/*
 * 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 org.apache.xerces.dom;

import org.w3c.dom.DocumentFragment;
import org.w3c.dom.Node;
import org.w3c.dom.Text;

DocumentFragment is a "lightweight" or "minimal" Document
object. It is very common to want to be able to extract a portion
of a document's tree or to create a new fragment of a
document. Imagine implementing a user command like cut or
rearranging a document by moving fragments around. It is desirable
to have an object which can hold such fragments and it is quite
natural to use a Node for this purpose. While it is true that a
Document object could fulfil this role, a Document object can
potentially be a heavyweight object, depending on the underlying
implementation... and in DOM Level 1, nodes aren't allowed to cross
Document boundaries anyway. What is really needed for this is a
very lightweight object.  DocumentFragment is such an object.

Furthermore, various operations -- such as inserting nodes as
children of another Node -- may take DocumentFragment objects as
arguments; this results in all the child nodes of the
DocumentFragment being moved to the child list of this node.

The children of a DocumentFragment node are zero or more nodes
representing the tops of any sub-trees defining the structure of
the document.  DocumentFragment do not need to be well-formed XML
documents (although they do need to follow the rules imposed upon
well-formed XML parsed entities, which can have multiple top
nodes). For example, a DocumentFragment might have only one child
and that child node could be a Text node. Such a structure model
represents neither an HTML document nor a well-formed XML document.

When a DocumentFragment is inserted into a Document (or indeed any
other Node that may take children) the children of the
DocumentFragment and not the DocumentFragment itself are inserted
into the Node. This makes the DocumentFragment very useful when the
user wishes to create nodes that are siblings; the DocumentFragment
acts as the parent of these nodes so that the user can use the
standard methods from the Node interface, such as insertBefore()
and appendChild().
@xerces.internal
Version:
$Id: DocumentFragmentImpl.java 447266 2006-09-18 05:57:49Z mrglavas $
Since:
 PR-DOM-Level-1-19980818./**
 * DocumentFragment is a "lightweight" or "minimal" Document
 * object. It is very common to want to be able to extract a portion
 * of a document's tree or to create a new fragment of a
 * document. Imagine implementing a user command like cut or
 * rearranging a document by moving fragments around. It is desirable
 * to have an object which can hold such fragments and it is quite
 * natural to use a Node for this purpose. While it is true that a
 * Document object could fulfil this role, a Document object can
 * potentially be a heavyweight object, depending on the underlying
 * implementation... and in DOM Level 1, nodes aren't allowed to cross
 * Document boundaries anyway. What is really needed for this is a
 * very lightweight object.  DocumentFragment is such an object.
 * <P>
 * Furthermore, various operations -- such as inserting nodes as
 * children of another Node -- may take DocumentFragment objects as
 * arguments; this results in all the child nodes of the
 * DocumentFragment being moved to the child list of this node.
 * <P>
 * The children of a DocumentFragment node are zero or more nodes
 * representing the tops of any sub-trees defining the structure of
 * the document.  DocumentFragment do not need to be well-formed XML
 * documents (although they do need to follow the rules imposed upon
 * well-formed XML parsed entities, which can have multiple top
 * nodes). For example, a DocumentFragment might have only one child
 * and that child node could be a Text node. Such a structure model
 * represents neither an HTML document nor a well-formed XML document.
 * <P>
 * When a DocumentFragment is inserted into a Document (or indeed any
 * other Node that may take children) the children of the
 * DocumentFragment and not the DocumentFragment itself are inserted
 * into the Node. This makes the DocumentFragment very useful when the
 * user wishes to create nodes that are siblings; the DocumentFragment
 * acts as the parent of these nodes so that the user can use the
 * standard methods from the Node interface, such as insertBefore()
 * and appendChild().
 * 
 * @xerces.internal

 *
 * @version $Id: DocumentFragmentImpl.java 447266 2006-09-18 05:57:49Z mrglavas $
 * @since  PR-DOM-Level-1-19980818.
 */
public class DocumentFragmentImpl 
    extends ParentNode
    implements DocumentFragment {

    //
    // Constants
    //

    
Serialization version. /** Serialization version. */
    static final long serialVersionUID = -7596449967279236746L;
    
    //
    // Constructors
    //

    
Factory constructor. /** Factory constructor. */
    public DocumentFragmentImpl(CoreDocumentImpl ownerDoc) {
        super(ownerDoc);
    }  
  
    
Constructor for serialization. /** Constructor for serialization. */
    public DocumentFragmentImpl() {}

    //
    // Node methods
    //

    
A short integer indicating what type of node this is. The named
constants for this value are defined in the org.w3c.dom.Node interface.
/** 
     * A short integer indicating what type of node this is. The named
     * constants for this value are defined in the org.w3c.dom.Node interface.
     */
    public short getNodeType() {
        return Node.DOCUMENT_FRAGMENT_NODE;
    }

    
Returns the node name. /** Returns the node name. */
    public String getNodeName() {
        return "#document-fragment";
    }
    
    
Override default behavior to call normalize() on this Node's
children. It is up to implementors or Node to override normalize()
to take action.
/**
     * Override default behavior to call normalize() on this Node's
     * children. It is up to implementors or Node to override normalize()
     * to take action.
     */
    public void normalize() {
        // No need to normalize if already normalized.
        if (isNormalized()) {
            return;
        }
        if (needsSyncChildren()) {
            synchronizeChildren();
        }
        ChildNode kid, next;

        for (kid = firstChild; kid != null; kid = next) {
            next = kid.nextSibling;

            // If kid is a text node, we need to check for one of two
            // conditions:
            //   1) There is an adjacent text node
            //   2) There is no adjacent text node, but kid is
            //      an empty text node.
            if ( kid.getNodeType() == Node.TEXT_NODE )
            {
                // If an adjacent text node, merge it with kid
                if ( next!=null && next.getNodeType() == Node.TEXT_NODE )
                {
                    ((Text)kid).appendData(next.getNodeValue());
                    removeChild( next );
                    next = kid; // Don't advance; there might be another.
                }
                else
                {
                    // If kid is empty, remove it
                    if ( kid.getNodeValue() == null || kid.getNodeValue().length() == 0 ) {
                        removeChild( kid );
                    }
                }
            }

            kid.normalize();
        }

        isNormalized(true);
    }

} // class DocumentFragmentImpl