// $Id$

/***********************************************************************
Moses - factored phrase-based language decoder
Copyright (C) 2006 University of Edinburgh

This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.

This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
***********************************************************************/

#ifndef moses_FactorCollection_h
#define moses_FactorCollection_h

#ifdef WITH_THREADS
#include <boost/thread/shared_mutex.hpp>
#endif

#include "util/murmur_hash.hh"
#include <boost/unordered_set.hpp>

#include <functional>
#include <string>

#include "util/string_piece.hh"
#include "util/pool.hh"
#include "Factor.h"

namespace Moses
{

/** We don't want Factor to be copyable by anybody.  But we also want to store
 * it in an STL container.  The solution is that Factor's copy constructor is
 * private and friended to FactorFriend.  The STL containers can delegate
 * copying, so friending the container isn't sufficient.  STL containers see
 * FactorFriend's public copy constructor and everybody else sees Factor's
 * private copy constructor.
 */
struct FactorFriend {
  Factor in;
};

/** collection of factors
 *
 * All Factors in moses are accessed and created by a FactorCollection.
 * By enforcing this strict creation processes (ie, forbidding factors
 * from being created on the stack, etc), their memory addresses can
 * be used as keys to uniquely identify them.
 * Only 1 FactorCollection object should be created.
 */
class FactorCollection
{
  friend std::ostream& operator<<(std::ostream&, const FactorCollection&);

  struct HashFactor : public std::unary_function<const FactorFriend &, std::size_t> {
    std::size_t operator()(const FactorFriend &factor) const {
      return util::MurmurHashNative(factor.in.m_string.data(), factor.in.m_string.size());
    }
  };
  struct EqualsFactor : public std::binary_function<const FactorFriend &, const FactorFriend &, bool> {
    bool operator()(const FactorFriend &left, const FactorFriend &right) const {
      return left.in.GetString() == right.in.GetString();
    }
  };
  typedef boost::unordered_set<FactorFriend, HashFactor, EqualsFactor> Set;
  Set m_set;

  util::Pool m_string_backing;

  static FactorCollection s_instance;
#ifdef WITH_THREADS
  //reader-writer lock
  mutable boost::shared_mutex m_accessLock;
#endif

  size_t m_factorId; /**< unique, contiguous ids, starting from 0, for each factor */

  //! constructor. only the 1 static variable can be created
  FactorCollection()
    :m_factorId(0) {
  }

public:
  static FactorCollection& Instance() {
    return s_instance;
  }

  ~FactorCollection();

  /** returns a factor with the same direction, factorType and factorString.
  *	If a factor already exist in the collection, return the existing factor, if not create a new 1
  */
  const Factor *AddFactor(const StringPiece &factorString);

  // TODO: remove calls to this function, replacing them with the simpler AddFactor(factorString)
  const Factor *AddFactor(FactorDirection /*direction*/, FactorType /*factorType*/, const StringPiece &factorString) {
    return AddFactor(factorString);
  }

  TO_STRING();

};

}
#endif