/**
 * DateEntryPanel provides a data entry panel for a Java Date.<p>
 *
 * Copyright &copy; 1998-89 Martin Minow. All Rights Reserved.<p>
 *
 * Permission to use, copy, modify, and redistribute this software and its
 * documentation for personal, non-commercial use is hereby granted provided that
 * this copyright notice and appropriate documentation appears in all copies. This
 * software may not be distributed for fee or as part of commercial, "shareware,"
 * and/or not-for-profit endevors including, but not limited to, CD-ROM collections,
 * online databases, and subscription services without specific license.<p>
 *
 * Based on DateGUI.java in Mastering JavaBeans.
 * @see <a href="http://www.sybase.com">Sybase</a>, click on
 *  "Catalog>Updates>Mastering JavaBeans".
 * @author <a href="mailto:minow@pobox.com">Martin Minow</a>
 * @version 1.0a0
 * Set tabs every 8 characters.
 *
 * Bugs: This should probably be in a utility path, rather than in
 * the astro bean path.
 *
 */
package org.minow.applets.sunsphere;
import java.beans.*;
import java.util.*;
import java.awt.*;
import java.awt.event.*;
import java.text.*;

public class DateEntryPanel extends PropertyPanel
	implements ItemListener
{
    /*
     * These are the property events we distribute.
     */
    public static final String DATE_CHANGE  = "date";
    
    /*
     * Since this panel will be used for the Astro Bean, we limit
     * the date range to values reasonable for the underlying
     * astronomical procedures. These constants could reasonably
     * be turned into properties, of course.
     */
    public static final int FIRST_YEAR	= 1978;
    public static final int LAST_YEAR	= 2005;
    
    protected GregorianCalendar		calendar;
    protected Locale			locale;
    
    /*
     * These are the popup-menu selections that we construct
     * and display. lastMaxDay minimizes menu rebuilding.
     */
    protected Choice			yearChoice;
    protected Choice			monthChoice;
    protected Choice			dayChoice;
    protected int			lastDayInMonth = -1;
        
