HTTP server API changes for improved extensibility (#684)

* refactored `HttpServer` so all subclass member functions are proctected, to make it easier to extend base functionality
* added API service, can be used to enumerate registered endpoints (at `/api`). Currently only very basic information is provided

2 files changed, 37 insertions, 5 deletions

diff --git a/src/zenhttp/include/zenhttp/httpapiservice.h b/src/zenhttp/include/zenhttp/httpapiservice.h
new file mode 100644
index 000000000..0270973bf
--- /dev/null
+++ b/src/zenhttp/include/zenhttp/httpapiservice.h
@@ -0,0 +1,21 @@
+// Copyright Epic Games, Inc. All Rights Reserved.
+
+#include <zenhttp/httpserver.h>
+
+namespace zen {
+
+class HttpApiService : public HttpService
+{
+public:
+	HttpApiService(HttpServer& Server);
+	~HttpApiService() override;
+
+	const char* BaseUri() const override;
+	void		HandleRequest(HttpServerRequest& HttpServiceRequest) override;
+
+private:
+	HttpServer&		  m_Server;
+	HttpRequestRouter m_Router;
+};
+
+}  // namespace zen
diff --git a/src/zenhttp/include/zenhttp/httpserver.h b/src/zenhttp/include/zenhttp/httpserver.h
index f95ec51d2..9e5c41ab7 100644
--- a/src/zenhttp/include/zenhttp/httpserver.h
+++ b/src/zenhttp/include/zenhttp/httpserver.h
@@ -175,11 +175,22 @@ private:
 class HttpServer : public RefCounted
 {
 public:
-	virtual void RegisterService(HttpService& Service)					 = 0;
-	virtual int	 Initialize(int BasePort, std::filesystem::path DataDir) = 0;
-	virtual void Run(bool IsInteractiveSession)							 = 0;
-	virtual void RequestExit()											 = 0;
-	virtual void Close()												 = 0;
+	void RegisterService(HttpService& Service);
+	void EnumerateServices(std::function<void(HttpService&)>&& Callback);
+
+	int	 Initialize(int BasePort, std::filesystem::path DataDir);
+	void Run(bool IsInteractiveSession);
+	void RequestExit();
+	void Close();
+
+private:
+	std::vector<HttpService*> m_KnownServices;
+
+	virtual void OnRegisterService(HttpService& Service)				   = 0;
+	virtual int	 OnInitialize(int BasePort, std::filesystem::path DataDir) = 0;
+	virtual void OnRun(bool IsInteractiveSession)						   = 0;
+	virtual void OnRequestExit()										   = 0;
+	virtual void OnClose()												   = 0;
 };
 
 struct HttpServerPluginConfig