/*
Wotonomy: OpenStep design patterns for pure Java applications.
Copyright (C) 2000 Blacksmith, Inc.

This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.

This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public
License along with this library; if not, see http://www.gnu.org
*/

package net.wotonomy.foundation;

import java.util.Date;
import java.util.GregorianCalendar;
import java.util.TimeZone;

/**
* A pure java implementation of NSDate that extends
* java.util.Date for greater java compatibility.
*
* @author michael@mpowers.net
* @author $Author: cgruber $
* @version $Revision: 892 $
*/
public class NSDate extends Date
{
	// NSComparisonResult compatibility
	
	public static final int NSOrderedAscending = -1;
	public static final int NSOrderedSame = 0;
	public static final int NSOrderedDescending = 1;

//    public static final double TimeIntervalSince1970;
//    public static final NSDate DateFor1970;

    /**
    * Default constructor represents the current date.
    */
    public NSDate ()
    {
    	super();
    }
    
    /**
    * Represents the specified number of seconds from the current date.
    */
    public NSDate (double seconds)
    {
    	super( (long) new NSDate().getTime() + 
	    	timeIntervalToMilliseconds(seconds) );	
    }
    
    /**
    * Represents the specified number of seconds from the specified date.
    */
    public NSDate (double seconds, Date sinceDate)
    {
    	super( (long) sinceDate.getTime() +
	    	timeIntervalToMilliseconds(seconds) );	
    }

    /**
    * Returns the interval between this date and 1 January 2001 GMT.
    */
    public double timeIntervalSinceReferenceDate ()
    {
		GregorianCalendar referenceDate = 
			new GregorianCalendar( TimeZone.getTimeZone( "GMT" ) );    
		referenceDate.set( 2001, 0, 0, 0, 0, 0 );
		return timeIntervalSinceDate( referenceDate.getTime() );
	}

    /**
    * Returns the interval between this date and the specified date
    * in seconds.
    */
    public double timeIntervalSinceDate (Date aDate)
    {
    	return millisecondsToTimeInterval( 
	    	this.getTime() - aDate.getTime() );
    }
    
    /**
    * Returns the interval between this date and the current date
    * in seconds.
    */
    public double timeIntervalSinceNow ()
    {
    	return timeIntervalSinceDate( new NSDate() );
    }
    
    /** 
    * Compares this date to the specified date and returns the
    * earlier date.  Unspecified which is returned if both are equal.
    */
    public NSDate earlierDate (NSDate aDate)
    {
    	if ( aDate == null ) return this;
    	if ( after( aDate ) ) return aDate;
	    return this;
    }

    /** 
    * Compares this date to the specified date and returns the
    * later date.  Unspecified which is returned if both are equal.
    */
    public NSDate laterDate (NSDate aDate)
    {
    	if ( aDate == null ) return this;
    	if ( before( aDate ) ) return aDate;
	    return this;
    }

    /** 
    * Returns a negative value if the specified date is later than
    * this date, a positive value if the specified date is earlier
    * than this date, or zero if the dates are equal.  The return
    * values are compatible with type NSComparisonResult.
    */
    public int compare (Date aDate)
    {
    	if ( before( aDate ) ) return NSOrderedAscending;
	    if ( after( aDate ) )  return NSOrderedDescending;
	    return NSOrderedSame;
    }
    
    /** 
    * Returns whether the this date is equal to the specified date,
    * per the result of equals().
    */
    public boolean isEqualToDate (Date aDate)
    {
    	return equals( aDate );
    }
    
    /**
    * Returns a date that differs from this date by the specified
    * number of seconds.
    */
    public NSDate dateByAddingTimeInterval (double seconds)
    {
    	return new NSDate( seconds, this );
    }
    
    /**
    * Returns the number of seconds between now and the reference date.
    */
    public static double currentTimeIntervalSinceReferenceDate ()
    {
    	return new NSDate().timeIntervalSinceReferenceDate();
    }
    
    /**
    * Converts seconds to milliseconds.  Included for compatibility.
    */
    public static long timeIntervalToMilliseconds (double seconds)
    {
    	return (long) seconds*1000;
    }
    
    /**
    * Converts milliseconds to seconds.  Included for compatibility.
    */
    public static double millisecondsToTimeInterval (long millis)
    {
    	return millis/1000.0;
    }
    
    /**
    * Returns a date that is greater than all representable dates.
    */
    public static NSDate distantFuture ()
    {
    	NSDate result = new NSDate();
	    result.setTime( Long.MAX_VALUE );
	    return result;
    }
    
    /**
    * Returns a date that is less than all representable dates.
    */
    public static NSDate distantPast ()
    {
    	NSDate result = new NSDate();
	    result.setTime( Long.MIN_VALUE );
	    return result;
    }

// inherited from java.util.Date
//    public java.lang.String toString ();
//    public boolean equals (java.lang.Object);
//    public int hashCode ();

}

/*
 * $Log$
 * Revision 1.1  2006/02/16 12:47:16  cgruber
 * Check in all sources in eclipse-friendly maven-enabled packages.
 *
 * Revision 1.1.1.1  2000/12/21 15:47:28  mpowers
 * Contributing wotonomy.
 *
 * Revision 1.3  2000/12/20 16:25:38  michael
 * Added log to all files.
 *
 *
 */