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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.extractor;

import org.archive.modules.CrawlURI;

/** 
 * Pseudo-extractor that suppresses link-extraction of likely trap pages,
 * by noticing when content's digest is identical to that of its 'via'. 
 *
 * @author gojomo
 *
 */
public class TrapSuppressExtractor extends ContentExtractor  {
    @SuppressWarnings("unused")
    private static final long serialVersionUID = -1028783453022579530L;

    /** ALIst attribute key for carrying-forward content-digest from 'via'*/
    public static String A_VIA_DIGEST = "via-digest";
    
    protected long numberOfCURIsHandled = 0;
    protected long numberOfCURIsSuppressed = 0;

    /**
     * Usual constructor. 
     */
    public TrapSuppressExtractor() {
    }

    protected boolean shouldExtract(CrawlURI uri) {
        return true; 
    }
    
    protected boolean innerExtract(CrawlURI curi){
        numberOfCURIsHandled++;

        String currentDigest = curi.getContentDigestSchemeString();
        String viaDigest = null;
        if(curi.containsDataKey(A_VIA_DIGEST)) {
            viaDigest = (String) curi.getData().get(A_VIA_DIGEST);
        }
        
        if(currentDigest!=null) {
            curi.makeHeritable(A_VIA_DIGEST);
            if(currentDigest.equals(viaDigest)) {
                curi.getAnnotations().add("trapSuppressExtractor");
                numberOfCURIsSuppressed++;
                // mark as already-extracted -- suppressing further extraction
                return true;
            }
            // already consulted; so clobber with current value to be 
            // inherited
            curi.getData().put(A_VIA_DIGEST, currentDigest);
        }
        return false; 
    }
}