// Interactive 2D Lagrange splines,  Evgeny Demidov 22 June 2001
import java.awt.*;
import java.awt.event.*;
import java.util.StringTokenizer;

public class @file extends java.applet.Applet
  implements MouseMotionListener{
Image buffImage;          Graphics buffGraphics;
int n = 4, n1,  w,h,h1,w2;
double[] Px,Py, ti;
double bF[][];

public void drawFun(){
  double step = 1./(w2-1), t = 0,  min = 0, max = 0;
  Color[] iColor = {Color.red, new Color(0f,.7f,0f), Color.blue, Color.magenta,
   new Color(0f,.8f,.8f), new Color(.9f,.9f,0f), Color.gray };
  buffGraphics.clearRect(0,0, w, h);

  for (int k = 0; k < w2; k++){        //  basis functions calculation
   for (int j = 0; j < n; j++){
    double P = 1;
    for (int i = 0; i < n; i++)
     if (i != j) P = P*(t-ti[i])/(ti[j] - ti[i]);

    if (P > max) max = P;
    if (P < min) min = P;
    bF[j][k] = P;}
   t += step;}
//  System.out.println("test");
  double M = h1/(max-min);
  for (int j = 0; j < n; j++){
   buffGraphics.setColor(iColor[j % 7]);
   for (int k = 1; k < w2; k++)
    buffGraphics.drawLine(w2+k-1, h1-(int)(M*(bF[j][k-1]-min)),
     w2+k, h1-(int)(M*(bF[j][k]-min)) );}
  int y0 = h1+(int)(M*min);
  buffGraphics.setColor(Color.black);
  buffGraphics.drawLine(w2,y0, w-1,y0);
  for (int i = 0; i < n; i++)
   buffGraphics.drawRect(w2+(int)(w2*ti[i])-1, y0-1, 3,3);
}

public void init() {
  w = Integer.parseInt(getParameter("width"));
  h = Integer.parseInt(getParameter("height"));  h1 = h-1; w2 = w/2;
  String s = getParameter("N"); if (s != null) n = Integer.parseInt(s);
  n1 = n+1;
  Px = new double[n];  Py = new double[n];  ti = new double[n];
  bF = new double[n][w2];
  s=getParameter("pts");
  if (s != null){
   StringTokenizer st = new StringTokenizer(s);
   for (int i = 0; i < n; i++){
    Px[i] = w2*Double.valueOf(st.nextToken()).doubleValue();
    Py[i] = h1*Double.valueOf(st.nextToken()).doubleValue();
    ti[i] = Double.valueOf(st.nextToken()).doubleValue();}}
  else{
   Px[0] = .1*w2; Px[1] = .1*w2; Px[2] = .9*w2; Px[3] = .9*w2;
   Py[0] = .1*h1; Py[1] = .9*h1; Py[2] = .9*h1; Py[3] = .1*h1;
   ti[0] = 0; ti[1] = .33; ti[2] = .66;  ti[3] = 1;}
  buffImage = createImage(w, h);
  buffGraphics = buffImage.getGraphics();
  setBackground(Color.white);
  buffGraphics.clearRect(0,0, w, h);
  addMouseMotionListener(this);
  drawFun();
  drawSpline();
}

public void destroy(){ removeMouseMotionListener(this); }
public void mouseMoved(MouseEvent e){}  //1.1 event handling

public void mouseDragged(MouseEvent e) {
  int y = h1 - e.getY();  if (y < 0) y = 0;  if (y > h1) y = h1;
  int x = e.getX();
   int iMin = 0;
   double Rmin = 1e10, r2,xi,yi;
  if ( x < w2){
   if (x > w2-5) return;
//   if (x > w2-3) x = w2-3;
   if (x < 0) x = 0;
   for (int i = 0; i < n; i++){
    xi = (x - Px[i]); yi = (y - Py[i]);
    r2 = xi*xi + yi*yi;
    if ( r2 < Rmin ){ iMin = i; Rmin = r2;}}
   Px[iMin] = x; Py[iMin] = y;
  }
  else{
   double t = (double)(x - w2)/w2;
   if ( t > 1 ) t = 1;
   for (int i = 0; i < n; i++)
    if ( (r2 = Math.abs(ti[i]-t) ) < Rmin ){ iMin = i; Rmin = r2;}
   ti[iMin] = t;
   drawFun();
  }
  drawSpline();
  repaint();
}


public void drawSpline(){
  int X,Y;
  buffGraphics.clearRect(0,0, w2, h);
  buffGraphics.setColor(Color.blue);
  for (int i = 0; i < n; i++){
   X = (int)Px[i];  Y = h1-(int)Py[i];
   buffGraphics.drawRect(X-1,Y-1, 3,3);}
  if ( n > 2 ){
   int Xo = (int)Px[0], Yo = h1-(int)Py[0];
   for (int i = 1; i < n; i++){
    X = (int)Px[i];  Y = h1-(int)Py[i];
    buffGraphics.drawLine(Xo,Yo, X,Y);
    Xo = X;  Yo = Y;}
  }
  buffGraphics.setColor(Color.red);
  double sX = 0, sY = 0;
  for (int j = 0; j < n; j++){
   sX += Px[j]*bF[j][0];  sY += Py[j]*bF[j][0];}
  int Xold = (int)sX, Yold = h1-(int)sY;
  for (int k = 1; k < w2; k++){
   sX = 0;  sY = 0;
   for (int j = 0; j < n; j++){
     sX += Px[j]*bF[j][k];  sY += Py[j]*bF[j][k];}
   X = (int)sX;  Y = h1-(int)sY;
   if ( (X < w2) && (Xold < w2) ) buffGraphics.drawLine(Xold,Yold, X,Y );
   Xold = X; Yold = Y;
  }
}

public void paint(Graphics g) {
  g.drawImage(buffImage, 0, 0, this);
//  showStatus( " " + x +"  " + y);
}

public void update(Graphics g){ paint(g); }

}