package org.codehaus.plexus.util.xml;

/*
 * Copyright The Codehaus Foundation.
 *
 * Licensed 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.
 */

import org.codehaus.plexus.util.xml.pull.XmlSerializer;

import java.io.IOException;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

Author:
Jason van Zyl/** @author Jason van Zyl */
public class Xpp3DomUtils
{
    public static final String CHILDREN_COMBINATION_MODE_ATTRIBUTE = "combine.children";

    public static final String CHILDREN_COMBINATION_MERGE = "merge";

    public static final String CHILDREN_COMBINATION_APPEND = "append";

    
This default mode for combining children DOMs during merge means that where element names match, the process will
try to merge the element data, rather than putting the dominant and recessive elements (which share the same
element name) as siblings in the resulting DOM.
/**
     * This default mode for combining children DOMs during merge means that where element names match, the process will
     * try to merge the element data, rather than putting the dominant and recessive elements (which share the same
     * element name) as siblings in the resulting DOM.
     */
    public static final String DEFAULT_CHILDREN_COMBINATION_MODE = CHILDREN_COMBINATION_MERGE;

    public static final String SELF_COMBINATION_MODE_ATTRIBUTE = "combine.self";

    public static final String SELF_COMBINATION_OVERRIDE = "override";

    public static final String SELF_COMBINATION_MERGE = "merge";

    
In case of complex XML structures, combining can be done based on id.
Since:
3.0.22/**
     * In case of complex XML structures, combining can be done based on id.
     * 
     * @since 3.0.22
     */
    public static final String ID_COMBINATION_MODE_ATTRIBUTE = "combine.id";

    
This default mode for combining a DOM node during merge means that where element names match, the process will
try to merge the element attributes and values, rather than overriding the recessive element completely with the
dominant one. This means that wherever the dominant element doesn't provide the value or a particular attribute,
that value or attribute will be set from the recessive DOM node.
/**
     * This default mode for combining a DOM node during merge means that where element names match, the process will
     * try to merge the element attributes and values, rather than overriding the recessive element completely with the
     * dominant one. This means that wherever the dominant element doesn't provide the value or a particular attribute,
     * that value or attribute will be set from the recessive DOM node.
     */
    public static final String DEFAULT_SELF_COMBINATION_MODE = SELF_COMBINATION_MERGE;

    public void writeToSerializer( String namespace, XmlSerializer serializer, Xpp3Dom dom )
        throws IOException
    {
        // TODO: WARNING! Later versions of plexus-utils psit out an <?xml ?> header due to thinking this is a new
        // document - not the desired behaviour!
        SerializerXMLWriter xmlWriter = new SerializerXMLWriter( namespace, serializer );
        Xpp3DomWriter.write( xmlWriter, dom );
        if ( xmlWriter.getExceptions().size() > 0 )
        {
            throw (IOException) xmlWriter.getExceptions().get( 0 );
        }
    }

    
Merges one DOM into another, given a specific algorithm and possible override points for that algorithm.

The algorithm is as follows:

 if the recessive DOM is null, there is nothing to do... return.
 Determine whether the dominant node will suppress the recessive one (flag=mergeSelf).
  

  
 retrieve the 'combine.self' attribute on the dominant node, and try to match against 'override'...
       if it matches 'override', then set mergeSelf == false...the dominant node suppresses the recessive one
       completely.
  
 otherwise, use the default value for mergeSelf, which is true...this is the same as specifying
       'combine.self' == 'merge' as an attribute of the dominant root node.
  
 If mergeSelf == true
  

  
 if the dominant root node's value is empty, set it to the recessive root node's value
  
 For each attribute in the recessive root node which is not set in the dominant root node, set it.
  
 Determine whether children from the recessive DOM will be merged or appended to the dominant DOM as
       siblings (flag=mergeChildren).
    

    
 if childMergeOverride is set (non-null), use that value (true/false)
    
 retrieve the 'combine.children' attribute on the dominant node, and try to match against
         'append'...
    
 if it matches 'append', then set mergeChildren == false...the recessive children will be appended as
         siblings of the dominant children.
    
 otherwise, use the default value for mergeChildren, which is true...this is the same as specifying
         'combine.children' == 'merge' as an attribute on the dominant root node.
    
