import java.awt.*;
import java.applet.*;

public class LBP extends Applet {
  DrawLBP drawingLBP;
  Panel InputPanel;
  Panel PointAPanel, PointBPanel;
  TextField TFPointAx, TFPointAy, TFPointBx, TFPointBy;
  double Ax = 4.0, Ay = 0.0, Bx=-3.0, By=2.0;
	
  public void init() {
    setLayout(new BorderLayout());

    PointAPanel = new Panel();
    PointAPanel.add(new Label("Point A(x,y)=(",Label.RIGHT));
    PointAPanel.add(TFPointAx = new TextField(String.valueOf(Ax),4));
    PointAPanel.add(new Label(",",Label.CENTER));
    PointAPanel.add(TFPointAy = new TextField(String.valueOf(Ay),4));
    PointAPanel.add(new Label(")",Label.LEFT));

    PointBPanel = new Panel();
    PointBPanel.add(new Label("Point B(x,y)=(",Label.RIGHT));
    PointBPanel.add(TFPointBx = new TextField(String.valueOf(Bx),4));
    PointBPanel.add(new Label(",",Label.CENTER));
    PointBPanel.add(TFPointBy = new TextField(String.valueOf(By),4));
    PointBPanel.add(new Label(")",Label.LEFT));

    InputPanel = new Panel();
    InputPanel.setLayout(new GridLayout(2,1));
    InputPanel.add(PointAPanel);
    InputPanel.add(PointBPanel);

    drawingLBP = new DrawLBP(Ax, Ay, Bx, By);

    add("Center", drawingLBP);
    add("South",  InputPanel);
  }

  public boolean action(Event ev, Object arg) {
    if (ev.target instanceof TextField) {
      Ax = Float.valueOf(TFPointAx.getText().trim()).floatValue();
      Ay = Float.valueOf(TFPointAy.getText().trim()).floatValue();
      Bx = Float.valueOf(TFPointBx.getText().trim()).floatValue();
      By = Float.valueOf(TFPointBy.getText().trim()).floatValue();
      drawingLBP.redraw(Ax, Ay, Bx, By);
      return true;
    } else if (ev.target instanceof Button) {
      return true;
    } else
      return true;
  }

  public boolean handleEvent(Event e) {
    if (e.id == Event.WINDOW_DESTROY) {
      stop();
      destroy();
      System.exit(0);
      return true;
    } else {
      return super.handleEvent(e);
    }
  }

  public static void main(String args[]) {
    PFrame f = new PFrame("LineBetweenPoints");
    LBP LBP_function = new LBP();

    LBP_function.init();
    LBP_function.start();

    f.add("Center", LBP_function);
    f.resize(420, 500);
    f.show();
  }
}

class PFrame extends Frame {
  PFrame(String title) {
    super(title);
  }

  public boolean handleEvent(Event e) {
    if (e.id == Event.WINDOW_DESTROY) {
      dispose();
      System.exit(0);
    }
    return false;
  }
}
    
class DrawLBP extends Canvas {
  Font	font;
  double prmAx = 0.0, prmAy = -3.0, 
         prmBx = -3.0, prmBy = 2.0;
  Point A = new Point(0,0), B = new Point(0,0);
  Point O = new Point(0,0);
  Point U = new Point(20,20);
  int Height, Width;

  DrawLBP(double prmAx, double prmAy, double prmBx, double prmBy) {
    this.prmAx = prmAx;
    this.prmAy = prmAy;
    this.prmBx = prmBx;
    this.prmBy = prmBy;
    repaint();
  }

  public void redraw(double prmAx, double prmAy, double prmBx, double prmBy) {
    this.prmAx = prmAx;
    this.prmAy = prmAy;
    this.prmBx = prmBx;
    this.prmBy = prmBy;
    repaint();
  }

  public void aw2px(Point t, int xx, int yy){
    t.x = (   xx * U.x) + O.x;
    t.y = ( - yy * U.y) + O.y;
  }

  public void aw2px(Point t, double x, double y){
    t.x = (int)(   x * (double)U.x + (double)O.x );
    t.y = (int)( - y * (double)U.y + (double)O.y );
  }

  public void draw_coordinate(Graphics g) {
    Height = size().height;
    Width  = size().width;
    O.x = Height / 2;
    O.y = Width  / 2;

    g.setColor(Color.pink);
    for (int i = -10; i <= 10; i++) {
      aw2px(A, -10,i);  aw2px(B,  10,i);
      g.drawLine(A.x, A.y, B.x, B.y);
    }
    for (int i = -10; i <= 10; i++) {
      aw2px(A, i,-10);  aw2px(B, i, 10);
      g.drawLine(A.x, A.y, B.x, B.y);
    }

    g.setColor(Color.black);
    g.setFont(font);
    aw2px(A,0,-10); aw2px(B,0, 10);
    g.drawLine(A.x, A.y, B.x, B.y);
    aw2px(A,-10,0); aw2px(B,10,0);
    g.drawLine(A.x, A.y, B.x, B.y);
  }

  public void paint(Graphics g) {
    draw_coordinate(g);

    g.setColor(Color.red);

    aw2px(A, prmAx, prmAy);
    g.fillOval(A.x -5, A.y -5, 10, 10);
    aw2px(A, prmBx, prmBy);
    g.fillOval(A.x -5, A.y -5, 10, 10);

    double slope, intercept;
    slope = (prmAy - prmBy) / (prmAx - prmBx);
    intercept = prmAy - slope * prmAx;

    aw2px(A, -10.0, slope * -10.0 + intercept);
    aw2px(B,  10.0, slope *  10.0 + intercept);
    g.drawLine(A.x, A.y, B.x, B.y);

    g.setColor(Color.black);
    g.setFont(font);

   g.drawString("Y = " + slope + "X + " + intercept, 10, Height - 14);

  }

}