src/main/java/org/apache/commons/net/ftp/parser/VMSVersioningFTPEntryParser.java

/*
 * 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.net.ftp.parser;

import java.util.HashMap;
import java.util.List;
import java.util.ListIterator;
import java.util.regex.MatchResult;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.regex.PatternSyntaxException;

import org.apache.commons.net.ftp.FTPClientConfig;

/**
 * Special implementation VMSFTPEntryParser with versioning turned on.
 * This parser removes all duplicates and only leaves the version with the highest
 * version number for each filename.
 *
 * This is a sample of VMS LIST output
 *
 *  "1-JUN.LIS;1              9/9           2-JUN-1998 07:32:04  [GROUP,OWNER]    (RWED,RWED,RWED,RE)",
 *  "1-JUN.LIS;2              9/9           2-JUN-1998 07:32:04  [GROUP,OWNER]    (RWED,RWED,RWED,RE)",
 *  "DATA.DIR;1               1/9           2-JUN-1998 07:32:04  [GROUP,OWNER]    (RWED,RWED,RWED,RE)",
 * <P>
 *
 *
 * @see org.apache.commons.net.ftp.FTPFileEntryParser FTPFileEntryParser (for usage instructions)
 */
public class VMSVersioningFTPEntryParser extends VMSFTPEntryParser
{

    private final Pattern _preparse_pattern_;
    private static final String PRE_PARSE_REGEX =
        "(.*?);([0-9]+)\\s*.*";

    /**
     * Constructor for a VMSFTPEntryParser object.
     *
     * @throws IllegalArgumentException
     * Thrown if the regular expression is unparseable.  Should not be seen
     * under normal conditions.  It it is seen, this is a sign that
     * <code>REGEX</code> is  not a valid regular expression.
     */
    public VMSVersioningFTPEntryParser()
    {
        this(null);
    }

    /**
     * This constructor allows the creation of a VMSVersioningFTPEntryParser
     * object with something other than the default configuration.
     *
     * @param config The {@link FTPClientConfig configuration} object used to
     * configure this parser.
     * @throws IllegalArgumentException
     * Thrown if the regular expression is unparseable.  Should not be seen
     * under normal conditions.  It it is seen, this is a sign that
     * <code>REGEX</code> is  not a valid regular expression.
     * @since 1.4
     */
    public VMSVersioningFTPEntryParser(FTPClientConfig config)
    {
        super();
        configure(config);
        try
        {
            //_preparse_matcher_ = new Perl5Matcher();
            _preparse_pattern_ = Pattern.compile(PRE_PARSE_REGEX);
        }
        catch (PatternSyntaxException pse)
        {
            throw new IllegalArgumentException (
                "Unparseable regex supplied:  " + PRE_PARSE_REGEX);
        }

   }

    /**
     * Implement hook provided for those implementers (such as
     * VMSVersioningFTPEntryParser, and possibly others) which return
     * multiple files with the same name to remove the duplicates ..
     *
     * @param original Original list
     *
     * @return Original list purged of duplicates
     */
    @Override
    public List<String> preParse(List<String> original) {
        HashMap<String, Integer> existingEntries = new HashMap<String, Integer>();
        ListIterator<String> iter = original.listIterator();
        while (iter.hasNext()) {
            String entry = iter.next().trim();
            MatchResult result = null;
            Matcher _preparse_matcher_ = _preparse_pattern_.matcher(entry);
            if (_preparse_matcher_.matches()) {
                result = _preparse_matcher_.toMatchResult();
                String name = result.group(1);
                String version = result.group(2);
                Integer nv = Integer.valueOf(version);
                Integer existing = existingEntries.get(name);
                if (null != existing) {
                    if (nv.intValue() < existing.intValue()) {
                        iter.remove();  // removes older version from original list.
                        continue;
                    }
                }
                existingEntries.put(name, nv);
            }

        }
        // we've now removed all entries less than with less than the largest
        // version number for each name that were listed after the largest.
        // we now must remove those with smaller than the largest version number
        // for each name that were found before the largest
        while (iter.hasPrevious()) {
            String entry = iter.previous().trim();
            MatchResult result = null;
            Matcher _preparse_matcher_ = _preparse_pattern_.matcher(entry);
            if (_preparse_matcher_.matches()) {
                result = _preparse_matcher_.toMatchResult();
                String name = result.group(1);
                String version = result.group(2);
                Integer nv = Integer.valueOf(version);
                Integer existing = existingEntries.get(name);
                if (null != existing) {
                    if (nv.intValue() < existing.intValue()) {
                        iter.remove(); // removes older version from original list.
                    }
                }
            }

        }
        return original;
    }


    @Override
    protected boolean isVersioning() {
        return true;
    }

}

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