package org.apache.maven.shared.dependency.graph.traversal;

 /*

  * 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.

  */

 import java.util.ArrayList;

 import java.util.Stack;

 import org.apache.maven.shared.dependency.graph.DependencyNode;

 import org.apache.maven.shared.dependency.graph.internal.DefaultDependencyNode;

 /**

  * A dependency node visitor that clones visited nodes into a new dependency tree. This can be used in conjunction with

  * a dependency node filter to construct subtrees.

  * 

  * @author <a href="mailto:markhobson@gmail.com">Mark Hobson</a>

  */

 public class BuildingDependencyNodeVisitor

     implements DependencyNodeVisitor

 {

     // fields -----------------------------------------------------------------

     /**

      * The dependency node visitor to apply on the resultant dependency tree, or <code>null</code> for none.

      */

     private final DependencyNodeVisitor visitor;

     /**

      * The resultant tree parent nodes for the currently visited node.

      */

     private final Stack<DependencyNode> parentNodes;

     /**

      * The root node of the resultant tree.

      */

     private DependencyNode rootNode;

     // constructors -----------------------------------------------------------

     /**

      * Creates a dependency node visitor that clones visited nodes into a new dependency tree.

      */

     public BuildingDependencyNodeVisitor()

     {

         this( null );

     }

     /**

      * Creates a dependency node visitor that clones visited nodes into a new dependency tree, and then applies the

      * specified dependency node visitor on the resultant dependency tree.

      * 

      * @param visitor

      *            the dependency node visitor to apply on the resultant dependency tree, or <code>null</code> for none

      */

     public BuildingDependencyNodeVisitor( DependencyNodeVisitor visitor )

     {

         this.visitor = visitor;

         parentNodes = new Stack<DependencyNode>();

     }

     // DependencyNodeVisitor methods ------------------------------------------

     /**

      * {@inheritDoc}

      */

     public boolean visit( DependencyNode node )

     {

         // clone the node

         DefaultDependencyNode newNode =

             new DefaultDependencyNode( parentNodes.isEmpty() ? null : parentNodes.peek(), node.getArtifact(),

                                        node.getPremanagedVersion(), node.getPremanagedScope(),

                                        node.getVersionConstraint() );

         newNode.setChildren( new ArrayList<DependencyNode>() );

         if ( parentNodes.empty() )

         {

             rootNode = newNode;

         }

         else

         {

             DependencyNode parentNode = parentNodes.peek();

             parentNode.getChildren().add( newNode );

         }

         parentNodes.push( newNode );

         return true;

     }

     /**

      * {@inheritDoc}

      */

     public boolean endVisit( DependencyNode node )

     {

         parentNodes.pop();

         // apply the visitor to the resultant tree on the last visit

         if ( parentNodes.empty() && visitor != null )

         {

             rootNode.accept( visitor );

         }

         return true;

     }

     // public methods ---------------------------------------------------------

     /**

      * Gets the dependency node visitor that this visitor applies on the resultant dependency tree.

      * 

      * @return the dependency node visitor, or <code>null</code> for none

      */

     public DependencyNodeVisitor getDependencyNodeVisitor()

     {

         return visitor;

     }

     /**

      * Gets the root node of the resultant dependency tree constructed by this visitor.

      * 

      * @return the root node, or <code>null</code> if the source tree has not yet been visited

      */

     public DependencyNode getDependencyTree()

     {

         return rootNode;

     }

 }