/***************************************************************************
 *   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();
    ~SampleQueue();

    enum {SAMPLE_COUNT_MAX = 20};

    /**
     * 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_count;

    int m_start;
    int m_end;

    Uint32 m_samples[SAMPLE_COUNT_MAX];
};

/**
 * 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();

private:
    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;
};

}

#endif
