/**
 * Java RTP Library (jlibrtp)
 * Copyright (C) 2006 Arne Kepp
 * 
 * This library 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 library 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 library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 */
package jlibrtp;

import java.net.InetAddress;

/**
 * Common RTCP packet headers.
 * 
 * @author Arne Kepp
 */
public class RtcpPkt {
	/** Whether a problem has been encountered during parsing */
	protected int problem = 0;
	/** The version, always 2, 2 bits */
	protected int version = 2;
	/** Padding , 1 bit */
	protected int padding = 0;
	/** Number of items, e.g. receiver report blocks. Usage may vary. 5 bits */
	protected int itemCount = 0;
	/** The type of RTCP packet, 8 bits */
	protected int packetType = -1;
	/** The length of the RTCP packet, in 32 bit blocks minus 1. 16 bits */
	protected int length = -1;
	/** The ssrc that sent this, usually dictated by RTP Session */
	protected long ssrc = -1;

	/** Contains the actual data (eventually) */
	protected byte[] rawPkt = null;

	/** Only used for feedback messages: Time message was generated */
	protected long time = -1;
	/** Only used for feedback message: Whether this packet was received */
	protected boolean received = false;

	/**
	 * Parses the common header of an RTCP packet
	 * 
	 * @param start
	 *            where in this.rawPkt the headers start
	 * @return true if parsing succeeded and header cheks
	 */
	protected boolean parseHeaders(int start) {
		version = ((rawPkt[start + 0] & 0xC0) >>> 6);
		padding = ((rawPkt[start + 0] & 0x20) >>> 5);
		itemCount = (rawPkt[start + 0] & 0x1F);
		packetType = (int) rawPkt[start + 1];
		if (packetType < 0) {
			packetType += 256;
		}
		length = StaticProcs.bytesToUIntInt(rawPkt, start + 2);

		if (RTPSession.rtpDebugLevel > 9) {
			System.out.println(" <-> RtcpPkt.parseHeaders() version:" + version
					+ " padding:" + padding + " itemCount:" + itemCount
					+ " packetType:" + packetType + " length:" + length);
		}

		if (packetType > 207 || packetType < 200)
			System.out
					.println("RtcpPkt.parseHeaders problem discovered, packetType "
							+ packetType);

		if (version == 2 && length < 65536) {
			return true;
		} else {
			System.out
					.println("RtcpPkt.parseHeaders() failed header checks, check size and version");
			this.problem = -1;
			return false;
		}
	}

	/**
	 * Writes the common header of RTCP packets. The values should be filled in
	 * when the packet is initiliazed and this function called at the very end
	 * of .encode()
	 */
	protected void writeHeaders() {
		byte aByte = 0;
		aByte |= (version << 6);
		aByte |= (padding << 5);
		aByte |= (itemCount);
		rawPkt[0] = aByte;
		aByte = 0;
		aByte |= packetType;
		rawPkt[1] = aByte;
		if (rawPkt.length % 4 != 0)
			System.out
					.println("!!!! RtcpPkt.writeHeaders() rawPkt was not a multiple of 32 bits / 4 octets!");
		StaticProcs.uIntIntToByteWord((rawPkt.length / 4) - 1, rawPkt, 2);
	}

	/**
	 * This is just a dummy to make Eclipse complain less.
	 */
	protected void encode() {
		System.out.println("RtcpPkt.encode() should never be invoked!! "
				+ this.packetType);
	}

	/**
	 * Check whether this packet came from the source we expected.
	 * 
	 * Not currently used!
	 * 
	 * @param adr
	 *            address that packet came from
	 * @param partDb
	 *            the participant database for the session
	 * @return true if this packet came from the expected source
	 */
	protected boolean check(InetAddress adr, ParticipantDatabase partDb) {
		// Multicast -> We have to be naive
		if (partDb.rtpSession.mcSession
				&& adr.equals(partDb.rtpSession.mcGroup))
			return true;

		// See whether this participant is known
		Participant part = partDb.getParticipant(this.ssrc);
		if (part != null && part.rtcpAddress.getAddress().equals(adr))
			return true;

		// If not, we should look for someone without SSRC with his ip-address?
		return false;
	}
}