/*
 *                 Sun Public License Notice
 * 
 * The contents of this file are subject to the Sun Public License
 * Version 1.0 (the "License"). You may not use this file except in
 * compliance with the License. A copy of the License is available at
 * http://www.sun.com/
 * 
 * The Original Code is Forte for Java, Community Edition. The Initial
 * Developer of the Original Code is Sun Microsystems, Inc. Portions
 * Copyright 1997-2002 Sun Microsystems, Inc. All Rights Reserved.
 */

package org.netbeans.modules.looks;

import org.netbeans.spi.looks.LookSelector;

import java.util.*;

/** Event fired from the LookSelector when it's content changes.
 *
 * @see org.netbeans.spi.looks.LookSelector
 * @see org.netbeans.spi.looks.SelectorListener
 * @author  Petr Hrebejk, Jaroslav Tulach
 */
public class SelectorEvent extends EventObject {
    
    private SelectorImpl impl;
    private HashMap oldCache;
    
    /** Creates a new instance of SelectorEvent 
     * @param source LookSelector whose content was changed
     */
    public SelectorEvent( LookSelector source ) {        
        super( source );
        impl = Accessor.DEFAULT.getSelectorImpl( source );
        oldCache = impl.getCache();
    }
    
    /** Determines whether the change in the content of the LookSelector 
     * affects nodes which are used for visualisation of given represented 
     * object.
     * 

     * The default implementation returns true for all objects. If extending
     * LookSelector the implementor is responsible for keeping semantics of 
     * looking for Looks/LookSelectors in sync with the semantics of decision 
     * whether objects are affected or node.
     * @param representedObject The represented object of node which may be
     *        affected by the change of LookSelector content.
     * @return True if node with given represented object is affected 
     *         false otherwise.
     */
    public boolean affectsObject( Object representedObject ) {
        return true;
    }
    
    public Collection getAddedLooks( Object representedObject ) {
        if ( oldCache == null ) {
            // No cache, no problem
            return Collections.EMPTY_SET;
        }
        
        Object key = impl.getKey4Object( representedObject );
        
        Set diff[] = getDiff4Key( key );
        if ( diff == null ) {
            return Collections.EMPTY_SET;
        }
        else {
            return diff[0];
        }
        
    }
    
    public Collection getRemovedLooks( Object representedObject ) {
        
        if ( oldCache == null ) {
            // No cache, no problem
            return Collections.EMPTY_SET;
        }
        
        Object key = impl.getKey4Object( representedObject );
        
        Set diff[] = getDiff4Key( key );
        if ( diff == null ) {
            return Collections.EMPTY_SET;
        }
        else {
            return diff[1];
        }
        
    }
    
    // Private methods ---------------------------------------------------------
    
    /** Computes diff for given key. When the diff is computed for the first
     * time it will put ito the old cache instad of the original CacheItem
     */
    private Set[] getDiff4Key( Object key ) {
        Object o = oldCache.get( key );
        
        if ( key instanceof Set[] ) {
            // It was already computed, just return
            return (Set[])o;
        }
        else {
            // We have to compute, And put it back into the cache
            
            Set[] diff = new Set[2];
            
            SelectorImplFactory.CacheItem oldItem = (SelectorImplFactory.CacheItem)oldCache.get( key ); 
            Collection oldLooks = oldItem.getCachedLooks( false );
            Collection newLooks = Collections.list( impl.getLooks4Key( key ) );
            
            // Newly added looks 
            diff[0] = new HashSet( newLooks );
            diff[0].removeAll( oldLooks );
            
            // Removed looks
            diff[1] = new HashSet( oldLooks );
            diff[1].removeAll( newLooks );
                        
            return diff;
        }
            
    }
    
    
}