/*

 * @(#)Easter.java	0.3 Paul Hardy 19/5/96

 *

 * Copyright (c) 1996 Paul Hardy

 *

 * Applet to Calculate the date of Easter Sunday.

 *

 * Algorithm is from the Book of Common Prayer of the Church of England

 *

 */

import java.awt.*;

import java.applet.*;

import java.util.*;





// new class, containing all necessary methods.

public class Easter extends Applet {

    static final int MAXYEAR = 2100;

    static final int MINYEAR = 1900;

    Date now=new Date();

    Date thatEasterDate=new Date();

    int thatYear;

    Scrollbar s;

    Button b;

    Label l;





// init gets called once,so set up interface items and initialise display.

    public void init() {

        resize(250,150);



        thatYear=now.getYear() + 1900;    // set Easter year to current year



        l = new Label(" From the 1662 Book of Common Prayer ");

        add(l);



        s = new Scrollbar(Scrollbar.HORIZONTAL,thatYear,20,MINYEAR,MAXYEAR);

        add(s);



        b = new Button("Reset");

        add(b);



        repaint();  // calculate date and display it.

        }





// method to calculate date of easter Sunday in a given year

    public Date easterDate(int eY) {

        Date eD=new Date();

        int prime,dominical;

        int i,j;

        int eMonth=0,eDay=0;

        int sundayLetter[]=new int[35];

        int goldenNumber[]={14,3,0,11,0,19,8,0,16,5,0,13,2,0,10,0,18,7,0,15,4,0,12,1,0,9,17,6,

                             0,0,0,0,0,0,0};



        System.out.println("Easter.easterDate called for " + eY);



        prime=(eY + 1) % 19;

        if (prime==0) prime=19;



        dominical=(eY + (eY / 4) + 6) % 7;



        System.out.println("Prime is " + prime + ", Dominical is " + dominical);



        for (i=0; i<35; i++) {

            sundayLetter[i]=6 - ((i + 6 - 4) % 7);

            }



lookup: for (i=0;i<35;i++) {

            if (prime==goldenNumber[i]) {

                for (j=i+1;j<35;j++) {

                    if (sundayLetter[j]==dominical) {

        System.out.println("i is " + i + ", j is " + j);

                        if (j>9) {

                            eMonth=4;

                            eDay=j - 9;

                            }

                        else {

                            eMonth=3;

                            eDay=j + 22;

                            }

                        break lookup;

                        }

                    }

                }

            }



        System.out.println("Day is " + eDay + ", month is " + eMonth);

        eD.setDate(eDay);

        eD.setMonth(eMonth-1);

        eD.setYear(eY - 1900);



        System.out.println("Date is " + eD);

        return eD;

        }





// Override Applet method to display interaction items plus results of date calculation.

    public synchronized void paint(Graphics g) {

        Date eD;

        String dateString,shortString;



        System.out.println("Easter.paint called for " + thatYear);



        g.setColor(Color.red);

        g.drawString("In " + thatYear,90,90);



        eD=easterDate(thatYear);

        dateString=eD.toString();

        shortString=dateString.substring(3,10);



        System.out.println("Date is " + dateString);

        g.drawString("Easter Day is on " + shortString,50,120);

        }





// method to receive events from scrollbar widget

    public boolean handleEvent(Event e) {

        if (e.target instanceof Scrollbar) {

            thatYear=((Scrollbar)e.target).getValue();

            System.out.println("Scroll value: " + thatYear);

            repaint();

            return true;

        }

        return super.handleEvent(e);

       }





// method to receive events from button widget.

    public boolean action(Event e, Object o) {

        if (e.target instanceof Button)

           if( "Reset".equals( ((Button)e.target).getLabel()) ) {

            System.out.println("reset button pressed");

            thatYear=now.getYear() + 1900;

            s.setValue(thatYear);

            repaint();

            return true;

        }

        System.out.println("some other event");

        return false;



    }



}

// that's all!