feat(*): add log file and message loop

Redcraft.FocusIME/Source/Private/Main.cpp

@@ -1,28 +1,104 @@
-#include <windows.h>
+#include "Defines.h"
+
+#include <windows.h>
 #include <iostream>
+#include <fstream>
 #include <thread>
 #include <chrono>
+#include <string>
+#include <filesystem>
+#include <ctime>
+#include <iomanip>
+#include <mutex>
 
 #pragma warning(disable: 4996)
 
 // ReSharper disable CppDeprecatedEntity
 // ReSharper disable CppClangTidyCertErr33C
 
+std::ofstream GLogFile;
+
+void PrintLog(const std::string& Text)
+{
+	const auto Now  = std::chrono::system_clock::now();
+	const auto Time = std::chrono::system_clock::to_time_t(Now);
+
+	const long long Milliseconds = (std::chrono::duration_cast<std::chrono::milliseconds>(Now.time_since_epoch()) % 1000).count();
+
+	static std::mutex Mutex; std::lock_guard Lock(Mutex);
+
+	const std::tm* LocalTime = std::localtime(&Time); // NOLINT(concurrency-mt-unsafe)
+
+	char Buffer[] = "[2025-06-21 20:05:04.305]: ";
+
+	std::strftime(&Buffer[1], 20, "%Y-%m-%d %H:%M:%S", LocalTime);
+
+	Buffer[20] = '.';
+
+	constexpr char Digits[] = "0123456789";
+
+	Buffer[21] = Digits[Milliseconds / 100 % 10];
+	Buffer[22] = Digits[Milliseconds /  10 % 10];
+	Buffer[23] = Digits[Milliseconds /   1 % 10];
+
+	GLogFile << Buffer << Text << std::endl;
+}
+
 int WINAPI WinMain(HINSTANCE, HINSTANCE, LPSTR, int)
 {
 	using namespace std::chrono_literals;
 
-	AllocConsole();
+	const HANDLE Mutex = CreateMutex(nullptr, TRUE, "FocusIME_SingleInstance_Mutex");
 
-	freopen("CONOUT$", "w", stdout);
+	if (Mutex == nullptr)
+	{
+		MessageBox(nullptr, "Failed to create mutex.", "FocusIME", MB_OK | MB_ICONERROR);
 
-	SetConsoleTitle("FocusIME");
+		return 1;
+	}
 
-	std::cout << "Hello, FocusIME!" << std::endl;
+	if (GetLastError() == ERROR_ALREADY_EXISTS)
+	{
+		MessageBox(nullptr, "FocusIME is already running.", "FocusIME", MB_OK | MB_ICONINFORMATION);
 
-	std::this_thread::sleep_for(3s);
+		CloseHandle(Mutex);
 
-	FreeConsole();
+		return 0;
+	}
+
+	GLogFile.open("Log.txt", std::ios::out | std::ios::app);
+
+	if (!GLogFile.is_open())
+	{
+		MessageBox(nullptr, "Failed to open log file.", "FocusIME", MB_OK | MB_ICONERROR);
+
+		CloseHandle(Mutex);
+
+		return 1;
+	}
+
+	PrintLog("FocusIME started successfully");
+
+	MSG Message = { };
+
+	while (true)
+	{
+		BOOL bResult = GetMessage(&Message, nullptr, 0, 0);
+
+		if (bResult > 0)
+		{
+			TranslateMessage(&Message);
+			DispatchMessage (&Message);
+		}
+
+		else break;
+	}
+
+	PrintLog("FocusIME is shutting down...");
+
+	GLogFile.close();
+
+	CloseHandle(Mutex);
 
 	return 0;
 }