/***************************************************************************
 *   Copyright (C) 2006 by Ivan Vasić   								   *
 *   ivasic@gmail.com   												   *
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 *   This program 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 General Public License for more details.                          *
 *                                                                         *
 *   You should have received a copy of the GNU General Public License     *
 *   along with this program; if not, write to the                         *
 *   Free Software Foundation, Inc.,                                       *
 *   51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.          *
 ***************************************************************************/
#ifndef BTTIMEESTIMATOR_H
#define BTTIMEESTIMATOR_H

#include <climits>
#include <ktorrent_export.h>
#include <util/constants.h>

namespace bt
{
	class TorrentControl;

	/**
	 * Simple queue class for samples. Optimized for speed and size
	 * without possibility to dynamically resize itself.
	 * @author Ivan Vasic <ivasic@gmail.com>
	 */
	class SampleQueue
	{
	public:
		SampleQueue(int max);
		~SampleQueue();

		/**
		 * Inserts new sample into the queue. The oldest sample is overwritten.
		 */
		void push(Uint32 sample);

		Uint32 first();
		Uint32 last();

		bool isFull();

		/**
		 * This function will return the number of samples in queue until it counts m_size number of elements.
		 * After this point it will always return m_size since no samples are being deleted.
		 */
		int count();

		/**
		 * Returns the sum of all samples.
		 */
		Uint32 sum();

	private:
		int m_size;
		int m_count;

		int m_start;
		int m_end;

		Uint32* m_samples;
	};

	/**
	 * ETA estimator class. It will use different algorithms for different download phases.
	 * @author Ivan Vasic <ivasic@gmail.com>
	*/
	class KTORRENT_EXPORT TimeEstimator
	{
	public:
		static const int NEVER = INT_MAX;
		static const int ALREADY_FINISHED = 0;

		enum ETAlgorithm
		{
			ETA_KT,		//ktorrent default algorithm - combination of the following according to our tests
			ETA_CSA, 	//current speed algorithm
			ETA_GASA,	//global average speed algorithm
			ETA_WINX,	//window of X algorithm
			ETA_MAVG	//moving average algorithm
		};

		TimeEstimator(TorrentControl* tc);
		~TimeEstimator();

		///Returns ETA for m_tc torrent.
		int estimate();

		static void setAlgorithm(ETAlgorithm theValue);
		static ETAlgorithm algorithm() { return m_algorithm; }

	private:

		int estimateCSA();
		int estimateGASA();
		int estimateWINX();
		int estimateMAVG();
		int estimateKT();

		Uint32 sample() const;
		Uint64 bytesLeft() const;

		TorrentControl* m_tc;
		SampleQueue* m_samples;

		Uint32 m_lastAvg;
		int m_lastETA;

		//last percentage
		double m_perc;

		static ETAlgorithm m_algorithm;
	};

}

#endif
