package org.mortbay.jetty.filters

import java.io.IOException;

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;

import org.mortbay.jetty.HttpHeaderValues;
import org.mortbay.jetty.HttpHeaders;

/**
 *	This filter enables the "Fast Web View" feature of the Adobe Acrobat plug-in. The filter
 *	should only be executed on .pdf files only.
 */
public class PDFFilter implements Filter {
	public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException,
			ServletException {
		HttpServletRequest httpRequest = (HttpServletRequest) request;
		HttpServletResponse httpResponse = (HttpServletResponse) response;
		
		// Add "Accept-Ranges: bytes" 
		httpResponse.addHeader(HttpHeaders.ACCEPT_RANGES, HttpHeaderValues.BYTES);
		String ranges = httpRequest.getHeader(HttpHeaders.RANGE);
		if (ranges != null) {
			/*
			* This allows to close the HTTP connection after a byte range has been downloaded 
			* by the Adobe Acrobat plug-in. Otherwise, the browser keeps the connection open until
			* the connection expires.
			*/ 
			httpResponse.addHeader(HttpHeaders.CONNECTION, HttpHeaderValues.CLOSE);
		}
		chain.doFilter(request, response);
	}

	public void destroy() {
	}

	public void init(FilterConfig arg0) throws ServletException {
	}
}