/*
 *  Copyright (C) 2015 Naios <naios-dev@live.de>
 *
 *  This program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#ifndef _CONTINUABLE_H_
#define _CONTINUABLE_H_

#include "Callback.h"

namespace detail
{
    template<typename _Cain, typename _Proxy>
    struct ContinuableState;

    template<typename... _Cain, typename _Proxy>
    struct ContinuableState<std::tuple<_Cain...>, _Proxy>
    {
    };

    typedef ContinuableState<std::tuple<>, void> EmptyContinuableState;

} // detail

template<typename _CTy, typename _State = detail::EmptyContinuableState>
class Continuable;

template<typename... _ATy, typename _State>
class Continuable<std::function<void(_ATy...)>, _State>
{
    /// Corrects void return types from functional types which should be Continuable<Callback<>>
    template<typename _RTy>
    struct convert_void_to_continuable;

    template<>
    struct convert_void_to_continuable<void>
    {
        typedef Continuable<Callback<>> type;
    };

    template<typename... _CArgs>
    struct convert_void_to_continuable<Continuable<_CArgs...>>
    {
        typedef Continuable<_CArgs...> type;
    };

public:
    typedef std::function<void(Callback<_ATy...>&&)> ForwardFunction;

private:
    /// Functional which expects a callback that is inserted from the Continuable
    /// to chain everything together
    ForwardFunction _callback_insert;

    bool _released;

    void Dispatch()
    {
    }

public:
    /// Deleted copy construct
    template<typename _RCTy, typename _RState>
    Continuable(Continuable<_RCTy, _RState> const&) = delete;

    /// Move construct
    template<typename _RCTy, typename _RState>
    Continuable(Continuable<_RCTy, _RState>&& right)
        : _released(right._released)
    {
        right._released = true;
    }

    // Construct through a ForwardFunction
    template<typename _FTy>
    Continuable(_FTy&& callback_insert)
        : _callback_insert(std::forward<_FTy>(callback_insert)), _released(false) { }

    /// Destructor which calls the dispatch chain if needed.
    ~Continuable()
    {
        if (!_released)
        {
            _released = true;
            Dispatch();
        }
    }

    /// Deleted copy assign
    template<typename _RCTy, typename _RState>
    Continuable& operator= (Continuable<_RCTy, _RState> const&) = delete;

    /// Move construct assign
    template<typename _RCTy, typename _RState>
    Continuable& operator= (Continuable<_RCTy, _RState>&& right)
    {
        _released = right._released;
        right._released = true;
        return *this;
    }

    // TODO Accept only correct callbacks
    template<typename _CTy>
    Continuable<Callback<_ATy...>> then(_CTy&&)
    {
        // TODO Transmute the returned callback here.
        return Continuable<Callback<_ATy...>>(std::move(*this));
    }

    /*
    // TODO Accept only correct callbacks
    template<typename... _CTy>
    Continuable<Callback<_ATy...>> all(_CTy&&...)
    {
        // TODO Transmute the returned callback here.
        return Continuable<Callback<_ATy...>>(std::move(*this));
    }
    */

    /// Invalidates the Continuable
    Continuable& invalidate()
    {
        _released = true;
        return *this;
    }
};

namespace detail
{
    template<typename _FTy, typename _RTy, typename... _ATy>
    struct ContinuableFactory;

    template<typename _FTy, typename _RTy, typename... _ATy>
    struct ContinuableFactory<_FTy, _RTy, ::fu::identity<std::function<void(_ATy...)>&&>>
    {
        static auto CreateFrom(_FTy&& functional)
            -> Continuable<Callback<_ATy...>>
        {
            return Continuable<Callback<_ATy...>>(
                typename Continuable<Callback<_ATy...>>::ForwardFunction(std::forward<_FTy>(functional)));
        }
    };

    template<typename _FTy>
    using continuable_factory_t = ContinuableFactory<
        _FTy, ::fu::return_type_of_t<_FTy>, ::fu::argument_type_of_t<_FTy>>;

} // detail

/// Wraps a functional object which expects a r-value callback as argument into a continuable.
/// The callable is invoked when the continuable shall continue.
/// For example:
/// make_continuable([](Callback<int>&& callback)
/// {
///     /* Continue here */
///     callback(5);
/// });
template<typename _FTy>
inline auto make_continuable(_FTy&& functional)
    -> decltype(detail::continuable_factory_t<_FTy>::CreateFrom(std::declval<_FTy>()))
{
    return detail::continuable_factory_t<_FTy>::CreateFrom(std::forward<_FTy>(functional));
}

#endif // _CONTINUABLE_H_