/*
 * 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 <memory>

#include <folly/Executor.h>
#include <folly/executors/IOExecutor.h>

namespace folly {

/**
 * Return the global executor.
 * The global executor is a CPU thread pool and is immutable.
 *
 * May return an invalid KeepAlive on shutdown.
 */
folly::Executor::KeepAlive<> getGlobalCPUExecutor();

/**
 * Return the global IO executor.
 * The global executor is an IO thread pool and is immutable.
 *
 * May return an invalid KeepAlive on shutdown.
 */
folly::Executor::KeepAlive<> getGlobalIOExecutor();

/**
 * Retrieve the global Executor. If there is none, a default InlineExecutor
 * will be constructed and returned. This is named CPUExecutor to distinguish
 * it from IOExecutor below and to hint that it's intended for CPU-bound tasks.
 *
 * Can return nullptr on shutdown.
 */
std::shared_ptr<folly::Executor> getCPUExecutor();

/**
 * Set an Executor to be the global Executor which will be returned by
 * subsequent calls to getCPUExecutor().
 */
void setCPUExecutor(std::weak_ptr<folly::Executor> executor);

/**
 * Set the CPU executor to the immutable default returned by
 * getGlobalCPUExecutor.
 */
void setCPUExecutorToGlobalCPUExecutor();

/**
 * Retrieve the global IOExecutor. If there is none, a default
 * IOThreadPoolExecutor will be constructed and returned.
 *
 * IOExecutors differ from Executors in that they drive and provide access to
 * one or more EventBases.
 *
 * Can return nullptr on shutdown.
 */
std::shared_ptr<IOExecutor> getIOExecutor();

/**
 * Set an IOExecutor to be the global IOExecutor which will be returned by
 * subsequent calls to getIOExecutor().
 */
void setIOExecutor(std::weak_ptr<IOExecutor> executor);

/**
 * Retrieve an event base from the global IOExecutor
 *
 * NOTE: This is not shutdown-safe, the returned pointer may be
 * invalid during shutdown.
 */
folly::EventBase* getEventBase();

} // namespace folly