/*
    This file is a part of libcds - Concurrent Data Structures library

    (C) Copyright Maxim Khizhinsky (libcds.dev@gmail.com) 2006-2016

    Source code repo: http://github.com/khizmax/libcds/
    Download: http://sourceforge.net/projects/libcds/files/
    
    Redistribution and use in source and binary forms, with or without
    modification, are permitted provided that the following conditions are met:

    * Redistributions of source code must retain the above copyright notice, this
      list of conditions and the following disclaimer.

    * Redistributions in binary form must reproduce the above copyright notice,
      this list of conditions and the following disclaimer in the documentation
      and/or other materials provided with the distribution.

    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
    AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
    IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
    DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
    FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
    DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
    SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
    CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
    OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
    OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.     
*/

#ifndef CDSLIB_OPT_HASH_H
#define CDSLIB_OPT_HASH_H

#include <tuple>
#include <functional>
#include <cds/opt/options.h>

namespace cds { namespace opt {

    /// [type-option] Option setter for a hash function
    /**
        This option setter specifies hash functor used in unordered containers.

        The default value  of template argument \p Functor is \p cds::opt::v::hash
        that is synonym for <tt>std::hash</tt> implementation of standard library.
    */
    template <typename Functor>
    struct hash {
        //@cond
        template <typename Base> struct pack: public Base
        {
            typedef Functor hash;
        };
        //@endcond
    };

    namespace v {
        //@cond
        using std::hash;

        /// Metafunction selecting default hash implementation
        /**
            The metafunction selects appropriate hash functor implementation.
            If \p Hash is not equal to opt::none, then result of metafunction is \p Hash.
            Otherwise, the result is <tt> std::hash<Q> </tt>.

            Note that default hash function like <tt> std::hash<Q> </tt>
            is generally not suitable for complex type \p Q and its derivatives.
            You should manually provide particular hash functor for such types.
        */
        template <typename Hash>
        struct hash_selector
        {
            typedef Hash    type;   ///< resulting implementation of hash functor
        };

        template <>
        struct hash_selector<opt::none>
        {
            struct type {
                template <typename Q>
                size_t operator()( Q const& key ) const
                {
                    return std::hash<Q>()( key );
                }
            };
        };
        //@endcond
    }   // namespace v

    //@cond
    namespace details {
        template <class> struct hash_list;
        template <typename... Functors>
        struct hash_list< std::tuple<Functors...> >
        {
            static size_t const size = sizeof...(Functors);
            typedef size_t values[size];
            typedef std::tuple<Functors...> hash_tuple_type;

            hash_tuple_type hash_tuple;

            hash_list()
            {}

            hash_list( hash_tuple_type const& t)
                : hash_tuple( t )
            {}
            hash_list( hash_tuple_type&& t)
                : hash_tuple( std::forward<hash_tuple_type>(t) )
            {}

            template <size_t I, typename T>
            typename std::enable_if< (I == sizeof...(Functors)) >::type apply( size_t * /*dest*/, T const& /*v*/ ) const
            {}

            template <size_t I, typename T>
            typename std::enable_if< (I < sizeof...(Functors)) >::type apply( size_t * dest, T const& v ) const
            {
                dest[I] = std::get<I>( hash_tuple )( v );
                apply<I+1>( dest, v );
            }

            template <typename T>
            void operator()( size_t * dest, T const& v ) const
            {
                apply<0>( dest, v );
            }
        };
    } // namespace details
    //@endcond

    /// Declare tuple for hash functors \p Functors
    template <typename... Functors>
    using hash_tuple = details::hash_list< std::tuple< Functors... >>;

    //@cond
    // At least, two functors must be provided. Single functor is not supported
    template <typename Functor> struct hash< std::tuple<Functor> >;
    //@endcond

    /// Multi-functor hash option setter - specialization for \p std::tuple
    template <typename... Functors>
    struct hash< std::tuple<Functors...> >
    {
        //@cond
        template <typename Base> struct pack: public Base
        {
            typedef details::hash_list< std::tuple<Functors...> >  hash;
        };
        //@endcond
    };


    //@cond
    namespace details {

        template <class HashList, typename WrappedType, typename Wrapper>
        struct hash_list_wrapper {
            typedef HashList                            hash_list;
            typedef WrappedType                         wrapped_type;
            typedef Wrapper                             wrapper_type;

            typedef typename hash_list::hash_tuple_type hash_tuple_type;
            static size_t const size = hash_list::size;

            hash_list   m_wrappedList;

            hash_list_wrapper()
            {}
            hash_list_wrapper( hash_tuple_type const& t)
                : m_wrappedList( t )
            {}
            hash_list_wrapper( hash_tuple_type&& t)
                : m_wrappedList( std::forward<hash_tuple_type>(t) )
            {}

            void operator()( size_t * dest, wrapped_type const& what ) const
            {
                m_wrappedList( dest, wrapper_type()( what ));
            }

            template <typename Q>
            void operator()( size_t * dest, Q const& what) const
            {
                m_wrappedList( dest, what );
            }
        };

    } // namespace details
    //@endcond

}} // namespace cds::opt

#endif // #ifndef CDSLIB_OPT_HASH_H
