using RNTupleModel = ROOT::Experimental::RNTupleModel;
using RNTupleWriter = ROOT::Experimental::RNTupleWriter;
using RNTupleReader = ROOT::Experimental::RNTupleReader;

struct Hit {
  float se_x;
  float se_y;
  float se_z;
  float ss_x;
  float ss_y;
  float ss_z;
};

struct Track {
  std::vector<Hit> hits;
};

struct Event {
  std::vector<Track> tracks;
};

void Generate() {
  auto model = RNTupleModel::Create();
  auto fldEvent = model->MakeField<Event>("events");

  auto writer = RNTupleWriter::Recreate(std::move(model), "NTuple", "data.root");

  TRandom r;
  for (int i = 0; i < 1000; ++i) {
    fldEvent->tracks.clear();

    auto nTracks = r.Integer(100);
    for (unsigned t = 0; t < nTracks; ++t) {
      Track track;

      auto nHits = r.Integer(10);
      for (auto h = 0; h < nHits; ++h) {
        Hit hit;
        hit.se_x = r.Gaus(100,10);
        hit.se_y = r.Gaus(200,10);
        hit.se_z = r.Gaus(300,10);
        hit.ss_x = r.Gaus(400,10);
        hit.ss_y = r.Gaus(500,10);
        hit.ss_z = r.Gaus(600,10);
        track.hits.emplace_back(hit);
      }

      fldEvent->tracks.emplace_back(track);
    }

    writer->Fill();
  }
}

void ReadWithViews() {
  TH1F h("se_z", "se_z", 100, 250, 350);

  auto reader = RNTupleReader::Open("NTuple", "data.root");

  auto view_tracks = reader->GetViewCollection("events.tracks");
  auto view_hits = view_tracks.GetViewCollection("Track.hits");
  auto view_se_z = view_hits.GetView<float>("Hit.se_z");
  for (auto i : view_se_z.GetFieldRange()) {
    h.Fill(view_se_z(i));
  }

  h.DrawCopy();
}

void traces() {
  Generate();

  // Only read se_z
  ReadWithViews();
}