// See www.openfst.org for extensive documentation on this weighted
// finite-state transducer library.
//
// Find shortest path(s) in an FST.

#include <cstring>

#include <memory>
#include <string>
#include <vector>

#include <fst/flags.h>
#include <fst/log.h>
#include <fst/script/getters.h>
#include <fst/script/shortest-path.h>

DECLARE_double(delta);
DECLARE_int32(nshortest);
DECLARE_int64(nstate);
DECLARE_string(queue_type);
DECLARE_bool(unique);
DECLARE_string(weight);

int fstshortestpath_main(int argc, char **argv) {
  namespace s = fst::script;
  using fst::script::FstClass;
  using fst::script::WeightClass;
  using fst::script::VectorFstClass;

  string usage = "Finds shortest path(s) in an FST.\n\n  Usage: ";
  usage += argv[0];
  usage += " [in.fst [out.fst]]\n";

  std::set_new_handler(FailedNewHandler);
  SET_FLAGS(usage.c_str(), &argc, &argv, true);
  if (argc > 3) {
    ShowUsage();
    return 1;
  }

  const string in_name =
      (argc > 1 && (strcmp(argv[1], "-") != 0)) ? argv[1] : "";
  const string out_name = argc > 2 ? argv[2] : "";

  std::unique_ptr<FstClass> ifst(FstClass::Read(in_name));
  if (!ifst) return 1;

  const auto weight_threshold =
      FLAGS_weight.empty() ? WeightClass::Zero(ifst->WeightType())
                           : WeightClass(ifst->WeightType(), FLAGS_weight);

  VectorFstClass ofst(ifst->ArcType());

  fst::QueueType queue_type;
  if (!s::GetQueueType(FLAGS_queue_type, &queue_type)) {
    LOG(ERROR) << "Unknown or unsupported queue type: " << FLAGS_queue_type;
    return 1;
  }

  const s::ShortestPathOptions opts(queue_type, FLAGS_nshortest,
                                    FLAGS_unique, FLAGS_delta,
                                    weight_threshold, FLAGS_nstate);

  s::ShortestPath(*ifst, &ofst, opts);

  return !ofst.Write(out_name);
}