/*
 * 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.
 */
/*
 * $Id$
 */

package org.apache.xalan.xsltc.dom;

import org.apache.xalan.xsltc.DOM;
import org.apache.xalan.xsltc.runtime.BasisLibrary;
import org.apache.xml.dtm.DTMAxisIterator;
import org.apache.xml.dtm.ref.DTMAxisIteratorBase;

/**
 * UnionIterator takes a set of NodeIterators and produces
 * a merged NodeSet in document order with duplicates removed
 * The individual iterators are supposed to generate nodes
 * in document order
 * @author Jacek Ambroziak
 * @author Santiago Pericas-Geertsen
 */
public final class UnionIterator extends MultiValuedNodeHeapIterator {
    /** wrapper for NodeIterators to support iterator
	comparison on the value of their next() method
    */
    final private DOM _dom;

    private final class LookAheadIterator
            extends MultiValuedNodeHeapIterator.HeapNode
    {
	public DTMAxisIterator iterator;
		
	public LookAheadIterator(DTMAxisIterator iterator) {
            super();
	    this.iterator = iterator;
	}
		
	public int step() {
	    _node = iterator.next();
	    return _node;
	}

	public HeapNode cloneHeapNode() {
            LookAheadIterator clone = (LookAheadIterator) super.cloneHeapNode();
            clone.iterator = iterator.cloneIterator();
	    return clone;
	}

	public void setMark() {
            super.setMark();
	    iterator.setMark();
	}

	public void gotoMark() {
            super.gotoMark();
	    iterator.gotoMark();
	}

        public boolean isLessThan(HeapNode heapNode) {
            LookAheadIterator comparand = (LookAheadIterator) heapNode;
            return _dom.lessThan(_node, heapNode._node);
        }

        public HeapNode setStartNode(int node) {
            iterator.setStartNode(node);
            return this;
        }

        public HeapNode reset() {
            iterator.reset();
            return this;
        }
    } // end of LookAheadIterator

    public UnionIterator(DOM dom) {
	_dom = dom;
    }

    public UnionIterator addIterator(DTMAxisIterator iterator) {
        addHeapNode(new LookAheadIterator(iterator));
        return this;
    }
}
