///////////////////////////////////////////////////////////////////////
//
// Collection of meta information about this processing.
//
// This singleton class stores the meta information. The meta
// information describes the state of RAT i.e. the rat version and the
// database settings.
//
// Producers should (if the information exists) pass the existing meta
// information to this class before any run intialises. This class on
// initialisation will create the meta information for the processing.
//
// Processings are distinguished by a pass number, with the initial
// creation being pass 0. This number then increments with each
// re-processing.
//
// Author: Phil G Jones <p.g.jones@qmul.ac.uk>
//
// REVISION HISTORY:
//     2014-04-18 : P G Jones - New file.
//     2016-07-20 :  M. Mottram: add ROOT IO constructor for ROOT6 compatibility.
//
///////////////////////////////////////////////////////////////////////

#ifndef __RAT_MetaInformation_hh__
#define __RAT_MetaInformation_hh__

#include <RAT/DS/Meta.hh>

class TRootIOCtor;

namespace RAT
{

class MetaHelper;

class MetaInformation
{
public:
  // Singleton class instance
  //
  // Returns a pointer to the MetaInformation
  inline static MetaInformation* Get();

  // Initialise the Meta Information
  //
  // This should be called whenever a simulation starts or a file is reprocessed
  // It will create Meta Information for the current rat instance
  void Initialise();

  // Initialise the Meta Information from an existing file
  //
  // This will create a new pass for the current rat instance
  //
  // meta: information to initialise from
  void Initialise( DS::Meta* const meta );

  // Finalise the Meta Information after the job is completed
  // called by IO processors to add information about #events stored etc.
  //
  // helper: a container class holding some meta information to write
  void Finalise(const MetaHelper& helper);

  // Add a database override command to the meta information
  //
  // tableField: descriptor
  // value is the value to override
  void AddOverrideCommand( const std::string& tableField, const std::string& value );

  // Add a database load command to the meta information
  //
  // Note that this could be a directory
  //
  // path is the path to load
  void AddLoadCommand( const std::string& path );

  // Get the meta information in DS format
  //
  // Returns a reference to the Meta information
  const DS::Meta& GetDSMeta() const { return fMeta; }

  // Get the current pass number
  //
  // Each processing of a file is a new pass
  //
  // Returns a the current pass number
  size_t GetCurrentPass() const { return fMeta.GetCurrentPass(); }

  // For ROOT6 build
  MetaInformation(TRootIOCtor*) {};

protected:

  void LoadDirectory( const std::string& directory );

  void LoadFile( const std::string& file );

  DS::Meta fMeta; // The actual meta information

  // Prevent usage of methods below
  MetaInformation() {};

};

inline MetaInformation*
MetaInformation::Get()
{
  static MetaInformation metaInformation;
  return &metaInformation;
}

} //::RAT

#endif