001package org.eclipse.aether.util.graph.transformer;
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 org.eclipse.aether.RepositoryException;
023import org.eclipse.aether.collection.DependencyGraphTransformationContext;
024import org.eclipse.aether.collection.DependencyGraphTransformer;
025import org.eclipse.aether.graph.DependencyNode;
026
027import static java.util.Objects.requireNonNull;
028
029/**
030 * A dependency graph transformer that chains other transformers.
031 */
032public final class ChainedDependencyGraphTransformer
033    implements DependencyGraphTransformer
034{
035
036    private final DependencyGraphTransformer[] transformers;
037
038    /**
039     * Creates a new transformer that chains the specified transformers.
040     * 
041     * @param transformers The transformers to chain, may be {@code null} or empty.
042     */
043    public ChainedDependencyGraphTransformer( DependencyGraphTransformer... transformers )
044    {
045        if ( transformers == null )
046        {
047            this.transformers = new DependencyGraphTransformer[0];
048        }
049        else
050        {
051            this.transformers = transformers;
052        }
053    }
054
055    /**
056     * Creates a new transformer that chains the specified transformers or simply returns one of them if the other one
057     * is {@code null}.
058     * 
059     * @param transformer1 The first transformer of the chain, may be {@code null}.
060     * @param transformer2 The second transformer of the chain, may be {@code null}.
061     * @return The chained transformer or {@code null} if both input transformers are {@code null}.
062     */
063    public static DependencyGraphTransformer newInstance( DependencyGraphTransformer transformer1,
064                                                          DependencyGraphTransformer transformer2 )
065    {
066        if ( transformer1 == null )
067        {
068            return transformer2;
069        }
070        else if ( transformer2 == null )
071        {
072            return transformer1;
073        }
074        return new ChainedDependencyGraphTransformer( transformer1, transformer2 );
075    }
076
077    public DependencyNode transformGraph( DependencyNode node, DependencyGraphTransformationContext context )
078        throws RepositoryException
079    {
080        requireNonNull( node, "node cannot be null" );
081        requireNonNull( context, "context cannot be null" );
082        for ( DependencyGraphTransformer transformer : transformers )
083        {
084            node = transformer.transformGraph( node, context );
085        }
086        return node;
087    }
088
089}