#include <fstream>
#include <iostream>  
#include <TFile.h>
#include <TTree.h>
#include <TBranch.h>
#include <TMath.h>
#include "TreeClass2.h"


void treesort2() {
  //example of script illustrating how to sort entries in a Tree in ONE file
  //the algorithm assumes that all buffers of one branch can fit in memory
  //This algorithm should be modified in case of one single top level branch
  //in case the buffers do not fit in memory. Instead one should loop
  //on its sub-branches.
  //This algorithm cannot be used to sort entries in a TChain. You should merge
  //your files in the TChain into one single big file first.
   
  TFile *fin = new TFile("small.root");  //the input file
  TTree *Tin = (TTree*)fin->Get("ntp1"); //get the input Tree
  TFile *fout = new TFile("small_sorted2.root","recreate");
  TTree *Tout = Tin->CloneTree(0);
  Long64_t N = Tin->GetEntries();

  TreeClass2 looper(Tin);

  Int_t *table = new Int_t[N];
  Int_t *sorted = new Int_t[N];
  Long64_t index;
 
  std::cout<<"Reading Run numbers"<<std::endl;
  for (index=0;index<N;index++) 
  {
    if (index % 1000 == 0 || index == 1) 
    {
      std::cout << "\r";
      std::cout <<" ------ PROCESSING ev NO. "<< index << " of "<< N <<" ------ ";
      std::cout.flush();
    }
    looper.GetEntry(index);
    table[index] = looper.runNumber;
  }

  std::cout<<std::endl<<"Sorting Run numbers"<<std::endl;

  TMath::Sort(N,table,sorted,kFALSE);

  // write a file containing the sorted run numbers to check that 
  // TMath::Sort is not to blame

  ofstream outfile;
  outfile.open("runlist.lst");

  for (index=0;index<N;index++)
  {
    outfile<<table[sorted[index]]<<std::endl;
  }
  outfile.close();
  
  //loop branch by branch on the input Tree and fill the output Tree
  TIter next(Tin->GetListOfBranches());
  TBranch *bin, *bout;
  while ((bin = (TBranch*)next())) {
    bout = Tout->GetBranch(bin->GetName());
    printf("processing branch: %s\n",bin->GetName());
    //load all baskets of this branch in memory (for performance)
    bin->LoadBaskets();
    //loop on entries and fill output Tree
    for (index=0;index<N;index++) {
      bin->GetEntry(sorted[index]);
      bout->Fill();
    }
    bin->DropBaskets();
    Tout->AutoSave();
  }
  Tout->SetEntries(N);
  Tout->Print();
  Tout->AutoSave();
  fout->Close();
}