#include <TFile.h>
#include <TTree.h>
#include <TDirectory.h>
#include <ROOT/RNTuple.hxx>
#include <ROOT/RNTupleModel.hxx>
#undef NDEBUG
#include <cassert>

int writeTree()
{
  TFile* f;
  int x = 0;
  f = new TFile("foo.root", "RECREATE");
  auto* dir = f->mkdir("dir");
  dir->cd();
  auto* tree = new TTree("T", "a Tree");
  tree->Branch("x", &x, "x/D");
  for (int i = 0; i < 10; i++) {
    x = i;
    tree->Fill();
  }
  tree->Write();

  using namespace ROOT::Experimental;
  // Create and fill an RNTuple
  auto model = RNTupleModel::Create();
  auto wrPt = model->MakeField<float>("pt", 42.0);

  {
    RNTupleWriteOptions options;
    options.SetContainerFormat(ENTupleContainerFormat::kBare);
    auto* bar = f->mkdir("bar");
    bar->cd();
    
    auto ntuple = RNTupleWriter::Append(std::move(model), "f", *f, options);
    bool ok = bar->cd();

    ntuple->Fill();
    ntuple->CommitCluster();
    *wrPt = 24.0;
    ntuple->Fill();
    *wrPt = 12.0;
    ntuple->Fill();
    ntuple->CommitCluster();
  }

  return 0;
}