#include "/home/eluiggi/work/cms/sharedBin/src/analysisUtils/pdfUtils.h"
#include <math.h>

double GetCentralPDF(std::vector<double> theWeightsVector){
  return theWeightsVector.at(0);
}

std::pair<double, double> GetPDFUncertaity(std::vector<double> theWeightsVector){
  std::pair<double, double> thePDFUncertainty;
  double pdf0 = GetCentralPDF(theWeightsVector);
  double deltaXPlusMax = 0.;
  double deltaXMinusMax = 0.;
  //std::vector<double> pdfWeightedEvents;
  for(unsigned int vIt = 1; vIt < theWeightsVector.size();){
    double xplus = theWeightsVector.at(vIt);
    double xminus = theWeightsVector.at(vIt+1);
    
    double deltaPlusCen = xplus - pdf0;
    double deltaMinusCen = xminus - pdf0;
    double theMaxPlusMinusCen = std::max(std::max(deltaPlusCen,deltaMinusCen),0.);
    deltaXPlusMax += theMaxPlusMinusCen*theMaxPlusMinusCen;
    
    double deltaCenPlus = pdf0 - xplus;
    double deltaCenMinus = pdf0 - xminus;
    double theMaxCenPlusMinus = std::max(std::max(deltaCenPlus,deltaCenMinus),0.);
    deltaXMinusMax += theMaxCenPlusMinus*theMaxCenPlusMinus;
    
    vIt += 2;
  }
  deltaXPlusMax = sqrt(deltaXPlusMax);
  deltaXMinusMax = sqrt(deltaXMinusMax);
  thePDFUncertainty = std::make_pair<double,double>(deltaXPlusMax, deltaXMinusMax);
  return thePDFUncertainty;
}