#include <fstream>
#include <iostream>

#include "yaml-cpp/emitterstyle.h"
#include "yaml-cpp/eventhandler.h"
#include "yaml-cpp/yaml.h"  // IWYU pragma: keep

class NullEventHandler : public YAML::EventHandler {
 public:
  typedef YAML::Mark Mark;
  typedef YAML::anchor_t anchor_t;

  NullEventHandler() {}

  virtual void OnDocumentStart(const Mark&) {}
  virtual void OnDocumentEnd() {}
  virtual void OnNull(const Mark&, anchor_t) {}
  virtual void OnAlias(const Mark&, anchor_t) {}
  virtual void OnScalar(const Mark&, const std::string&, anchor_t,
                        const std::string&) {}
  virtual void OnSequenceStart(const Mark&, const std::string&, anchor_t,
                               YAML::EmitterStyle::value style) {}
  virtual void OnSequenceEnd() {}
  virtual void OnMapStart(const Mark&, const std::string&, anchor_t,
                          YAML::EmitterStyle::value style) {}
  virtual void OnMapEnd() {}
};

void run(YAML::Parser& parser) {
  NullEventHandler handler;
  parser.HandleNextDocument(handler);
}

int main(int argc, char** argv) {
  if (argc > 1) {
    std::ifstream in(argv[1]);
    YAML::Parser parser(in);
    run(parser);
  } else {
    YAML::Parser parser(std::cin);
    run(parser);
  }
  return 0;
}