///////////////////////////////////////////////////////////////////////
//
//  blaise.java
//
//  Copyright (c) 1997 by Jeremy Baer
//  jbaer@cs.washington.edu
//  http://www.cs.washington.edu/homes/jbaer
//
//  The applet contained in this file implements a tool to visualize
//  numeric patterns in Pascal's triangle.
//
//  There is nothing particularly mystical about this code -- the
//  applet itself is incredibly simple.  It's what the applet does
//  that's interesting.
//
//  Permission to study and modify this code for educational purposes
//  only is hereby granted.  No commercial use of this code is 
//  permitted without the express permission of the author.
//
//////////////////////////////////////////////////////////////////////
 
import java.awt.*;
import java.awt.image.*;
import java.applet.*;
import java.lang.*;
import java.util.*;

import BigInt; // from the MIT Scheme project


public class blaise extends Applet
{
    int TABLE_SIZE = 0; 
    int TRI_SIZE = 128;

    /* offscreen image for redrawing the board */
    Image     offscreenImage;
    Graphics  offscreenGraphics;	

    Vector    triangle;
    BigInt    divisor = new BigInt(2);
    TextField divTF;
    
    boolean   newDivis = true;
  

    
    /**
     * Initialize the applet.
     */
    public void init()
    {
        int row, col, count = 0;

	// get the rows parameter
	String tempStr = getParameter("rows");
	try {
	    TRI_SIZE = Integer.parseInt(tempStr);
	}
	catch(NumberFormatException ex) {;}

	// compute the size of the table
	for(count = 1; count <= TRI_SIZE; count++)
	    TABLE_SIZE += count;
	count = 0;

        triangle = new Vector(TABLE_SIZE);

	/* Build the table of numbers representing Pascal's triangle. 
	   Note that the triangle is stored in a linear vector, as we
	   can easily compute offsets into that vector given row and 
	   column numbers 
        */
	for(row = 0; row < TRI_SIZE; row++)
	{    
	    for(col = 0; col <= row; col++)
	    {
	        /* If we're on the edge, the number is a one */
	        if(col == 0 || col == row)
	            triangle.addElement(new BigInt(1));

		/* otherwise, it is the sum of the two numbers 
		   above it in the triangle */
	        else 
	        {
	            int prev1, prev2;
		    
		    prev1 = (count - (row + 1));
		    prev2 = (count - row);

		    triangle.addElement(BigInt.add((BigInt)triangle.elementAt(prev1),
						   (BigInt)triangle.elementAt(prev2)));
		}
		count++;
	    }
	}

	/* make the text field and "Set Divisor" button */
	setLayout(new BorderLayout());
	Panel p = new Panel();
	add("South", p);
	divTF = new TextField("2", 4);
	p.add(divTF);
	p.add(new Button("Set Divisor"));
    }


    /* 
     * Handle updates
     */
    public void update(Graphics g)
    {
        /* init our offscreen image if it hasn't already been done */ 
	if(offscreenImage == null)
	{
	    offscreenImage = createImage(size().width, size().height);
	    offscreenGraphics = offscreenImage.getGraphics();
	}

        /* if we just entered a new divisor, then we actually have to redraw the 
	   thing -- otherwise, just copy it from offscreen 
	*/
       	if(newDivis) 
	{
	    offscreenGraphics.setColor(Color.lightGray);
	    offscreenGraphics.fillRect(0,0,size().width, size().height);
	    painter(offscreenGraphics, g);
	}
       	else g.drawImage(offscreenImage, 0, 0, null);
    }


    public void paint(Graphics g)
    {
        /* init our offscreen image if it hasn't already been done */ 
	if(offscreenImage == null)
	{
	    offscreenImage = createImage(size().width, size().height);
	    offscreenGraphics = offscreenImage.getGraphics();
	}

        /* if we just entered a new divisor, then we actually have to redraw the 
	   thing -- otherwise, just copy it from offscreen 
	*/
       	if(newDivis) 
	{
	    offscreenGraphics.setColor(Color.lightGray);
	    offscreenGraphics.fillRect(0,0,size().width, size().height);
	    painter(offscreenGraphics, g);
	}
       	else g.drawImage(offscreenImage, 0, 0, null);
    }

    
    /**
     * This actually performs the drawing, on both Graphics objects passed to 
     * it (offscreen and onscreen).
     */
    public void painter(Graphics g, Graphics g2)
    {
	int row, col, count = 0;
	Rectangle drawRect = new Rectangle((TRI_SIZE + 20), 10, 2, 2);

	newDivis = false;

	g.setColor(Color.black);
	g2.setColor(Color.black);

	/* loop through the rows and columns, drawing each cell */
	for(row = 0; row < TRI_SIZE; row++)
	{    
	    drawRect.reshape((TRI_SIZE + 20) - row, 10 + (2 * row), 2, 2);
	    for(col = 0; col <= row; col++)
	    {
		/* see if it's divisible and set the right color */
		if((BigInt.remainder((BigInt)triangle.elementAt(count), divisor)).isZero())
		{
		    g.setColor(Color.black);
		    g2.setColor(Color.black);
		}
		else 
		{ 
		    g.setColor(Color.red);
		    g2.setColor(Color.red);
		}

		/* draw the cell on both Graphics objects */
		g.fillRect(drawRect.x, drawRect.y, drawRect.width, drawRect.height);
		g2.fillRect(drawRect.x, drawRect.y, drawRect.width, drawRect.height);
                
		/* move the drawing rect */
		drawRect.translate(2, 0);

		count++;
	    }
	}
	
    }


    /*
     * This handles the user's clicks on the "Set Divisor" button 
     */
    public boolean action(Event evt, Object obj)
    {
	if ("Set Divisor".equals(obj)) 
	{
	    String divStr = divTF.getText();
	    Long   newDiv = new Long(divStr);
	    long   newDiv2 = newDiv.longValue();
	    divisor = null;
	    divisor = new BigInt(newDiv2);
	    newDivis = true;
	    repaint();
	    return true;
	}

	else { return false; }

    }
    
    public String getAppletInfo() {
	return "blaise (c) 1997 by Jeremy Baer";
    }
}