/*
 * Copyright (C) 2019 The Android Open Source Project
 *
 * 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 INCLUDE_PERFETTO_EXT_BASE_THREAD_TASK_RUNNER_H_
#define INCLUDE_PERFETTO_EXT_BASE_THREAD_TASK_RUNNER_H_

#include <functional>
#include <thread>

#include "perfetto/ext/base/lock_free_task_runner.h"

namespace perfetto {
namespace base {

// A MaybeLockFreeTaskRunner backed by a dedicated task thread. Shuts down the
// runner and joins the thread upon destruction. Can be moved to transfer
// ownership.
//
// Guarantees that:
// * the MaybeLockFreeTaskRunner will be constructed and destructed on the task
// thread.
// * the task thread will live for the lifetime of the MaybeLockFreeTaskRunner.
//
class PERFETTO_EXPORT_COMPONENT ThreadTaskRunner : public TaskRunner {
 public:
  static ThreadTaskRunner CreateAndStart(const std::string& name = "") {
    return ThreadTaskRunner(name);
  }

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

  ThreadTaskRunner(ThreadTaskRunner&&) noexcept;
  ThreadTaskRunner& operator=(ThreadTaskRunner&&);
  ~ThreadTaskRunner() override;

  // Executes the given function on the task runner thread and blocks the caller
  // thread until the function has run.
  void PostTaskAndWaitForTesting(std::function<void()>);

  // Can be called from another thread to get the CPU time of the thread the
  // task-runner is executing on.
  uint64_t GetThreadCPUTimeNsForTesting();

  PlatformThreadId GetThreadIdForTesting();

  // Returns a pointer to the MaybeLockFreeTaskRunner, which is valid for the
  // lifetime of this ThreadTaskRunner object (unless this object is moved-from,
  // in which case the pointer remains valid for the lifetime of the new owning
  // ThreadTaskRunner).
  //
  // Warning: do not call Quit() on the returned runner pointer, the termination
  // should be handled exclusively by this class' destructor.
  MaybeLockFreeTaskRunner* get() const { return task_runner_; }

  // TaskRunner implementation.
  // These methods just proxy to the underlying task_runner_.
  void PostTask(std::function<void()>) override;
  void PostDelayedTask(std::function<void()>, uint32_t delay_ms) override;
  void AddFileDescriptorWatch(PlatformHandle, std::function<void()>) override;
  void RemoveFileDescriptorWatch(PlatformHandle) override;
  bool RunsTasksOnCurrentThread() const override;

 private:
  explicit ThreadTaskRunner(const std::string& name);
  void RunTaskThread(std::function<void(MaybeLockFreeTaskRunner*)> initializer);

  std::thread thread_;
  std::string name_;
  MaybeLockFreeTaskRunner* task_runner_ = nullptr;
};

}  // namespace base
}  // namespace perfetto

#endif  // INCLUDE_PERFETTO_EXT_BASE_THREAD_TASK_RUNNER_H_