  
 Iterate through the recessive children, and:
    

    
 if 'combine.id' is set and there is a corresponding dominant child (matched by value of 'combine.id'),
         merge the two.
    
 if mergeChildren == true and there is a corresponding dominant child (matched by element name),
         merge the two.
    
 otherwise, add the recessive child as a new child on the dominant root node.
    
  

/**
     * Merges one DOM into another, given a specific algorithm and possible override points for that algorithm.<p>
     * The algorithm is as follows:
     * <ol>
     * <li> if the recessive DOM is null, there is nothing to do... return.</li>
     * <li> Determine whether the dominant node will suppress the recessive one (flag=mergeSelf).
     *   <ol type="A">
     *   <li> retrieve the 'combine.self' attribute on the dominant node, and try to match against 'override'...
     *        if it matches 'override', then set mergeSelf == false...the dominant node suppresses the recessive one
     *        completely.</li>
     *   <li> otherwise, use the default value for mergeSelf, which is true...this is the same as specifying
     *        'combine.self' == 'merge' as an attribute of the dominant root node.</li>
     *   </ol></li>
     * <li> If mergeSelf == true
     *   <ol type="A">
     *   <li> if the dominant root node's value is empty, set it to the recessive root node's value</li>
     *   <li> For each attribute in the recessive root node which is not set in the dominant root node, set it.</li>
     *   <li> Determine whether children from the recessive DOM will be merged or appended to the dominant DOM as
     *        siblings (flag=mergeChildren).
     *     <ol type="i">
     *     <li> if childMergeOverride is set (non-null), use that value (true/false)</li>
     *     <li> retrieve the 'combine.children' attribute on the dominant node, and try to match against
     *          'append'...</li>
     *     <li> if it matches 'append', then set mergeChildren == false...the recessive children will be appended as
     *          siblings of the dominant children.</li>
     *     <li> otherwise, use the default value for mergeChildren, which is true...this is the same as specifying
     *          'combine.children' == 'merge' as an attribute on the dominant root node.</li>
     *     </ol></li>
     *   <li> Iterate through the recessive children, and:
     *     <ol type="i">
     *     <li> if 'combine.id' is set and there is a corresponding dominant child (matched by value of 'combine.id'),
     *          merge the two.</li>
     *     <li> if mergeChildren == true and there is a corresponding dominant child (matched by element name),
     *          merge the two.</li>
     *     <li> otherwise, add the recessive child as a new child on the dominant root node.</li>
     *     </ol></li>
     *   </ol></li>
     * </ol>
     */
    private static void mergeIntoXpp3Dom( Xpp3Dom dominant, Xpp3Dom recessive, Boolean childMergeOverride )
    {
        // TODO: share this as some sort of assembler, implement a walk interface?
        if ( recessive == null )
        {
            return;
        }

        boolean mergeSelf = true;

        String selfMergeMode = dominant.getAttribute( SELF_COMBINATION_MODE_ATTRIBUTE );

        if ( isNotEmpty( selfMergeMode ) && SELF_COMBINATION_OVERRIDE.equals( selfMergeMode ) )
        {
            mergeSelf = false;
        }

        if ( mergeSelf )
        {
            if ( isEmpty( dominant.getValue() ) && !isEmpty( recessive.getValue() ) )
            {
                dominant.setValue( recessive.getValue() );
                dominant.setInputLocation( recessive.getInputLocation() );
            }

            String[] recessiveAttrs = recessive.getAttributeNames();
            for ( String attr : recessiveAttrs )
            {
                if ( isEmpty( dominant.getAttribute( attr ) ) )
                {
                    dominant.setAttribute( attr, recessive.getAttribute( attr ) );
                }
            }

            boolean mergeChildren = true;

            if ( childMergeOverride != null )
            {
                mergeChildren = childMergeOverride;
            }
            else
            {
                String childMergeMode = dominant.getAttribute( CHILDREN_COMBINATION_MODE_ATTRIBUTE );

                if ( isNotEmpty( childMergeMode ) && CHILDREN_COMBINATION_APPEND.equals( childMergeMode ) )
                {
                    mergeChildren = false;
                }
            }

