#include <windows.h>
#include <string.h>
#include <stdio.h>

#pragma comment(lib, "user32.lib")


void TrackChildProcess(LPVOID param)
{
    while (1)
    {
        STARTUPINFO si;
        PROCESS_INFORMATION pi;
        CHAR szExePath[MAX_PATH];
        CHAR szCmdLine[MAX_PATH];
        DWORD pid = GetCurrentProcessId();

        GetModuleFileName(GetModuleHandle(NULL), szExePath, MAX_PATH);
        wsprintf(szCmdLine, "%s %d\0", szExePath, pid);

        ZeroMemory(&si, sizeof(STARTUPINFO));
        si.cb = sizeof(STARTUPINFO);
        CreateProcess(NULL,
            szCmdLine,
            NULL,
            NULL,
            FALSE,
            CREATE_NEW_CONSOLE,
            NULL,
            NULL,
            &si,
            &pi);

        WaitForSingleObject(pi.hProcess, INFINITE);
    }
}

void TrackParentProcess(LPVOID hParentProcess)
{
    STARTUPINFO si;
    PROCESS_INFORMATION pi;
    CHAR szExePath[MAX_PATH];

    WaitForSingleObject((HANDLE)hParentProcess, INFINITE);

    GetModuleFileName(GetModuleHandle(NULL), szExePath, MAX_PATH);

    ZeroMemory(&si, sizeof(STARTUPINFO));
    si.cb = sizeof(STARTUPINFO);
    CreateProcess(NULL,
        szExePath,
        NULL,
        NULL,
        FALSE,
        CREATE_NEW_CONSOLE,
        NULL,
        NULL,
        &si,
        &pi);
    ExitProcess(0);
}

void ShowMainWindow(void);

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)
{
    HANDLE hParentProcess = NULL;
    DWORD  ProcessID = 0;

    if (lpCmdLine != NULL)
        ProcessID = atoi(lpCmdLine);

    if (ProcessID == 0)
    {
        CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)TrackChildProcess, NULL, 0, NULL);
    }
    else
    {
        hParentProcess = OpenProcess(PROCESS_ALL_ACCESS, FALSE, ProcessID);
        if (hParentProcess)
        {
            CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)TrackParentProcess, (LPVOID)hParentProcess, 0, NULL);
            while (1)
            {
                Sleep(500);
            }
        }
    }

    // Main logic goes here...
    ShowMainWindow();
}

void RegisterWndClass(WNDPROC Proc, LPCTSTR szName, UINT brBackground)
{
    WNDCLASSEX wc;

    wc.cbSize = sizeof(wc);
    wc.style = CS_HREDRAW | CS_VREDRAW;
    wc.lpfnWndProc = Proc;
    wc.cbClsExtra = 0;
    wc.cbWndExtra = 0;
    wc.hInstance = GetModuleHandle(NULL);
    wc.hIcon = LoadIcon(NULL, IDI_APPLICATION);
    wc.hCursor = LoadCursor(NULL, IDC_ARROW);
    wc.hbrBackground = (HBRUSH)brBackground;
    wc.lpszMenuName = NULL;
    wc.lpszClassName = szName;
    wc.hIconSm = LoadIcon(NULL, IDI_APPLICATION);

    if (!RegisterClassEx(&wc))
    {
        MessageBox(NULL, TEXT("Cannot register class"), TEXT("Error"), MB_OK);
    }
}

LRESULT CALLBACK WndProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
    HDC hDC;
    PAINTSTRUCT ps;
    RECT rect;

    switch (uMsg)
    {
    case WM_CREATE:
        break;
    case WM_PAINT:
        hDC = BeginPaint(hWnd, &ps);
        GetClientRect(hWnd, &rect);
        EndPaint(hWnd, &ps);
        break;
    case WM_SIZE:
        break;
    case WM_CLOSE:
        DestroyWindow(hWnd);
        break;
    case WM_DESTROY:
        PostQuitMessage(0);
        break;
    default:
        return DefWindowProc(hWnd, uMsg, wParam, lParam);
    }
    return 0;
}

void ShowMainWindow(void)
{
    HWND hMainWnd;
    MSG msg;

    RegisterWndClass(WndProc, TEXT("Info"), COLOR_WINDOW);
    hMainWnd = CreateWindow(TEXT("Info"), TEXT("Info"),
        WS_CAPTION | WS_SYSMENU | WS_MINIMIZEBOX,
        CW_USEDEFAULT, 0, 250, 130, (HWND)NULL, (HMENU)NULL,
        (HINSTANCE)GetModuleHandle(NULL), NULL);

    if (!hMainWnd)
    {
        MessageBox(NULL, TEXT("Can\'t create main window."), TEXT("Error"), MB_OK);
        return GetLastError();
    }

    ShowWindow(hMainWnd, SW_SHOW);

    while (GetMessage(&msg, NULL, 0, 0))
    {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }
}