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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.io.Serializable;
import java.util.regex.Matcher;

import org.archive.spring.HasKeyedProperties;
import org.archive.spring.KeyedProperties;
import org.archive.util.TextUtils;

/**
 * Base of all rules applied canonicalizing a URL that are configurable
 * via the Heritrix settings system.
 * 
 * This base class is abstact.  Subclasses must implement the
 * {@link #canonicalize(String)} method.
 * 
 * @author stack
 * @version $Date$, $Revision$
 */
public abstract class BaseRule
implements CanonicalizationRule, Serializable, HasKeyedProperties {
    private static final long serialVersionUID = 1L;
    protected KeyedProperties kp = new KeyedProperties();
    public KeyedProperties getKeyedProperties() {
        return kp;
    }
    
    {
        setEnabled(true);
    }
    public boolean getEnabled() {
        return (Boolean) kp.get("enabled");
    }
    public void setEnabled(boolean enabled) {
        kp.put("enabled",enabled);
    }

    /**
     * Constructor.
     */
    public BaseRule() {
    }
    
    /**
     * Run a regex that strips elements of a string.
     * 
     * Assumes the regex has a form that wants to strip elements of the passed
     * string.  Assumes that if a match, appending group 1
     * and group 2 yields desired result.
     * @param url Url to search in.
     * @param pat
     * @return Original url else concatenization of group 1
     * and group 2.
     */
    protected String doStripRegexMatch(String url, String pat) {
        Matcher matcher = TextUtils.getMatcher(pat, url);
        String retVal = (matcher != null && matcher.matches())?
            checkForNull(matcher.group(1)) + checkForNull(matcher.group(2)):
            url;
        TextUtils.recycleMatcher(matcher); 
        return retVal;
    }

    /**
     * @param string String to check.
     * @return string if non-null, else empty string ("").
     */
    private String checkForNull(String string) {
        return (string != null)? string: "";
    }
    
}