/**

 * 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.util.Enumeration;

import java.net.DatagramSocket;

import java.net.InetAddress;

import java.net.MulticastSocket;

import java.util.LinkedList;

import java.util.Hashtable;

import java.util.ListIterator;

import java.util.Arrays;

/**

 * This class acts as an organizer for most of the information

 * and functions pertaining to RTCP packet generation and reception 

 * 

 * @author Arne Kepp

 *

 */

public class RTCPSession {

	/** Parent session */

	protected RTPSession rtpSession = null;

	/** Unicast socket */

	protected DatagramSocket rtcpSock = null;

	/** Multicast socket */

	protected MulticastSocket rtcpMCSock = null;

	/** Multicast group */

	protected InetAddress mcGroup = null;

	/** RTCP Receiver thread */

	protected RTCPReceiverThread recvThrd = null;

	/** RTCP Sender thread */

	protected RTCPSenderThread senderThrd = null;

	/** Previous time a delay was calculated */

	protected long prevTime = System.currentTimeMillis();

	/** Delay between RTCP transmissions, in ms. Initialized in start() */

	protected int nextDelay = -1; //

	/** The average compound RTCP packet size, in octets, including UDP and IP headers */

	protected int avgPktSize = 200; //

	/** Pessimistic case estimate of the current number of senders */

	protected int senderCount = 1;

	/** Whether next RTCP packet can be sent early */

	protected boolean fbAllowEarly = false;

	/** Feedback queue , index is SSRC of target */

	protected Hashtable<Long, LinkedList<RtcpPkt>> fbQueue = null;

	/** APP queue , index is SSRC of target */

	protected Hashtable<Long, LinkedList<RtcpPktAPP>> appQueue = null;

	/** Are we just starting up? */

	protected boolean initial = true;

	/** Is there a feedback packet waiting? SSRC of destination */

	protected long fbWaiting = -1;

	/**

	 * Constructor for unicast sessions

	 * 

	 * @param parent RTPSession that started this

	 * @param rtcpSocket the socket to use for listening and sending

	 */

	protected RTCPSession(RTPSession parent, DatagramSocket rtcpSocket) {

		this.rtcpSock = rtcpSocket;

		rtpSession = parent;

	}

	/**

	 * Constructor for multicast sessions

	 * 

	 * @param parent parent RTPSession

	 * @param rtcpSocket parent RTPSession that started this

	 * @param multicastGroup multicast group to bind the socket to

	 */

	protected RTCPSession(RTPSession parent, MulticastSocket rtcpSocket, InetAddress multicastGroup) {

		mcGroup = multicastGroup;

		this.rtcpSock = rtcpSocket;

		rtpSession = parent;

	}

	/**

	 * Starts the session, calculates delays and fires up the threads.

	 *

	 */

	protected void start() {

		//nextDelay = 2500 + rtpSession.random.nextInt(1000) - 500;

		this.calculateDelay();

		recvThrd = new RTCPReceiverThread(this, this.rtpSession);

		senderThrd = new RTCPSenderThread(this, this.rtpSession);

		recvThrd.start();

		senderThrd.start();

	}

	/**

	 * Send bye packets, handled by RTCP Sender thread

	 *

	 */

	protected void sendByes() {

		senderThrd.sendByes();

	}

	/**

	 * Calculate the delay before the next RTCP packet can be sent

	 *

	 */

	protected void calculateDelay() {

		switch(rtpSession.rtcpMode) {

		case 0: calculateRegularDelay(); break;

		default:

			System.out.println("RTCPSession.calculateDelay() unknown .mode");

		}

	}

	/**

	 * Calculates a delay value in accordance with RFC 3550

	 *

	 */

	protected void calculateRegularDelay() {

		long curTime = System.currentTimeMillis();

		if(rtpSession.bandwidth != 0 && ! this.initial && rtpSession.partDb.ssrcTable.size() > 4) {

			// RTPs mechanisms for RTCP scalability

			int rand = rtpSession.random.nextInt(10000) - 5000; //between -500 and +500

			double randDouble =  ((double) 1000 + rand)/1000.0;

