc_manager.rs
@@ -652,6 +652,7 @@ async fn payment_lifecycle<B, N, P, S>(
                 .notify_payment_failed(NotifyPaymentFailedRequest {
                     destination: trampoline.payee,
                     error: e,
+                    hints: trampoline.invoice.route_hints(),
                     payment_hash: *trampoline.invoice.payment_hash(),
                     invoice: trampoline.bolt11,
                 })