/*
 * 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;

/**
 * Filters are objects that know how to "filter out" nodes. If a
 * <code>NodeIterator</code> or <code>TreeWalker</code> is given a
 * <code>NodeFilter</code>, it applies the filter before it returns the
 * next node. If the filter says to accept the node, the traversal logic
 * returns it; otherwise, traversal looks for the next node and pretends that
 * the node that was rejected was not there.
 * <p>
 * The DOM does not provide any filters. <code>NodeFilter</code> is just an
 * interface that users can implement to provide their own filters.
 * <p>
 * <code>NodeFilters</code> do not need to know how to traverse from node to
 * node, nor do they need to know anything about the data structure that is
 * being traversed. This makes it very easy to write filters, since the only
 * thing they have to know how to do is evaluate a single node. One filter may
 * be used with a number of different kinds of traversals, encouraging code
 * reuse.
 * <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 NodeFilter {
	// Constants returned by acceptNode
	/**
	 * Accept the node. Navigation methods defined for
	 * <code>NodeIterator</code> or <code>TreeWalker</code> will return
	 * this node.
	 */
	public static final short FILTER_ACCEPT = 1;
	/**
	 * Reject the node. Navigation methods defined for
	 * <code>NodeIterator</code> or <code>TreeWalker</code> will not
	 * return this node. For <code>TreeWalker</code>, the children of this
	 * node will also be rejected. <code>NodeIterators</code> treat this as
	 * a synonym for <code>FILTER_SKIP</code>.
	 */
	public static final short FILTER_REJECT = 2;
	/**
	 * Skip this single node. Navigation methods defined for
	 * <code>NodeIterator</code> or <code>TreeWalker</code> will not
	 * return this node. For both <code>NodeIterator</code> and
	 * <code>TreeWalker</code>, the children of this node will still be
	 * considered.
	 */
	public static final short FILTER_SKIP = 3;

	// Constants for whatToShow
	/**
	 * Show all <code>Nodes</code>.
	 */
	public static final int SHOW_ALL = 0xFFFFFFFF;
	/**
	 * Show <code>Element</code> nodes.
	 */
	public static final int SHOW_ELEMENT = 0x00000001;
	/**
	 * Show <code>Attr</code> nodes. This is meaningful only when creating
	 * an iterator or tree-walker with an attribute node as its
	 * <code>root</code>; in this case, it means that the attribute node
	 * will appear in the first position of the iteration or traversal. Since
	 * attributes are never children of other nodes, they do not appear when
	 * traversing over the document tree.
	 */
	public static final int SHOW_ATTRIBUTE = 0x00000002;
	/**
	 * Show <code>Text</code> nodes.
	 */
	public static final int SHOW_TEXT = 0x00000004;
	/**
	 * Show <code>CDATASection</code> nodes.
	 */
	public static final int SHOW_CDATA_SECTION = 0x00000008;
	/**
	 * Show <code>EntityReference</code> nodes.
	 */
	public static final int SHOW_ENTITY_REFERENCE = 0x00000010;
	/**
	 * Show <code>Entity</code> nodes. This is meaningful only when creating
	 * an iterator or tree-walker with an<code> Entity</code> node as its
	 * <code>root</code>; in this case, it means that the
	 * <code>Entity</code> node will appear in the first position of the
	 * traversal. Since entities are not part of the document tree, they do
	 * not appear when traversing over the document tree.
	 */
	public static final int SHOW_ENTITY = 0x00000020;
	/**
	 * Show <code>ProcessingInstruction</code> nodes.
	 */
	public static final int SHOW_PROCESSING_INSTRUCTION = 0x00000040;
	/**
	 * Show <code>Comment</code> nodes.
	 */
	public static final int SHOW_COMMENT = 0x00000080;
	/**
	 * Show <code>Document</code> nodes.
	 */
	public static final int SHOW_DOCUMENT = 0x00000100;
	/**
	 * Show <code>DocumentType</code> nodes.
	 */
	public static final int SHOW_DOCUMENT_TYPE = 0x00000200;
	/**
	 * Show <code>DocumentFragment</code> nodes.
	 */
	public static final int SHOW_DOCUMENT_FRAGMENT = 0x00000400;
	/**
	 * Show <code>Notation</code> nodes. This is meaningful only when
	 * creating an iterator or tree-walker with a <code>Notation</code> node
	 * as its <code>root</code>; in this case, it means that the
	 * <code>Notation</code> node will appear in the first position of the
	 * traversal. Since notations are not part of the document tree, they do
	 * not appear when traversing over the document tree.
	 */
	public static final int SHOW_NOTATION = 0x00000800;

	/**
	 * Test whether a specified node is visible in the logical view of a
	 * <code>TreeWalker</code> or <code>NodeIterator</code>. This
	 * function will be called by the implementation of
	 * <code>TreeWalker</code> and <code>NodeIterator</code>; it is not
	 * normally called directly from user code. (Though you could do so if you
	 * wanted to use the same filter to guide your own application logic.)
	 * 
	 * @param nThe
	 *            node to check to see if it passes the filter or not.
	 * @return a constant to determine whether the node is accepted, rejected,
	 *         or skipped, as defined above.
	 */
	public short acceptNode(Node n);

}