001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      https://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017
018package org.apache.commons.net.ftp.parser;
019
020import java.util.HashMap;
021import java.util.List;
022import java.util.ListIterator;
023import java.util.regex.MatchResult;
024import java.util.regex.Matcher;
025import java.util.regex.Pattern;
026
027import org.apache.commons.net.ftp.FTPClientConfig;
028
029/**
030 * Special implementation VMSFTPEntryParser with versioning turned on. This parser removes all duplicates and only leaves the version with the highest version
031 * number for each file name.
032 * <p>
033 * This is a sample of VMS LIST output
034 * </p>
035 *
036 * <pre>
037 *  "1-JUN.LIS;1              9/9           2-JUN-1998 07:32:04  [GROUP,OWNER]    (RWED,RWED,RWED,RE)",
038 *  "1-JUN.LIS;2              9/9           2-JUN-1998 07:32:04  [GROUP,OWNER]    (RWED,RWED,RWED,RE)",
039 *  "DATA.DIR;1               1/9           2-JUN-1998 07:32:04  [GROUP,OWNER]    (RWED,RWED,RWED,RE)",
040 * </pre>
041 *
042 * @see org.apache.commons.net.ftp.FTPFileEntryParser FTPFileEntryParser (for usage instructions)
043 */
044public class VMSVersioningFTPEntryParser extends VMSFTPEntryParser {
045
046    /**
047     * Guard against polynomial regular expression used on uncontrolled data.
048     * Don't look for more than 20 digits for the version.
049     * Don't look for more than 80 spaces after the version.
050     * Don't look for more than 80 characters after the spaces.
051     */
052    private static final String REGEX = "(.*?);([0-9]{1,20})\\s{0,80}.{0,80}";
053    private static final Pattern PATTERN = Pattern.compile(REGEX);
054
055    /**
056     * Constructor for a VMSFTPEntryParser object.
057     *
058     * @throws IllegalArgumentException Thrown if the regular expression is unparseable. Should not be seen under normal conditions. If the exception is seen,
059     *                                  this is a sign that {@code REGEX} is not a valid regular expression.
060     */
061    public VMSVersioningFTPEntryParser() {
062        this(null);
063    }
064
065    /**
066     * This constructor allows the creation of a VMSVersioningFTPEntryParser object with something other than the default configuration.
067     *
068     * @param config The {@link FTPClientConfig configuration} object used to configure this parser.
069     * @throws IllegalArgumentException Thrown if the regular expression is unparseable. Should not be seen under normal conditions. If the exception is seen,
070     *                                  this is a sign that {@code REGEX} is not a valid regular expression.
071     * @since 1.4
072     */
073    public VMSVersioningFTPEntryParser(final FTPClientConfig config) {
074        configure(config);
075    }
076
077    @Override
078    protected boolean isVersioning() {
079        return true;
080    }
081
082    /**
083     * Implement hook provided for those implementers (such as VMSVersioningFTPEntryParser, and possibly others) which return multiple files with the same name
084     * to remove the duplicates.
085     *
086     * @param original Original list
087     * @return Original list purged of duplicates
088     */
089    @Override
090    public List<String> preParse(final List<String> original) {
091        final HashMap<String, Integer> existingEntries = new HashMap<>();
092        final ListIterator<String> iter = original.listIterator();
093        while (iter.hasNext()) {
094            final String entry = iter.next().trim();
095            final MatchResult result;
096            final Matcher matcher = PATTERN.matcher(entry);
097            if (matcher.matches()) {
098                result = matcher.toMatchResult();
099                final String name = result.group(1);
100                final String version = result.group(2);
101                final Integer nv = Integer.valueOf(version);
102                final Integer existing = existingEntries.get(name);
103                if (null != existing && nv.intValue() < existing.intValue()) {
104                    iter.remove(); // removes older version from original list.
105                    continue;
106                }
107                existingEntries.put(name, nv);
108            }
109
110        }
111        // we've now removed all entries less than with less than the largest
112        // version number for each name that were listed after the largest.
113        // we now must remove those with smaller than the largest version number
114        // for each name that were found before the largest
115        while (iter.hasPrevious()) {
116            final String entry = iter.previous().trim();
117            MatchResult result = null;
118            final Matcher matcher = PATTERN.matcher(entry);
119            if (matcher.matches()) {
120                result = matcher.toMatchResult();
121                final String name = result.group(1);
122                final String version = result.group(2);
123                final int nv = Integer.parseInt(version);
124                final Integer existing = existingEntries.get(name);
125                if (null != existing && nv < existing.intValue()) {
126                    iter.remove(); // removes older version from original list.
127                }
128            }
129
130        }
131        return original;
132    }
133
134}