/*
 * CompressionFilter.java
 * $Header: /cvsroot/mvnforum/myvietnam/src/net/myvietnam/mvncore/servlet/filter/CompressionFilter.java,v 1.6 2004/12/12 18:05:35 minhnn Exp $
 * $Revision: 1.6 $
 * $Date: 2004/12/12 18:05:35 $
 *
 * ====================================================================
 *
 * 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
 *    permission of the Apache Group.
 *
 * 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
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 *
 * [Additional notices, if required by prior licensing conditions]
 *
 */

package net.myvietnam.mvncore.servlet.filter;

import java.io.IOException;
import java.util.Enumeration;

import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;


/**
 * Implementation of <code>javax.servlet.Filter used to compress
 * the ServletResponse if it is bigger than a threshold.
 *
 * @author Amy Roh
 * @author Dmitri Valdin
 * @version $Revision: 1.6 $, $Date: 2004/12/12 18:05:35 $
 */

public class CompressionFilter implements Filter{

    private static Log log = LogFactory.getLog(CompressionFilter.class);

    /**
     * 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) {
                    log.info("compressionThreshold should be either 0 - no compression or >= " + minThreshold);
                    log.info("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 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()), 

     **/

    public void doFilter ( ServletRequest request, ServletResponse response, FilterChain chain )
        throws IOException, ServletException {
        /*
        Currently, many browsers do not send character encoding information in the
        Content-Type header of an HTTP request. If an encoding has not been specified
        by the client request, the container uses a default encoding to parse request
        parameters. If the client hasn't set character encoding and the request parameters
        are encoded with a different encoding than the default, the parameters will be
        parsed incorrectly. You can use the method setCharacterEncoding in ServletRequest
        interface to set the encoding. Since this method must be called
        prior to parsing any post data or reading any input from the request, this function
        is a prime application for filters(http://java.sun.com/products/servlet/Filters.pdf.)
        In this case, it may be caused by parsing parameter "gzip". And charset should be UTF-8.
        You can use another filter for the encoding.(see Tomcat's examples)

        */
        request.setCharacterEncoding("utf-8");
        if (compressionThreshold == 0) {
            //log.trace("doFilter gets called, but compressionTreshold is set to 0 - no compression");
            chain.doFilter(request, response);
            return;
        }
        boolean supportCompression = false;
        if (request instanceof HttpServletRequest) {
            //log.trace("requestURI = " + ((HttpServletRequest)request).getRequestURI());

            // Are we allowed to compress ?
            String s = request.getParameter("gzip");
            if ("false".equals(s)) {
                //log.trace("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) {
                    //log.trace("supports compression");
                    supportCompression = true;
                } else {
                    //log.trace("no support for compresion");
                }
            }
        }

        if (!supportCompression) {
            //log.trace("doFilter gets called wo compression");
            chain.doFilter(request, response);
            return;
        } else {
            if (response instanceof HttpServletResponse) {
                CompressionServletResponseWrapper wrappedResponse =
                    new CompressionServletResponseWrapper((HttpServletResponse)response);
                //minhnn
                //wrappedResponse.setDebugLevel(debug);
                wrappedResponse.setCompressionThreshold(compressionThreshold);
                //log.trace("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;
    }

}