// Autor: Krzysztof Zajączkowski
// www.algorytm.org

#include <windows.h>

#include <math.h>

class dPoint2D{
	  double x;
	  double y;
public:
	   dPoint2D(double x,double y);
	   
	   dPoint2D operator -(dPoint2D p);
	   dPoint2D operator +(dPoint2D p);
	   dPoint2D operator *(double k);
	   double operator *(dPoint2D p);
	   double SickDistance2D(dPoint2D p);
	   double Length();
	   dPoint2D GetPointOnLine(dPoint2D &fP,dPoint2D &lP);
	   
	   double X();
	   double Y();
	   void X(double x);
	   void Y(double y);
};

dPoint2D::dPoint2D(double x,double y){
	this->x = x;
	this->y = y;
}

double dPoint2D::X(){
     return x;
}
double dPoint2D::Y(){
     return y;
}
void dPoint2D::Y(double y){
	 this->y = y;
}
void dPoint2D::X(double x){
	 this->x = x;
}

dPoint2D dPoint2D::operator *(double k){
     dPoint2D temp(x * k,y * k);
     return temp;
}

double dPoint2D::operator *(dPoint2D p){
	return p.X() * x + p.Y() * y;
}

double dPoint2D::SickDistance2D(dPoint2D p){
	   return pow(x - p.X(),2.0) + pow(y - p.Y(),2.0);
}

double dPoint2D::Length(){
	return sqrt(x * x + y * y);
}

dPoint2D dPoint2D::operator -(dPoint2D p){
     dPoint2D temp(this->x - p.X(),this->y - p.Y());
     return temp;
}

dPoint2D dPoint2D::operator +(dPoint2D p){
     dPoint2D temp(this->x + p.X(),this->y + p.Y());
     return temp;
}

dPoint2D dPoint2D::GetPointOnLine(dPoint2D &fP,dPoint2D &lP){
	 //double u = ((x - fP.X()) * (lP.X() - fP.X()) + (y - fP.Y()) * (lP.Y() - fP.Y())) / (lP.SickDistance2D(fP));
	double u = (((*this) - fP) * (lP - fP))/ ((fP - lP) * (fP - lP));
	return fP + (lP - fP) * u;
}

LRESULT CALLBACK WndProc(HWND hWnd,UINT msg,WPARAM wParam,LPARAM lParam){
	static dPoint2D v1(20,300); // Punkty linii L1
	static dPoint2D v2(300,20);
	static dPoint2D v3(500,500); // Punkty linii L2
	static dPoint2D v4(100,100);
	static dPoint2D v5(0,0);	// Punkt przecięcia
	static POINT MousePos;

	static dPoint2D *pt = NULL;
	switch(msg)
	{
		case WM_CREATE:
			{
				dPoint2D v6(0,0);
				v6 = v1 + v4 - v3;

				dPoint2D v7(0,0);
				dPoint2D v8(0,0);

				v7 = v6.GetPointOnLine(v1,v2);
				v8 = v4.GetPointOnLine(v1,v2);
				
				double v4v5_length = (v6 - v1).Length() / (v6 - v7).Length() * (v8 - v4).Length();

				dPoint2D v9(0,0);

				v9 = v8.GetPointOnLine(v3,v4);

				v5 = (v9 - v4) * (v4v5_length / (v4 - v9).Length());

				double l = v5.Length();

				v5 = v5 + v4;
			}
			break;
	 	case WM_PAINT:
		{
			PAINTSTRUCT ps;
            HDC hdc = BeginPaint(hWnd,&ps);
            HPEN hPen = CreatePen(PS_SOLID,2,RGB(0,0,255));

			SelectObject(hdc,hPen);

			MoveToEx(hdc,(int)v1.X(),(int)v1.Y(),NULL);
			LineTo(hdc,(int)v2.X(),(int)v2.Y());

			MoveToEx(hdc,(int)v3.X(),(int)v3.Y(),NULL);
			LineTo(hdc,(int)v4.X(),(int)v4.Y());

			Ellipse(hdc,(int)(v5.X() - 5),(int)(v5.Y() - 5),(int)(v5.X() + 5),(int)(v5.Y() + 5));

			DeleteObject(hPen);
            EndPaint(hWnd,&ps);
		}
 		break;
		case WM_LBUTTONDOWN:
			{
				if( 5 > abs(MousePos.x - v1.X()) && 5 > abs(MousePos.y - v1.Y())){
					pt = &v1;
				}else if( 5 > abs(MousePos.x - v2.X()) && 5 > abs(MousePos.y - v2.Y())){
					pt = &v2;
				}else if( 5 > abs(MousePos.x - v3.X()) && 5 > abs(MousePos.y - v3.Y())){
					pt = &v3;
				}else if( 5 > abs(MousePos.x - v4.X()) && 5 > abs(MousePos.y - v4.Y())){
					pt = &v4;
				}
			}
			break;
		case WM_LBUTTONUP:
			{
				pt = NULL;
			}
			break;
		case WM_RBUTTONDOWN:
			{

			}
			break;
		case WM_MOUSEMOVE:
			{
				MousePos.x = LOWORD(lParam); 
				MousePos.y = HIWORD(lParam);
				if(pt){
					//POINT pt;

					pt->X(MousePos.x);
					pt->Y(MousePos.y);

					dPoint2D v6(0,0);
					v6 = v1 + v4 - v3;

					dPoint2D v7(0,0);
					dPoint2D v8(0,0);

					v7 = v6.GetPointOnLine(v1,v2);
					v8 = v4.GetPointOnLine(v1,v2);
					
					double v4v5_length = (v6 - v1).Length() / (v6 - v7).Length() * (v8 - v4).Length();

					dPoint2D v9(0,0);

					v9 = v8.GetPointOnLine(v3,v4);

					v5 = (v9 - v4) * (v4v5_length / (v4 - v9).Length());

					double l = v5.Length();

					v5 = v5 + v4;

					InvalidateRect(hWnd,NULL,true);
				}
			}
			break;
		case WM_DESTROY:
		{
  		      PostQuitMessage(0);
  		}
  		break;
	}
	return DefWindowProc(hWnd,msg,wParam,lParam);
}

int WINAPI WinMain(HINSTANCE hInstance,HINSTANCE ,LPSTR ,int ){
	WNDCLASS wnd;

	wnd.cbClsExtra = NULL;
	wnd.cbWndExtra = NULL;
	wnd.hbrBackground = CreateSolidBrush(RGB(0,0,0));
	wnd.hCursor = LoadCursor(NULL,IDC_ARROW);
	wnd.hIcon = LoadIcon(NULL, IDI_APPLICATION);
	wnd.hInstance = hInstance;
	wnd.lpfnWndProc = WndProc;
	wnd.lpszClassName = "PunktPrzecieciaProstych";
	wnd.lpszMenuName = NULL;
	wnd.style = CS_VREDRAW|CS_HREDRAW;

	if(!RegisterClass(&wnd)){
		MessageBox(NULL,"Coś nie tak","Informacja",MB_OK);
		return 0;
	}

	HWND hwnd = CreateWindow("PunktPrzecieciaProstych","Autor: Krzysztof Zajączkowski, kontakt: malyszkz@wp.pl",WS_OVERLAPPEDWINDOW,0,0,800,600,NULL,NULL,hInstance,NULL);

	ShowWindow(hwnd, SW_SHOWNORMAL);
	UpdateWindow(hwnd);

	MSG msg;

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

	return 0;
}