import java.applet.*;
import java.awt.*;
import java.awt.event.*;
import java.util.*;
public class Jooned3 extends Applet 
    implements MouseListener, MouseMotionListener{
  Vector hoidla=new Vector();
  int algx, algy;
  int otsx, otsy;
  static final int puutekaugus=10;
  Graphics gr;
  public Jooned3(){
    addMouseListener(this);    
    addMouseMotionListener(this);
  }
  public void mousePressed(MouseEvent e){
    algx=e.getX();
    algy=e.getY();
    otsx=algx; otsy=algy;
    gr=getGraphics();
    gr.drawLine(algx, algy, otsx, otsy);
    gr.setXORMode(Color.white);
  }
  public void mouseReleased(MouseEvent e){
    hoidla.addElement(new Joon(algx, algy, e.getX(), e.getY()));
    repaint();
  }
  public void mouseEntered(MouseEvent e){}
  public void mouseExited(MouseEvent e){}
  public void mouseClicked(MouseEvent e){}
  
  public void mouseDragged(MouseEvent e){
    gr.drawLine(algx, algy, otsx, otsy);
    otsx=e.getX();
    otsy=e.getY();
    gr.drawLine(algx, algy, otsx, otsy);
  }
  public void mouseMoved(MouseEvent me){
    Enumeration e=hoidla.elements();
    Graphics g=getGraphics();
    while(e.hasMoreElements()){
      Joon j=(Joon)e.nextElement();
      if(punktiKaugusJoonest(me.getX(), me.getY(), j.x1, j.y1, j.x2, j.y2)>puutekaugus){
        g.setColor(Color.black);
      } else {
        g.setColor(Color.yellow);
      }
      g.drawLine(j.x1, j.y1, j.x2, j.y2);
    }  
  }
  
  public void paint(Graphics g){
    Enumeration e=hoidla.elements();
    while(e.hasMoreElements()){
      Joon j=(Joon)e.nextElement();
      g.drawLine(j.x1, j.y1, j.x2, j.y2);
    }
  }

  static double punktiKaugusJoonest(int px, int py, int x1, int y1, int x2, int y2){
    //nihutan joone algama algpunktist, kõigest lahutan joone esimese punkti asukoha.
    px-=x1; py-=y1;
    x2-=x1; y2-=y1;
    //jäi järele joon punktist 0, 0; x2, y2
    //Joone võrrand: y=(y2/x2)*x ehk (y2/x2)*x-y=0
    //kui x2==0, siis joon vertikaalne, kaugus joonest == |px|
    //Muul juhul avaldatakse kaugus valemist
    //  a(px)+b(py)/sqrt(a*a+b*b)
    //
    if(x2==0){return (px>0)?px:-px;}
    double a=y2/(double)x2;
    double b=-1;
    
    double vastus= Math.abs((a*px+b*py)/Math.sqrt(a*a+b*b));
    return vastus;
  }

  public static void main(String[] arg){
    Frame f=new Frame();
    f.add(new Jooned3());
    f.setSize(300, 300);
    f.setVisible(true);
  }
  class Joon{
    int x1, y1, x2, y2;
    Joon(int ux1, int uy1, int ux2, int uy2){
      x1=ux1; y1=uy1; x2=ux2; y2=uy2; 
    }
  }
}