////////////////////////////////////////////////////////////////////////////////
/// DISCLAIMER
///
/// Copyright 2018 ArangoDB GmbH, Cologne, Germany
///
/// 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.
///
/// Copyright holder is ArangoDB GmbH, Cologne, Germany
///
/// @author Simon Grätzer
////////////////////////////////////////////////////////////////////////////////

#ifndef ARANGOD_FUTURES_UTILITIES_H
#define ARANGOD_FUTURES_UTILITIES_H 1

#include "Futures/Future.h"
#include "Futures/Unit.h"

namespace arangodb {
namespace futures {

template <class T>
Future<T> makeFuture(Try<T>&& t) {
  return Future<T>(detail::SharedState<T>::make(std::move(t)));
}

Future<Unit> makeFuture() { return Future<Unit>(unit); }

template <class T>
Future<typename std::decay<T>::type> makeFuture(T&& t) {
  return makeFuture(Try<typename std::decay<T>::type>(std::forward<T>(t)));
}

/// Make a failed Future from an std::exception_ptr.
template <class T>
Future<T> makeFuture(std::exception_ptr const& e) {
  return makeFuture(Try<T>(e));
}

/// Make a Future from an exception type E that can be passed to
/// std::make_exception_ptr().
template <class T, class E>
typename std::enable_if<std::is_base_of<std::exception, E>::value, Future<T>>::type makeFuture(E const& e) {
  return makeFuture(Try<T>(std::make_exception_ptr<E>(e)));
}

// makeFutureWith(Future<T>()) -> Future<T>
template <typename F, typename R = std::result_of_t<F()>>
typename std::enable_if<isFuture<R>::value, R>::type makeFutureWith(F&& func) {
  using InnerType = typename isFuture<R>::inner;
  try {
    return std::forward<F>(func)();
  } catch (...) {
    return makeFuture<InnerType>(std::current_exception());
  }
}

// makeFutureWith(T()) -> Future<T>
// makeFutureWith(void()) -> Future<Unit>
template <typename F, typename R = std::result_of_t<F()>>
typename std::enable_if<!isFuture<R>::value, Future<R>>::type makeFutureWith(F&& func) {
  return makeFuture<R>(
      makeTryWith([&func]() mutable { return std::forward<F>(func)(); }));
}

}  // namespace futures
}  // namespace arangodb
#endif  // ARANGOD_FUTURES_UTILITIES_H