Implemented the real server

src/game_server/NetworkProtocol.cpp

@@ -0,0 +1,46 @@
+#include "NetworkProtocol.h"
+#include <exception>
+
+namespace FRG {
+
+std::string makeStateMessage(const nlohmann::json& state)
+{
+	return nlohmann::json{
+		{"protocolVersion", kGameProtocolVersion},
+		{"type", "state"},
+		{"payload", state}
+	}.dump();
+}
+
+bool parseStateMessage(
+	const std::string& message, nlohmann::json& state,
+	std::string& error)
+{
+	try {
+		const nlohmann::json envelope = nlohmann::json::parse(message);
+		if (!envelope.is_object()) {
+			error = "message must be a JSON object";
+			return false;
+		}
+		if (envelope.value("protocolVersion", -1) != kGameProtocolVersion) {
+			error = "unsupported protocol version";
+			return false;
+		}
+		if (envelope.value("type", std::string()) != "state") {
+			error = "unsupported message type";
+			return false;
+		}
+		if (!envelope.contains("payload") || !envelope["payload"].is_object()) {
+			error = "state payload must be an object";
+			return false;
+		}
+		state = envelope["payload"];
+		error.clear();
+		return true;
+	} catch (const std::exception& exception) {
+		error = exception.what();
+		return false;
+	}
+}
+
+} // namespace FRG