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This project contains some of the configurable modules used within the Heritrix application to crawl the web. The modules in this project can be used in applications other than Heritrix, however.

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/*
 *  This file is part of the Heritrix web crawler (crawler.archive.org).
 *
 *  Licensed to the Internet Archive (IA) by one or more individual 
 *  contributors. 
 *
 *  The IA 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.archive.modules.canonicalize;

import java.util.regex.Pattern;

/**
 * Strip any 'www[0-9]*' found on http/https URLs IF they have some
 * path/query component (content after third slash). Top 'slash page' 
 * URIs are left unstripped: we prefer crawling redundant
 * top pages to missing an entire site only available from either
 * the www-full or www-less hostname, but not both. 
 * @author stack
 * @version $Date$, $Revision$
 */
public class StripWWWNRule extends BaseRule {
    private static final long serialVersionUID = 3L;

//    private static final String DESCRIPTION = "Strip any 'www[0-9]*' found. " +
//        "Use this rule to equate 'http://www.archive.org/index.html' and " +
//        "'http://www0001.archive.org/index.html' with " +
//        "'http://archive.org/index.html'.  The resulting canonicalization " +
//        "returns 'http://archive.org/index.html'.  It removes any www's " +
//        "or wwwNNN's found, where 'N' is one or more numerics, EXCEPT " +
//        "on URIs that have no path/query component " +
//        ". Top-level 'slash page' URIs are left unstripped: we prefer " +
//        "crawling redundant top pages to missing an entire site only " +
//        "available from either the www-full or www-less hostname, but not " +
//        "both.  Operates on http and https schemes only. " +
//        "Use StripWWWRule to strip a lone 'www' only (This rule is a " +
//        "more general version of StripWWWRule).";
    
    private static final Pattern REGEX =
        Pattern.compile("(?i)^(https?://)(?:www[0-9]*\\.)([^/]*/.+)$");
    
    public StripWWWNRule() {
    }

    public String canonicalize(String url) {
        return doStripRegexMatch(url, REGEX.pattern());
    }
}