// Copyright (c) 2006-2009 Max-Planck-Institute Saarbruecken (Germany).
// All rights reserved.
//
// This file is part of CGAL (www.cgal.org)
//
// $URL: https://github.com/CGAL/cgal/blob/v5.6.1/Algebraic_kernel_d/include/CGAL/Algebraic_kernel_d/LRU_hashed_map.h $
// $Id: LRU_hashed_map.h 0779373 2020-03-26T13:31:46+01:00 Sébastien Loriot
// SPDX-License-Identifier: LGPL-3.0-or-later OR LicenseRef-Commercial
//
//
// Author(s)     : Pavel Emeliyanenko <asm@mpi-sb.mpg.de>
//
//
// ============================================================================

#ifndef CGAL_ALGEBRAIC_CURVE_KERNEL_HASHED_MAP_H
#define CGAL_ALGEBRAIC_CURVE_KERNEL_HASHED_MAP_H

#include <CGAL/basic.h>

#include <CGAL/function_objects.h>

#include <limits>
#include <boost/multi_index_container.hpp>
#include <boost/multi_index/member.hpp>
#include <boost/multi_index/hashed_index.hpp>
#include <boost/multi_index/ordered_index.hpp>
#include <boost/multi_index/sequenced_index.hpp>

using boost::multi_index::multi_index_container;
using boost::multi_index::get;
using boost::multi_index::project;

namespace CGAL {

namespace internal {


//! \brief this class defines hashed map container with LRU capabilities,
//!
//! stores pair of \c KeyType_ and \c ValueType_. Before adding to
//! the map the input is normialized using \c Canonicalizer_
//! \c Pred_ is binary predicate acting as an equivalence relation on
//! values of \c KeyType_, \c Creator_ is a mapping from \c KeyType_ to
//! \c ValueType_, \c Hash_ is function object which returns hash values
//! for the keys
template <
    class KeyType_, class ValueType_,
    class Hash_ = boost::hash<KeyType_>,
    class Pred_ = std::equal_to<KeyType_>,
    class Canonicalizer_ = CGAL::Identity<KeyType_>,
    class Creator_ = CGAL::Creator_1<KeyType_, ValueType_> >
class LRU_hashed_map
{
public:
    //!\name public typedefs
    //!@{

    //! this instance's first argument
    typedef KeyType_ Key_type;
    //! this instance's second argument
    typedef ValueType_ Value_type;
    //! hash function
    typedef Hash_ Hash;
    //! equality predicate
    typedef Pred_ Pred;
    //! input data canonicalizer
    typedef Canonicalizer_ Canonicalizer;
    //! mapping \c KeyType_ -> \c ValueType_
    typedef Creator_ Creator;

    //! hashed map data type
    typedef std::pair<Key_type, Value_type> Data_type;


    // We don't use BOOST_MULTI_INDEX_MEMBER but ::boost::multi_index::member_offset
    // because VC10 had a problem with it. The reason is that the
    // implementation std::pair uses a base class, and std::pair::first is
    // not a member of the pair class but of its base class.
    // In the following, we assume that the offset of 'first' in
    // std::pair<T1, T2> is always 0.
    typedef boost::multi_index::multi_index_container<
        Data_type,
        boost::multi_index::indexed_by<
            boost::multi_index::sequenced<>,
            boost::multi_index::hashed_unique<
                  ::boost::multi_index::member_offset<Data_type,Key_type,0>,
                    Hash, Pred > > > Hashed_map;



    //!@}
protected:
    //!\name private members
    //!@{


    //! hashed map instance
    mutable Hashed_map _m_hashed_map;

    //! maximal size allowed
    unsigned _m_max_size;

    //!@}
public:
    //!\name iterator types
    //!@{

    //! hashed index iterator
    typedef typename
        boost::multi_index::nth_index_iterator<Hashed_map,1>::type
            Hashed_iterator;

    //! sequenced index iterator
    typedef typename
        boost::multi_index::nth_index_iterator<Hashed_map,0>::type
            Sequenced_iterator;

    //! sequenced index const iterator
    typedef typename
        boost::multi_index::nth_index_const_iterator<Hashed_map,0>::type
            Sequenced_const_iterator;

    //! result type of \c find operation: a pair of iterator pointing to
    //! \c Data_type and a boolean indicating whether an element with
    //! specified key was found
    typedef std::pair<Hashed_iterator, bool> Find_result;

