// HTrack.h

#ifndef HTrack_H
#define HTrack_H

// This class describes a track as an ordered list of hits plus
// an ETrack (fitted vector and error matrix at a surface) and
// the fit chi-square.
//
// Hits are ordered as they were fit.
//
// The access to the list of hits is minimal.  Users are expected to
// construct a new object to do more than update the fit or add a
// hit to the end of the list.
//
// The method is_fit returns true if the track has been fit with all its hits.
// This state is set by calling set_fit and is unset when hits are added.
// No hits are required to be on the track (so one can store a fit without
// any hits).
// 

#include "ref_count/RefCounter.hpp"
#include "trfbase/ETrack.h"
#include "trfbase/Hit.h"
#include "trfbase/Propagator.h"

#include "TrackMcHitInfo.h"

namespace trf {

class Surface;
class PropStat;
class PropDir;
class HTrack;

// friend output stream
std::ostream& operator<<(std::ostream& stream, const HTrack& trh);

class HTrack : public RefCounter {

private:

  // Number of hits used in the current fit.
  // -1 for a track which has never been fit
  int _nfit;

protected:

  // list of hits
  HitList _hits;

  // fitted track (or starting track)
  ETrack _tre;

  // fit chi-square
  double _chisq;

protected:

  // output stream called from subclass
  virtual void ostr(std::ostream& stream) const;

public:

  // Default constructor (for STL)
  HTrack();

  // Constructor specifying the starting track.
  // There are no hits on the track.
  HTrack(const ETrack& tre);

  // Destructor.
  virtual ~HTrack();

  // Add a hit to the back of the list.
  virtual void add_hit(const HitPtr& phit);

  // Drop the last hit on the list.
  virtual void drop_hit();

  // Drop all hits.
  virtual void drop_hits();

  // Set the fit parameters for the current list of hits.
  // Be sure to add all relevant hits before invocation.
  // It is assumed the track has been fit with all of its hits.
  void set_fit(const ETrack& tre, double chisq);

  // Unset the fit.
  void unset_fit();

  // Unset the fit and reset the starting track.
  void unset_fit(const ETrack& tre);

  // Fetch the list of hits.
  const HitList& get_hits() const { return _hits; };

  // Fetch the fit track.
  const ETrack& get_track() const { return _tre; };

  // Fetch the chi-square.
  double get_chi_square() const { return _chisq; };

  //Fetch the number of measurements on this track
  int get_num_meas() const;

  //Return the MC track information for hits on this track
  TrackMcHitInfo get_mcinfo() const;

  // Return the ID's of the intersection of the MC tracks contributing 
  // to the clusters on this track.
  McIdList get_mc_ids() const;

  // Return the fit status: true if track has one or more hits
  // and has been fit with all of its hits.
  bool is_fit() const {
    return _tre.is_valid() && ( _nfit == _hits.size() );
  }

  // propagate the fit track
  PropStat propagate(const Propagator& prop, const Surface& srf);

  // propagate the fit track in a specified direction
  PropStat propagate(const Propagator& prop, const Surface& srf,
                     Propagator::PropDir dir);

  // friend output stream
  friend std::ostream&
  operator<<(std::ostream& stream, const HTrack& trh);

};

}  // end namespace trf

// Equality.
// Same hits, ETrack, chi_square and is_fit().
bool operator==(const trf::HTrack& lhs, const trf::HTrack& rhs);

// Inequality.
// Opposite of above.
bool operator!=(const trf::HTrack& lhs, const trf::HTrack& rhs);

#endif