//
//  ========================================================================
//  Copyright (c) 1995-2014 Mort Bay Consulting Pty. Ltd.
//  ------------------------------------------------------------------------
//  All rights reserved. This program and the accompanying materials
//  are made available under the terms of the Eclipse Public License v1.0
//  and Apache License v2.0 which accompanies this distribution.
//
//      The Eclipse Public License is available at
//      http://www.eclipse.org/legal/epl-v10.html
//
//      The Apache License v2.0 is available at
//      http://www.opensource.org/licenses/apache2.0.php
//
//  You may elect to redistribute this code under either of these licenses.
//  ========================================================================
//

package org.eclipse.jetty.server.handler;

import java.io.IOException;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.io.UnsupportedEncodingException;
import java.util.HashSet;
import java.util.Set;
import java.util.StringTokenizer;
import java.util.zip.DeflaterOutputStream;
import java.util.zip.GZIPOutputStream;

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

import org.eclipse.jetty.continuation.Continuation;
import org.eclipse.jetty.continuation.ContinuationListener;
import org.eclipse.jetty.http.HttpMethods;
import org.eclipse.jetty.http.gzip.CompressedResponseWrapper;
import org.eclipse.jetty.http.gzip.AbstractCompressedStream;
import org.eclipse.jetty.server.Request;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/* ------------------------------------------------------------ */
/**
 * GZIP Handler This handler will gzip the content of a response if:
 * <ul>
 * <li>The filter is mapped to a matching path</li>
 * <li>The response status code is >=200 and <300
 * <li>The content length is unknown or more than the <code>minGzipSize</code> initParameter or the minGzipSize is 0(default)</li>
 * <li>The content-type is in the comma separated list of mimeTypes set in the <code>mimeTypes</code> initParameter or if no mimeTypes are defined the
 * content-type is not "application/gzip"</li>
 * <li>No content-encoding is specified by the resource</li>
 * </ul>
 * 
 * <p>
 * Compressing the content can greatly improve the network bandwidth usage, but at a cost of memory and CPU cycles. If this handler is used for static content,
 * then use of efficient direct NIO may be prevented, thus use of the gzip mechanism of the <code>org.eclipse.jetty.servlet.DefaultServlet</code> is advised instead.
 * </p>
 */
public class GzipHandler extends HandlerWrapper
{
	private static final Logger LOG = LoggerFactory.getLogger(GzipHandler.class);

	protected Set<String> _mimeTypes;
	protected Set<String> _excluded;
	protected int _bufferSize = 8192;
	protected int _minGzipSize = 256;
	protected String _vary = "Accept-Encoding, User-Agent";

	/* ------------------------------------------------------------ */
	/**
	 * Instantiates a new gzip handler.
	 */
	public GzipHandler()
	{
	}

	/* ------------------------------------------------------------ */
	/**
	 * Get the mime types.
	 * 
	 * @return mime types to set
	 */
	public Set<String> getMimeTypes()
	{
		return _mimeTypes;
	}

	/* ------------------------------------------------------------ */
	/**
	 * Set the mime types.
	 * 
	 * @param mimeTypes
	 *            the mime types to set
	 */
	public void setMimeTypes(Set<String> mimeTypes)
	{
		_mimeTypes = mimeTypes;
	}

	/* ------------------------------------------------------------ */
	/**
	 * Set the mime types.
	 * 
	 * @param mimeTypes
	 *            the mime types to set
	 */
	public void setMimeTypes(String mimeTypes)
	{
		if (mimeTypes != null)
		{
			_mimeTypes = new HashSet<String>();
			StringTokenizer tok = new StringTokenizer(mimeTypes,",",false);
			while (tok.hasMoreTokens())
			{
				_mimeTypes.add(tok.nextToken());
			}
		}
	}

	/* ------------------------------------------------------------ */
	/**
	 * Get the excluded user agents.
	 * 
	 * @return excluded user agents
	 */
	public Set<String> getExcluded()
	{
		return _excluded;
	}

	/* ------------------------------------------------------------ */
	/**
	 * Set the excluded user agents.
	 * 
	 * @param excluded
	 *            excluded user agents to set
	 */
	public void setExcluded(Set<String> excluded)
	{
		_excluded = excluded;
	}

	/* ------------------------------------------------------------ */
	/**
	 * Set the excluded user agents.
	 * 
	 * @param excluded
	 *            excluded user agents to set
	 */
	public void setExcluded(String excluded)
	{
		if (excluded != null)
		{
			_excluded = new HashSet<String>();
			StringTokenizer tok = new StringTokenizer(excluded,",",false);
			while (tok.hasMoreTokens())
				_excluded.add(tok.nextToken());
		}
	}

