/*******************************************************************************
 * Copyright (c) 2006, 2009 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *     Matthew Hall - bugs 251884, 194734
 *******************************************************************************/

package org.eclipse.core.databinding.observable.map;

import java.util.Iterator;
import java.util.Map;
import java.util.Set;

import org.eclipse.core.databinding.observable.IDiff;

/**
 * @since 1.1
 * 
 */
public abstract class MapDiff implements IDiff {
    /**
     * Returns true if the diff has no added, removed or changed entries.
     * 
     * @return true if the diff has no added, removed or changed entries.
     * @since 1.2
     */
    public boolean isEmpty() {
        return getAddedKeys().isEmpty() && getRemovedKeys().isEmpty()
                && getChangedKeys().isEmpty();
    }

    /**
     * Applies the changes in this diff to the given map
     * 
     * @param map
     *            the map to which the diff will be applied
     * @since 1.2
     */
    public void applyTo(Map map) {
        for (Iterator it = getAddedKeys().iterator(); it.hasNext();) {
            Object key = it.next();
            map.put(key, getNewValue(key));
        }
        for (Iterator it = getChangedKeys().iterator(); it.hasNext();) {
            Object key = it.next();
            map.put(key, getNewValue(key));
        }
        for (Iterator it = getRemovedKeys().iterator(); it.hasNext();) {
            map.remove(it.next());
        }
    }

    /**
     * @return the set of keys which were added
     */
    public abstract Set getAddedKeys();

    /**
     * @return the set of keys which were removed
     */
    public abstract Set getRemovedKeys();

    /**
     * @return the set of keys for which the value has changed
     */
    public abstract Set getChangedKeys();

    /**
     * Returns the old value for the given key, which must be an element of
     * {@link #getRemovedKeys()} or {@link #getChangedKeys()}.
     * 
     * @param key
     * @return the old value for the given key.
     */
    public abstract Object getOldValue(Object key);

    /**
     * Returns the new value for the given key, which must be an element of
     * {@link #getChangedKeys()} or {@link #getAddedKeys()}.
     * 
     * @param key
     * @return the new value for the given key.
     */
    public abstract Object getNewValue(Object key);
}