// (C) Copyright 2008-2009 SDML (www.sdml.info)
//
// Use, modification and distribution is subject to the Boost Software
// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)


#ifndef KEY_TRAITS_HPP
#define KEY_TRAITS_HPP

#include <boost/mpl/bool.hpp>

// Forward declarations of standard types.
namespace std {
    template <typename, typename, typename> class basic_string;
    template <typename, typename> class vector;
};

namespace gpld {

// A couple of tags used to help differentiate operations between bitstring
// iterable objects and element-iterable objects.
struct bit_iterable_tag { };
struct element_iterable_tag { };

// TODO Implement this (later).
template <typename T>
struct bitstring_iterator { };

/**
 * Key traits define information and functionality associated with the use of
 * different types as keys, especially the iterator type used when finding
 * or inserting elements in a prefix or suffix tree.
 */
template <typename T>
struct key_traits
{
    typedef bit_iterable_tag category;
    typedef bitstring_iterator<T> iterator;
};

// A helper struct that defines element iterability for container overloads.
template <typename Container>
struct fwd_container_key_traits
{
    typedef element_iterable_tag category;
    typedef typename Container::const_iterator iterator;
};

// Specializations for common key types.
template <typename Char, typename Traits, typename Alloc>
struct key_traits<std::basic_string<Char, Traits, Alloc>>
    : fwd_container_key_traits<std::basic_string<Char, Traits, Alloc>>
{ };

// TODO: Create more specializations as needed.

} /* namespace gpld */

#endif