
/*
 * Copyright (c) 2023, Alibaba Group Holding Limited;
 *
 * 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 ASYNC_SIMPLE_LOCALSTATE_H
#define ASYNC_SIMPLE_LOCALSTATE_H

#include <atomic>
#include <condition_variable>
#include <functional>
#include <mutex>
#include <stdexcept>
#include <thread>
#include <utility>

#include "async_simple/Common.h"
#include "async_simple/Executor.h"
#include "async_simple/MoveWrapper.h"
#include "async_simple/Try.h"

namespace async_simple {

// A component of Future/Promise. LocalState is owned by
// Future only. LocalState should be valid after
// Future and Promise disconnects.
//
// Users should never use LocalState directly.
template <typename T>
class LocalState {
 private:
  using Continuation = std::function<void(Try<T>&& value)>;

 public:
  LocalState() : _executor(nullptr) {}
  LocalState(T&& v) : _try_value(std::forward<T>(v)), _executor(nullptr) {}
  LocalState(Try<T>&& t) : _try_value(std::move(t)), _executor(nullptr) {}

  ~LocalState() {}

  LocalState(const LocalState&) = delete;
  LocalState& operator=(const LocalState&) = delete;

  LocalState(LocalState&& other)
      : _try_value(std::move(other._try_value)),
        _executor(std::exchange(other._executor, nullptr)) {}
  LocalState& operator=(LocalState&& other) {
    if (this != &other) {
      std::swap(_try_value, other._try_value);
      std::swap(_executor, other._executor);
    }
    return *this;
  }

 public:
  bool hasResult() const noexcept { return _try_value.available(); }

 public:
  Try<T>& getTry() noexcept { return _try_value; }
  const Try<T>& getTry() const noexcept { return _try_value; }

  void setExecutor(Executor* ex) { _executor = ex; }

  Executor* getExecutor() { return _executor; }

  bool currentThreadInExecutor() const {
    if (!_executor) {
      return false;
    }
    return _executor->currentThreadInExecutor();
  }

  template <typename F>
  void setContinuation(F&& f) {
    assert(_try_value.available());
    std::forward<F>(f)(std::move(_try_value));
  }

 private:
  Try<T> _try_value;
  Executor* _executor;
};
}  // namespace async_simple

#endif