			Enumeration<Participant> enu = rtpSession.partDb.getParticipants();

			while(enu.hasMoreElements()) {

				Participant part = enu.nextElement();

				if(part.lastRtpPkt > this.prevTime)

					senderCount++;

			}

			double bw;

			if(rtpSession.rtcpBandwidth > -1) {

				bw = rtpSession.rtcpBandwidth;

			}else {

				bw = rtpSession.bandwidth*0.05;

			}

			if(senderCount*2 > rtpSession.partDb.ssrcTable.size()) {

				if(rtpSession.lastTimestamp > this.prevTime) {

					//We're a sender

					double numerator = ((double) this.avgPktSize)*((double) senderCount);

					double denominator = 0.25*bw;

					this.nextDelay = (int) Math.round((numerator/denominator)*randDouble);

				} else {

					//We're a receiver

					double numerator = ((double) this.avgPktSize)*((double) rtpSession.partDb.ssrcTable.size());

					double denominator = 0.75*bw;

					this.nextDelay = (int) Math.round((numerator/denominator)*randDouble);

				}

			} else {

				double numerator = ((double) this.avgPktSize)*((double) rtpSession.partDb.ssrcTable.size());;

				double denominator = bw;

				this.nextDelay = (int) Math.round(1000.0*(numerator/denominator)) * (1000 + rand);

			}

		} else {

			// Not enough data to scale, use random values

			int rand = rtpSession.random.nextInt(1000) - 500; //between -500 and +500

			if(this.initial) {

				// 2.5 to 3.5 seconds, randomly

				this.nextDelay = 3000 + rand;

				this.initial = false;

			} else {

				// 4.5 to 5.5 seconds, randomly

				this.nextDelay = 5500 + rand;

			}

		}

		// preflight check

		if(this.nextDelay < 1000) {

			int rand = rtpSession.random.nextInt(1000) - 500; //between -500 and +500

			System.out.println("RTCPSession.calculateDelay() nextDelay was too short (" 

					+this.nextDelay+"ms), setting to "+(this.nextDelay = 2000 + rand));

		}

		this.prevTime = curTime;

	}

	/**

	 * Update the average packet size

	 * @param length of latest packet

	 */

	synchronized protected void updateAvgPacket(int length) {

		double tempAvg = (double) this.avgPktSize;

		tempAvg = (15*tempAvg + ((double) length))/16;

		this.avgPktSize = (int) tempAvg;

	}

	/**

	 * Adds an RTCP APP (application) packet to the queue

	 *

	 * @param targetSsrc the SSRC of the recipient

	 * @param aPkt 

	 */

	synchronized protected void addToAppQueue(long targetSsrc, RtcpPktAPP aPkt) {

		aPkt.time = System.currentTimeMillis();

		if(this.appQueue == null)

			this.appQueue = new Hashtable<Long, LinkedList<RtcpPktAPP>>();

		LinkedList<RtcpPktAPP> ll = this.appQueue.get(targetSsrc);

		if(ll == null) {

			// No list, create and add

			ll = new LinkedList<RtcpPktAPP>();

			this.appQueue.put(targetSsrc, ll);

		}

		ll.add(aPkt);

	}

	/**

	 * Adds an RTCP APP (application) packet to the queue

	 *

	 * @param targetSsrc the SSRC of the recipient

	 * @return array of RTCP Application packets 

	 */

	synchronized protected RtcpPktAPP[] getFromAppQueue(long targetSsrc) {		

		if(this.appQueue == null)

			return null;

		LinkedList<RtcpPktAPP> ll = this.appQueue.get(targetSsrc);

		if(ll == null || ll.isEmpty()) {

			return null;

		} else {

			RtcpPktAPP[] ret = new RtcpPktAPP[ll.size()];

			ListIterator<RtcpPktAPP> li = ll.listIterator();

			int i = 0;

			while(li.hasNext()) {

				ret[i] = li.next();

				i++;

			}

			return ret;

		}

	}

	/**

	 * Cleans the TCP APP (application) packet queues of any packets that are

	 * too old, defined as 60 seconds since insertion.

