text: /*
   * Copyright (c) Facebook, Inc. and its affiliates.
   *
   * 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.
   */
  
  #pragma once
  
  #include <folly/futures/Future.h>
  
  namespace facebook::velox {
  /// Simple wrapper around folly's promise to track down destruction of
  /// unfulfilled promises.
  template <class T>
  class VeloxPromise : public folly::Promise<T> {
   public:
    VeloxPromise() : folly::Promise<T>() {}
  
    explicit VeloxPromise(const std::string& context)
        : folly::Promise<T>(), context_(context) {}
  
    VeloxPromise(
        folly::futures::detail::EmptyConstruct,
        const std::string& context) noexcept
        : folly::Promise<T>(folly::futures::detail::EmptyConstruct{}),
          context_(context) {}
  
    ~VeloxPromise() {
      if (!this->isFulfilled()) {
        LOG(WARNING) << "PROMISE: Unfulfilled promise is being deleted. Context: "
                     << context_;
      }
    }
  
    explicit VeloxPromise(VeloxPromise<T>&& other)
        : folly::Promise<T>(std::move(other)),
          context_(std::move(other.context_)) {}
  
    VeloxPromise& operator=(VeloxPromise<T>&& other) noexcept {
      folly::Promise<T>::operator=(std::move(other));
      context_ = std::move(other.context_);
      return *this;
    }
  
    static VeloxPromise makeEmpty(const std::string& context = "") noexcept {
      return VeloxPromise<T>(folly::futures::detail::EmptyConstruct{}, context);
    }
  
   private:
    /// Optional parameter to understand where this promise was created.
    std::string context_;
  };
  
  /// Equivalent of folly's makePromiseContract for VeloxPromise.
  template <class T>
  std::pair<VeloxPromise<T>, folly::SemiFuture<T>> makeVeloxPromiseContract(
      const std::string& promiseContext = "") {
    auto p = VeloxPromise<T>(promiseContext);
    auto f = p.getSemiFuture();
    return std::make_pair(std::move(p), std::move(f));
  }
  } // namespace facebook::velox
  