Add on_write_buffer_drained

src/server.cpp

@@ -485,6 +485,7 @@ void Server::process_connection_writes(std::unique_ptr<Connection> &conn,
   // Send immediately if we have outgoing messages (either from EPOLLOUT or
   // after reading)
   if ((events & EPOLLOUT) || ((events & EPOLLIN) && conn->hasMessages())) {
+    bool had_messages = conn->hasMessages();
     bool error = conn->writeBytes();
     if (error) {
       conn.reset(); // Connection should be closed
@@ -499,8 +500,17 @@ void Server::process_connection_writes(std::unique_ptr<Connection> &conn,
       return;
     }
 
+    // Check if buffer became empty (transition from non-empty -> empty)
+    if (had_messages && !conn->hasMessages()) {
+      handler_.on_write_buffer_drained(conn);
+      // If handler took ownership (conn is now null), return
+      if (!conn) {
+        return;
+      }
+    }
+
     // Check if we should close the connection according to application
-    if (!conn->hasMessages() && conn->closeConnection_) {
+    if (!conn->hasMessages() && conn->shouldClose()) {
       conn.reset(); // Connection should be closed
       return;
     }