/*
 * Copyright 2009-2010, James Leigh and Zepheira LLC Some rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 * 
 * - Redistributions of source code must retain the above copyright notice, this
 *   list of conditions and the following disclaimer.
 * - 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. 
 * - Neither the name of the openrdf.org nor the names of its contributors may
 *   be used to endorse or promote products derived from this software without
 *   specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS 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 COPYRIGHT OWNER OR 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 USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND 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.
 * 
 */
package org.openrdf.http.object.filters;

import java.io.IOException;

import org.apache.http.Header;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.openrdf.http.object.model.Filter;
import org.openrdf.http.object.model.Request;

/**
 * Compresses safe responses.
 */
public class GZipFilter extends Filter {

	public GZipFilter(Filter delegate) {
		super(delegate);
	}

	public HttpResponse filter(Request req, HttpResponse resp) throws IOException {
		resp = super.filter(req, resp);
		String method = req.getMethod();
		int code = resp.getStatusLine().getStatusCode();
		boolean safe = method.equals("HEAD") || method.equals("GET") || method.equals("PROFIND");
		if (code < 400 && safe &&  isCompressable(resp)) {
			Header length = resp.getFirstHeader("Content-Length");
			if (length == null || Integer.parseInt(length.getValue()) > 500) {
				resp.removeHeaders("Content-MD5");
				resp.removeHeaders("Content-Length");
				resp.setHeader("Transfer-Encoding", "chunked");
				resp.setHeader("Content-Encoding", "gzip");
				HttpEntity entity = resp.getEntity();
				if (entity instanceof GUnzipEntity) {
					resp.setEntity(((GUnzipEntity) entity).getEntityDelegate());
				} else {
					resp.setEntity(new GZipEntity(entity));
				}
			}
		}
		return resp;
	}

	private boolean isCompressable(HttpResponse msg) {
		Header contentType = msg.getFirstHeader("Content-Type");
		if (contentType == null || msg.getEntity() == null)
			return false;
		Header encoding = msg.getFirstHeader("Content-Encoding");
		boolean identity = encoding == null || "identity".equals(encoding.getValue());
		String type = contentType.getValue();
		boolean compressable = type.startsWith("text/")
				|| type.startsWith("application/xml")
				|| type.startsWith("application/x-turtle")
				|| type.startsWith("application/sparql-quey")
				|| type.startsWith("application/trix")
				|| type.startsWith("application/x-trig")
				|| type.startsWith("application/postscript")
				|| type.startsWith("application/javascript")
				|| type.startsWith("application/json")
				|| type.startsWith("application/mbox")
				|| type.startsWith("application/")
				&& (type.endsWith("+xml") || type.contains("+xml;"));
		return identity && compressable;
	}
}

@@ -2297,9 +2297,9 @@
 e %3C 
-4
+5
 00 &

Compress responses to bad requests