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1   package org.apache.maven.shared.dependency.graph.traversal;
2   
3   /*
4    * Licensed to the Apache Software Foundation (ASF) under one
5    * or more contributor license agreements.  See the NOTICE file
6    * distributed with this work for additional information
7    * regarding copyright ownership.  The ASF licenses this file
8    * to you under the Apache License, Version 2.0 (the
9    * "License"); you may not use this file except in compliance
10   * with the License.  You may obtain a copy of the License at
11   *
12   *  http://www.apache.org/licenses/LICENSE-2.0
13   *
14   * Unless required by applicable law or agreed to in writing,
15   * software distributed under the License is distributed on an
16   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
17   * KIND, either express or implied.  See the License for the
18   * specific language governing permissions and limitations
19   * under the License.
20   */
21  
22  import java.util.ArrayList;
23  import java.util.Stack;
24  
25  import org.apache.maven.shared.dependency.graph.DependencyNode;
26  import org.apache.maven.shared.dependency.graph.internal.DefaultDependencyNode;
27  
28  /**
29   * A dependency node visitor that clones visited nodes into a new dependency tree. This can be used in conjunction with
30   * a dependency node filter to construct subtrees.
31   * 
32   * @author <a href="mailto:markhobson@gmail.com">Mark Hobson</a>
33   */
34  public class BuildingDependencyNodeVisitor
35      implements DependencyNodeVisitor
36  {
37      // fields -----------------------------------------------------------------
38  
39      /**
40       * The dependency node visitor to apply on the resultant dependency tree, or <code>null</code> for none.
41       */
42      private final DependencyNodeVisitor visitor;
43  
44      /**
45       * The resultant tree parent nodes for the currently visited node.
46       */
47      private final Stack<DependencyNode> parentNodes;
48  
49      /**
50       * The root node of the resultant tree.
51       */
52      private DependencyNode rootNode;
53  
54      // constructors -----------------------------------------------------------
55  
56      /**
57       * Creates a dependency node visitor that clones visited nodes into a new dependency tree.
58       */
59      public BuildingDependencyNodeVisitor()
60      {
61          this( null );
62      }
63  
64      /**
65       * Creates a dependency node visitor that clones visited nodes into a new dependency tree, and then applies the
66       * specified dependency node visitor on the resultant dependency tree.
67       * 
68       * @param visitor the dependency node visitor to apply on the resultant dependency tree, or <code>null</code> for
69       *            none
70       */
71      public BuildingDependencyNodeVisitor( DependencyNodeVisitor visitor )
72      {
73          this.visitor = visitor;
74  
75          parentNodes = new Stack<DependencyNode>();
76      }
77  
78      // DependencyNodeVisitor methods ------------------------------------------
79  
80      /**
81       * {@inheritDoc}
82       */
83      public boolean visit( DependencyNode node )
84      {
85          // clone the node
86          DefaultDependencyNode newNode =
87              new DefaultDependencyNode( parentNodes.isEmpty() ? null : parentNodes.peek(), node.getArtifact(),
88                                         node.getPremanagedVersion(), node.getPremanagedScope(),
89                                         node.getVersionConstraint() );
90          newNode.setChildren( new ArrayList<DependencyNode>() );
91  
92          if ( parentNodes.empty() )
93          {
94              rootNode = newNode;
95          }
96          else
97          {
98              DependencyNode parentNode = parentNodes.peek();
99              parentNode.getChildren().add( newNode );
100         }
101 
102         parentNodes.push( newNode );
103 
104         return true;
105     }
106 
107     /**
108      * {@inheritDoc}
109      */
110     public boolean endVisit( DependencyNode node )
111     {
112         parentNodes.pop();
113 
114         // apply the visitor to the resultant tree on the last visit
115         if ( parentNodes.empty() && visitor != null )
116         {
117             rootNode.accept( visitor );
118         }
119 
120         return true;
121     }
122 
123     // public methods ---------------------------------------------------------
124 
125     /**
126      * Gets the dependency node visitor that this visitor applies on the resultant dependency tree.
127      * 
128      * @return the dependency node visitor, or <code>null</code> for none
129      */
130     public DependencyNodeVisitor getDependencyNodeVisitor()
131     {
132         return visitor;
133     }
134 
135     /**
136      * Gets the root node of the resultant dependency tree constructed by this visitor.
137      * 
138      * @return the root node, or <code>null</code> if the source tree has not yet been visited
139      */
140     public DependencyNode getDependencyTree()
141     {
142         return rootNode;
143     }
144 }