CollectionNodeIterator.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one 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 under the License.
 */
/*******************************************************************************
 * Copyright (c) 2010 BestSolution.at 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: Tom Schindl <tom.schindl@bestsolution.at> - adjustment to EObject
 ******************************************************************************/
package org.eclipse.e4.emf.internal.xpath;

import java.util.ArrayList;
import java.util.List;

import org.apache.commons.jxpath.JXPathException;
import org.apache.commons.jxpath.ri.model.NodeIterator;
import org.apache.commons.jxpath.ri.model.NodePointer;

/**
 * Combines node iterators of all elements of a collection into one aggregate node iterator.
 * 
 */
public abstract class CollectionNodeIterator implements NodeIterator {
	private CollectionPointer pointer;
	private boolean reverse;
	private NodePointer startWith;
	private int position;
	private List<Object> collection;

	/**
	 * Create a new CollectionNodeIterator.
	 * 
	 * @param pointer
	 *            collection pointer
	 * @param reverse
	 *            iteration order
	 * @param startWith
	 *            starting pointer
	 */
	protected CollectionNodeIterator(CollectionPointer pointer, boolean reverse, NodePointer startWith) {
		this.pointer = pointer;
		this.reverse = reverse;
		this.startWith = startWith;
	}

	/**
	 * Implemented by subclasses to produce child/attribute node iterators.
	 * 
	 * @param elementPointer
	 *            owning pointer
	 * @return NodeIterator
	 */
	protected abstract NodeIterator getElementNodeIterator(NodePointer elementPointer);

	@Override
	public int getPosition() {
		return position;
	}

	@Override
	public boolean setPosition(int position) {
		if (collection == null) {
			prepare();
		}

		if (position < 1 || position > collection.size()) {
			return false;
		}
		this.position = position;
		return true;
	}

	@Override
	public NodePointer getNodePointer() {
		if (position == 0) {
			return null;
		}
		return (NodePointer) collection.get(position - 1);
	}

	/**
	 * Prepare...
	 */
	private void prepare() {
		collection = new ArrayList<Object>();
		NodePointer ptr = (NodePointer) pointer.clone();
		int length = ptr.getLength();
		for (int i = 0; i < length; i++) {
			ptr.setIndex(i);
			NodePointer elementPointer = ptr.getValuePointer();
			NodeIterator iter = getElementNodeIterator(elementPointer);

			for (int j = 1; iter.setPosition(j); j++) {
				NodePointer childPointer = iter.getNodePointer();
				if (reverse) {
					collection.add(0, childPointer);
				}
				else {
					collection.add(childPointer);
				}
			}
		}
		if (startWith != null) {
			int index = collection.indexOf(startWith);
			if (index == -1) {
				throw new JXPathException("Invalid starting pointer for iterator: " + startWith);
			}
			while (collection.size() > index) {
				if (!reverse) {
					collection.remove(collection.size() - 1);
				}
				else {
					collection.remove(0);
				}
			}
		}
	}
}