#include "Fit/Fitter.h"
#include "Fit/BinData.h"
#include "Fit/Chi2FCN.h"
#include "TList.h"
#include "Math/WrappedMultiTF1.h"
#include "HFitInterface.h"
#include "TCanvas.h"
#include "TStyle.h"
#include "TGraphMultiErrors.h"

ROOT::Fit::FitResult GaussFit(TH1D* h1D, TF1* ffit);

void ParamScan()  {

   ROOT::Fit::FitResult fit_results;

   auto h1 = new TH1D("h1","h1",100,-5,5);
   h1->FillRandom("gaus");

   TF1 * f1 = new TF1("f1","gaus", -5,5);

   fit_results = GaussFit(h1, f1);

   double pmin = fit_results.Parameter(2) - 10*fit_results.ParError(2);
   double pmax = fit_results.Parameter(2) + 10*fit_results.ParError(2);

   unsigned int Npts = 100;
   double xarr[Npts], chiarr[Npts];

   fit_results.Scan(2, Npts, xarr, chiarr, pmin, pmax);

   TGraph *gr = new TGraph(Npts, xarr, chiarr);

   gr->Draw("AL");
}
//___________________________________________________________________________________________________
ROOT::Fit::FitResult GaussFit(TH1D* h1D, TF1* ffit) { //Fit with ROOT::Fit method

	ROOT::Fit::DataOptions opt;
	ROOT::Fit::DataRange range;

	ROOT::Fit::BinData data(opt,range);
	ROOT::Fit::FillData(data, h1D);

	ROOT::Math::WrappedMultiTF1 fitfunc(*ffit,1);

	ROOT::Fit::Fitter fitter;
	fitter.SetFunction(fitfunc, false);

   fitter.Config().ParSettings(0).SetLimits(0,1.E6);
   fitter.Config().ParSettings(2).SetLowerLimit(0);

	ROOT::Math::MinimizerOptions(mopt);

   mopt.SetMinimizerType("Minuit2");

   mopt.SetPrintLevel(1);
	// print the default minimizer option values
	mopt.Print();
   fitter.Config().SetMinimizerOptions(mopt);
   fitter.Fit(data); // chi2 fit'

   ROOT::Fit::FitResult result = fitter.Result();

	result.Print(std::cout);
	ffit ->SetFitResult(result);
   h1D ->GetListOfFunctions()->Add(ffit);

   return result;
}