///////////////////////////////////////////////////////////////////////////////////
// Copyright (C) 2019-2021 Edouard Griffiths, F4EXB <f4exb06@gmail.com>          //
// Copyright (C) 2020-2023 Jon Beniston, M7RCE <jon@beniston.com>                //
// Copyright (C) 2020 Kacper Michajłow <kasper93@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 as version 3 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 V3 for more details.                               //
//                                                                               //
// You should have received a copy of the GNU General Public License             //
// along with this program. If not, see <http://www.gnu.org/licenses/>.          //
///////////////////////////////////////////////////////////////////////////////////

#ifndef INCLUDE_AISDEMODSINK_H
#define INCLUDE_AISDEMODSINK_H

#include <QVector>

#include "dsp/channelsamplesink.h"
#include "dsp/phasediscri.h"
#include "dsp/nco.h"
#include "dsp/interpolator.h"
#include "dsp/gaussian.h"
#include "dsp/gmskmlse.h"
#include "util/movingaverage.h"
#include "util/messagequeue.h"
#include "util/crc.h"

#include "aisdemodsettings.h"

#include <vector>
#include <iostream>
#include <fstream>

#define AISDEMOD_MAX_BYTES  160

// Symbols searched for the HDLC start flag before giving up on a correlation trigger
#define AISDEMOD_SOP_SYMBOLS 16

// Symbols the MLSE decodes once a start flag has been found. One AIS slot is about 256
// symbols; longer messages occupy several slots and the span doubles until they fit
#define AISDEMOD_MLSE_SYMBOLS 320

// Preamble symbols decoded to pull the per survivor phase loop in, then discarded. The
// demodulator starts 18 symbols into the 24 bit training sequence, so there is room for at
// most that many - beyond it the look back is clamped rather than reading off the start of
// the receive buffer
#define AISDEMOD_MLSE_WARMUP 12

// Symbol timing offsets tried either side of the nominal start, in samples. The correlator
// locates the burst to about a sample, but the sequence detector wants better than that, and
// one sample is a tenth of a symbol at 96 kHz. Retries only happen when the nominal timing
// fails to produce a good frame, so the cost falls on bursts that would otherwise be lost.
#define AISDEMOD_TIMING_PHASES 2

// Per survivor phase tracking loop gains. The optimum is broad
#define AISDEMOD_MLSE_PHASE_GAIN 0.3
#define AISDEMOD_MLSE_FREQ_GAIN  0.05

class ChannelAPI;
class AISDemod;
class ScopeVis;

class AISDemodSink : public ChannelSampleSink {
public:
    AISDemodSink(AISDemod *aisDemod);
    ~AISDemodSink();

    virtual void feed(const SampleVector::const_iterator& begin, const SampleVector::const_iterator& end);

    void setScopeSink(ScopeVis* scopeSink) { m_scopeSink = scopeSink; }
    void applyChannelSettings(int channelSampleRate, int channelFrequencyOffset, bool force = false);
    void applySettings(const AISDemodSettings& settings, const QStringList& settingsKeys, bool force = false);
    void setMessageQueueToChannel(MessageQueue *messageQueue) { m_messageQueueToChannel = messageQueue; }
    void setChannel(ChannelAPI *channel) { m_channel = channel; }

    double getMagSq() const { return m_magsq; }

    void getMagSqLevels(double& avg, double& peak, int& nbSamples)
    {
        if (m_magsqCount > 0)
        {
            m_magsq = m_magsqSum / m_magsqCount;
            m_magSqLevelStore.m_magsq = m_magsq;
            m_magSqLevelStore.m_magsqPeak = m_magsqPeak;
        }

        avg = m_magSqLevelStore.m_magsq;
        peak = m_magSqLevelStore.m_magsqPeak;
        nbSamples = m_magsqCount == 0 ? 1 : m_magsqCount;

        m_magsqSum = 0.0f;
        m_magsqPeak = 0.0f;
        m_magsqCount = 0;
    }


private:
    struct MagSqLevelsStore
    {
        MagSqLevelsStore() :
            m_magsq(1e-12),
            m_magsqPeak(1e-12)
        {}
        double m_magsq;
        double m_magsqPeak;
    };

    ScopeVis* m_scopeSink;    // Scope GUI to display baseband waveform
    AISDemod *m_aisDemod;
    AISDemodSettings m_settings;
    ChannelAPI *m_channel;
    int m_channelSampleRate;
    int m_channelFrequencyOffset;
    int m_samplesPerSymbol;
    quint64 m_sampleCounter;    //!< Monotonic, so already tried alignments can be skipped
    qint64 m_lastAttemptPos;
    bool m_haveAttempted;             // Number of samples per symbol

    NCO m_nco;
    Interpolator m_interpolator;
    Real m_interpolatorDistance;
    Real m_interpolatorDistanceRemain;

    double m_magsq;
    double m_magsqSum;
    double m_magsqPeak;
    int  m_magsqCount;
    MagSqLevelsStore m_magSqLevelStore;

    MessageQueue *m_messageQueueToChannel;

    MovingAverageUtil<Real, double, 16> m_movingAverage;

    PhaseDiscriminators m_phaseDiscri;  // FM demodulator
    Gaussian<Real> m_pulseShape;        // Pulse shaping filter
    Real *m_rxBuf;                      // Receive sample buffer, large enough for one max length message
    int m_rxBufLength;                  // Size in elements in m_rxBuf
    int m_rxBufIdx;                     // Index in to circular buffer
    int m_rxBufCnt;                     // Number of valid samples in buffer
    Real *m_train;
    std::vector<std::complex<double>> m_trainIQ; //!< Preamble as transmitted, for matched filtering                      // Training sequence to look for
    int m_correlationLength;
    Real m_trainEnergy;                 // Sum of squares of m_train, for the normalised correlation

    GmskMlse m_mlse;                    // Coherent sequence detector, used instead of the slicer
    std::vector<std::complex<double>> m_iqBuf; // Complex baseband, in step with m_rxBuf
    std::vector<Real> m_mlseSoft;       // Viterbi output, including the warm up symbols
    std::vector<Real> m_symSoft;        // Symbol decisions handed to the deframer

    unsigned char m_bytes[AISDEMOD_MAX_BYTES]{};
    crc16x25 m_crc;

    QVector<qint16> m_demodBuffer;
    int m_demodBufferFill;

    ComplexVector m_sampleBuffer[AISDemodSettings::m_scopeStreams];
    static const int m_sampleBufferSize = AISDemodSettings::AISDEMOD_CHANNEL_SAMPLE_RATE / 20;
    int m_sampleBufferIndex;

    enum DemodResult
    {
        FrameNone,      //!< Nothing that looked like a frame
        FrameGood,      //!< Complete frame, CRC passed
        FrameBadCrc,    //!< Complete frame, CRC failed
        FrameTruncated  //!< Started a frame but ran out of decoded symbols
    };

    void processOneSample(Complex &ci);
    double estimateFrequency() const;
    void computeSymbols(int x, int n);
    DemodResult deframe(int& endSampleIdx, bool& crcValid, bool& crcInvalid);
    void sendMessage(const QByteArray& packet, int totalBitCount);
    MessageQueue *getMessageQueueToChannel() { return m_messageQueueToChannel; }
    void sampleToScope(Complex sample, Real magsq, Real fmDemod, Real filt, Real rxBuf, Real corr, Real thresholdMet, Real dcOffset, Real crcValid);
};

#endif // INCLUDE_AISDEMODSINK_H