	/* ------------------------------------------------------------ */
	/**
	 * @return The value of the Vary header set if a response can be compressed.
	 */
	public String getVary()
	{
		return _vary;
	}

	/* ------------------------------------------------------------ */
	/**
	 * Set the value of the Vary header sent with responses that could be compressed.  
	 * <p>
	 * By default it is set to 'Accept-Encoding, User-Agent' since IE6 is excluded by 
	 * default from the excludedAgents. If user-agents are not to be excluded, then 
	 * this can be set to 'Accept-Encoding'.  Note also that shared caches may cache 
	 * many copies of a resource that is varied by User-Agent - one per variation of the 
	 * User-Agent, unless the cache does some normalization of the UA string.
	 * @param vary The value of the Vary header set if a response can be compressed.
	 */
	public void setVary(String vary)
	{
		_vary = vary;
	}

	/* ------------------------------------------------------------ */
	/**
	 * Get the buffer size.
	 * 
	 * @return the buffer size
	 */
	public int getBufferSize()
	{
		return _bufferSize;
	}

	/* ------------------------------------------------------------ */
	/**
	 * Set the buffer size.
	 * 
	 * @param bufferSize
	 *            buffer size to set
	 */
	public void setBufferSize(int bufferSize)
	{
		_bufferSize = bufferSize;
	}

	/* ------------------------------------------------------------ */
	/**
	 * Get the minimum reponse size.
	 * 
	 * @return minimum reponse size
	 */
	public int getMinGzipSize()
	{
		return _minGzipSize;
	}

	/* ------------------------------------------------------------ */
	/**
	 * Set the minimum reponse size.
	 * 
	 * @param minGzipSize
	 *            minimum reponse size
	 */
	public void setMinGzipSize(int minGzipSize)
	{
		_minGzipSize = minGzipSize;
	}

	/* ------------------------------------------------------------ */
	/**
	 * @see org.eclipse.jetty.server.handler.HandlerWrapper#handle(java.lang.String, org.eclipse.jetty.server.Request, javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse)
	 */
	@Override
	public void handle(String target, Request baseRequest, HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException
	{
		if (_handler!=null && isStarted())
		{
			String ae = request.getHeader("accept-encoding");
			if (ae != null && ae.indexOf("gzip")>=0 && !response.containsHeader("Content-Encoding")
					&& !HttpMethods.HEAD.equalsIgnoreCase(request.getMethod()))
			{
				if (_excluded!=null)
				{
					String ua = request.getHeader("User-Agent");
					if (_excluded.contains(ua))
					{
						_handler.handle(target,baseRequest, request, response);
						return;
					}
				}

				final CompressedResponseWrapper wrappedResponse = newGzipResponseWrapper(request,response);
				
				boolean exceptional=true;
				try
				{
					_handler.handle(target, baseRequest, request, wrappedResponse);
					exceptional=false;
				}
				finally
				{
					if (exceptional && !response.isCommitted())
					{
						wrappedResponse.resetBuffer();
						wrappedResponse.noCompression();
					}
					else
						wrappedResponse.finish();
				}
			}
			else
			{
				_handler.handle(target,baseRequest, request, response);
			}
		}
	}

	/**
	 * Allows derived implementations to replace ResponseWrapper implementation.
	 *
	 * @param request the request
	 * @param response the response
	 * @return the gzip response wrapper
	 */
	protected CompressedResponseWrapper newGzipResponseWrapper(HttpServletRequest request, HttpServletResponse response)
	{
		return new CompressedResponseWrapper(request,response)
		{
			{
				super.setMimeTypes(GzipHandler.this._mimeTypes);
				super.setBufferSize(GzipHandler.this._bufferSize);
				super.setMinCompressSize(GzipHandler.this._minGzipSize);
			}
			
			@Override
			protected AbstractCompressedStream newCompressedStream(HttpServletRequest request,HttpServletResponse response) throws IOException
			{
				return new AbstractCompressedStream("gzip",request,this,_vary)
				{
					@Override
					protected DeflaterOutputStream createStream() throws IOException
					{
						return new GZIPOutputStream(_response.getOutputStream(),_bufferSize);
					}
				};
			}
			
			@Override
			protected PrintWriter newWriter(OutputStream out,String encoding) throws UnsupportedEncodingException
			{
				return GzipHandler.this.newWriter(out,encoding);
			}
		};
	}
	
	/**
	 * Allows derived implementations to replace PrintWriter implementation.
	 *
	 * @param out the out
	 * @param encoding the encoding
	 * @return the prints the writer
	 * @throws UnsupportedEncodingException
	 */
	protected PrintWriter newWriter(OutputStream out,String encoding) throws UnsupportedEncodingException
	{
		return encoding==null?new PrintWriter(out):new PrintWriter(new OutputStreamWriter(out,encoding));
	}
}