/*
 * This software is distributed as-is with no warranty of any kind and I accept no responsibility
 * for its use.  You may use this software however you wish, just give me credit.
 *
 * Mike Cynn (http://mike.cynn.com/applets/pascal/PascalPanel.java)
 */
import javax.swing.*;
import javax.swing.text.*;
import java.awt.event.*;
import java.awt.*;
import java.text.*;

public class PascalPanel extends JPanel implements ActionListener {
    private JTextField NUMROWS;
    private JTextArea DISPLAY;
    private JButton DOIT;
    private JButton CLR;
    private static String CLEAR_COMMAND = "clear";
    private PascalPanel treePanel;

    public PascalPanel() {
        super(new FlowLayout());

        DOIT = new JButton("Do it!");        
        CLR = new JButton("Clear");
        NUMROWS = new JTextField(10);
        DISPLAY = new JTextArea(20,100);

        DISPLAY.setLineWrap(false);
        DISPLAY.setEditable(false);
        setLayout(new BorderLayout());
        Font font = new Font("fixed",1,10);
        DISPLAY.setFont(font);
        JScrollPane sp = new JScrollPane(DISPLAY);
        sp.setPreferredSize(new Dimension(800,1000));
        sp.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);
        sp.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);

        add("Center", sp);

        Panel SouthPanel = new Panel();
        Panel NorthPanel = new Panel();
        NorthPanel.setLayout(new FlowLayout(FlowLayout.LEFT));
        NorthPanel.add("North",new Label("Rows: "));
        NorthPanel.add("North",NUMROWS);

        DOIT.addActionListener(this);
        CLR.addActionListener(this);

        NorthPanel.add("North",DOIT);
        NorthPanel.add("North",CLR);

        add("South",SouthPanel);
        add("North",NorthPanel);
    }

    public void printOut(String s) {
        int maxDig=0; // number of digits in biggest number in triangle
        int curDig=0; // number of digits in current element
        double result; // the value of the entry
        /*
        NumberFormat nf = NumberFormat.getInstance();
        nf.setMaximumFractionDigits(0);
        nf.setGroupingUsed(false);
        */


        int num = Integer.parseInt(s);

        int prev[][] = new int[num][num]; // lengths of string bet each num
        String vals[][] = new String[num][num]; // the PT values
        StringBuffer strBuf = new StringBuffer();
        DecimalFormat df = new DecimalFormat();
        df.setGroupingUsed(false);
        df.setMaximumFractionDigits(0);
        DecimalFormat dfexp = new DecimalFormat("#.##############################E0");

        initArray(num,vals);

        DISPLAY.append("\n"+s+" Rows of Pascal's Triangle:	\n\n");
        double largest = 0;

        for(int i=0;i<num;i++) { // rows
            for(int j=0;j<=i;j++) { // elements
                result = calcEntry(vals,i,j);
                if(Double.valueOf(result) > 10000000000.0) {
                    vals[i][j] = dfexp.format(result);
                }
                else {
                    vals[i][j] = df.format(result);
                }
                if(result > largest) {
                    largest = result; // find largest number to count digits
                }
            } // end of one row
        } // end of all rows

        maxDig = df.format(largest).length();

        for(int n=0;n<num;n++) { // rows
            for(int m=0;m<=n;m++) { // elements
                curDig = vals[n][m].length(); // digits in current entry
                if(m==0) { // if this is the first element in the row
                    for(int k=num;k>n;k--) {
                        for(int a=maxDig;a>=0;a--) {
                            strBuf.append(" ");	// spaces in front of first element
                        }
                    }
                }
                strBuf.append(vals[n][m]); // the element/number
                prev[n][m] = strBuf.toString().length();
                if(n!=0) { // after first row
                    int nextDig;  // number of digits in next value
                    if(m < vals[n].length-1) {
                        nextDig = vals[n][m+1].length();
                    }
                    else {
                        nextDig = 0;
                    }
                    int len = strBuf.toString().length();
                    int mx;
                    if(m == n) {
                        mx = len + 2*(prev[n-1][1]-len); 
                    }
                    else {
                        mx = len + 2*(prev[n-1][m]-len) - nextDig;
                    }
                    while(len <= mx) {
                        strBuf.append(" "); // spaces between values
                        len++;
                    }
                }
            } // end of one row
            strBuf.append("\n");
            DISPLAY.append(strBuf.toString());
            strBuf.setLength(0);
        } // end of all rows
    } // end printOut method

    public void initArray(int num,String vals[][]) {
        for(int goo=0;goo<num;goo++) {
            for(int foo=0;foo<num;foo++) {
                vals[goo][foo] = "";
            }
        }
    }

    public double calcEntry(String vals[][],int row,int element) {
        if(element == 0 || element == row) {
            return 1;
        }
        else {
            double one = Double.valueOf(vals[row-1][element-1]).doubleValue();
            double two = Double.valueOf(vals[row-1][element]).doubleValue();
            return(one+two);
        }
    }

    public void actionPerformed (ActionEvent e) {
        String actionCommand = e.getActionCommand();
        if(actionCommand.equals("Do it!")) {
            DISPLAY.setText("");
            printOut(NUMROWS.getText());
        }
        else if(actionCommand.equals("Clear")) {
            DISPLAY.setText("");
        }
    }

}