001package org.eclipse.aether.util.graph.visitor;
002
003/*
004 * Licensed to the Apache Software Foundation (ASF) under one
005 * or more contributor license agreements.  See the NOTICE file
006 * distributed with this work for additional information
007 * regarding copyright ownership.  The ASF licenses this file
008 * to you under the Apache License, Version 2.0 (the
009 * "License"); you may not use this file except in compliance
010 * with the License.  You may obtain a copy of the License at
011 * 
012 *  http://www.apache.org/licenses/LICENSE-2.0
013 * 
014 * Unless required by applicable law or agreed to in writing,
015 * software distributed under the License is distributed on an
016 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
017 * KIND, either express or implied.  See the License for the
018 * specific language governing permissions and limitations
019 * under the License.
020 */
021
022import java.util.ArrayList;
023import java.util.Arrays;
024import java.util.IdentityHashMap;
025import java.util.List;
026import java.util.Map;
027
028import org.eclipse.aether.graph.DependencyFilter;
029import org.eclipse.aether.graph.DependencyNode;
030import org.eclipse.aether.graph.DependencyVisitor;
031
032/**
033 * A dependency visitor that records all paths leading to nodes matching a certain filter criteria.
034 */
035public final class PathRecordingDependencyVisitor
036    implements DependencyVisitor
037{
038
039    private final DependencyFilter filter;
040
041    private final List<List<DependencyNode>> paths;
042
043    private final Stack<DependencyNode> parents;
044
045    private final Map<DependencyNode, Object> visited;
046
047    private final boolean excludeChildrenOfMatches;
048
049    /**
050     * Creates a new visitor that uses the specified filter to identify terminal nodes of interesting paths. The visitor
051     * will not search for paths going beyond an already matched node.
052     * 
053     * @param filter The filter used to select terminal nodes of paths to record, may be {@code null} to match any node.
054     */
055    public PathRecordingDependencyVisitor( DependencyFilter filter )
056    {
057        this( filter, true );
058    }
059
060    /**
061     * Creates a new visitor that uses the specified filter to identify terminal nodes of interesting paths.
062     * 
063     * @param filter The filter used to select terminal nodes of paths to record, may be {@code null} to match any node.
064     * @param excludeChildrenOfMatches Flag controlling whether children of matched nodes should be excluded from the
065     *            traversal, thereby ignoring any potential paths to other matching nodes beneath a matching ancestor
066     *            node. If {@code true}, all recorded paths will have only one matching node (namely the terminal node),
067     *            if {@code false} a recorded path can consist of multiple matching nodes.
068     */
069    public PathRecordingDependencyVisitor( DependencyFilter filter, boolean excludeChildrenOfMatches )
070    {
071        this.filter = filter;
072        this.excludeChildrenOfMatches = excludeChildrenOfMatches;
073        paths = new ArrayList<List<DependencyNode>>();
074        parents = new Stack<DependencyNode>();
075        visited = new IdentityHashMap<DependencyNode, Object>( 128 );
076    }
077
078    /**
079     * Gets the filter being used to select terminal nodes.
080     * 
081     * @return The filter being used or {@code null} if none.
082     */
083    public DependencyFilter getFilter()
084    {
085        return filter;
086    }
087
088    /**
089     * Gets the paths leading to nodes matching the filter that have been recorded during the graph visit. A path is
090     * given as a sequence of nodes, starting with the root node of the graph and ending with a node that matched the
091     * filter.
092     * 
093     * @return The recorded paths, never {@code null}.
094     */
095    public List<List<DependencyNode>> getPaths()
096    {
097        return paths;
098    }
099
100    public boolean visitEnter( DependencyNode node )
101    {
102        boolean accept = filter == null || filter.accept( node, parents );
103
104        parents.push( node );
105
106        if ( accept )
107        {
108            DependencyNode[] path = new DependencyNode[parents.size()];
109            for ( int i = 0, n = parents.size(); i < n; i++ )
110            {
111                path[n - i - 1] = parents.get( i );
112            }
113            paths.add( Arrays.asList( path ) );
114
115            if ( excludeChildrenOfMatches )
116            {
117                return false;
118            }
119        }
120
121        if ( visited.put( node, Boolean.TRUE ) != null )
122        {
123            return false;
124        }
125
126        return true;
127    }
128
129    public boolean visitLeave( DependencyNode node )
130    {
131        parents.pop();
132        visited.remove( node );
133
134        return true;
135    }
136
137}