/*

 */

/*

 * 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.

 */

package com.sun.org.apache.xerces.internal.dom;

import org.w3c.dom.Node;

import org.w3c.dom.NodeList;

/**

 * This class implements the DOM's NodeList behavior for

 * Element.getElementsByTagName()

 * <P>

 * The DOM describes NodeList as follows:

 * <P>

 * 1) It may represent EITHER nodes scattered through a subtree (when

 * returned by Element.getElementsByTagName), or just the immediate

 * children (when returned by Node.getChildNodes). The latter is easy,

 * but the former (which this class addresses) is more challenging.

 * <P>

 * 2) Its behavior is "live" -- that is, it always reflects the

 * current state of the document tree. To put it another way, the

 * NodeLists obtained before and after a series of insertions and

 * deletions are effectively identical (as far as the user is

 * concerned, the former has been dynamically updated as the changes

 * have been made).

 * <P>

 * 3) Its API accesses individual nodes via an integer index, with the

 * listed nodes numbered sequentially in the order that they were

 * found during a preorder depth-first left-to-right search of the tree.

 * (Of course in the case of getChildNodes, depth is not involved.) As

 * nodes are inserted or deleted in the tree, and hence the NodeList,

 * the numbering of nodes that follow them in the NodeList will

 * change.

 * <P>

 * It is rather painful to support the latter two in the

 * getElementsByTagName case. The current solution is for Nodes to

 * maintain a change count (eventually that may be a Digest instead),

 * which the NodeList tracks and uses to invalidate itself.

 * <P>

 * Unfortunately, this does _not_ respond efficiently in the case that

 * the dynamic behavior was supposed to address: scanning a tree while

 * it is being extended. That requires knowing which subtrees have

 * changed, which can become an arbitrarily complex problem.

 * <P>

 * We save some work by filling the vector only as we access the

 * item()s... but I suspect the same users who demanded index-based

 * access will also start by doing a getLength() to control their loop,

 * blowing this optimization out of the water.

 * <P>

 * NOTE: Level 2 of the DOM will probably _not_ use NodeList for its

 * extended search mechanisms, partly for the reasons just discussed.

 *

 * @xerces.internal

 *

 * @since  PR-DOM-Level-1-19980818.

 */

public class DeepNodeListImpl

    //

    // Data

    //

    protected NodeImpl rootNode; // Where the search started

    protected String tagName;   // Or "*" to mean all-tags-acceptable

    protected String nsName;

    protected boolean enableNS = false;

    //

    // Constructors

    //

    /** Constructor. */

    public DeepNodeListImpl(NodeImpl rootNode, String tagName) {

        this.rootNode = rootNode;

    }

    /** Constructor for Namespace support. */

    public DeepNodeListImpl(NodeImpl rootNode,

        this(rootNode, tagName);

        enableNS = true;

    }

    //

    // NodeList methods

    //

    /** Returns the length of the node list. */

    public int getLength() {

        // Preload all matching elements. (Stops when we run out of subtree!)

        item(java.lang.Integer.MAX_VALUE);

        return nodes.size();

    }

    /** Returns the node at the specified index. */

    public Node item(int index) {

        Node thisNode;

        // Tree changed. Do it all from scratch!

            changes = rootNode.changes();

        }

        // In the cache

        else {

            // Pick up where we left off (Which may be the beginning)

            // Either what we want, or null (not avail.)

    } // item(int):Node

    //

    // Protected methods (might be overridden by an extending DOM)

    //

    /**

     * Iterative tree-walker. When you have a Parent link, there's often no

     * need to resort to recursion. NOTE THAT only Element nodes are matched

     * since we're specifically supporting getElementsByTagName().

     */

    protected Node nextMatchingElementAfter(Node current) {

                        // Have we found an Element with the right tagName?

                                return current;

                            }

                                        || (nsName != null

                                }

                            }

                        }

                    }

            }

    } // nextMatchingElementAfter(int):Node

} // class DeepNodeListImpl