/* ======================================================================
The Bodington System Software License, Version 1.0
  
Copyright (c) 2001 The University of Leeds.  All rights reserved.
  
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:

1.  Redistributions of source code must retain the above copyright notice,
this list of conditions and the following disclaimer.

2.  Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.

3.  The end-user documentation included with the redistribution, if any,
must include the following acknowledgement:  "This product includes
software developed by the University of Leeds
(http://www.bodington.org/)."  Alternately, this acknowledgement may
appear in the software itself, if and wherever such third-party
acknowledgements normally appear.

4.  The names "Bodington", "Nathan Bodington", "Bodington System",
"Bodington Open Source Project", and "The University of Leeds" must not be
used to endorse or promote products derived from this software without
prior written permission. For written permission, please contact
d.gardner@leeds.ac.uk.

5.  The name "Bodington" may not appear in the name of products derived
from this software without prior written permission of the University of
Leeds.

THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
WARRANTIES, INCLUDING, BUT NOT LIMITED TO,  TITLE,  THE IMPLIED WARRANTIES 
OF QUALITY  AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO 
EVENT SHALL THE UNIVERSITY OF LEEDS OR ITS CONTRIBUTORS BE LIABLE FOR 
ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE 
GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 
HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 
STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN 
ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 
POSSIBILITY OF SUCH DAMAGE.
=========================================================

This software was originally created by the University of Leeds and may contain voluntary 
contributions from others.  For more information on the Bodington Open Source Project, please 
see http://bodington.org/

====================================================================== */

package org.bodington.util;

import java.io.*;

/**
 * This is a class that can help with code to handle collapsing/expanding 
 * trees in a servlet.  It can be stored in a Hashtable against a key where
 * the key is something that identifies the node of a tree.  When the tree
 * is to be displayed the servlet can consult a Hashtable for each node to
 * decide if the node is open/closed visible/invisible.  There are four
 * static members of the class that are references to instances of the class
 * showing all four permutations of state.
 * 
 * @author Jon Maber
 * @version 1.0
 */
public class Visibility implements java.io.Serializable
	{

	/**
	 * A convenience instance that is set to invisible and closed.
	 */
	public static Visibility INVISIBLE_CLOSED = new Visibility( false, false );

	/**
	 * A convenience instance that is set to invisible and open.
	 */
	public static Visibility INVISIBLE_OPEN = new Visibility( false, true );

	/**
	 * A convenience instance that is set to visible and closed.
	 */
	public static Visibility VISIBLE_CLOSED = new Visibility( true, false );

	/**
	 * A convenience instance that is set to visible and open.
	 */
	public static Visibility VISIBLE_OPEN = new Visibility( true, true );
	
	
	
	/**
	 * The only instance member.  Stores the state.
	 */
	private byte flags;
	
	/**
	 * Convenience flag for private use.
	 */
	private static final byte FLAG_VISIBLE =1;

	/**
	 * Convenience flag for private use.
	 */
	private static final byte FLAG_OPEN    =2;
	
	/**
	 * The constructor is used to set the flags because the state of
	 * the object can't be changed later.
	 * 
	 * @param visible Should the new instance be visible?
	 * @param open Should the new instance be open?
	 */
	public Visibility( boolean visible, boolean open )
		{
		flags = 0;
		if ( visible )
			flags = (byte)(flags | FLAG_VISIBLE);
		if ( open )
			flags = (byte)(flags | FLAG_OPEN);
		}
	
	/**
	 * Tests the visibility flag.
	 * 
	 * @return True is the object is visible.
	 */
	public boolean isVisible()
		{
		return (flags & FLAG_VISIBLE)!=0;
		}
	
	/**
	 * Tests the open flag.
	 * 
	 * @return Returns true if the object is open.
	 */
	public boolean isOpen()
		{
		return (flags & FLAG_OPEN)!=0;
		}
	
    /**
     * Tests equality.
     * 
     * @param obj The object to compare with.
     * @return True if the comparison object is an object of type Visibility and
     * has the same visibility and openness.
     */
    public boolean equals(Object obj)
	    {
	    if ( !(obj instanceof Visibility) )
	    	return false;
	    	
	    Visibility vobj = (Visibility)obj;
	    
	    return vobj.flags == this.flags;
    	}

	}