// $Id$
//-----------------------------------------------------------------------
//       The GSI Online Offline Object Oriented (Go4) Project
//         Experiment Data Processing at EE department, GSI
//-----------------------------------------------------------------------
// Copyright (C) 2000- GSI Helmholtzzentrum fuer Schwerionenforschung GmbH
//                     Planckstr. 1, 64291 Darmstadt, Germany
// Contact:            http://go4.gsi.de
//-----------------------------------------------------------------------
// This software can be used under the license agreements as stated
// in Go4License.txt file which is part of the distribution.
//-----------------------------------------------------------------------

#ifndef TGO4FITMODELFORMULA_H
#define TGO4FITMODELFORMULA_H

#include "TGo4FitModel.h"

class TFormula;

/**
 * @brief Model object, which uses ROOT TFormula class facility.
 *
 * @details Any kind of one-line expression can be analyzed by TFormula object and evaluated for given set of axis values and set of parameters.
 * TGo4FitModelFormula in constructor creates additional parameters with names "Par0", "Par1" and so on,
 * which can be used in equation and can be optimized. Optionally amplitude parameters with name "Ampl" can be created.
 * In constructor expression, number of additional parameters and using of amplitude parameter should be specified.
 * Fort instance, equation with 3 parameters and amplitude:
 * ~~~{cpp}
 *   auto f = new TGo4FitModelFormula("Form","(x-Par0)*(y-Par1)*(z-Par2)", 3, kTRUE);
 * ~~~
 *
 * @ingroup go4_fit
 */
class TGo4FitModelFormula : public TGo4FitModel {
   public:

      /**
       * Default constructor
       */
      TGo4FitModelFormula();

      /**
       * Create TGo4FitModelFormula object with given names.
       * Formula expression and number of parameters can be sets up. All using of amplitude parameter can be invoked.
       */
      TGo4FitModelFormula(const char *iName, const char *iExpressionStr = "", Int_t iNPars = 0, Bool_t AddAmplitude = kFALSE);

      /**
       * Destroys TGo4FitModelFormula object.
       */
      virtual ~TGo4FitModelFormula();

      /**
       * Signals that amplitude parameter can be removed from or introduced to object.
       */
      Bool_t CanAmplTouch() override { return kTRUE; }

      /**
       * Return formula expression.
       */
      const char *GetExpression() const { return fxExpression.Data(); }

      /**
       * Sets formula expression.
       */
      void SetExpression(const char *expr) { fxExpression = expr; }

      /**
       * Get number of parameters, which can be used in expression.
       */
      Int_t GetNumberOfExprPar();

      /**
       * Sets number of parameters, which can be used in expression.
       */
      Bool_t SetNumberOfExprPar(Int_t num);

      void SetPosParIndex(Int_t naxis, Int_t indx = -1);
      void SetWidthParIndex(Int_t naxis, Int_t indx = -1);

      Bool_t BeforeEval(Int_t ndim) override;
      Double_t EvalN(const Double_t *v) override;
      void AfterEval() override;

      /**
       * Print information on standard output.
       */
      void Print(Option_t *option = "") const override;

   protected:

      Bool_t Initialize(Int_t UseBuffers = -1) override;
      void Finalize() override;

      TGo4FitParameter *GetExprPar(Int_t n);
      TString GetExprParName(Int_t n);

      Bool_t CompileFormula();
      void CloseFormula();

      Int_t GetPosParIndex(Int_t naxis) override;
      Int_t GetWidthParIndex(Int_t naxis) override;

      /**
       * String, containing formula expression.
       */
      TString fxExpression;

      TArrayI fxPosIndex;

      TArrayI fxWidthIndex;

      /**
       * formula for evaluation expression in EvalN() method.
       */
      TFormula *fxFormula{nullptr};               //!
   private:

      /**
       * temporary variable for formula calculation in EvalN() method.
       */
      Int_t Par_ndim{0};                  //!

   ClassDefOverride(TGo4FitModelFormula,1)
};

#endif // TGO4FITMODELFORMULA_H