	 * 

	 * @param ssrc The SSRC of the user who has left, negative value -> general cleanup

	 */

	synchronized protected void cleanAppQueue(long ssrc) {

		if(this.appQueue == null)

			return;

		if(ssrc > 0) {

			this.appQueue.remove(ssrc);

		} else {

			Enumeration<LinkedList<RtcpPktAPP>> enu = this.appQueue.elements();

			long curTime = System.currentTimeMillis();

			while(enu.hasMoreElements()) {

				ListIterator<RtcpPktAPP> li = enu.nextElement().listIterator();

				while(li.hasNext()) {

					RtcpPkt aPkt = li.next();

					//Remove after 60 seconds

					if(curTime - aPkt.time > 60000) {

						li.remove();

					}

				}

			}	

		}

	}

	/**

	 * Check the feedback queue for similar packets and adds

	 * the new packet if it is not redundant

	 * 

	 * @param aPkt

	 * @return 0 if the packet was added, 1 if it was dropped

	 */

	synchronized protected int addToFbQueue(long targetSsrc, RtcpPkt aPkt) {

		if(this.fbQueue == null)

			this.fbQueue = new Hashtable<Long, LinkedList<RtcpPkt>>();

		LinkedList<RtcpPkt> ll = this.fbQueue.get(targetSsrc);

		if(ll == null) {

			// No list, create and add

			ll = new LinkedList<RtcpPkt>();

			ll.add(aPkt);

			this.fbQueue.put(targetSsrc, ll);

		} else {

			// Check for matching packets, else add to end

			ListIterator<RtcpPkt> li = ll.listIterator();

			while(li.hasNext()) {

				RtcpPkt tmp = li.next();

				if(equivalent(tmp, aPkt))

					return -1;

			}

			ll.addLast(aPkt);

		}

		return 0;

	}

	/**

	 * Checks whether there are ny feedback packets waiting

	 * to be sent.

	 * 

	 * @param ssrc of the participant we are notifying

	 * @return all relevant feedback packets, or null

	 */

	synchronized protected RtcpPkt[] getFromFbQueue(long ssrc) {

		if(this.fbQueue == null)

			return null;

		LinkedList<RtcpPkt> ll = this.fbQueue.get(ssrc);

		if(ll == null)

			return null;

		ListIterator<RtcpPkt> li = ll.listIterator();

		if(li.hasNext()) {

			long curTime = System.currentTimeMillis();

			long maxDelay = curTime - rtpSession.fbMaxDelay;

			long keepDelay =  curTime - 2000;

			int count = 0;

			//TODO below the indeces should be collected instead of looping twice

			// Clean out what we dont want and count what we want

			while(li.hasNext()) {

				RtcpPkt aPkt = li.next();

				if(aPkt.received) {

					//This is a packet received, we keep these for

					// 2000ms to avoid redundant feedback

					if(aPkt.time < keepDelay)

						li.remove();

				} else {

					//This is a packet we havent sent yet

					if(aPkt.time < maxDelay) {

						li.remove();

					} else {

						count++;

					}

				}

			}

			// Gather what we want to return

			if(count != 0) {

				li = ll.listIterator();

				RtcpPkt[] ret = new RtcpPkt[count];

				while(count > 0) {

					RtcpPkt aPkt = li.next();

					if(! aPkt.received) {

						ret[ret.length - count] = aPkt; 

						count--;

					}

				}

				return ret;

			}

		}

		return null;

	}

	/**

	 * Cleans the feeback queue of any packets that have expired,

	 * ie feedback packet that are no longer relevant.

	 * 

	 * @param ssrc The SSRC of the user who has left, negative value -> general cleanup

	 */

	synchronized protected void cleanFbQueue(long ssrc) {

		if(this.fbQueue == null)

			return;

		if(ssrc > 0) {

			this.fbQueue.remove(ssrc);

		} else { 

			Enumeration<LinkedList<RtcpPkt>> enu = this.fbQueue.elements();

			long curTime = System.currentTimeMillis();

			long maxDelay = curTime - rtpSession.fbMaxDelay;

			long keepDelay =  curTime - 2000;

			while(enu.hasMoreElements()) {

				ListIterator<RtcpPkt> li = enu.nextElement().listIterator();

				while(li.hasNext()) {

					RtcpPkt aPkt = li.next();

					if(aPkt.received) {

						//This is a packet received, we keep these for

						// 2000ms to avoid redundant feedback

						if(aPkt.time < keepDelay)

							li.remove();

					} else {

						//This is a packet we havent sent yet

						if(aPkt.time < maxDelay)

							li.remove();

					}

				}

			}

		}

	}

	/**

	 * Check whether the conditions are satisfied to send a feedbkac packet immediately.

