/**
 * Helios, OpenSource Monitoring
 * Brought to you by the Helios Development Group
 *
 * Copyright 2013, Helios Development Group and individual contributors
 * as indicated by the @author tags. See the copyright.txt file in the
 * distribution for a full listing of individual contributors.
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org. 
 *
 */
package org.helios.apmrouter.server.unification.protocol.compression;

import org.helios.apmrouter.server.unification.protocol.AbstractProtocolInitiator;
import org.jboss.netty.buffer.ChannelBuffer;
import org.jboss.netty.channel.Channel;
import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.handler.codec.compression.ZlibDecoder;
import org.jboss.netty.handler.codec.compression.ZlibWrapper;

/**
 * <p>Title: GZipDecompressionProtocolInitiator</p>
 * <p>Description: </p> 
 * <p>Company: Helios Development Group LLC</p>
 * @author Whitehead (nwhitehead AT heliosdev DOT org)
 * <p><code>org.helios.apmrouter.server.unification.protocol.compression.GZipDecompressionProtocolInitiator</code></p>
 */

public class GZipDecompressionProtocolInitiator extends AbstractProtocolInitiator {
	
	/**
	 * Creates a new GZipDecompressionProtocolInitiator
	 */
	public GZipDecompressionProtocolInitiator() {
		super("gzip");
	}

	/**
	 * {@inheritDoc}
	 * @see org.helios.apmrouter.server.unification.protocol.ProtocolInitiator#requiredBytes()
	 */
	@Override
	public int requiredBytes() {
		return 2;
	}

	/**
	 * {@inheritDoc}
	 * @see org.helios.apmrouter.server.unification.protocol.ProtocolInitiator#match(org.jboss.netty.buffer.ChannelBuffer)
	 */
	@Override
	public boolean match(ChannelBuffer buff) {
		return isGzip(buff);
	}

	/**
	 * {@inheritDoc}
	 * @see org.helios.apmrouter.server.unification.protocol.ProtocolInitiator#modifyPipeline(org.jboss.netty.channel.ChannelHandlerContext, org.jboss.netty.channel.Channel, org.jboss.netty.buffer.ChannelBuffer)
	 */
	@Override
	public void modifyPipeline(ChannelHandlerContext ctx, Channel channel, ChannelBuffer buffer) {
		ctx.getPipeline().addAfter("exec", "gzip", new ZlibDecoder(ZlibWrapper.GZIP) {
			@Override
			protected Object decode(ChannelHandlerContext ctx, Channel channel, Object msg) throws Exception {
				incr("ZlibDecoderCalls");
				ChannelBuffer cb = (ChannelBuffer)super.decode(ctx, channel, msg);
				info("ZLib Decoder Inflated to [" + cb.readableBytes() + "] Bytes");
				return cb;
			}
		});	


	}


	
	/**
	 * Determines if the two passed bytes represent a gzipped stream of data
	 * @param magic1 The first byte of the incoming request
	 * @param magic2 The second byte of the incoming request
	 * @return true if the incoming payload is gzipped, false otherwise
	 */
	public static boolean isGzip(int magic1, int magic2) {
		return magic1 == 31 && magic2 == 139;	
	}	
	
	
	/**
	 * Determines if the channel is carrying a gzipped payload
	 * @param buffer The channel buffer to check
	 * @return true if the incoming payload is gzipped, false otherwise
	 */
	public static boolean isGzip(ChannelBuffer buffer) {
		return isGzip(buffer.getUnsignedByte(0), buffer.getUnsignedByte(1));
	}	
	

}