    //!@}
public:
    //!\name constructors and access functions
    //!@{

    //! \brief default constructor
    LRU_hashed_map(unsigned max_size =
            (std::numeric_limits< unsigned >::max)()) :
        _m_hashed_map(),_m_max_size(max_size)
    {  }

    virtual ~LRU_hashed_map()
    {  }

    /*! \brief implements cache-like behaviour of the map
    *
    *  If the object is not in the map, it is constructed using \c Creator
    *  and added to the map
    */
    Value_type operator()(const Key_type& key_) const
    {
        Canonicalizer canonicalize;
        Key_type key = canonicalize(key_);

        Find_result p = find(key);
        if(!p.second) {
            Creator create;
            Value_type val = create(key);
            insert(Data_type(key, val));
            return val;
        }
        return (p.first)->second;
    }

    //! \brief looks for an entry with a specified key in the map
    //!
    //! returns a pair of iterator pointing to \c Data_type and a boolean
    //! indicating whether an element with specified key was found
    Find_result find(const Key_type& key) const
    {
        typename boost::multi_index::nth_index<Hashed_map,1>::type&
        idx = _m_hashed_map.template get<1>();
        Hashed_iterator it = idx.find(key);
        if(it == idx.end()) {
            return Find_result(it, false);
        }

        // otherwise put the accessed element on the top
        // Comment out because of compiler problems with 3.4
        /*
        _m_hashed_map.relocate(_m_hashed_map.begin(),
                _m_hashed_map.project<0>(it));
        */
        return Find_result(it, true);
    }

    //! \brief inserts an entry to the map
    //!
    //! on successful insertion, \c p.first points to the element
    //! inserted; otherwise \c p.first points to an element that caused
    //! the insertion to be banned. If the map's size exceeds \c max_size
    //! the least recently used entry is dropped
    std::pair<Sequenced_iterator, bool> insert(const Data_type& data) const
    {
        if(_m_hashed_map.size() > _m_max_size)
            _m_hashed_map.pop_back();
        return _m_hashed_map.push_front(data);
    }

    //! clears the map contents
    void clear() { _m_hashed_map.clear(); }

    //! returns whether the map is empty.
    bool is_empty() const { return _m_hashed_map.empty(); }

    //! returns the number of items in the map
    unsigned size() { return _m_hashed_map.size(); }

    //! returns the largest possible size of the map (-1 if not set)
    unsigned max_size() const { return _m_max_size; }

    //! \brief returns an iterator pointing to the beginning of the map
    //!
    //! all iterators run over sequenced indices
    Sequenced_iterator begin() { return _m_hashed_map.begin(); }

    //! returns an iterator pointing to the end of the map
    Sequenced_iterator end() { return _m_hashed_map.end(); }

    //! returns a const_iterator pointing to the beginning of the map
    Sequenced_const_iterator begin() const
    { return _m_hashed_map.begin(); }

    //! Returns a const_iterator pointing to the end of the map
    Sequenced_const_iterator end() const
    { return _m_hashed_map.end(); }

    //!@}
}; // class LRU_hashed_map_with_kernel


//! \brief this class defines hashed map container with LRU capabilities,
//!
//! stores pair of \c KeyType_ and \c ValueType_. Before adding to
//! the map the input is normialized using \c Canonicalizer_
//! \c Pred_ is binary predicate acting as an equivalence relation on
//! values of \c KeyType_, \c Creator_ is a mapping from \c KeyType_ to
//! \c ValueType_, \c Hash_ is function object which returns hash values
//! for the keys
template <
    class AlgebraicKernelWithAnalysis_2,
    class KeyType_, class ValueType_,
    class Hash_ = boost::hash<KeyType_>,
    class Pred_ = std::equal_to<KeyType_>,
    class Canonicalizer_ = CGAL::Identity<KeyType_>,
    class Creator_ = CGAL::Creator_1<KeyType_, ValueType_> >
class LRU_hashed_map_with_kernel
  : public LRU_hashed_map<KeyType_,ValueType_,Hash_,
                          Pred_,Canonicalizer_,Creator_>
{

public:

    typedef AlgebraicKernelWithAnalysis_2 Algebraic_kernel_with_analysis_2;

    typedef LRU_hashed_map<KeyType_,ValueType_,
                           Hash_,Pred_,Canonicalizer_,Creator_> Base;

