Add /r/tx/<txid> (#4147)

docs/src/guides/api.md

@@ -5129,4 +5129,4 @@ curl -s -H "Accept: application/json" \
 
 See [Recursion](../inscriptions/recursion.md) for an explanation of these.
 
-{{#include ../inscriptions/recursion.md:35:3429}}
+{{#include ../inscriptions/recursion.md:35:3483}}

docs/src/inscriptions/recursion.md

@@ -3399,6 +3399,30 @@ Hello, world!
 
 </details>
 
+<details>
+  <summary>
+    <code>GET</code>
+    <code><b>/r/tx/&lt;TRANSACTION_ID&gt;</b></code>
+  </summary>
+
+### Description
+
+Get hex-encoded transaction with `<TRANSACTION_ID>`. In the event of a future
+change to Bitcoin that changes transaction serialization in a
+backwards-incompatible fashion, such as SegWit, this endpoint is guaranteed to
+remain backwards compatible.
+
+### Example
+
+```bash
+curl -s http://0.0.0.0:80/r/tx/60bcf821240064a9c55225c4f01711b0ebbcab39aa3fafeefe4299ab158536fa
+```
+
+```json
+"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"
+```
+</details>
+
 <details>
   <summary>
     <code>GET</code>

src/index.rs

@@ -1615,6 +1615,19 @@ impl Index {
     self.client.get_raw_transaction(&txid, None).into_option()
   }
 
+  pub fn get_transaction_hex_recursive(&self, txid: Txid) -> Result<Option<String>> {
+    if txid == self.genesis_block_coinbase_txid {
+      return Ok(Some(consensus::encode::serialize_hex(
+        &self.genesis_block_coinbase_transaction,
+      )));
+    }
+
+    self
+      .client
+      .get_raw_transaction_hex(&txid, None)
+      .into_option()
+  }
+
   pub fn find(&self, sat: Sat) -> Result<Option<SatPoint>> {
     let sat = sat.0;
     let rtx = self.begin_read()?;

src/subcommand/server.rs

@@ -263,6 +263,7 @@ impl Server {
           "/r/parents/{inscription_id}/{page}",
           get(Self::parents_recursive_paginated),
         )
+        .route("/r/tx/{txid}", get(Self::get_transaction_hex_recursive))
         .route("/r/sat/{sat_number}", get(Self::sat_inscriptions))
         .route(
           "/r/sat/{sat_number}/at/{index}",
@@ -1195,6 +1196,19 @@ impl Server {
     })
   }
 
+  async fn get_transaction_hex_recursive(
+    Extension(index): Extension<Arc<Index>>,
+    Path(txid): Path<Txid>,
+  ) -> ServerResult<Json<String>> {
+    task::block_in_place(|| {
+      Ok(Json(
+        index
+          .get_transaction_hex_recursive(txid)?
+          .ok_or_not_found(|| format!("transaction {txid}"))?,
+      ))
+    })
+  }
+
   async fn decode(
     Extension(index): Extension<Arc<Index>>,
     Path(txid): Path<Txid>,
@@ -4519,6 +4533,33 @@ mod tests {
     );
   }
 
+  #[test]
+  fn recursive_transaction_hex_endpoint() {
+    let test_server = TestServer::new();
+
+    let coinbase_tx = test_server.mine_blocks(1)[0].txdata[0].clone();
+    let txid = coinbase_tx.compute_txid();
+
+    test_server.assert_response(
+      format!("/r/tx/{txid}"),
+      StatusCode::OK,
+      "\"02000000010000000000000000000000000000000000000000000000000000000000000000ffffffff0151ffffffff0100f2052a01000000225120be7cbbe9ca06a7d7b2a17c6b4ff4b85b362cbcd7ee1970daa66dfaa834df59a000000000\""
+    );
+  }
+
+  #[test]
+  fn recursive_transaction_hex_endpoint_for_genesis_transaction() {
+    let test_server = TestServer::new();
+
+    test_server.mine_blocks(1);
+
+    test_server.assert_response(
+      "/r/tx/4a5e1e4baab89f3a32518a88c31bc87f618f76673e2cc77ab2127b7afdeda33b",
+      StatusCode::OK,
+      "\"01000000010000000000000000000000000000000000000000000000000000000000000000ffffffff4d04ffff001d0104455468652054696d65732030332f4a616e2f32303039204368616e63656c6c6f72206f6e206272696e6b206f66207365636f6e64206261696c6f757420666f722062616e6b73ffffffff0100f2052a01000000434104678afdb0fe5548271967f1a67130b7105cd6a828e03909a67962e0ea1f61deb649f6bc3f4cef38c4f35504e51ec112de5c384df7ba0b8d578a4c702b6bf11d5fac00000000\""
+    );
+  }
+
   #[test]
   fn detect_unrecoverable_reorg() {
     let test_server = TestServer::new();