Add DebugServer for fgdbg with support for Websockets (#6169)

* Add dummy DebugServer for fgdbg with support for Websockets

* PR feedback

filament/src/details/Engine.cpp

@@ -646,6 +646,16 @@ int FEngine::loop() {
     uint32_t id = std::thread::hardware_concurrency() - 1;
 
     while (true) {
+#if FILAMENT_ENABLE_FGDBG
+        // TODO (@feresr): Only for testing purposes, remove
+        if (debug.fgdbg) {
+            static int fgdbgMessage = 0;
+            fgdbgMessage++;
+            if (fgdbgMessage % 100 == 0) {
+                debug.fgdbg->sendMessage(fgdbgMessage/100);
+            }
+        }
+#endif
         // looks like thread affinity needs to be reset regularly (on Android)
         JobSystem::setThreadAffinityById(id);
         if (!execute()) {

libs/fgdbg/CMakeLists.txt

@@ -17,6 +17,6 @@ set(SRCS src/DebugServer.cpp)
 # ==================================================================================================
 
 add_library(${TARGET} STATIC ${PUBLIC_HDRS} ${SRCS})
-target_link_libraries(${TARGET} PUBLIC utils)
+target_link_libraries(${TARGET} PUBLIC civetweb utils)
 target_include_directories(${TARGET} PUBLIC ${PUBLIC_HDR_DIR})
 include_directories(${PUBLIC_HDR_DIR})

libs/fgdbg/include/fgdbg/DebugServer.h

@@ -17,15 +17,26 @@
 #ifndef FGDBG_DEBUGSERVER_H
 #define FGDBG_DEBUGSERVER_H
 
-namespace filament {
-namespace fgdbg {
+class CivetServer;
+
+namespace filament::fgdbg {
 
 class DebugServer {
 public:
     DebugServer();
     ~DebugServer();
+
+    void sendMessage(int number);
+
+private:
+    CivetServer* mServer;
+
+    class RestRequestHandler *mRestRequestHandler = nullptr;
+    class WebSocketHandler* mWebSocketHandler = nullptr;
+
+    friend class RestRequestHandler;
+    friend class WebSocketHandler;
 };
 }
-}
 
 #endif  // FGDBG_DEBUGSERVER_H

libs/fgdbg/src/DebugServer.cpp

@@ -15,16 +15,96 @@
  */
 
 #include "fgdbg/DebugServer.h"
+#include <CivetServer.h>
 #include <utils/Log.h>
+#include <tsl/robin_set.h>
+
+namespace filament::fgdbg {
 
 using namespace utils;
-namespace filament::fgdbg {
+
+static const std::string_view kSuccessHeader =
+        "HTTP/1.1 200 OK\r\nContent-Type: %s\r\n"
+        "Connection: close\r\n\r\n";
+
+class RestRequestHandler : public CivetHandler {
+
+public:
+    RestRequestHandler() = default;
+
+    bool handleGet(CivetServer *server, struct mg_connection *conn) override {
+        mg_printf(conn, kSuccessHeader.data(), "application/json");
+        mg_printf(conn, "{ RestRequestHandler is working! }");
+        return true;
+    }
+};
+
+class WebSocketHandler : public CivetWebSocketHandler {
+
+public:
+    WebSocketHandler() = default;
+
+    bool handleConnection(CivetServer *server, const struct mg_connection *conn) override {
+        return true;
+    }
+
+    void handleReadyState(CivetServer *server, struct mg_connection *conn) override {
+        mConnections.insert(conn);
+    }
+
+    void handleClose(CivetServer *server, const struct mg_connection *conn) override {
+        auto *key = const_cast<struct mg_connection *>(conn);
+        mConnections.erase(key);
+    }
+
+    void send(int number) {
+        auto string = std::to_string(number);
+        for (auto connection : mConnections) {
+            mg_websocket_write(connection,
+                    MG_WEBSOCKET_OPCODE_TEXT,
+                    string.c_str(),
+                    string.length());
+        }
+    }
+
+private:
+    tsl::robin_set<struct mg_connection*> mConnections;
+};
 
 DebugServer::DebugServer() {
     slog.d << "FrameGraph debug server created" << io::endl;
+
+    //TODO (@feresr): Make port param customizable
+    const char* kServerOptions[] = {
+            "listening_ports", "8082",
+            "num_threads", "10",
+            "error_log_file", "civetweb.txt",
+            nullptr
+    };
+
+    mServer = new CivetServer(kServerOptions);
+    if (!mServer->getContext()) {
+        delete mServer;
+        mServer = nullptr;
+        slog.e << "Unable to start fgdbg DebugServer, see civetweb.txt for details." << io::endl;
+        return;
+    }
+    slog.i << "Server started successfully" << io::endl;
+
+    mRestRequestHandler = new RestRequestHandler();
+    mWebSocketHandler = new WebSocketHandler();
+
+    mServer->addHandler("", mRestRequestHandler);
+    mServer->addWebSocketHandler("", mWebSocketHandler);
+}
+
+void DebugServer::sendMessage(int number) {
+    mWebSocketHandler->send(number);
 }
 
 DebugServer::~DebugServer() {
     slog.d << "FrameGraph debug server destroyed" << io::endl;
+    delete mRestRequestHandler;
+    delete mWebSocketHandler;
 }
 }