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//          Copyright Oliver Kowalke 2013.
// 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 BOOST_FIBERS_ASYNC_HPP
#define BOOST_FIBERS_ASYNC_HPP

#include <algorithm>
#include <memory>
#include <type_traits>
#include <utility>

#include <boost/config.hpp>

#include <boost/fiber/future/future.hpp>
#include <boost/fiber/future/packaged_task.hpp>
#include <boost/fiber/policy.hpp>

namespace boost {
namespace fibers {

#if defined(BOOST_MSVC) && (_MSC_VER >= 1911 && _MSVC_LANG >= 201703)
template <typename>
struct result_of;
template <typename F, typename... Args>
struct result_of<F(Args...)> : std::invoke_result<F, Args...> {};
#else
using std::result_of;
#endif


template< typename Fn, typename ... Args >
future<
    typename result_of<
        typename std::enable_if<
            ! detail::is_launch_policy< typename std::decay< Fn >::type >::value,
            typename std::decay< Fn >::type
        >::type( typename std::decay< Args >::type ... )
    >::type
>
async( Fn && fn, Args ... args) {
    typedef typename result_of<
        typename std::decay< Fn >::type( typename std::decay< Args >::type ... )
    >::type     result_type;

    packaged_task< result_type( typename std::decay< Args >::type ... ) > pt{
        std::forward< Fn >( fn) };
    future< result_type > f{ pt.get_future() };
    fiber{ std::move( pt), std::forward< Args >( args) ... }.detach();
    return f;
}

template< typename Policy, typename Fn, typename ... Args >
future<
    typename result_of<
        typename std::enable_if<
            detail::is_launch_policy< Policy >::value,
            typename std::decay< Fn >::type
        >::type( typename std::decay< Args >::type ...)
    >::type
>
async( Policy policy, Fn && fn, Args ... args) {
    typedef typename result_of<
        typename std::decay< Fn >::type( typename std::decay< Args >::type ... )
    >::type     result_type;

    packaged_task< result_type( typename std::decay< Args >::type ... ) > pt{
        std::forward< Fn >( fn) };
    future< result_type > f{ pt.get_future() };
    fiber{ policy, std::move( pt), std::forward< Args >( args) ... }.detach();
    return f;
}

template< typename Policy, typename StackAllocator, typename Fn, typename ... Args >
future<
    typename result_of<
        typename std::enable_if<
            detail::is_launch_policy< Policy >::value,
            typename std::decay< Fn >::type
        >::type( typename std::decay< Args >::type ... )
    >::type
>
async( Policy policy, std::allocator_arg_t, StackAllocator salloc, Fn && fn, Args ... args) {
    typedef typename result_of<
        typename std::decay< Fn >::type( typename std::decay< Args >::type ... )
    >::type     result_type;

    packaged_task< result_type( typename std::decay< Args >::type ... ) > pt{
        std::forward< Fn >( fn) };
    future< result_type > f{ pt.get_future() };
    fiber{ policy, std::allocator_arg, salloc,
        std::move( pt), std::forward< Args >( args) ... }.detach();
    return f;
}

template< typename Policy, typename StackAllocator, typename Allocator, typename Fn, typename ... Args >
future<
    typename result_of<
        typename std::enable_if<
            detail::is_launch_policy< Policy >::value,
            typename std::decay< Fn >::type
        >::type( typename std::decay< Args >::type ... )
    >::type
>
async( Policy policy, std::allocator_arg_t, StackAllocator salloc, Allocator alloc, Fn && fn, Args ... args) {
    typedef typename result_of<
        typename std::decay< Fn >::type( typename std::decay< Args >::type ... )
    >::type     result_type;

    packaged_task< result_type( typename std::decay< Args >::type ... ) > pt{
        std::allocator_arg, alloc, std::forward< Fn >( fn) };
    future< result_type > f{ pt.get_future() };
    fiber{ policy, std::allocator_arg, salloc,
        std::move( pt), std::forward< Args >( args) ... }.detach();
    return f;
}

}}

#endif // BOOST_FIBERS_ASYNC_HPP