/*
 * Copyright (c) 2000 World Wide Web Consortium,
 * (Massachusetts Institute of Technology, Institut National de
 * Recherche en Informatique et en Automatique, Keio University). All
 * Rights Reserved. This program is distributed under the W3C's Software
 * Intellectual Property License. This program is distributed in the
 * hope that it will be useful, but WITHOUT ANY WARRANTY; without even
 * the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
 * PURPOSE.
 * See W3C License http://www.w3.org/Consortium/Legal/ for more details.
 */

package org.w3c.dom.traversal;

import org.w3c.dom.Node;
import org.w3c.dom.DOMException;

/**
 * <code>Iterators</code> are used to step through a set of nodes, e.g. the
 * set of nodes in a <code>NodeList</code>, the document subtree governed
 * by a particular <code>Node</code>, the results of a query, or any other
 * set of nodes. The set of nodes to be iterated is determined by the
 * implementation of the <code>NodeIterator</code>. DOM Level 2 specifies a
 * single <code>NodeIterator</code> implementation for document-order
 * traversal of a document subtree. Instances of these iterators are created
 * by calling <code>DocumentTraversal</code>
 * <code>.createNodeIterator()</code>.
 * <p>
 * See also the <a
 * href='http://www.w3.org/TR/2000/REC-DOM-Level-2-Traversal-Range-20001113'>Document
 * Object Model (DOM) Level 2 Traversal and Range Specification</a>.
 * 
 * @since DOM Level 2
 */
public interface NodeIterator {
	/**
	 * The root node of the <code>NodeIterator</code>, as specified when it
	 * was created.
	 */
	public Node getRoot();

	/**
	 * This attribute determines which node types are presented via the
	 * iterator. The available set of constants is defined in the
	 * <code>NodeFilter</code> interface. Nodes not accepted by
	 * <code>whatToShow</code> will be skipped, but their children may still
	 * be considered. Note that this skip takes precedence over the filter, if
	 * any.
	 */
	public int getWhatToShow();

	/**
	 * The <code>NodeFilter</code> used to screen nodes.
	 */
	public NodeFilter getFilter();

	/**
	 * The value of this flag determines whether the children of entity
	 * reference nodes are visible to the iterator. If false, they and their
	 * descendants will be rejected. Note that this rejection takes precedence
	 * over <code>whatToShow</code> and the filter. Also note that this is
	 * currently the only situation where <code>NodeIterators</code> may
	 * reject a complete subtree rather than skipping individual nodes. <br>
	 * <br>
	 * To produce a view of the document that has entity references expanded
	 * and does not expose the entity reference node itself, use the
	 * <code>whatToShow</code> flags to hide the entity reference node and
	 * set <code>expandEntityReferences</code> to true when creating the
	 * iterator. To produce a view of the document that has entity reference
	 * nodes but no entity expansion, use the <code>whatToShow</code> flags
	 * to show the entity reference node and set
	 * <code>expandEntityReferences</code> to false.
	 */
	public boolean getExpandEntityReferences();

	/**
	 * Returns the next node in the set and advances the position of the
	 * iterator in the set. After a <code>NodeIterator</code> is created,
	 * the first call to <code>nextNode()</code> returns the first node in
	 * the set.
	 * 
	 * @return The next <code>Node</code> in the set being iterated over, or
	 *         <code>null</code> if there are no more members in that set.
	 * @exception DOMException
	 *                INVALID_STATE_ERR: Raised if this method is called after
	 *                the <code>detach</code> method was invoked.
	 */
	public Node nextNode() throws DOMException;

	/**
	 * Returns the previous node in the set and moves the position of the
	 * <code>NodeIterator</code> backwards in the set.
	 * 
	 * @return The previous <code>Node</code> in the set being iterated
	 *         over, or <code>null</code> if there are no more members in
	 *         that set.
	 * @exception DOMException
	 *                INVALID_STATE_ERR: Raised if this method is called after
	 *                the <code>detach</code> method was invoked.
	 */
	public Node previousNode() throws DOMException;

	/**
	 * Detaches the <code>NodeIterator</code> from the set which it iterated
	 * over, releasing any computational resources and placing the iterator in
	 * the INVALID state. After <code>detach</code> has been invoked, calls
	 * to <code>nextNode</code> or <code>previousNode</code> will raise
	 * the exception INVALID_STATE_ERR.
	 */
	public void detach();

}