// @(#)root/minuit2:$Id$
// Author: L. Moneta    10/2006  

/**********************************************************************
 *                                                                    *
 * Copyright (c) 2006 ROOT Foundation,  CERN/PH-SFT                   *
 *                                                                    *
 **********************************************************************/

#ifndef ROOT_Minuit2_FumiliFCNAdapter
#define ROOT_Minuit2_FumiliFCNAdapter

#ifndef ROOT_Minuit2_FumiliFCNBase
#include "Minuit2/FumiliFCNBase.h"
#endif

#ifndef ROOT_Math_FitMethodFunction
#include "Math/FitMethodFunction.h"
#endif

#ifndef ROOT_Minuit2_MnPrint
#include "Minuit2/MnPrint.h"
#endif

// #ifndef ROOT_Math_Util
// #include "Math/Util.h"
// #endif

#include <cmath>

namespace ROOT {

   namespace Minuit2 {

/** 


template wrapped class for adapting to FumiliFCNBase signature

@author Lorenzo Moneta

@ingroup Minuit

*/

template< class Function> 
class FumiliFCNAdapter : public FumiliFCNBase {

public:

//   typedef ROOT::Math::FitMethodFunction Function; 
   typedef typename Function::Type_t Type_t; 

   FumiliFCNAdapter(const Function & f, unsigned int ndim, double up = 1.) : 
      FumiliFCNBase( ndim ),
      fFunc(f) , 
      fUp (up)
   {}

   ~FumiliFCNAdapter() {}

  
   double operator()(const std::vector<double>& v) const { 
      return fFunc.operator()(&v[0]); 
   }
   double operator()(const double *  v) const { 
      return fFunc.operator()(v); 
   }
   double Up() const {return fUp;}

   void SetErrorDef(double up) { fUp = up; } 
  
   //virtual std::vector<double> Gradient(const std::vector<double>&) const;

   // forward interface
   //virtual double operator()(int npar, double* params,int iflag = 4) const;


 /**
     evaluate gradient hessian and function value needed by fumili 
   */
   void EvaluateAll( const std::vector<double> & v);

private:
   

//data member

   const Function & fFunc; 
   double fUp; 
};


template<class Function>
void FumiliFCNAdapter<Function>::EvaluateAll( const std::vector<double> & v) { 

   //typedef FumiliFCNAdapter::Function Function; 

   //evaluate all elements
   unsigned int npar = Dimension();
   if (npar != v.size() ) std::cout << "npar = " << npar << "  " << v.size() << std::endl;
   assert(npar == v.size());
   //must distinguish case of likelihood or LS

   std::vector<double> & grad = Gradient(); 
   std::vector<double> & hess = Hessian(); 
   // reset  
   assert(grad.size() == npar);
   grad.assign( npar, 0.0); 
   hess.assign( hess.size(), 0.0);
   
   double sum = 0; 
   unsigned int ndata = fFunc.NPoints();

   std::vector<double> gf(npar); 
 
   //loop on the data points

   
   // assume for now least-square
   if (fFunc.Type() == Function::kLeastSquare) { 

      for (unsigned int i = 0; i < ndata; ++i) { 
         // calculate data element and gradient 
         double fval = fFunc.DataElement(&v.front(), i, &gf[0]);

         // t.b.d should protect for bad  values of fval
         sum += fval*fval;

         for (unsigned int j = 0; j < npar; ++j) { 
            grad[j] += 2. * fval * gf[j];
            for (unsigned int k = j; k < npar; ++ k) { 
               int idx =  j + k*(k+1)/2; 
               hess[idx] += 2.0 * gf[j] * gf[k];  
            }
         }
      }
   }
   else if (fFunc.Type() == Function::kLogLikelihood) {  


      for (unsigned int i = 0; i < ndata; ++i) { 

         // calculate data element and gradient 
         // return value is log of pdf and derivative of the log(Pdf)
         double fval = fFunc.DataElement(&v.front(), i, &gf[0]);

         sum -= fval;
         
         for (unsigned int j = 0; j < npar; ++j) { 
            double gfj = gf[j] ; 
            grad[j] -= gfj;
            for (unsigned int k = j; k < npar; ++ k) { 
               int idx =  j + k*(k+1)/2; 
               hess[idx] +=  gfj * gf[k] ;  
            }
         }
      }
   }
   else { 
      MN_ERROR_MSG("FumiliFCNAdapter: type of fit method is not supported, it must be chi2 or log-likelihood");
   }
}
      

   } // end namespace Minuit2

} // end namespace ROOT




#endif //ROOT_Minuit2_FCNAdapter
