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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 java.util.ArrayList;
import java.util.List;
import java.util.logging.Level;
import java.util.logging.Logger;
import java.util.regex.Matcher;

import org.apache.commons.codec.DecoderException;
import org.apache.commons.httpclient.URIException;
import org.archive.modules.CrawlURI;
import org.archive.url.LaxURLCodec;
import org.archive.net.UURI;
import org.archive.net.UURIFactory;
import org.archive.util.TextUtils;

/**
 * An extractor for finding URIs inside other URIs. Unlike most other
 * extractors, this works on URIs discovered by previous extractors. Thus 
 * it should appear near the end of any set of extractors.
 *
 * Initially, only finds absolute HTTP(S) URIs in query-string or its 
 * parameters.
 *
 * TODO: extend to find URIs in path-info
 *
 * @author Gordon Mohr
 *
 **/

public class ExtractorURI extends Extractor {

    @SuppressWarnings("unused")
    private static final long serialVersionUID = 3L;

    private static Logger LOGGER =
        Logger.getLogger(ExtractorURI.class.getName());

    protected static final String ABS_HTTP_URI_PATTERN = "^https?://[^\\s<>]*$";

    /**
     * Constructor
     */
    public ExtractorURI() {
    }

    
    @Override
    protected boolean shouldProcess(CrawlURI uri) {
        return true;
    }
    
    /**
     * Perform usual extraction on a CrawlURI
     * 
     * @param curi Crawl URI to process.
     */
    @Override
    public void extract(CrawlURI curi) {
        for (CrawlURI link : curi.getOutLinks()) {
            extractLink(curi, link);
        }
    }

    /**
     * Consider a single Link for internal URIs
     * 
     * @param curi CrawlURI to add discoveries to 
     * @param wref Link to examine for internal URIs
     */
    protected void extractLink(CrawlURI curi, CrawlURI wref) {
        UURI source = null;
        try {
            source = UURIFactory.getInstance(wref.getURI());
        } catch (URIException e) {
            LOGGER.log(Level.FINE,"bad URI",e);
        }
        if(source == null) {
            // shouldn't happen
            return; 
        }
        List found = extractQueryStringLinks(source);
        for (String uri : found) {
            try {
                UURI dest = UURIFactory.getInstance(uri);
                LinkContext lc = LinkContext.SPECULATIVE_MISC;
                Hop hop = Hop.SPECULATIVE;
                addOutlink(curi, dest, lc, hop);
                numberOfLinksExtracted.incrementAndGet();
            } catch (URIException e) {
                LOGGER.log(Level.FINE, "bad URI", e);
            }
        }
        // TODO: consider path URIs too
        
    }

    /**
     * Look for URIs inside the supplied UURI.
     * 
     * Static for ease of testing or outside use. 
     * 
     * @param source UURI to example
     * @return List of discovered String URIs.
     */
    protected static List extractQueryStringLinks(UURI source) {
        List results = new ArrayList(); 
        String decodedQuery;
        try {
            decodedQuery = source.getQuery();
        } catch (URIException e1) {
            // shouldn't happen
            return results;
        }
        if(decodedQuery==null) {
            return results;
        }
        // check if full query-string appears to be http(s) URI
        Matcher m = TextUtils.getMatcher(ABS_HTTP_URI_PATTERN,decodedQuery);
        if(m.matches()) {
            TextUtils.recycleMatcher(m);
            results.add(decodedQuery);
        }
        // split into params, see if any param value is http(s) URI
        String rawQuery = new String(source.getRawQuery());
        String[] params = rawQuery.split("&");
        for (String param : params) {
            String[] keyVal = param.split("=");
            if(keyVal.length==2) {
                String candidate;
                try {
                    candidate = LaxURLCodec.DEFAULT.decode(keyVal[1]);
                } catch (DecoderException e) {
                    continue;
                }
                // TODO: use other non-UTF8 codecs when appropriate
                m.reset(candidate);
                if(m.matches()) {
                    results.add(candidate);
                }
            }
        }
        return results;
    }
}