// See www.openfst.org for extensive documentation on this weighted
  // finite-state transducer library.
  //
  // Reweights an FST.
  
  #include <cstring>
  
  #include <memory>
  #include <string>
  #include <vector>
  
  #include <fst/flags.h>
  #include <fst/script/getters.h>
  #include <fst/script/reweight.h>
  #include <fst/script/text-io.h>
  
  DECLARE_bool(to_final);
  
  int fstreweight_main(int argc, char **argv) {
    namespace s = fst::script;
    using fst::script::MutableFstClass;
    using fst::script::WeightClass;
  
    string usage = "Reweights an FST.
  
    Usage: ";
    usage += argv[0];
    usage += " in.fst potential.txt [out.fst]
  ";
  
    std::set_new_handler(FailedNewHandler);
    SET_FLAGS(usage.c_str(), &argc, &argv, true);
    if (argc < 3 || argc > 4) {
      ShowUsage();
      return 1;
    }
  
    const string in_name = argv[1];
    const string potentials_name = argv[2];
    const string out_name = argc > 3 ? argv[3] : "";
  
    std::unique_ptr<MutableFstClass> fst(MutableFstClass::Read(in_name, true));
    if (!fst) return 1;
  
    std::vector<WeightClass> potential;
    if (!s::ReadPotentials(fst->WeightType(), potentials_name, &potential)) {
      return 1;
    }
  
    s::Reweight(fst.get(), potential, s::GetReweightType(FLAGS_to_final));
  
    return !fst->Write(out_name);
  }