/// \file ROOT/RPageNullSink.hxx
/// \ingroup NTuple
/// \author Jonas Hahnfeld <jonas.hahnfeld@cern.ch>
/// \date 2024-01-31
/// \warning This is part of the ROOT 7 prototype! It will change without notice. It might trigger earthquakes. Feedback
/// is welcome!

/*************************************************************************
 * Copyright (C) 1995-2024, Rene Brun and Fons Rademakers.               *
 * All rights reserved.                                                  *
 *                                                                       *
 * For the licensing terms see $ROOTSYS/LICENSE.                         *
 * For the list of contributors see $ROOTSYS/README/CREDITS.             *
 *************************************************************************/

#ifndef ROOT_RPageNullSink
#define ROOT_RPageNullSink

#include <ROOT/RColumn.hxx>
#include <ROOT/RFieldBase.hxx>
#include <ROOT/RNTupleModel.hxx>
#include <ROOT/RPageStorage.hxx>

namespace ROOT {
namespace Experimental {
namespace Internal {

/**
\class ROOT::Experimental::Internal::RPageNullSink
\ingroup NTuple
\brief Dummy sink that discards all pages

The RPageNullSink class is for internal testing only and can be used to measure the software overhead of serializing
elements into pages, without actually writing them onto disk or even serializing the RNTuple headers and footers.
*/
class RPageNullSink : public ROOT::Internal::RPageSink {
   ROOT::DescriptorId_t fNColumns = 0;
   std::uint64_t fNBytesCurrentCluster = 0;

public:
   RPageNullSink(std::string_view ntupleName, const ROOT::RNTupleWriteOptions &options) : RPageSink(ntupleName, options)
   {
   }

   ColumnHandle_t AddColumn(ROOT::DescriptorId_t, ROOT::Internal::RColumn &column) final
   {
      return {fNColumns++, &column};
   }

   const ROOT::RNTupleDescriptor &GetDescriptor() const final
   {
      static ROOT::RNTupleDescriptor descriptor;
      return descriptor;
   }

   ROOT::NTupleSize_t GetNEntries() const final { return 0; }

   void ConnectFields(const std::vector<ROOT::RFieldBase *> &fields, ROOT::NTupleSize_t firstEntry)
   {
      auto connectField = [&](ROOT::RFieldBase &f) {
         ROOT::Internal::CallConnectPageSinkOnField(f, *this, firstEntry);
      };
      for (auto *f : fields) {
         connectField(*f);
         for (auto &descendant : *f) {
            connectField(descendant);
         }
      }
   }
   void InitImpl(ROOT::RNTupleModel &model) final
   {
      auto &fieldZero = ROOT::Internal::GetFieldZeroOfModel(model);
      ConnectFields(fieldZero.GetMutableSubfields(), 0);
   }
   void UpdateSchema(const ROOT::Internal::RNTupleModelChangeset &changeset, ROOT::NTupleSize_t firstEntry) final
   {
      ConnectFields(changeset.fAddedFields, firstEntry);
   }
   void UpdateExtraTypeInfo(const ROOT::RExtraTypeInfoDescriptor &) final {}

   void CommitSuppressedColumn(ColumnHandle_t) final {}
   void CommitPage(ColumnHandle_t, const ROOT::Internal::RPage &page) final
   {
      fNBytesCurrentCluster += page.GetNBytes();
   }
   void CommitSealedPage(ROOT::DescriptorId_t, const RSealedPage &page) final
   {
      fNBytesCurrentCluster += page.GetBufferSize();
   }
   void CommitSealedPageV(std::span<RSealedPageGroup> ranges) final
   {
      for (auto &range : ranges) {
         for (auto sealedPageIt = range.fFirst; sealedPageIt != range.fLast; ++sealedPageIt) {
            fNBytesCurrentCluster += sealedPageIt->GetBufferSize();
         }
      }
   }

   RStagedCluster StageCluster(ROOT::NTupleSize_t) final
   {
      RStagedCluster stagedCluster;
      stagedCluster.fNBytesWritten = fNBytesCurrentCluster;
      fNBytesCurrentCluster = 0;
      return stagedCluster;
   }
   void CommitStagedClusters(std::span<RStagedCluster>) final {}
   void CommitClusterGroup() final {}
   ROOT::Internal::RNTupleLink CommitDatasetImpl() final { return {}; }
   void CommitAttributeSet(std::string_view, const ROOT::Internal::RNTupleLink &) final {}

   std::unique_ptr<RPageSink> CloneAsHidden(std::string_view, const RNTupleWriteOptions &) const final
   {
      throw ROOT::RException(R__FAIL("cannot clone null sink"));
   }
};

} // namespace Internal
} // namespace Experimental
} // namespace ROOT

#endif