//----------------------------------------------------------------------
// Example on how to use this contribution
//
// run it with
//  ./example_areasub < ../data/Pythia-Zp2jets-lhc-pileup-1ev.dat
//----------------------------------------------------------------------

// $Id: example.cc 3001 2013-01-29 10:41:40Z soyez $
//
// Copyright (c) 2012-, Matteo Cacciari, Jihun Kim, Gavin P. Salam and Gregory Soyez
//
//----------------------------------------------------------------------
// This file is part of FastJet contrib.
//
// It is free software; you can redistribute it and/or modify it under
// the terms of the GNU General Public License as published by the
// Free Software Foundation; either version 2 of the License, or (at
// your option) any later version.
//
// It is distributed in the hope that it will be useful, but WITHOUT
// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
// or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
// License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this code. If not, see <http://www.gnu.org/licenses/>.
//----------------------------------------------------------------------

//----------------------------------------------------------
// GS notes for CHS events
//----------------------------------------------------------

// Is we want to show an example of what happens for CHS events. we
// need to introduce a UserInfo class similar to what is in example 09
// in FastJet. For area wsubtraction, we'd just discard charged-PU
// tracks and that's mostly it (watching out that the Selector needs
// to be passed to the subtractor to properly handle the safety
// tests). But for NpC, we'd need a transformer (unless we use a loop)
// that rescales aprticles.
//
// Question: do we do that at all? Only Area? In this example or in
// another?

#include <iostream>
#include <iomanip>

#include "fastjet/PseudoJet.hh"
#include "fastjet/ClusterSequenceArea.hh"
#include "fastjet/Selector.hh"
#include "fastjet/tools/JetMedianBackgroundEstimator.hh"

//#include "fastjet/tools/Subtractor.hh"
#include "SafeSubtractor.hh"  // we'll use the implementation provided
                              // in this contrib
#include "GenericSubtractor.hh"

using namespace std;
using namespace fastjet;

void read_event(vector<PseudoJet> &hard_event, vector<PseudoJet> &full_event);
void print_jet(const PseudoJet &jet);

//----------------------------------------------------------------------
int main(){
  // read in input particles
  //
  // since we use here simulated data we can split the hard event
  // from the full (i.e. with pileup added) one
  //
  // (see also example 07 in FastJet)
  //----------------------------------------------------------
  vector<PseudoJet> hard_event, full_event;
  read_event(hard_event, full_event);

  // keep the particles up to 4 units in rapidity
  hard_event = SelectorAbsRapMax(4.0)(hard_event);
  full_event = SelectorAbsRapMax(4.0)(full_event);
  
  // do the clustering and get the jets
  //----------------------------------------------------------
  JetDefinition jet_def(antikt_algorithm, 0.7);
  AreaDefinition area_def(active_area_explicit_ghosts,
                          GhostedAreaSpec(SelectorAbsRapMax(4.0)));

  ClusterSequenceArea clust_seq_hard(hard_event, jet_def, area_def);
  ClusterSequenceArea clust_seq_full(full_event, jet_def, area_def);

  Selector sel_jets = SelectorNHardest(2) * SelectorAbsRapMax(3.0);

  vector<PseudoJet> hard_jets = sel_jets(clust_seq_hard.inclusive_jets());
  vector<PseudoJet> full_jets = sel_jets(clust_seq_full.inclusive_jets());

  // print the results without subtraction
  //----------------------------------------------------------
  cout << setprecision(4);
  cout << "# original hard jets" << endl;
  for (unsigned int i=0; i<hard_jets.size(); i++){
    const PseudoJet &jet = hard_jets[i];
    print_jet(jet);
  }
  cout << endl;

  cout << "# unsubtracted full jets" << endl;
  for (unsigned int i=0; i<full_jets.size(); i++){
    const PseudoJet &jet = full_jets[i];
    print_jet(jet);
  }
  cout << endl;

  // Area-median subtraction
  //----------------------------------------------------------
  // create what we need for the background estimation
  //
  // Here we shall take into account both the "standard" backgroudn
  // density per unit area (rho) but also the (optional) contribution
  // from particle masses (rho_m in arXiv:1211.2811)
  //
  // Note that the standrard workflow would be to create two
  // BackgroundEstimators from the rho_range, jet_def_for_rho,
  // area_def defined below. But this would mean calling
  // set_particles(...) on each BackgroundEstimator, i.e. clustering
  // the event twice. To avoid that, we do the clustering manually and
  // construct both BackgroundEstimators from that single clustering.
  JetDefinition jet_def_for_rho(kt_algorithm, 0.4);
  Selector rho_range =  SelectorAbsRapMax(3.0);
  ClusterSequenceArea clust_seq_rho(full_event, jet_def_for_rho, area_def);  
  
  // the two background estimators
  JetMedianBackgroundEstimator bge_rho(rho_range, clust_seq_rho);
  JetMedianBackgroundEstimator bge_rhom(rho_range, clust_seq_rho);
  BackgroundJetPtMDensity m_density;
  bge_rhom.set_jet_density_class(&m_density);

  // declare an area-median subtractor from this
  contrib::SafeAreaSubtractor area_subtractor(&bge_rho, &bge_rhom);

  // Note that is we instead want to work with CHS events, we'd
  // instead declare
  //    area_subtractor(&bge_rho, &bge_rhom,
  //                    SelectorIsCharged(),
  //                    SelectorIsLeadingVertex());
  // with the selector defined as in example_npcsub.cc


  cout << "# " << area_subtractor.description() << endl;
  cout << "# area-median subtracted jets" << endl;
  for (unsigned int i=0; i<full_jets.size(); i++){
    PseudoJet subtracted_jet = area_subtractor(full_jets[i]);
    print_jet(subtracted_jet);
  }
  cout << endl;

  return 0;
}

//------------------------------------------------------------------------
// read the event with and without pileup
void read_event(vector<PseudoJet> &hard_event, vector<PseudoJet> &full_event){
  string line;
  int  nsub  = 0; // counter to keep track of which sub-event we're reading
  while (getline(cin, line)) {
    istringstream linestream(line);
    // take substrings to avoid problems when there are extra "pollution"
    // characters (e.g. line-feed).
    if (line.substr(0,4) == "#END") {break;}
    if (line.substr(0,9) == "#SUBSTART") {
      // if more sub events follow, make copy of first one (the hard one) here
      if (nsub == 1) hard_event = full_event;
      nsub += 1;
    }
    if (line.substr(0,1) == "#") {continue;}
    double px,py,pz,E;
    linestream >> px >> py >> pz >> E;
    PseudoJet particle(px,py,pz,E);

    // push event onto back of full_event vector
    full_event.push_back(particle);
  }

  // if we have read in only one event, copy it across here...
  if (nsub == 1) hard_event = full_event;

  // if there was nothing in the event 
  if (nsub == 0) {
    cerr << "Error: read empty event\n";
    exit(-1);
  }

  cout << "# " << nsub-1 << " pileup events on top of the hard event" << endl;
}

//------------------------------------------------------------------------
// print iut some info about a giben jet
void print_jet(const PseudoJet &jet){
  cout << "pt = " << jet.pt()
       << ", rap = " << jet.rap()
       << ", mass = " << jet.m() << endl;
}