// -------------------------------------------------------------------------
// -----                 MpdDecayerPyt8 header file                    -----
// -----                      Created 23/07/2020                       -----
// -----                          A. Zinchenko                         -----
// -----             External decayer for MPD using Pythia8            -----
// -----                (adapted from TPythia8Decayer)                 -----
// -------------------------------------------------------------------------

#ifndef MPDDECAYERPYT8_H
#define MPDDECAYERPYT8_H

#include <TLorentzVector.h>
#include <TVirtualMCDecayer.h>
#include <TRotation.h>

#include <Pythia8/Pythia.h>

class TClonesArrray;
class TObjArrray;
class TParticle;
class TPythia8;
class TRandom;

#include <set>
#if PYTHIA_VERSION_INTEGER < 8304
 typedef Pythia8::ParticleDataEntry* ParticleDataEntryPtr;
#else
 typedef Pythia8::ParticleDataEntryPtr ParticleDataEntryPtr;
#endif

class MpdDecayerPyt8 : public TVirtualMCDecayer 
{

 public:
  enum SourceFlag {kPythia, kCustom}; // particle container source

  virtual ~MpdDecayerPyt8(){;}

  virtual void    Init();
  virtual void    Decay(Int_t pdg, TLorentzVector* p);
  virtual Int_t   ImportParticles(TClonesArray *particles);
  virtual void    SetForceDecay(Int_t type);
  virtual void    ForceDecay();
  virtual Float_t GetPartialBranchingRatio(Int_t ipart);
  virtual Float_t GetLifetime(Int_t kf);
  virtual void    ReadDecayTable();

  virtual void    SetDebugLevel(Int_t debug) { fDebug = debug; }
  virtual void    SetGlobalPolar(Int_t glob = 1) { fGlobalPolar = glob; } 
  
  static  MpdDecayerPyt8 *Instance();
  void    Decay(TParticle* part);
  void    AddMotherPdg(Int_t pdg);
  //using   TPythia8Decayer::Decay; // makes base class function visible
  
 protected:
  MpdDecayerPyt8(); 
  void AppendParticle(Int_t pdg, TLorentzVector* p);
  void ClearEvent();

 private:
  void Gdecay (Int_t idpart, TLorentzVector* p);
  void Gdeca2 (Double_t xm0, Double_t xm1, Double_t xm2, Double_t pcm[2][4]);
  //void Anisotropy (Double_t* pvert, Double_t *rndm, Double_t polar, Double_t &phi, Double_t &costh);
  void Anisotropy (Double_t* pvert, Double_t *rndm, TVector3& polar, Double_t &phi, Double_t &costh);
  void ChangeBranchings();
  void ChangeParticleBr(TObjArray *tokens);

  static MpdDecayerPyt8 *fgInstance; // singleton instance
   
  TPythia8* fPythia8;          // Pointer to pythia8
  Int_t     fDebug;            // Debug level
  Int_t     fGlobalPolar;      // global polarization flag
  
  Float_t fBranch; // branching of lambda to p + \pi-
  ParticleDataEntryPtr fLambda; // pointer to Lambda in Pythia8 database
  TLorentzVector fMother; // mother decay point position
  TClonesArray *fParticles;
  TRotation fRotation;
  SourceFlag fSourceFlag;
  std::set<Int_t> fMothersPdg;
  TRandom *fRandom;
  
  ClassDef(MpdDecayerPyt8, 0) // MPD Particle Decayer using Pythia8

};
#endif