From 112828f548b3e67dec163acdaaa1923dbc5fa90c Mon Sep 17 00:00:00 2001
From: Arik <arik-so@users.noreply.github.com>
Date: Mon, 24 Feb 2025 16:22:37 -0800
Subject: [PATCH] Proxy `/r/sat/{sat}/at/{index}` endpoint (#4022)

---
 src/subcommand/server.rs | 101 ++++++++++++++++++++++++++++++++++-----
 1 file changed, 90 insertions(+), 11 deletions(-)

diff --git a/src/subcommand/server.rs b/src/subcommand/server.rs
index 1ccc556bcb..40e63e5fc6 100644
--- a/src/subcommand/server.rs
+++ b/src/subcommand/server.rs
@@ -79,6 +79,10 @@ struct Search {
 #[folder = "static"]
 struct StaticAssets;
 
+lazy_static! {
+  static ref SAT_AT_INDEX_PATH: Regex = Regex::new(r"^/r/sat/[^/]+/at/[^/]+$").unwrap();
+}
+
 #[derive(Debug, Parser, Clone)]
 pub struct Server {
   #[arg(
@@ -273,7 +277,6 @@ impl Server {
           get(r::parent_inscriptions_paginated),
         )
         .route("/r/sat/{sat_number}", get(r::sat))
-        .route("/r/sat/{sat_number}/at/{index}", get(r::sat_at_index))
         .route("/r/sat/{sat_number}/{page}", get(r::sat_paginated))
         .route("/r/tx/{txid}", get(r::tx))
         .route(
@@ -291,11 +294,12 @@ impl Server {
         )
         .route("/r/inscription/{inscription_id}", get(r::inscription))
         .route("/r/metadata/{inscription_id}", get(r::metadata))
+        .route("/r/sat/{sat_number}/at/{index}", get(r::sat_at_index))
         .route(
           "/r/sat/{sat_number}/at/{index}/content",
           get(r::sat_at_index_content),
         )
-        .layer(axum::middleware::from_fn(Self::proxy_fallback));
+        .layer(axum::middleware::from_fn(Self::proxy_layer));
 
       let router = router.merge(proxiable_routes);
 
@@ -529,22 +533,37 @@ impl Server {
     Ok(acceptor)
   }
 
-  async fn proxy_fallback(
-    Extension(server_config): Extension<Arc<ServerConfig>>,
+  async fn proxy_layer(
+    server_config: Extension<Arc<ServerConfig>>,
     request: http::Request<axum::body::Body>,
     next: axum::middleware::Next,
   ) -> ServerResult {
-    let mut path = request.uri().path().to_string();
-
-    path.remove(0); // remove leading slash
+    let path = request.uri().path().to_owned();
 
     let response = next.run(request).await;
-    let status = response.status();
 
-    if let Some(proxy) = server_config.proxy.as_ref() {
-      if status == StatusCode::NOT_FOUND {
+    if let Some(proxy) = &server_config.proxy {
+      if response.status() == StatusCode::NOT_FOUND {
         return task::block_in_place(|| Server::proxy(proxy, &path));
       }
+
+      // `/r/sat/<SAT_NUMBER>/at/<INDEX>` does not return a 404 when no
+      // inscription is present, so we must deserialize and check the body.
+      if SAT_AT_INDEX_PATH.is_match(&path) {
+        let (parts, body) = response.into_parts();
+
+        let bytes = axum::body::to_bytes(body, usize::MAX)
+          .await
+          .map_err(|err| anyhow!(err))?;
+
+        if let Ok(api::SatInscription { id: None }) =
+          serde_json::from_slice::<api::SatInscription>(&bytes)
+        {
+          return task::block_in_place(|| Server::proxy(proxy, &path));
+        }
+
+        return Ok(Response::from_parts(parts, axum::body::Body::from(bytes)));
+      }
     }
 
     Ok(response)
@@ -1856,7 +1875,7 @@ impl Server {
 
   fn proxy(proxy: &Url, path: &str) -> ServerResult<Response> {
     let response = reqwest::blocking::Client::new()
-      .get(format!("{}{}", proxy, path))
+      .get(format!("{}{}", proxy, &path[1..]))
       .send()
       .map_err(|err| anyhow!(err))?;
 
@@ -7039,6 +7058,66 @@ next
     );
   }
 
+  #[test]
+  fn sat_at_index_proxy() {
+    let server = TestServer::builder()
+      .index_sats()
+      .chain(Chain::Regtest)
+      .build();
+
+    server.mine_blocks(1);
+
+    let inscription = Inscription {
+      content_type: Some("text/html".into()),
+      body: Some("foo".into()),
+      ..default()
+    };
+
+    let txid = server.core.broadcast_tx(TransactionTemplate {
+      inputs: &[(1, 0, 0, inscription.to_witness())],
+      ..default()
+    });
+
+    server.mine_blocks(1);
+
+    let id = InscriptionId { txid, index: 0 };
+    let ordinal: u64 = 5000000000;
+
+    pretty_assert_eq!(
+      server.get_json::<api::SatInscription>(format!("/r/sat/{ordinal}/at/-1")),
+      api::SatInscription { id: Some(id) }
+    );
+
+    let server_with_proxy = TestServer::builder()
+      .chain(Chain::Regtest)
+      .server_option("--proxy", server.url.as_ref())
+      .build();
+    let sat_indexed_server_with_proxy = TestServer::builder()
+      .index_sats()
+      .chain(Chain::Regtest)
+      .server_option("--proxy", server.url.as_ref())
+      .build();
+
+    server_with_proxy.mine_blocks(1);
+    sat_indexed_server_with_proxy.mine_blocks(1);
+
+    pretty_assert_eq!(
+      server.get_json::<api::SatInscription>(format!("/r/sat/{ordinal}/at/-1")),
+      api::SatInscription { id: Some(id) }
+    );
+
+    pretty_assert_eq!(
+      server_with_proxy.get_json::<api::SatInscription>(format!("/r/sat/{ordinal}/at/-1")),
+      api::SatInscription { id: Some(id) }
+    );
+
+    pretty_assert_eq!(
+      sat_indexed_server_with_proxy
+        .get_json::<api::SatInscription>(format!("/r/sat/{ordinal}/at/-1")),
+      api::SatInscription { id: Some(id) }
+    );
+  }
+
   #[test]
   fn sat_at_index_content_proxy() {
     let server = TestServer::builder()