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Apache Commons Compress defines an API for working with compression and archive formats. These include bzip2, gzip, pack200, LZMA, XZ, Snappy, traditional Unix Compress, DEFLATE, DEFLATE64, LZ4, Brotli, Zstandard and ar, cpio, jar, tar, zip, dump, 7z, arj.
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/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.commons.compress.changes;

import java.io.InputStream;
import java.util.Iterator;
import java.util.LinkedHashSet;
import java.util.Set;

import org.apache.commons.compress.archivers.ArchiveEntry;

/**
 * ChangeSet collects and performs changes to an archive.
 * Putting delete changes in this ChangeSet from multiple threads can
 * cause conflicts.
 * 
 * @NotThreadSafe
 */
public final class ChangeSet {

    private final Set changes = new LinkedHashSet();

    /**
     * Deletes the file with the filename from the archive. 
     * 
     * @param filename
     *            the filename of the file to delete
     */
    public void delete(final String filename) {
        addDeletion(new Change(filename, Change.TYPE_DELETE));
    }

    /**
     * Deletes the directory tree from the archive. 
     * 
     * @param dirName
     *            the name of the directory tree to delete
     */
    public void deleteDir(final String dirName) {
        addDeletion(new Change(dirName, Change.TYPE_DELETE_DIR));
    }

    /**
     * Adds a new archive entry to the archive.
     * 
     * @param pEntry
     *            the entry to add
     * @param pInput
     *            the datastream to add
     */
    public void add(final ArchiveEntry pEntry, final InputStream pInput) {
        this.add(pEntry, pInput, true);
    }

    /**
     * Adds a new archive entry to the archive.
     * If replace is set to true, this change will replace all other additions
     * done in this ChangeSet and all existing entries in the original stream.
     * 
     * @param pEntry
     *            the entry to add
     * @param pInput
     *            the datastream to add
     * @param replace
     *            indicates the this change should replace existing entries
     */
    public void add(final ArchiveEntry pEntry, final InputStream pInput, final boolean replace) {
        addAddition(new Change(pEntry, pInput, replace));
    }

    /**
     * Adds an addition change.
     * 
     * @param pChange
     *            the change which should result in an addition
     */
    private void addAddition(Change pChange) {
        if (Change.TYPE_ADD != pChange.type() ||
            pChange.getInput() == null) {
            return;
        }

        if (!changes.isEmpty()) {
            for (Iterator it = changes.iterator(); it.hasNext();) {
                Change change = it.next();
                if (change.type() == Change.TYPE_ADD
                        && change.getEntry() != null) {
                    ArchiveEntry entry = change.getEntry();

                    if(entry.equals(pChange.getEntry())) {
                        if(pChange.isReplaceMode()) {
                            it.remove();
                            changes.add(pChange);
                            return;
                        } else {
                            // do not add this change
                            return;
                        }
                    }
                }
            }
        }
        changes.add(pChange);
    }

    /**
     * Adds an delete change.
     * 
     * @param pChange
     *            the change which should result in a deletion
     */
    private void addDeletion(Change pChange) {
        if ((Change.TYPE_DELETE != pChange.type() &&
            Change.TYPE_DELETE_DIR != pChange.type()) ||
            pChange.targetFile() == null) {
            return;
        }
        String source = pChange.targetFile();

        if (!changes.isEmpty()) {
            for (Iterator it = changes.iterator(); it.hasNext();) {
                Change change = it.next();
                if (change.type() == Change.TYPE_ADD
                        && change.getEntry() != null) {
                    String target = change.getEntry().getName();

                    if (Change.TYPE_DELETE == pChange.type() && source.equals(target)) {
                        it.remove();
                    } else if (Change.TYPE_DELETE_DIR == pChange.type() && 
                               target.matches(source + "/.*")) {
                        it.remove();
                    }
                }
            }
        }
        changes.add(pChange);
    }

    /**
     * Returns the list of changes as a copy. Changes on this set
     * are not reflected on this ChangeSet and vice versa.
     * @return the changes as a copy
     */
    Set getChanges() {
        return new LinkedHashSet(changes);
    }
}