	 * 

	 * @return true if they are, false otherwise

	 */

	protected boolean fbSendImmediately() {

		if(rtpSession.partDb.ssrcTable.size() > this.rtpSession.fbEarlyThreshold 

				&& rtpSession.partDb.receivers.size() > this.rtpSession.fbEarlyThreshold)

			return false;

		return true;

	}

	/**

	 * Check whether the conditions are satisfied to send a feedbkac packet immediately.

	 * 

	 * @return true if they are, false otherwise

	 */

	protected boolean fbSendEarly() {

		if(rtpSession.partDb.ssrcTable.size() > this.rtpSession.fbRegularThreshold 

				&& rtpSession.partDb.receivers.size() > this.rtpSession.fbRegularThreshold)

			return false;

		return true;

	}

	/**

	 * Wake the sender thread because of this ssrc

	 * 

	 * @param ssrc that has feedback waiting.

	 */

	protected void wakeSenderThread(long ssrc) {

		this.fbWaiting = ssrc;

		this.senderThrd.interrupt();

		// Give it a chance to catch up

		try { Thread.sleep(0,1); } catch (Exception e){ };

	}

	/**

	 * Compares two packets to check whether they are equivalent feedback messages,

	 * to avoid sending the same feedback to a host twice.

	 * 

	 * Expect false negatives, but not false positives.

	 * 

	 * @param one packet

	 * @param two packet

	 * @return true if they are equivalent, false otherwise 

	 */

	private boolean equivalent(RtcpPkt one, RtcpPkt two) {

		// Cheap checks

		if(one.packetType != two.packetType)

			return false;

		if(one.itemCount != two.itemCount)

			return false;

		if(one.packetType == 205) {

			// RTP Feedback, i.e. a NACK

			RtcpPktRTPFB pktone = (RtcpPktRTPFB) one;

			RtcpPktRTPFB pkttwo = (RtcpPktRTPFB) two;

			if(pktone.ssrcMediaSource != pkttwo.ssrcMediaSource)

				return false;

			if(Arrays.equals(pktone.BLP,pkttwo.BLP) 

					&& Arrays.equals(pktone.BLP,pkttwo.BLP))

				return true;

			return true;

		} else if(one.packetType == 206) {

			RtcpPktPSFB pktone = (RtcpPktPSFB) one;

			RtcpPktPSFB pkttwo = (RtcpPktPSFB) two;

			if(pktone.ssrcMediaSource != pkttwo.ssrcMediaSource)

				return false;

			switch(one.itemCount) {

			case 1: // Picture Loss Indication 

				return true;

			case 2: // Slice Loss Indication

				// This will not work if the slice loss indicators are in different order

				if(pktone.sliFirst.length == pkttwo.sliFirst.length

						&& Arrays.equals(pktone.sliFirst, pkttwo.sliFirst) 

						&& Arrays.equals(pktone.sliNumber, pkttwo.sliNumber)

						&& Arrays.equals(pktone.sliPictureId, pkttwo.sliPictureId))

					return true;

				break;

			case 3: // Reference Picture Selection Indication 

				if(Arrays.equals(pktone.rpsiBitString, pkttwo.rpsiBitString))

					return true;

				break;

			case 15: // Application Layer Feedback Messages

				// This will not work if the padding scheme is different

				if(pktone.sliFirst.length == pkttwo.sliFirst.length

						&& Arrays.equals(pktone.alfBitString, pkttwo.alfBitString))

					return true;

				break;

			default:

			}

			return true;

		} else {

			System.out.println("!!!! RTCPSession.equivalentPackets() encountered unexpected packet type!");

		}

		return false;

	}

}