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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.apache.commons.httpclient.URIException;
import org.archive.modules.CrawlURI;
import org.archive.modules.CrawlURI.FetchType;
import org.archive.net.UURI;
import org.archive.net.UURIFactory;


/**
 * Extracts URIs from HTTP response headers.
 * @author gojomo
 */
public class ExtractorHTTP extends Extractor {

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

    public ExtractorHTTP() {
    }

    /** should all HTTP URIs be used to infer a link to the site's root? */
    protected boolean inferRootPage = false; 
    public boolean getInferRootPage() {
        return inferRootPage;
    }
    public void setInferRootPage(boolean inferRootPage) {
        this.inferRootPage = inferRootPage;
    }


    @Override
    protected boolean shouldProcess(CrawlURI uri) {
        if (uri.getFetchStatus() <= 0) {
            return false;
        }
        FetchType ft = uri.getFetchType();
        return (ft == FetchType.HTTP_GET) || (ft == FetchType.HTTP_POST);
    }


    @Override
    protected void extract(CrawlURI curi) {
        // discover headers if present
        addHeaderLink(curi, "Location");
        addContentLocationHeaderLink(curi, "Content-Location");
        addRefreshHeaderLink(curi, "Refresh");

        // try /favicon.ico for every HTTP(S) URI
        addOutlink(curi, "/favicon.ico", LinkContext.INFERRED_MISC, Hop.INFERRED);
        if(getInferRootPage()) {
            addOutlink(curi, "/", LinkContext.INFERRED_MISC, Hop.INFERRED);
        }
    }

    protected void addRefreshHeaderLink(CrawlURI curi, String headerKey) {
        String headerValue = curi.getHttpResponseHeader(headerKey);
        if (headerValue != null) {
            // parsing logic copied from ExtractorHTML meta-refresh handling
            int urlIndex = headerValue.indexOf("=") + 1;
            if (urlIndex > 0) {
                String refreshUri = headerValue.substring(urlIndex);
                addHeaderLink(curi, headerKey, refreshUri);
            }
        }
    }

    protected void addHeaderLink(CrawlURI curi, String headerKey) {
        String headerValue = curi.getHttpResponseHeader(headerKey);
        if (headerValue != null) {
            addHeaderLink(curi, headerKey, headerValue);
        }
    }

    protected void addContentLocationHeaderLink(CrawlURI curi, String headerKey) {
        String headerValue = curi.getHttpResponseHeader(headerKey);
        if (headerValue != null) {
            try {
                UURI dest = UURIFactory.getInstance(curi.getUURI(), headerValue);
                addOutlink(curi, dest.toString(), LinkContext.INFERRED_MISC, Hop.INFERRED);
                numberOfLinksExtracted.incrementAndGet();
            } catch (URIException e) {
                logUriError(e, curi.getUURI(), headerValue);
            }
        }
    }
    
    protected void addHeaderLink(CrawlURI curi, String headerName, String url) {
        try {
            UURI dest = UURIFactory.getInstance(curi.getUURI(), url);
            LinkContext lc = HTMLLinkContext.get(headerName+":");
            addOutlink(curi, dest.toString(), lc, Hop.REFER);
            numberOfLinksExtracted.incrementAndGet();
        } catch (URIException e) {
            logUriError(e, curi.getUURI(), url);
        }
    }
}