Scaffold C++20 screencast project with Meson, agent workflow, and phase plan

include/screencast/network/signaling.h

@@ -0,0 +1,47 @@
+#pragma once
+
+#include "screencast/network/transport.h"
+
+#include <functional>
+#include <memory>
+#include <string>
+
+namespace sc {
+
+// JSON-based control messages exchanged before or during a session.
+struct SessionOffer {
+    std::string session_id;
+    std::string codec_name;
+    int width = 0;
+    int height = 0;
+    int frame_rate_num = 30;
+    int frame_rate_den = 1;
+    Endpoint rtp_endpoint;
+};
+
+struct SessionAnswer {
+    std::string session_id;
+    Endpoint rtp_endpoint;
+};
+
+using SignalingMessage = std::variant<SessionOffer, SessionAnswer>;
+
+class SignalingChannel {
+  public:
+    using MessageCallback = std::function<void ( const SignalingMessage & )>;
+
+    virtual ~SignalingChannel () = default;
+
+    virtual bool connect ( const Endpoint &server ) = 0;
+    virtual void send ( const SignalingMessage &message ) = 0;
+    virtual void on_message ( MessageCallback callback ) = 0;
+    virtual void disconnect () = 0;
+};
+
+class SignalingFactory {
+  public:
+    static std::unique_ptr<SignalingChannel> create_websocket_client ();
+    static std::unique_ptr<SignalingChannel> create_websocket_server ( uint16_t port );
+};
+
+}  // namespace sc