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.repository;
020
021import java.io.File;
022import java.util.ArrayList;
023import java.util.Arrays;
024import java.util.Collection;
025import java.util.Collections;
026import java.util.LinkedHashSet;
027import java.util.List;
028import java.util.Objects;
029import java.util.concurrent.atomic.AtomicReference;
030
031import org.eclipse.aether.artifact.Artifact;
032import org.eclipse.aether.repository.WorkspaceReader;
033import org.eclipse.aether.repository.WorkspaceRepository;
034
035import static java.util.Objects.requireNonNull;
036
037/**
038 * A workspace reader that delegates to a chain of other readers, effectively aggregating their contents.
039 */
040public final class ChainedWorkspaceReader implements WorkspaceReader {
041    private final List<WorkspaceReader> readers;
042    private final AtomicReference<WorkspaceRepository> repository;
043
044    /**
045     * Creates a new workspace reader by chaining the specified readers.
046     *
047     * @param readers the readers to chain, may be {@code null}
048     * @see #newInstance(WorkspaceReader, WorkspaceReader)
049     */
050    public ChainedWorkspaceReader(WorkspaceReader... readers) {
051        ArrayList<WorkspaceReader> list = new ArrayList<>();
052        if (readers != null) {
053            Arrays.stream(readers).filter(Objects::nonNull).forEach(list::add);
054        }
055        StringBuilder buffer = new StringBuilder();
056        for (WorkspaceReader reader : list) {
057            if (buffer.length() > 0) {
058                buffer.append('+');
059            }
060            buffer.append(reader.getRepository().getContentType());
061        }
062        this.readers = Collections.unmodifiableList(list);
063        this.repository = new AtomicReference<>(new WorkspaceRepository(buffer.toString(), new Key(list)));
064    }
065
066    /**
067     * Creates a new workspace reader by chaining the specified readers. In contrast to the constructor, this factory
068     * method will avoid creating an actual chained reader if one of the specified readers is actually {@code null}.
069     *
070     * @param reader1 the first workspace reader, may be {@code null}
071     * @param reader2 the second workspace reader, may be {@code null}
072     * @return the chained reader or {@code null} if no workspace reader was supplied
073     */
074    public static WorkspaceReader newInstance(WorkspaceReader reader1, WorkspaceReader reader2) {
075        if (reader1 == null) {
076            return reader2;
077        } else if (reader2 == null) {
078            return reader1;
079        }
080        return new ChainedWorkspaceReader(reader1, reader2);
081    }
082
083    @Override
084    public File findArtifact(Artifact artifact) {
085        requireNonNull(artifact, "artifact cannot be null");
086        File file = null;
087
088        for (WorkspaceReader reader : readers) {
089            file = reader.findArtifact(artifact);
090            if (file != null) {
091                break;
092            }
093        }
094
095        return file;
096    }
097
098    @Override
099    public List<String> findVersions(Artifact artifact) {
100        requireNonNull(artifact, "artifact cannot be null");
101        Collection<String> versions = new LinkedHashSet<>();
102
103        for (WorkspaceReader reader : readers) {
104            versions.addAll(reader.findVersions(artifact));
105        }
106
107        return Collections.unmodifiableList(new ArrayList<>(versions));
108    }
109
110    @Override
111    public WorkspaceRepository getRepository() {
112        Key key = new Key(readers);
113        return repository.updateAndGet(r -> {
114            if (!key.equals(r.getKey())) {
115                return new WorkspaceRepository(r.getContentType(), key);
116            } else {
117                return r;
118            }
119        });
120    }
121
122    private static class Key {
123        private final List<Object> keys;
124
125        Key(List<WorkspaceReader> readers) {
126            ArrayList<Object> keys = new ArrayList<>();
127            for (WorkspaceReader reader : readers) {
128                keys.add(reader.getRepository().getKey());
129            }
130            this.keys = keys;
131        }
132
133        @Override
134        public boolean equals(Object obj) {
135            if (this == obj) {
136                return true;
137            }
138            if (obj == null || !getClass().equals(obj.getClass())) {
139                return false;
140            }
141            return keys.equals(((Key) obj).keys);
142        }
143
144        @Override
145        public int hashCode() {
146            return keys.hashCode();
147        }
148    }
149}