/**
 * Copyright 2015-2016 Denis Blank <denis.blank@outlook.com>
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <tuple>
#include <type_traits>
#include <string>

namespace detail {
  template<typename... T>
  struct Identity { };

  template<typename T, typename... Rest>
  struct IdentityInheritenceWrapper
    : Identity<T>, IdentityInheritenceWrapper<Rest...> { };

  enum class NamedParameterId {
    NAMED_PARAMATER_CALLBACK,
    NAMED_PARAMATER_REJECTOR
  };

  template <NamedParameterId Value, typename T>
  struct NamedParameter
    : std::integral_constant<NamedParameterId, Value>,
      std::common_type<T> { };

  template <NamedParameterId Value, typename Default, typename... Args>
  using GetNamedParameterOrDefault = void;

  template<typename, typename>
  class ContinuableBase;

  template<typename T>
  struct ReturnTypeToContinuableConverter;

  template<typename... Args>
  struct 

  template<typename... Args, typename CallbackType>
  class ContinuableBase<Identity<Args...>, typename CallbackType> {
    CallbackType callback_;

  public:
    explicit ContinuableBase(CallbackType&& callback)
      : callback_(std::move(callback)) { }

    template<typename C>
    auto then(C&& continuation) {
      // The type the callback will evaluate to
      using EvaluatedTo = decltype(std::declval<C>()(std::declval<Args>()...));


      return EvaluatedTo{ };
    }
  };
} // namespace detail

using namespace detail;

template<typename... Args>
using Continuable = detail::ContinuableBase<detail::Identity<Args...>>;

template <typename... Args>
struct Callback {
  void operator() (Args... ) { }
};

template <typename... Args>
auto make_continuable(Args&&...) {
  return Continuable<> { };
}

auto http_request(std::string url) {
  return make_continuable([url](auto&& callback) {

    callback("<br>hi<br>");
  });
}

void testNextGen() {
  using t = GetNamedParameterOrDefault<
    NamedParameterId::NAMED_PARAMATER_CALLBACK,
    Identity<>,
    void,
    int,
    NamedParameter<NamedParameterId::NAMED_PARAMATER_CALLBACK, std::string>,
    float
  >;

  http_request("github.com")
    .then([](std::string content) {
      
      return 
    })
    .then([] {

    });
}