feat(oracle): emit admin_rot event when admin is rotated (#559)

contracts/oracle/src/lib.rs

@@ -168,6 +168,7 @@ impl OracleContract {
     }
 
     /// Rotate the admin to a new address. Requires current admin auth.
+    /// Emits an `admin / admin_rot` event with `(old_admin, new_admin)`.
     ///
     /// # Errors
     /// - [`Error::Unauthorized`] — contract has not been initialized or caller is not the current admin.
@@ -180,6 +181,10 @@ impl OracleContract {
             .ok_or(Error::Unauthorized)?;
         current_admin.require_auth();
         env.storage().instance().set(&DataKey::Admin, &new_admin);
+        env.events().publish(
+            (Symbol::new(&env, "admin"), symbol_short!("admin_rot")),
+            (current_admin, new_admin),
+        );
         Ok(())
     }
 
@@ -867,4 +872,31 @@ mod tests {
         let entry = client.get_result(&0u64);
         assert_eq!(entry.result, Winner::Player1);
     }
+
+    /// Issue #559 — update_admin must emit an admin_rot event with old and new admin.
+    #[test]
+    fn test_update_admin_emits_rotation_event() {
+        let (env, contract_id, _escrow_id, old_admin, ..) = setup();
+        let client = OracleContractClient::new(&env, &contract_id);
+
+        let new_admin = Address::generate(&env);
+        client.update_admin(&new_admin);
+
+        let events = env.events().all();
+        let expected_topics = soroban_sdk::vec![
+            &env,
+            Symbol::new(&env, "admin").into_val(&env),
+            symbol_short!("admin_rot").into_val(&env),
+        ];
+        let matched = events
+            .iter()
+            .find(|(_, topics, _)| *topics == expected_topics);
+        assert!(matched.is_some(), "admin_rot event not emitted");
+
+        let (_, _, data) = matched.unwrap();
+        let (ev_old, ev_new): (Address, Address) =
+            soroban_sdk::TryFromVal::try_from_val(&env, &data).unwrap();
+        assert_eq!(ev_old, old_admin);
+        assert_eq!(ev_new, new_admin);
+    }
 }