for_each.hpp

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// ****************************************************************************
// entity/algotithm/for_each.hpp
//
// Algorithm to call a functor for an entity with the supplied component
// types.  If the entity does not have all of the supplied compnent types
// f is not called.
// 
// Copyright Chris Glover 2014-2015
//
// Distributed under 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 _ENTITY_ALGORITHM_FOREACH_H_INCLUDED_
#define _ENTITY_ALGORITHM_FOREACH_H_INCLUDED_

#include <boost/fusion/algorithm/iteration/fold.hpp>
#include <boost/fusion/algorithm/query/all.hpp>
#include <boost/fusion/algorithm/transformation/transform.hpp>
#include <boost/fusion/container/vector/convert.hpp>
#include <boost/fusion/functional/invocation/invoke.hpp>
#include <algorithm>

#include "entity/config.hpp" // IWYU pragma: keep
#include "entity/entity_range.hpp"
#include "entity/functional/window.hpp"
#include "entity/traits/iterator_traits.hpp"

// ----------------------------------------------------------------------------
//
namespace entity
{
    // ------------------------------------------------------------------------
    //
    template<typename EntityList, typename ComponentPoolTuple, typename Fn>
    void for_each(EntityList const& entities, ComponentPoolTuple&& p, iterator_traits::is_incremental_tag, Fn f)
    {
        auto i = begin(entities); 
        auto e = end(entities);

        auto c = boost::fusion::as_vector(
            boost::fusion::transform(
            std::forward<ComponentPoolTuple>(p),
            functional::get_window()
            )
        );

        if(i != e)
        {
            if(boost::fusion::all(c, functional::is_entity(*i)))
            {
                boost::fusion::invoke(
                    f, 
                    boost::fusion::transform(c, functional::get_component())
                );
            }

            ++i;
        }

        for(; i != e; ++i)
        {
            if(boost::fusion::fold(c, true, functional::increment_window(*i)))
            {
                boost::fusion::invoke(
                    f, 
                    boost::fusion::transform(c, functional::get_component())
                );
            }   
        }
    }

    // ------------------------------------------------------------------------
    //
    template<typename EntityList, typename ComponentPoolTuple, typename Fn>
    void for_each(EntityList const& entities, ComponentPoolTuple&& p, iterator_traits::is_skipping_tag, Fn f)
    {
        auto i = begin(entities); 
        auto e = end(entities);

        auto c = boost::fusion::as_vector(
            boost::fusion::transform(
            std::forward<ComponentPoolTuple>(p),
            functional::get_window()
            )
        );

        if(i != e)
        {
            if(boost::fusion::all(c, functional::is_entity(*i)))
            {
                boost::fusion::invoke(
                    f, 
                    boost::fusion::transform(c, functional::get_component())
                );
            }

            ++i;
        }

        for(; i != e; ++i)
        {
            if(boost::fusion::fold(c, true, functional::advance_window(*i)))
            {
                boost::fusion::invoke(
                    f, 
                    boost::fusion::transform(c, functional::get_component())
                );
            }   
        }
    }

    template<typename EntityList, typename ComponentPoolTuple, typename Fn>
    void for_each(EntityList const& entities, ComponentPoolTuple&& p, Fn f)
    {
        for_each(entities, p, iterator_traits::entity_list_is_incremental<EntityList>(), f);
    }
}

#endif // _ENTITY_ALGORITHM_FOREACH_H_INCLUDED_