Fiix fee-spent inscription track (ordinals#1971)

Assign inscriptions spent as fees to the correct
sat in the coinbase output.

---------

Co-authored-by: Greg Martin <[email protected]>
Co-authored-by: raphjaph <[email protected]>

src/index.rs

@@ -1588,7 +1588,7 @@ mod tests {
   }
 
   #[test]
-  fn fee_spent_inscriptions_are_tracked_correctly() {
+  fn one_input_fee_spent_inscriptions_are_tracked_correctly() {
     for context in Context::configurations() {
       context.mine_blocks(1);
 
@@ -1623,6 +1623,42 @@ mod tests {
     }
   }
 
+  #[test]
+  fn two_input_fee_spent_inscriptions_are_tracked_correctly() {
+    for context in Context::configurations() {
+      context.mine_blocks(2);
+
+      let txid = context.rpc_server.broadcast_tx(TransactionTemplate {
+        inputs: &[(1, 0, 0)],
+        witness: inscription("text/plain", "hello").to_witness(),
+        ..Default::default()
+      });
+      let inscription_id = InscriptionId::from(txid);
+
+      context.mine_blocks(1);
+
+      context.rpc_server.broadcast_tx(TransactionTemplate {
+        inputs: &[(2, 0, 0), (3, 1, 0)],
+        fee: 50 * COIN_VALUE,
+        ..Default::default()
+      });
+
+      let coinbase_tx = context.mine_blocks(1)[0].txdata[0].txid();
+
+      context.index.assert_inscription_location(
+        inscription_id,
+        SatPoint {
+          outpoint: OutPoint {
+            txid: coinbase_tx,
+            vout: 0,
+          },
+          offset: 50 * COIN_VALUE,
+        },
+        50 * COIN_VALUE,
+      );
+    }
+  }
+
   #[test]
   fn inscription_can_be_fee_spent_in_first_transaction() {
     for context in Context::configurations() {

src/index/updater/inscription_updater.rs

@@ -178,7 +178,7 @@ impl<'a, 'db, 'tx> InscriptionUpdater<'a, 'db, 'tx> {
       Ok(self.reward - output_value)
     } else {
       self.flotsam.extend(inscriptions.map(|flotsam| Flotsam {
-        offset: self.reward + flotsam.offset,
+        offset: self.reward + flotsam.offset - output_value,
         ..flotsam
       }));
       self.reward += input_value - output_value;