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 *  or more contributor license agreements.  See the NOTICE file
 *  distributed with this work for additional information
 *  regarding copyright ownership.  The ASF licenses this file
 *  to you under the Apache License, Version 2.0 (the
 *  "License"); you may not use this file except in compliance
 *  with the License.  You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing,
 *  software distributed under the License is distributed on an
 *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 *  KIND, either express or implied.  See the License for the
 *  specific language governing permissions and limitations
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package org.apache.cayenne.graph;

/**
 * An abstract superclass of operations on individual nodes and arcs in a
 * digraph.
 * 
 * @since 1.2
 */
public abstract class NodeDiff implements GraphDiff, Comparable<NodeDiff> {

	private static final long serialVersionUID = -6108147375331011556L;
	
	protected int diffId;
	protected Object nodeId;

	public NodeDiff(Object nodeId) {
		this.nodeId = nodeId;
	}

	public NodeDiff(Object nodeId, int diffId) {
		this.nodeId = nodeId;
		this.diffId = diffId;
	}

	@Override
	public boolean isNoop() {
		return false;
	}

	@Override
	public abstract void apply(GraphChangeHandler tracker);

	@Override
	public abstract void undo(GraphChangeHandler tracker);

	public Object getNodeId() {
		return nodeId;
	}

	/**
	 * Returns an id of this diff that can be used for various purposes, such as
	 * identifying the order of the diff in a sequence.
	 */
	public int getDiffId() {
		return diffId;
	}

	/**
	 * Sets an id of this diff that can be used for various purposes, such as
	 * identifying the order of the diff in a sequence.
	 */
	public void setDiffId(int diffId) {
		this.diffId = diffId;
	}

	/**
	 * Implements a Comparable interface method to compare based on diffId
	 * property.
	 */
	@Override
	public int compareTo(NodeDiff o) {
		return diffId - o.getDiffId();
	}
}