MarleyParameterSetWalker.h

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//////////////////////////////////////////////////////////////////////////////
/// \file MarleyParameterSetWalker.h
/// \brief Concrete fhicl::ParameterSetWalker that converts a
/// fhicl::ParameterSet into a marley::JSON object
///
/// \author Steven Gardiner <gardiner@fnal.gov>
//////////////////////////////////////////////////////////////////////////////

#ifndef LARSIM_MARLEY_PARAMETERSET_WALKER_H
#define LARSIM_MARLEY_PARAMETERSET_WALKER_H

// standard library includes
#include <string>
#include <vector>

// framework includes
#include "fhiclcpp/ParameterSetWalker.h"
#include "fhiclcpp/detail/printing_helpers.h"

// MARLEY includes
#include "marley/JSON.hh"

namespace evgen {

  class MarleyParameterSetWalker : public fhicl::ParameterSetWalker {

    public:

      inline const marley::JSON& get_json() const { return full_json_; }
      inline marley::JSON& get_json() { return full_json_; }

    private:

      inline void enter_table( const key_t& key, const any_t& ) override {
        auto& json = json_refs_.back().get();
        json_refs_.emplace_back( json[ key ]
          = marley::JSON::make(marley::JSON::DataType::Object) );
      }

      inline void enter_sequence( const key_t& key, const any_t& ) override {
        auto& json = json_refs_.back().get();
        in_seq_ = true;
        seq_index_ = 0u;
        json_refs_.emplace_back( json[ key ]
          = marley::JSON::make(marley::JSON::DataType::Array) );
      }

      inline void atom( const key_t& key, const any_t& any ) override {
        auto& json = json_refs_.back().get();
        // Convert the atom to a string. Add an extra space to keep some
        // of MARLEY's JSON parsing routines (which rely on looking ahead
        // in some cases) happy
        std::string atom_val = fhicl::detail::atom::value( any ) + ' ';
        marley::JSON json_atom;
        // Hard-coded value taken from fhiclcpp/detail/printing_helpers.cc
        if ( atom_val != "@nil" ) {
          std::istringstream iss( atom_val );
          // Utility function defined in marley/JSON.hh
          json_atom = marley::parse_next( iss );
        }
        if ( in_seq_ ) {
          json[ seq_index_++ ] = json_atom;
        }
        else {
          json[ key ] = json_atom;
        }
      }

      inline void exit_table( const key_t&, const any_t& ) override {
        json_refs_.pop_back();
      }

      inline void exit_sequence( const key_t&, const any_t& ) override {
        json_refs_.pop_back();
        in_seq_ = false;
      }

      /// Owned JSON object used to store the converted FHiCL parameters
      marley::JSON full_json_;

      /// References to the owned JSON object or a sub-object thereof
      std::vector< std::reference_wrapper<marley::JSON> >
        json_refs_ = { full_json_ };

      unsigned seq_index_ = 0u;
      bool in_seq_ = false;
  };

}

#endif // LARSIM_MARLEY_PARAMETERSET_WALKER_H