Separate Connection, ConnectionHandler, Server

src/connection_handler.hpp

@@ -0,0 +1,72 @@
+#pragma once
+
+#include <memory>
+#include <string_view>
+
+// Forward declaration to avoid circular dependency
+struct Connection;
+
+enum class ProcessResult {
+  Continue,       // Keep connection open, continue processing
+  CloseAfterSend, // Send response then close connection
+  CloseNow        // Close connection immediately
+};
+
+/**
+ * Abstract interface for handling connection data processing.
+ *
+ * This interface decouples protocol-specific logic (HTTP, WebSocket, etc.)
+ * from the underlying networking infrastructure. Implementations handle
+ * parsing incoming data and generating appropriate responses.
+ *
+ * The networking layer manages connection lifecycle, I/O multiplexing,
+ * and efficient data transfer, while handlers focus purely on protocol logic.
+ */
+class ConnectionHandler {
+public:
+  virtual ~ConnectionHandler() = default;
+
+  /**
+   * Process incoming data from a connection.
+   *
+   * @param data Incoming data buffer (may be partial message)
+   * @param conn_ptr Unique pointer to connection - handler can take ownership
+   * by releasing it
+   * @return ProcessResult indicating how to handle the connection
+   *
+   * Implementation should:
+   * - Parse incoming data using arena allocator when needed
+   * - Use conn_ptr->appendMessage() to queue response data
+   * - Return appropriate ProcessResult for connection management
+   * - Handle partial messages and streaming protocols appropriately
+   * - Can take ownership by calling conn_ptr.release() to pass to other threads
+   * - If ownership is taken, handler must call conn->releaseBackToServer() when
+   * done
+   */
+  virtual ProcessResult process_data(std::string_view data,
+                                     std::unique_ptr<Connection> &conn_ptr) = 0;
+
+  /**
+   * Called when a new connection is established.
+   *
+   * @param conn Newly established connection
+   *
+   * Use this for:
+   * - Connection-specific initialization
+   * - Sending greeting messages
+   * - Setting up connection state
+   */
+  virtual void on_connection_established(Connection &) {}
+
+  /**
+   * Called when a connection is about to be closed.
+   *
+   * @param conn Connection being closed
+   *
+   * Use this for:
+   * - Cleanup of connection-specific resources
+   * - Logging connection statistics
+   * - Finalizing protocol state
+   */
+  virtual void on_connection_closed(Connection &) {}
+};