/*
    * Copyright 2009-2012 Capgemini and others
    * 
    * Licensed 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 net.sourceforge.statelessfilter.wrappers.headers;
  
  import java.io.IOException;
  import java.io.PrintWriter;
  
  import javax.servlet.ServletOutputStream;
  import javax.servlet.http.HttpServletResponse;
  import javax.servlet.http.HttpServletResponseWrapper;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import net.sourceforge.statelessfilter.wrappers.BufferedHttpResponseWrapper;
  import net.sourceforge.statelessfilter.wrappers.StatelessRequestWrapper;
  
  /**
   * A custom response wrapper that inject session data before sending content
   * output.
   * <p>
   * Session data can no longer be modified after the application has started to
   * write to output stream.
   * <p>
   * This changes slightly the behavior of the container since it would usually
   * prevent session creation in this case, but not session data modifications.
   * However, most frameworks ensure to have updated session and application data
   * BEFORE doing any output. As a result, this wrapper is safe for most uses.
   * 
   * <p>
   * This wrappers uses much less memory than {@link BufferedHttpResponseWrapper}
   * since it does not cache the whole response data.
   * 
   * @author Nicolas Richeton
   */
  public class HeaderBufferedHttpResponseWrapper extends
  		HttpServletResponseWrapper {
  	Logger logger = LoggerFactory
  			.getLogger(HeaderBufferedHttpResponseWrapper.class);
  
  	private StatelessRequestWrapper statelessRequest = null;
  	HttpServletResponse origResponse = null;
  
  	public HeaderBufferedHttpResponseWrapper(StatelessRequestWrapper request,
  			HttpServletResponse origResponse) {
  		super(origResponse);
  		this.origResponse = origResponse;
  		this.statelessRequest = request;
  		logger.debug("Init HeaderBufferedHttpResponseWrapper");
  	}
  
  	/**
  	 * Write session data if necessary (session not already written).
  	 * 
  	 * @throws IOException
  	 */
  	private void writeSession() throws IOException {
  		if (!statelessRequest.isSessionWritten()) {
  			logger.debug("writting session");
  
  			statelessRequest.writeSession(statelessRequest, origResponse);
  		} else {
  			logger.debug("session already written");
  
  		}
  	}
  
  	/**
  	 * {@inheritDoc} javax.servlet.ServletResponseWrapper#flushBuffer()
  	 */
  	@Override
  	public void flushBuffer() throws IOException {
  		logger.debug("flushBuffer()");
  		// Write session before invoking the standard behavior
  		writeSession();
  		super.flushBuffer();
  	}
  
  	/**
  	 * {@inheritDoc} javax.servlet.ServletResponseWrapper#getOutputStream()
  	 */
  	@Override
  	public ServletOutputStream getOutputStream() throws IOException {
  		logger.debug("getOutputStream() has been called");
  		// Write session before invoking the standard behavior
 		writeSession();
 		return super.getOutputStream();
 	}
 
 	/**
 	 * {@inheritDoc} javax.servlet.ServletResponseWrapper#getWriter()
 	 */
 	@Override
 	public PrintWriter getWriter() throws IOException {
 		logger.debug("getWriter() has been called");
 		// Write session before invoking the standard behavior
 		writeSession();
 
 		return super.getWriter();
 	}
 
 	/**
 	 * {@inheritDoc}
 	 * javax.servlet.http.HttpServletResponseWrapper#sendError(int)
 	 */
 	@Override
 	public void sendError(int sc) throws IOException {
 		logger.debug("sendError() has been called");
 		// Write session before invoking the standard behavior
 		writeSession();
 		super.sendError(sc);
 	}
 
 	/**
 	 * {@inheritDoc}
 	 * javax.servlet.http.HttpServletResponseWrapper#sendError(int,
 	 * java.lang.String)
 	 */
 	@Override
 	public void sendError(int sc, String msg) throws IOException {
 		logger.debug("sendError() has been called");
 		// Write session before invoking the standard behavior
 		writeSession();
 		super.sendError(sc, msg);
 	}
 
 	/**
 	 * {@inheritDoc}
 	 * javax.servlet.http.HttpServletResponseWrapper#sendRedirect(java.lang.
 	 * String)
 	 */
 	@Override
 	public void sendRedirect(String location) throws IOException {
 		logger.debug("sendRedirect() has been called");
 		// Write session before invoking the standard behavior
 		writeSession();
 		super.sendRedirect(location);
 	}
 
 }