/*
 * CompressionFilter.java
 * $Header: /home/cvs/jakarta-tomcat-4.0/webapps/examples/WEB-INF/classes/compressionFilters/CompressionFilter.java,v 1.8 2002/07/16 17:19:13 amyroh Exp $
 * $Revision: 1.8 $
 * $Date: 2002/07/16 17:19:13 $
 *
 * ====================================================================
 *
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 1999 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution, if
 *    any, must include the following acknowlegement:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowlegement may appear in the software itself,
 *    if and wherever such third-party acknowlegements normally appear.
 *
 * 4. The names "The Jakarta Project", "Tomcat", and "Apache Software
 *    Foundation" must not be used to endorse or promote products derived
 *    from this software without prior written permission. For written
 *    permission, please contact apache@apache.org.
 *
 * 5. Products derived from this software may not be called "Apache"
 *    nor may "Apache" appear in their names without prior written
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 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
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 * This software consists of voluntary contributions made by many
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 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 *
 * [Additional notices, if required by prior licensing conditions]
 *
 */

package compressionFilters;

import java.io.IOException;
import java.util.Enumeration;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;


/**
 * Implementation of <code>javax.servlet.Filter</code> used to compress
 * the ServletResponse if it is bigger than a threshold.
 *
 * @author Amy Roh
 * @author Dmitri Valdin
 * @version $Revision: 1.8 $, $Date: 2002/07/16 17:19:13 $
 */

public class CompressionFilter implements Filter{

    /**
     * The filter configuration object we are associated with.  If this value
     * is null, this filter instance is not currently configured.
     */
    private FilterConfig config = null;

    /**
     * Minimal reasonable threshold
     */
    private int minThreshold = 128;


    /**
     * The threshold number to compress
     */
    protected int compressionThreshold;

    /**
     * Debug level for this filter
     */
    private int debug = 0;

    /**
     * Place this filter into service.
     *
     * @param filterConfig The filter configuration object
     */

    public void init(FilterConfig filterConfig) {

        config = filterConfig;
        if (filterConfig != null) {
            String value = filterConfig.getInitParameter("debug");
            if (value!=null) {
                debug = Integer.parseInt(value);
            } else {
                debug = 0;
            }
            String str = filterConfig.getInitParameter("compressionThreshold");
            if (str!=null) {
                compressionThreshold = Integer.parseInt(str);
                if (compressionThreshold != 0 && compressionThreshold < minThreshold) {
                    if (debug > 0) {
                        System.out.println("compressionThreshold should be either 0 - no compression or >= " + minThreshold);
                        System.out.println("compressionThreshold set to " + minThreshold);
                    }
                    compressionThreshold = minThreshold;
                }
            } else {
                compressionThreshold = 0;
            }

        } else {
            compressionThreshold = 0;
        }

    }

    /**
    * Take this filter out of service.
    */
    public void destroy() {

        this.config = null;

    }

    /**
     * The <code>doFilter</code> method of the Filter is called by the container
     * each time a request/response pair is passed through the chain due
     * to a client request for a resource at the end of the chain.
     * The FilterChain passed into this method allows the Filter to pass on the
     * request and response to the next entity in the chain.<p>
     * This method first examines the request to check whether the client support
     * compression. <br>
     * It simply just pass the request and response if there is no support for
     * compression.<br>
     * If the compression support is available, it creates a
     * CompressionServletResponseWrapper object which compresses the content and
     * modifies the header if the content length is big enough.
     * It then invokes the next entity in the chain using the FilterChain object
     * (<code>chain.doFilter()</code>), <br>
     **/

    public void doFilter ( ServletRequest request, ServletResponse response,
                        FilterChain chain ) throws IOException, ServletException {

        if (debug > 0) {
            System.out.println("@doFilter");
        }

        if (compressionThreshold == 0) {
            if (debug > 0) {
                System.out.println("doFilter gets called, but compressionTreshold is set to 0 - no compression");
            }
            chain.doFilter(request, response);
            return;
        }

        boolean supportCompression = false;
        if (request instanceof HttpServletRequest) {
            if (debug > 1) {
                System.out.println("requestURI = " + ((HttpServletRequest)request).getRequestURI());
            }

            // Are we allowed to compress ?
            String s = (String) ((HttpServletRequest)request).getParameter("gzip");
            if ("false".equals(s)) {
                if (debug > 0) {
                    System.out.println("got parameter gzip=false --> don't compress, just chain filter");
                }
                chain.doFilter(request, response);
                return;
            }

            Enumeration e =
                ((HttpServletRequest)request).getHeaders("Accept-Encoding");
            while (e.hasMoreElements()) {
                String name = (String)e.nextElement();
                if (name.indexOf("gzip") != -1) {
                    if (debug > 0) {
                        System.out.println("supports compression");
                    }
                    supportCompression = true;
                } else {
                    if (debug > 0) {
                        System.out.println("no support for compresion");
                    }
                }
            }
        }

        if (!supportCompression) {
            if (debug > 0) {
                System.out.println("doFilter gets called wo compression");
            }
            chain.doFilter(request, response);
            return;
        } else {
            if (response instanceof HttpServletResponse) {
                CompressionServletResponseWrapper wrappedResponse =
                    new CompressionServletResponseWrapper((HttpServletResponse)response);
                wrappedResponse.setDebugLevel(debug);
                wrappedResponse.setCompressionThreshold(compressionThreshold);
                if (debug > 0) {
                    System.out.println("doFilter gets called with compression");
                }
                try {
                    chain.doFilter(request, wrappedResponse);
                } finally {
                    wrappedResponse.finishResponse();
                }
                return;
            }
        }
    }

    /**
     * Set filter config
     * This function is equivalent to init. Required by Weblogic 6.1
     *
     * @param filterConfig The filter configuration object
     */
    public void setFilterConfig(FilterConfig filterConfig) {
        init(filterConfig);
    }

    /**
     * Return filter config
     * Required by Weblogic 6.1
     */
    public FilterConfig getFilterConfig() {
        return config;
    }

}