    //! this instance's first argument
    typedef typename Base::Key_type Key_type;
    //! this instance's second argument
    typedef typename Base::Value_type Value_type;
    //! hash function
    typedef typename Base::Hash Hash;
    //! equality predicate
    typedef typename Base::Pred Pred;
    //! input data canonicalizer
    typedef typename Base::Canonicalizer Canonicalizer;
    //! mapping \c KeyType_ -> \c ValueType_
    typedef typename Base::Creator Creator;

    //! hashed map data type
    typedef typename Base::Data_type Data_type;

    typedef typename Base::Hashed_map Hashed_map;


protected:

    Algebraic_kernel_with_analysis_2* _m_kernel;


public:

    //!\name iterator types
    //!@{

    //! hashed index iterator
    typedef typename Base::Hashed_iterator Hashed_iterator;

    //! sequenced index iterator
    typedef typename Base::Sequenced_iterator Sequenced_iterator;

    //! sequenced index const iterator
    typedef typename Base::Sequenced_const_iterator Sequenced_const_iterator;

    //! result type of \c find operation: a pair of iterator pointing to
    //! \c Data_type and a boolean indicating whether an element with
    //! specified key was found
    typedef typename Base::Find_result Find_result;

    //!@}

    //!\name constructors and access functions
    //!@{

    //! \brief default constructor
    LRU_hashed_map_with_kernel(Algebraic_kernel_with_analysis_2* kernel,
                               unsigned max_size = (std::numeric_limits<unsigned>::max)()) :
        Base(max_size),
        _m_kernel(kernel)
    {  }

    ~LRU_hashed_map_with_kernel()
    {  }

    /*! \brief implements cache-like behaviour of the map
    *
    *  If the object is not in the map, it is constructed using \c Creator
    *  and added to the map
    */
    Value_type operator()(const Key_type& key_) const
    {
        Canonicalizer canonicalize;
        Key_type key = canonicalize(key_);

        Find_result p = this->find(key);
        if(!p.second) {
            Creator create(_m_kernel);
            Value_type val = create(key);
            this->insert(Data_type(key, val));
            return val;
        }
        return (p.first)->second;
    }

    //!@}

}; // class LRU_hashed_map_with_kernel

/*! \brief
 *  returns representation id as a hash value
 */
struct Id_hasher
{
    template <class T>
    size_t operator()(const T& x) const {
        return static_cast<size_t>(x.id());
    }
};

struct To_double_hasher
{
    template <class T>
    size_t operator()(const T& x) const {
        return static_cast<size_t>(CGAL::to_double(x));
    }
};



struct Id_equal_to
{
   template <class T>
   bool operator()(const T& x1, const T& x2) const {
        return (x1.id() == x2.id());
   }
};

struct Poly_hasher {

    template <class Poly_2>
    std::size_t operator()(const Poly_2& p) const {

        if(p.is_zero())
            return 0xDeadBeef;

        typedef typename Poly_2::NT Poly_1;
        typedef typename Poly_1::NT NT;

        const Poly_1& v = p[0];
        typename Poly_1::const_iterator cit;
        NT res(0);
        int i=0;
        // take at most 3 trailing coeffs
        for (cit = v.begin(), i = 0; i < 3 && cit != v.end(); cit++, i++) {
            res += *cit;
        }
        if(res == NT(0))
            return 0xDeadBeef;
        // randomization of the result
        return static_cast<std::size_t>(CGAL::to_double(res));
    }
};

struct Pair_id_hasher {
    typedef size_t result_type;

    template <class T1, class T2>
    size_t operator()(const std::pair<T1, T2>& p) const {

        std::size_t seed = p.first.id() + 0x9e3779b9;
        seed ^= p.second.id() + 0x9e3779b9 + (seed << 6) + (seed >> 2);
        return seed;
    }
};

struct Pair_hasher {

    typedef size_t result_type;

    template <class T1, class T2>
    size_t operator()(const std::pair<T1, T2>& p) const
    {
        std::size_t seed = 0;
        boost::hash_combine(seed, p.first);
        boost::hash_combine(seed, p.second);
        return seed;
    }
};

} // namespace internal

} //namespace CGAL

#endif // CGAL_ALGEBRAIC_CURVE_KERNEL_HASHED_MAP_H

