001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *   http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing,
013 * software distributed under the License is distributed on an
014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 * KIND, either express or implied.  See the License for the
016 * specific language governing permissions and limitations
017 * under the License.
018 */
019package org.eclipse.aether.util.graph.transformer;
020
021import org.eclipse.aether.RepositoryException;
022import org.eclipse.aether.collection.DependencyGraphTransformationContext;
023import org.eclipse.aether.collection.DependencyGraphTransformer;
024import org.eclipse.aether.graph.DependencyNode;
025
026import static java.util.Objects.requireNonNull;
027
028/**
029 * A dependency graph transformer that chains other transformers.
030 */
031public final class ChainedDependencyGraphTransformer implements DependencyGraphTransformer {
032
033    private final DependencyGraphTransformer[] transformers;
034
035    /**
036     * Creates a new transformer that chains the specified transformers.
037     *
038     * @param transformers The transformers to chain, may be {@code null} or empty.
039     */
040    public ChainedDependencyGraphTransformer(DependencyGraphTransformer... transformers) {
041        if (transformers == null) {
042            this.transformers = new DependencyGraphTransformer[0];
043        } else {
044            this.transformers = transformers;
045        }
046    }
047
048    /**
049     * Creates a new transformer that chains the specified transformers or simply returns one of them if the other one
050     * is {@code null}.
051     *
052     * @param transformer1 The first transformer of the chain, may be {@code null}.
053     * @param transformer2 The second transformer of the chain, may be {@code null}.
054     * @return The chained transformer or {@code null} if both input transformers are {@code null}.
055     */
056    public static DependencyGraphTransformer newInstance(
057            DependencyGraphTransformer transformer1, DependencyGraphTransformer transformer2) {
058        if (transformer1 == null) {
059            return transformer2;
060        } else if (transformer2 == null) {
061            return transformer1;
062        }
063        return new ChainedDependencyGraphTransformer(transformer1, transformer2);
064    }
065
066    public DependencyNode transformGraph(DependencyNode node, DependencyGraphTransformationContext context)
067            throws RepositoryException {
068        requireNonNull(node, "node cannot be null");
069        requireNonNull(context, "context cannot be null");
070        for (DependencyGraphTransformer transformer : transformers) {
071            node = transformer.transformGraph(node, context);
072        }
073        return node;
074    }
075}