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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.deciderules;

import java.util.logging.Level;
import java.util.logging.Logger;

import org.apache.commons.httpclient.HttpMethod;
import org.archive.modules.CrawlURI;

/**
 * Applies configured decision for URIs with content length less than or equal
 * to a given threshold length value. Examines either HTTP header Content-Length
 * or actual downloaded content length (based on the useHeaderLength property), 
 * and has no effect on resources longer than the given threshold value.
 * 
 * Note that because neither the Content-Length header nor the actual size are
 * available at URI-scoping time, this rule is unusable in crawl scopes. 
 * Instead, the earliest it can be used is as a mid-fetch rule (in FetchHTTP), 
 * when the headers are available but not yet the body. It can also be used 
 * to affect processing after the URI is fully fetched. 
 */
public class ResourceNoLongerThanDecideRule extends PredicatedDecideRule {
    private static final long serialVersionUID = -8774160016195991876L;

    private static final Logger logger = Logger.
    	getLogger(ResourceNoLongerThanDecideRule.class.getName());
    
    /**
     * Shall this rule be used as a midfetch rule? If true, this rule will
     * determine content length based on HTTP header information, otherwise
     * the size of the already downloaded content will be used.
     */
    {
        setUseHeaderLength(true);
    }
    public boolean getUseHeaderLength() {
        return (Boolean) kp.get("useHeaderLength");
    }
    public void setUseHeaderLength(boolean useHeaderLength) {
        kp.put("useHeaderLength",useHeaderLength);
    }
    
    /**
     * Max content-length this filter will allow to pass through. If -1, 
     * then no limit.
     */
    {
        setContentLengthThreshold(-1L);
    }
    public long getContentLengthThreshold() {
        return (Long) kp.get("contentLengthThreshold");
    }
    public void setContentLengthThreshold(long threshold) {
        kp.put("contentLengthThreshold",threshold);
    }

    // Header predictor state constants
    public static final int HEADER_PREDICTS_MISSING = -1;
	
    public ResourceNoLongerThanDecideRule() {
    }
    
    protected boolean evaluate(CrawlURI curi) {
        int contentlength = HEADER_PREDICTS_MISSING;

        // filter used as midfetch filter
        if (getUseHeaderLength()) {

            // get content-length
            String newContentlength = null;
            if (curi.getHttpResponseHeader("content-length") != null) {
                newContentlength = curi.getHttpResponseHeader("content-length");
            }

            if (newContentlength != null && newContentlength.length() > 0) {
                try {
                    contentlength = Integer.parseInt(newContentlength);
                } catch (NumberFormatException nfe) {
                    // Ignore.
                }
            }

            // If no document length was reported or format was wrong,
            // let pass
            if (contentlength == HEADER_PREDICTS_MISSING) {
                return false;
            }
        } else {
            contentlength = (int) curi.getContentSize();
        }
        
        return test(contentlength);
    }
    
    
    protected boolean test(int contentlength) {
        return contentlength < getContentLengthThreshold();        
    }
}