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// $Maintainer: Chris Bielow $
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#ifndef OPENMS_FILTERING_NOISEESTIMATION_SIGNALTONOISEESTIMATOR_H
#define OPENMS_FILTERING_NOISEESTIMATION_SIGNALTONOISEESTIMATOR_H

#include <OpenMS/KERNEL/MSSpectrum.h>
#include <OpenMS/DATASTRUCTURES/DefaultParamHandler.h>
#include <OpenMS/CONCEPT/ProgressLogger.h>

#include <vector>
#include <cmath>
#include <map>

namespace OpenMS
{
  /**
    @brief This class represents the abstract base class of a signal to noise estimator.

    A signal to noise estimator should provide the signal to noise ratio of all raw data points
    in a given interval [first_,last_).
  */

  template <typename Container = MSSpectrum<> >
  class SignalToNoiseEstimator :
    public DefaultParamHandler, public ProgressLogger
  {
public:

    /** @name Type definitions
     */
    //@{
    typedef typename Container::const_iterator PeakIterator;
    typedef typename PeakIterator::value_type PeakType;


    //@}

    /// Constructor
    inline SignalToNoiseEstimator() :
      DefaultParamHandler("SignalToNoiseEstimator"),
      ProgressLogger(),
      first_(),
      last_(),
      is_result_valid_(false)
    {
    }

    /// Copy constructor
    inline SignalToNoiseEstimator(const SignalToNoiseEstimator & source) :
      DefaultParamHandler(source),
      ProgressLogger(source),
      stn_estimates_(source.stn_estimates_),
      first_(source.first_),
      last_(source.last_),
      is_result_valid_(source.is_result_valid_)
    {}

    /// Assignment operator
    inline SignalToNoiseEstimator & operator=(const SignalToNoiseEstimator & source)
    {
      if (&source == this) return *this;

      DefaultParamHandler::operator=(source);
      ProgressLogger::operator=(source);
      stn_estimates_ = source.stn_estimates_;
      first_ = source.first_;
      last_  = source.last_;
      return *this;
    }

    /// Destructor
    virtual ~SignalToNoiseEstimator()
    {}


    /// Set the start and endpoint of the raw data interval, for which signal to noise ratios will be estimated immediately
    virtual void init(const PeakIterator & it_begin, const PeakIterator & it_end)
    {
      first_ = it_begin;
      last_ = it_end;
      computeSTN_(first_, last_);
      is_result_valid_ = true;
    }

    /// Set the start and endpoint of the raw data interval, for which signal to noise ratios will be estimated immediately
    virtual void init(const Container & c)
    {
      init(c.begin(), c.end());
    }

    /// Return to signal/noise estimate for data point @p data_point
    /// @note the first query to this function will take longer, as
    ///       all SignalToNoise values are calculated
    /// @note you will get a warning to stderr if more than 20% of the
    ///       noise estimates used sparse windows
    virtual double getSignalToNoise(const PeakIterator & data_point)
    {
      if (!is_result_valid_)
      {
        // recompute ...
        init(first_, last_);
      }

      return stn_estimates_[*data_point];
    }

    virtual double getSignalToNoise(const PeakType & data_point)
    {
      if (!is_result_valid_)
      {
        // recompute ...
        init(first_, last_);
      }

      return stn_estimates_[data_point];
    }

protected:

    /**
         * @brief computes the S/N values when init() is called
         *
         * @exception Throws Exception::InvalidValue
         */
    virtual void computeSTN_(const PeakIterator & scan_first_, const PeakIterator & scan_last_) = 0;



    /**
      @brief protected struct to store parameters my, sigma for a Gaussian distribution

      Accessors are : mean and variance
    */
    struct GaussianEstimate
    {
      double mean;   ///mean of estimated Gaussian
      double variance; ///variance of estimated Gaussian
    };


    /// calculate mean & stdev of intensities of a spectrum
    inline GaussianEstimate estimate_(const PeakIterator & scan_first_, const PeakIterator & scan_last_) const
    {
      int size = 0;
      // add up
      double v = 0;
      double m = 0;
      PeakIterator run = scan_first_;
      while (run != scan_last_)
      {
        m += (*run).getIntensity();
        ++size;
        ++run;
      }
      //average
      m = m / size;

      //determine variance
      run = scan_first_;
      while (run != scan_last_)
      {
        double tmp(m - (*run).getIntensity());
        v += tmp * tmp;
        ++run;
      }
      v = v / ((double)size); // divide by n

      GaussianEstimate value = {m, v};
      return value;
    }

    //MEMBERS:

    /// stores the noise estimate for each peak
    std::map<PeakType, double, typename PeakType::PositionLess> stn_estimates_;

    /// points to the first raw data point in the interval
    PeakIterator first_;
    /// points to the right position next to the last raw data point in the interval
    PeakIterator last_;
    /// flag: set to true if SignalToNoise estimates are calculated and none of the params were changed. otherwise false.
    mutable bool is_result_valid_;
  };

} // namespace OpenMS

#endif //OPENMS_FILTERING_NOISEESTIMATION_SIGNALTONOISEESTIMATOR_H
