//

#ifndef moses_SyntacticLanguageModel_h
#define moses_SyntacticLanguageModel_h

#include "FeatureFunction.h"
#include <stdexcept>

class YModel; // hidden model
class XModel; // observed model

namespace Moses
{

template <class MH, class MO> class SyntacticLanguageModelFiles;

class SyntacticLanguageModel : public StatefulFeatureFunction
{

public:
  SyntacticLanguageModel(const std::string &line);

  ~SyntacticLanguageModel();

  size_t GetNumScoreComponents() const;

  const FFState* EmptyHypothesisState(const InputType &input) const;

  FFState* Evaluate(const Hypothesis& cur_hypo,
                    const FFState* prev_state,
                    ScoreComponentCollection* accumulator) const;

  FFState* EvaluateChart(const ChartHypothesis& cur_hypo,
                         int featureID,
                         ScoreComponentCollection* accumulator) const {
    throw std::runtime_error("Syntactic LM can only be used with phrase-based decoder.");
  }


  //    double perplexity();

private:

  const size_t m_NumScoreComponents;
  SyntacticLanguageModelFiles<YModel,XModel>* m_files;
  const FactorType m_factorType;
  const size_t m_beamWidth;

};


}

#endif