/////////////////////////////////////////////////////
//
// To run Macro type in terminal:  root stack_hist.C 
//
////////////////////////////////////////////////////

#include <TROOT.h>
#include <TFile.h>
#include <TCanvas.h>
#include <TPad.h>
#include <TH1.h>
#include <THStack.h>
#include <THistPainter.h>
#include <TAxis.h>
#include <TLegend.h>
#include <iostream>
using namespace std;
#include <string>


void stack_hist(){


  // Load Samples files

  cout<<"Loading Samples Files....."<<endl;

  TFile *file1 = TFile::Open("/home/ahmed/h1_e3e3bar.root","READ");
  TFile *file2 = TFile::Open("/home/ahmed/h2_e3e3bar.root","READ");
  TFile *file3 = TFile::Open("/home/ahmed/z_e3e3bar.root","READ");
  TFile *file4 = TFile::Open("/home/ahmed/e3e3bar.root","READ");

  
  // Call histos from Samples files

  cout<<"Calling Histograms....."<<endl;
 
 TH1* h1 = dynamic_cast<TH1*> (file1->Get("gaussian"));
  TH1* h2 = dynamic_cast<TH1*>(file2->Get("gaussian"));
  TH1* h3 = dynamic_cast<TH1*>(file3->Get("gaussian"));
  TH1* h4 = dynamic_cast<TH1*>(file4->Get("gaussian"));  
 



  // Adjust Appearance of Histos

  h1->SetFillColor(kRed);
  h1->SetLineColor(kBlack);
  h1->SetLineWidth(2);
  h1->Draw();

  h2->SetFillColor(kBlue);
  h2->SetLineColor(kBlack);
  h2->SetLineWidth(2);
 h2->Draw();

  h3->SetLineColor(kOrange );
  h3->SetLineColor(kBlack);
  h3->SetLineWidth(4);
  h3->Draw();

  h4->SetFillColor(kViolet+3);
  h4->SetLineColor(kBlack);
  h4->SetLineWidth(2);
  h4->Draw();



  // Define output file for saving stacked histos

  TFile *out_stack = new TFile("output_stack.root","RECREATE");


  // Build Canvas

  TCanvas *cnv = new TCanvas("c1","stacked histo",600,600);


  // Define Stacked Histo

  cout<<"Building Stacked Histo....."<<endl;

  THStack *stk = new THStack("stacked_histo","");

  stk->Add(h2,"HIST SAME");
  stk->Add(h3,"HIST SAME");
  stk->Add(h4,"HIST SAME");
  

  cnv->cd();
  gPad->SetLogy(1);
  stk->Draw();
  h1->Draw("HIST SAME") ;

  stk->GetXaxis()->SetTitle("x label");
  stk->GetYaxis()->SetTitle("Events");

  stk->GetXaxis()->SetLimits(-10,10);
  gPad->BuildLegend(0.75,0.75,0.95,0.95,"");        // automatic build legend from objects in current pad-> ok if histos have different titles


  // Build a Legend

  TLegend *lg = new TLegend(0.7,0.7,0.9,0.9);
  lg->SetHeader("analysis","C");
  lg->AddEntry(h2,"bkg 1","f");
  lg->AddEntry(h3,"bkg 2","f");
  lg->AddEntry(h4,"bkg 3","f");
  lg->AddEntry(h1,"signal","l");
  lg->Draw();

  cnv->Write();
  out_stack->Close();

  
  
  return;

}