            Xpp3Dom[] children = recessive.getChildren();
            for ( Xpp3Dom recessiveChild : children )
            {
                String idValue = recessiveChild.getAttribute( ID_COMBINATION_MODE_ATTRIBUTE );

                Xpp3Dom childDom = null;
                if ( isNotEmpty( idValue ) )
                {
                    for ( Xpp3Dom dominantChild : dominant.getChildren() )
                    {
                        if ( idValue.equals( dominantChild.getAttribute( ID_COMBINATION_MODE_ATTRIBUTE ) ) )
                        {
                            childDom = dominantChild;
                            // we have a match, so don't append but merge
                            mergeChildren = true;
                        }
                    }
                }
                else
                {
                    childDom = dominant.getChild( recessiveChild.getName() );
                }

                if ( mergeChildren && childDom != null )
                {
                    mergeIntoXpp3Dom( childDom, recessiveChild, childMergeOverride );
                }
                else
                {
                    dominant.addChild( new Xpp3Dom( recessiveChild ) );
                }
            }
        }
    }

    
Merge two DOMs, with one having dominance in the case of collision.
Params:
dominant – The dominant DOM into which the recessive value/attributes/children will be merged
recessive – The recessive DOM, which will be merged into the dominant DOM
childMergeOverride – Overrides attribute flags to force merging or appending of child elements into the
           dominant DOM
See Also:
CHILDREN_COMBINATION_MODE_ATTRIBUTE
SELF_COMBINATION_MODE_ATTRIBUTE/**
     * Merge two DOMs, with one having dominance in the case of collision.
     *
     * @see #CHILDREN_COMBINATION_MODE_ATTRIBUTE
     * @see #SELF_COMBINATION_MODE_ATTRIBUTE
     * @param dominant The dominant DOM into which the recessive value/attributes/children will be merged
     * @param recessive The recessive DOM, which will be merged into the dominant DOM
     * @param childMergeOverride Overrides attribute flags to force merging or appending of child elements into the
     *            dominant DOM
     */
    public static Xpp3Dom mergeXpp3Dom( Xpp3Dom dominant, Xpp3Dom recessive, Boolean childMergeOverride )
    {
        if ( dominant != null )
        {
            mergeIntoXpp3Dom( dominant, recessive, childMergeOverride );
            return dominant;
        }
        return recessive;
    }

    
Merge two DOMs, with one having dominance in the case of collision. Merge mechanisms (vs. override for nodes, or
vs. append for children) is determined by attributes of the dominant root node.
Params:
dominant – The dominant DOM into which the recessive value/attributes/children will be merged
recessive – The recessive DOM, which will be merged into the dominant DOM
See Also:
CHILDREN_COMBINATION_MODE_ATTRIBUTE
SELF_COMBINATION_MODE_ATTRIBUTE/**
     * Merge two DOMs, with one having dominance in the case of collision. Merge mechanisms (vs. override for nodes, or
     * vs. append for children) is determined by attributes of the dominant root node.
     *
     * @see #CHILDREN_COMBINATION_MODE_ATTRIBUTE
     * @see #SELF_COMBINATION_MODE_ATTRIBUTE
     * @param dominant The dominant DOM into which the recessive value/attributes/children will be merged
     * @param recessive The recessive DOM, which will be merged into the dominant DOM
     */
    public static Xpp3Dom mergeXpp3Dom( Xpp3Dom dominant, Xpp3Dom recessive )
    {
        if ( dominant != null )
        {
            mergeIntoXpp3Dom( dominant, recessive, null );
            return dominant;
        }
        return recessive;
    }

    public static boolean isNotEmpty( String str )
    {
        return ( str != null && str.length() > 0 );
    }

    public static boolean isEmpty( String str )
    {
        return ( str == null || str.trim().length() == 0 );
    }
}