    public DateEntryPanel()
    {
	this(new Date());
    }
    public DateEntryPanel(
	    Date		initialDate
	)
    {
	locale	    = Locale.getDefault();
	calendar    = new GregorianCalendar(locale);
	/*
	 * Build the initial popup menus.
	 */
	yearChoice  = buildYearChoice();
	yearChoice.addItemListener(this);
	monthChoice = buildMonthChoice();
	monthChoice.addItemListener(this);
	dayChoice   = buildDayChoice();
	dayChoice.addItemListener(this);
	/*
	 * Construct the display Panel. We might consider
	 * using the locale information to build the
	 * data in the user's preferred organization, but
	 * ISO date seems to be more appropriate for
	 * astronomical data.
	 */
	GridBagLayout gridbag	= new GridBagLayout();
	setLayout(gridbag);
	GridBagConstraints c	= new GridBagConstraints();
	c.gridy			= 0;
	c.anchor		= GridBagConstraints.WEST;
	c.fill			= GridBagConstraints.NONE;
	addField(c, yearChoice);
	addField(c, monthChoice);
	addField(c, dayChoice);
	/*
	 * Display the current date in the menu.
	 */
	setDate(initialDate);
    }
    private void addField(
	    GridBagConstraints	c,
	    Component		component
	)
    {
	add(component);
	((GridBagLayout) getLayout()).setConstraints(component, c);
    }
    /*
     * Accessor functions.
     */
    public void setDate(
	    Date	    newDate
	)
    {
    	setDate(newDate, true);
    }
    public void setDate(
    	    Date		newDate,
    	    boolean		informClients
    	)
    {
	Date oldDate	    = getDate();
	calendar.setTime(newDate);
	reflectNewDate();
	if (informClients) {
	    firePropertyChange(DATE_CHANGE, oldDate, getDate());
	}
    }
    public Date getDate()
    {
	return (calendar.getTime());
    }
    /*
     * Build menus.
     */
    protected Choice buildYearChoice()
    {
	Choice years	    = buildChoiceFromRange(FIRST_YEAR, LAST_YEAR);
	return (years);
    }
    protected Choice buildMonthChoice()
    {
	String[] monthNames = (new DateFormatSymbols(locale)).getShortMonths();
	Choice months	    = buildChoiceFromStringList(monthNames);
	return (months);
    }
    protected Choice buildDayChoice()
    {
	Choice days	    = buildChoiceFromRange(1, 31);
	return (days);
    }
    /*
     * Update the choices to reflect the new date. This is called at
     * initialization, and whenever the date changes.
     */
    protected void reflectNewDate()
    {
	int currentYear	    = calendar.get(Calendar.YEAR);
	int currentMonth    = calendar.get(Calendar.MONTH);	    /* 0-based	*/
	int currentDay	    = calendar.get(Calendar.DAY_OF_MONTH);  /* 1-based	*/
	/*
	 * Fix the month end and fix February for leap years.
	 */
	setLastDayInMonth(currentYear, currentMonth);
	dayChoice.select(currentDay - 1);
	monthChoice.select(currentMonth);
	yearChoice.select(currentYear - FIRST_YEAR);
    }
    /*
     * Implement the ItemListener interface.
     */
    public void itemStateChanged(
	    ItemEvent	event
	)
    {
	Choice choice	    = (Choice) event.getSource();
	int currentYear	    = calendar.get(Calendar.YEAR);
	int currentMonth    = calendar.get(Calendar.MONTH);	    /* 0-based	*/
	int currentDay	    = calendar.get(Calendar.DAY_OF_MONTH);  /* 1-based	*/
	/*
	 * Remember the current state of each selection.
	 */
	int newYear	= yearChoice.getSelectedIndex() + FIRST_YEAR;
	int newMonth	= monthChoice.getSelectedIndex();	    /* 0-based	*/
	int newDay	= dayChoice.getSelectedIndex() + 1;	    /* 1-based	*/
	/*
	 * If the user changes the month or year, update the days Choice
	 * to reflect the correct maximum number of days in this month.
	 */
	if (choice == monthChoice || choice == yearChoice) {
	    /*
	     * If the user had selected a 31 day month, but changed to a
	     * shorter day, force the selection to the last day of the month.
	     */
	    int newLastDay = setLastDayInMonth(newYear, newMonth);
	    if (newDay > newLastDay) {
		dayChoice.select(newLastDay - 1);
	    }
	}
	/*
	 * Now that we've handled the menu updating, change our
	 * date property to reflect the new values and issue the
	 * PropertyChangeEvent to the listeners.
	 */
	Date oldDate		= getDate();
	newDay			= dayChoice.getSelectedIndex() + 1;
	calendar.set(newYear, newMonth, newDay);
	firePropertyChange(DATE_CHANGE, oldDate, getDate());
    }
    /*
     * Make sure that the days choice has the correct number of
     * days for this month.
     */
    protected int setLastDayInMonth(
	    int		    year,
	    int		    month
	)
    {
	GregorianCalendar temp = (GregorianCalendar) calendar.clone();
	/*
	 * To get the last day in the desired month, we get the zero'th day
	 * in the next month. This is a sick, but apparently necessary, hack.
	 */
	temp.set(year, month + 1, 0);
	int lastDayInMonth  = temp.get(Calendar.DAY_OF_MONTH);	/* 1-based  */
	// System.out.println("Month: " + month + ", last day: " + lastDayInMonth);
	if (lastDayInMonth != this.lastDayInMonth) {
	    String[] list   = buildStringListFromRange(1, lastDayInMonth);
	    setChoiceList(dayChoice, list);
	    this.lastDayInMonth = lastDayInMonth;
	}
	return (lastDayInMonth);
    }	
    /*
     * Utility functions.
     */
    /*
     * Create a choice of integers.
     */
    public static Choice buildChoiceFromRange(
	    int		first,
	    int		last
	)
    {
	String[] list	= buildStringListFromRange(first, last);
	Choice choice	= buildChoiceFromStringList(list);
	return (choice);
    }
    /*
     * Create a choice from a list of strings.
     */
    public static Choice buildChoiceFromStringList(
	    String[]	list
	)
    {
	Choice choice	= new Choice();
	setChoiceList(choice, list);
	return (choice);
    }
    /*
     * Create an array of strings containing a range of integers.
     */
    public static String[] buildStringListFromRange(
	    int		first,
	    int		last
	)
    {
	String[] list	= new String[last - first + 1];
	for (int i = first; i <= last; i++) {
	    list[i - first] = String.valueOf(i);
	}
	return (list);
    }
    /*
     * Set the choice list item to the argument value.
     */
    public static void setChoiceList(
	    Choice	choice,
	    String[]	list
	)
    {
	choice.removeAll();
	for (int i = 0; i < list.length; i++) {
	    choice.add(list[i]);
	}
    }
    /*
     * Test
     */
    public static void main(
	    String[]	    args
	)
    {
	final Label	    label   = new Label();
	Frame		    window  = new Frame("DateEntryPanel test");
	window.addWindowListener(
	    new WindowAdapter()
	    {
		public void windowClosing(
			WindowEvent	event
		    )
		{
		    System.exit(0);
		}
	    }
	);
	DateEntryPanel   dateEntryPanel  = new DateEntryPanel();
	dateEntryPanel.addPropertyChangeListener(
	    new PropertyChangeListener()
	    {
		public void propertyChange(
			PropertyChangeEvent event
		    )
		{
		    Date date	= (Date) event.getNewValue();
		    label.setText(date.toString());
		}
	    }
	);
	window.add("Center",	dateEntryPanel);
	window.add("South",	label);
	window.setSize(new Dimension(240, 90));
	window.setVisible(true);
    }
}