// Class:   RAT::Methods::HitTimeProbabilityFactor
//  
// Brief:   Calculate probaility of observed PMT hit time given oberved charge
//  
// Author:  W. Heintzelman <billh@hep.upenn.edu>
//  
// REVISION HISTORY:
//     06/10/2016 : W Heintzelman - New class
//
// Detail:  For a given number of PEs, loop over the PEs in the order of their
//          arrival, calculating for each one the probability that it caused
//          the PMT discriminator to fire (i.e., that with the charge it
//          produced  the accumulated charge exceeded the PMT threshold) given
//          the observed charge, times the probability of the observed hit time
//          given that the discriminator fired upon its arrival.  Accumulate
//          the sum of the probabilty products, which is then the probability
//          of the observed hit time given the oberved charge and assuming that
//          fNPE photoelectrons were generated.
//          See discussion in SNO+-doc-2871.
//
/////////////////////////////////////////////////////////////////////////////


#ifndef __RAT_Method_HitTimeProbabilityFactor
#define __RAT_Method_HitTimeProbabilityFactor

#include <RAT/PMTChgpdf.hh>

namespace RAT
{
namespace Methods
{

class HitTimeProbabilityFactor{
    public:
        HitTimeProbabilityFactor( int maxPE ) ;
        void SetChargeParameters (
                    double threshold, double highHalfPt, double charge);
        void SetTimeParameters ( double pdfPtVal, double cdfPtVal);
        double GetTimeProbabilityFactor( int _nPE );

    private:
        double GetPEFireProb( int firePE);
        double PQSum(int PECount, int q);
        double PSumF(int precQ);
        PMTChgpdf* fPMTChgPdfPtr;
        int    fMaxPE;
        int    fFirePE, fNPE;
        int    fThrIdx, fQIdx;
        std::vector<double> fFactorial;
        std::vector<double*> fQpdf;
        double fPdfPtVal, fCdfPtVal;
};

} // namespace Methods
} // namespace RAT
#endif