#include <windows.h>
#define DIVISIONS 5

LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, PSTR szCmdLine, int iCmdShow)
{
	static TCHAR szAppName[] = TEXT("Click Check");
	HWND hwnd;
	MSG msg;
	WNDCLASS wndclass;

	wndclass.style = CS_HREDRAW | CS_VREDRAW;
	wndclass.lpfnWndProc = WndProc;
	wndclass.cbClsExtra = 0;
	wndclass.cbWndExtra = 0;
	wndclass.hInstance = hInstance;
	wndclass.hIcon = LoadIcon(NULL, IDI_APPLICATION);
	wndclass.hCursor = LoadCursor(NULL, IDC_ARROW);
	wndclass.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);
	wndclass.lpszMenuName = NULL;
	wndclass.lpszClassName = szAppName;

	if (!RegisterClass(&wndclass))
	{
		MessageBox(NULL, TEXT("Nie udało się zarejestrować klasy okna!"), szAppName, MB_ICONERROR);
		return 0;
	}

	hwnd = CreateWindow(szAppName, TEXT("Click Box"),
		WS_OVERLAPPEDWINDOW,
		CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT,
		NULL, NULL, hInstance, NULL);

	ShowWindow(hwnd, iCmdShow);
	UpdateWindow(hwnd);

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

LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
	static BOOL fState[DIVISIONS][DIVISIONS];
	static int cxBlock, cyBlock;
	HDC hdc;
	int x, y;
	PAINTSTRUCT ps;
	RECT rect;

	switch (msg)
	{
	case WM_SIZE:
		cxBlock = LOWORD(lParam) / DIVISIONS;
		cyBlock = HIWORD(lParam) / DIVISIONS;
		return 0;

	case WM_LBUTTONDOWN:
		x = LOWORD(lParam) / cxBlock;
		y = HIWORD(lParam) / cyBlock;

		if (x < DIVISIONS && y < DIVISIONS)
		{
			fState[x][y] ^= 1;

			rect.left = x * cxBlock;
			rect.top = y * cyBlock;
			rect.right = (x + 1) * cxBlock;
			rect.bottom = (y + 1) * cyBlock;

			InvalidateRect(hwnd, &rect, FALSE);
		}
		else
			MessageBeep(0);
		return 0;

	case WM_PAINT:
		hdc = BeginPaint(hwnd, &ps);

		for (x = 0; x < DIVISIONS; x++)
			for (y = 0; y < DIVISIONS; y++)
			{
				Rectangle(hdc, x * cxBlock, y * cyBlock, (x + 1) * cxBlock, (y + 1) * cyBlock);

				if (fState[x][y])
				{
					MoveToEx(hdc, x * cxBlock, y * cyBlock, NULL);
					LineTo(hdc, (x + 1) * cxBlock, (y + 1) * cyBlock);
					MoveToEx(hdc, x * cxBlock, (y + 1) * cyBlock, NULL);
					LineTo(hdc, (x + 1) * cxBlock, y * cyBlock);
				}
			}
		EndPaint(hwnd, &ps);
		return 0;

	case WM_DESTROY:
		PostQuitMessage(0);
		return 0;
	}
	return DefWindowProc(hwnd, msg, wParam, lParam);
}