Continuation.h

/*
 * Copyright (C) 2022 HERE Europe B.V.
 *
 * 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.
 *
 * SPDX-License-Identifier: Apache-2.0
 * License-Filename: LICENSE
 */
 
#pragma once
 
#include <deque>
#include <functional>
#include <memory>
 
#include <olp/core/client/ApiError.h>
#include <olp/core/client/ApiResponse.h>
#include <olp/core/client/TaskContext.h>
#include <olp/core/thread/ExecutionContext.h>
#include <olp/core/thread/TypeHelpers.h>
 
namespace olp {
namespace thread {
 
class TaskScheduler;
 
namespace internal {
 
class CORE_API ContinuationImpl final {
 public:
  using FailedCallback = std::function<void(client::ApiError)>;
  using OutResultType = std::unique_ptr<UntypedSmartPointer>;
  using TaskType = std::function<OutResultType(void*)>;
  using CallbackType = std::function<void(void*)>;
  using AsyncTaskType = std::function<void(void*, CallbackType)>;
  using FinalCallbackType = std::function<void(void*, bool)>;
  using ContinuationTask = std::pair<AsyncTaskType, TaskType>;
 
  ContinuationImpl() = default;
 
  ContinuationImpl(std::shared_ptr<TaskScheduler> task_scheduler,
                   ExecutionContext context, ContinuationTask task);
 
  ContinuationImpl Then(ContinuationTask task);
 
  void Run(FinalCallbackType callback);
 
  const ExecutionContext& GetExecutionContext() const;
 
  bool Cancelled() const;
 
  void SetFailedCallback(FailedCallback callback);
 
  void Clear();
 
 private:
  std::shared_ptr<thread::TaskScheduler> task_scheduler_;
  std::deque<ContinuationTask> tasks_;
  ExecutionContext execution_context_;
 
  bool change_allowed{true};
};
 
}  // namespace internal
 
template <typename ResultType>
class CORE_API Continuation final {
  using Response = client::ApiResponse<ResultType, client::ApiError>;
  using FinallyCallbackType = std::function<void(Response)>;
  using ContinuationImplType = internal::ContinuationImpl;
  using OutResultType = ContinuationImplType::OutResultType;
  using TaskType = ContinuationImplType::TaskType;
  using CallbackType = ContinuationImplType::CallbackType;
  using ContinuationTaskType =
      std::function<void(ExecutionContext, std::function<void(ResultType)>)>;
 
 public:
  Continuation() = default;
 
  Continuation(std::shared_ptr<thread::TaskScheduler> scheduler,
               ExecutionContext context, ContinuationTaskType task);
 
  Continuation(ContinuationImplType continuation);
 
  template <typename Callable>
  Continuation<internal::DeducedType<Callable>> Then(Callable task);
 
  void Run();
 
  client::CancellationToken CancelToken();
 
  template <typename NewType>
  Continuation<internal::RemoveRefAndConst<NewType>> Then(
      std::function<void(ExecutionContext, ResultType,
                         std::function<void(NewType)>)>
          execution_func);
 
  Continuation& Finally(FinallyCallbackType finally_callback);
 
 private:
  FinallyCallbackType finally_callback_;
  ContinuationImplType impl_;
};
 
template <>
class CORE_API Continuation<void> final {
 public:
  Continuation() = delete;
 
  template <typename Callable>
  Continuation<internal::AsyncResultType<Callable>> Then(Callable task);
 
 private:
  using CallbackType = internal::ContinuationImpl::CallbackType;
  using ContinuationImplType = internal::ContinuationImpl;
  using OutResultType = ContinuationImplType::OutResultType;
  using TaskType = ContinuationImplType::TaskType;
 
  template <typename ResultType>
  friend class Continuation;
 
  template <typename NewType>
  static ContinuationImplType::ContinuationTask ToAsyncTask(
      ExecutionContext context,
      std::function<void(ExecutionContext, std::function<void(NewType)>)> task);
 
  ContinuationImplType impl_;
};
 
}  // namespace thread
}  // namespace olp
 
#include "Continuation.inl"