// Copyright 2022 Huawei Cloud Computing Technology Co., Ltd.
//
// 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.

#ifndef INCLUDED_SRC_BUILDTOOL_MULTITHREADING_TASK_HPP
#define INCLUDED_SRC_BUILDTOOL_MULTITHREADING_TASK_HPP

#include <functional>
#include <type_traits>
#include <utility>  // std::move

class Task {
  public:
    using TaskFunc = std::function<void()>;

    Task() noexcept = default;

    // NOLINTNEXTLINE(modernize-pass-by-value)
    explicit Task(TaskFunc const& function) noexcept : f_{function} {}
    explicit Task(TaskFunc&& function) noexcept : f_{std::move(function)} {}

    void operator()() { f_(); }

    // To be able to discern whether the internal f_ has been set or not,
    // allowing us to write code such as:
    /*
    Task t;
    while (!t) {
        t = TryGetTaskFromQueue(); // (*)
    }
    t(); // (**)
    */
    // (*) does `return Task();` or `return {};` if queue is empty or locked)
    // (**) we can now surely execute the task (and be sure it won't throw any
    // exception) (for the sake of the example, imagine we are sure that the
    // queue wasn't empty, otherwise this would be an infinite loop)
    explicit operator bool() const noexcept { return f_.operator bool(); }

  private:
    TaskFunc f_{};
};

#endif  // INCLUDED_SRC_BUILDTOOL_MULTITHREADING_TASK_HPP