FindManyInChainP.h

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#ifndef LARDATA_UTILITIES_FINDMANYINCHAINP_H
#define LARDATA_UTILITIES_FINDMANYINCHAINP_H

// framework
#include "canvas/Persistency/Common/Ptr.h"
#include "canvas/Utilities/InputTag.h"

// C/C++ standard library
#include <vector>
#include <utility> // std::forward()
#include <initializer_list>
#include <cstdlib> // std::size_t



namespace lar {
  
  namespace details {
    
    template <typename T, typename R = void>
    struct enable_if_type_exists;
    
    template <typename T, typename R = void>
    using enable_if_type_exists_t = typename enable_if_type_exists<T, R>::type;
    
    template <typename H, typename R = void>
    using enable_if_is_handle_t
      = enable_if_type_exists_t<typename std::decay_t<H>::HandleTag, R>;
    
  } // namespace details
  
  
  struct SameAsDataTag {};
  
  constexpr SameAsDataTag SameAsData;
  
  template <typename Target, typename... Intermediate>
  class FindManyInChainP {
    
      public:
    using Target_t = Target; 
    using TargetPtr_t = art::Ptr<Target_t>; 
    
    
    using TargetPtrCollection_t = std::vector<TargetPtr_t>;
    
    template <typename Source, typename Event, typename... InputTags>
    FindManyInChainP(Source&& source, Event const& event, InputTags... tags)
      : results(find(std::forward<Source>(source), event, tags...))
      {}
    
    
    
    std::size_t size() const noexcept;
    
    TargetPtrCollection_t const& at(std::size_t i) const;
    
    
    template <typename Source, typename Event, typename... InputTags>
    static std::vector<TargetPtrCollection_t> find
      (Source&& source, Event const& event, InputTags... tags);
    
      private:
    std::vector<TargetPtrCollection_t> results; 
    
  }; // class FindManyInChainP<>
  
  
} // namespace lar


//------------------------------------------------------------------------------
//---  template implementation
//---
#include "FindManyInChainP.tcc" // expected in the same directory as this file

//------------------------------------------------------------------------------


#endif // LARDATA_UTILITIES_FINDMANYINCHAINP_H