/*
 *  Copyright 2019 The WebRTC Project Authors. All rights reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree. An additional intellectual property rights grant can be found
 *  in the file PATENTS.  All contributing project authors may
 *  be found in the AUTHORS file in the root of the source tree.
 */
#include "api/task_queue/task_queue_base.h"

#include "absl/base/attributes.h"
#include "absl/base/config.h"
#include "absl/functional/any_invocable.h"
#include "api/units/time_delta.h"
#include "rtc_base/checks.h"
#include "rtc_base/voucher.h"

#if defined(ABSL_HAVE_THREAD_LOCAL)

namespace webrtc {
namespace {

ABSL_CONST_INIT thread_local TaskQueueBase* current = nullptr;

}  // namespace

TaskQueueBase* TaskQueueBase::Current() {
  return current;
}

void TaskQueueBase::PostTask(absl::AnyInvocable<void() &&> task,
                             const Location& location) {
  PostTaskInternal(std::move(task), PostTaskTraits{}, location);
}

void TaskQueueBase::PostTaskInternal(absl::AnyInvocable<void() &&> task,
                                     const PostTaskTraits& traits,
                                     const Location& location) {
  auto current = Voucher::Current();
  PostTaskImpl(
      [task = std::move(task), current = std::move(current)]() mutable {
        Voucher::ScopedSetter setter(std::move(current));
        std::move(task)();
      },
      traits, location);
}

TaskQueueBase::CurrentTaskQueueSetter::CurrentTaskQueueSetter(
    TaskQueueBase* task_queue)
    : previous_(current) {
  current = task_queue;
}

TaskQueueBase::CurrentTaskQueueSetter::~CurrentTaskQueueSetter() {
  current = previous_;
}
}  // namespace webrtc

#elif defined(WEBRTC_POSIX)

#include <pthread.h>

namespace webrtc {
namespace {

ABSL_CONST_INIT pthread_key_t g_queue_ptr_tls = 0;

void InitializeTls() {
  RTC_CHECK(pthread_key_create(&g_queue_ptr_tls, nullptr) == 0);
}

pthread_key_t GetQueuePtrTls() {
  static pthread_once_t init_once = PTHREAD_ONCE_INIT;
  RTC_CHECK(pthread_once(&init_once, &InitializeTls) == 0);
  return g_queue_ptr_tls;
}

}  // namespace

TaskQueueBase* TaskQueueBase::Current() {
  return static_cast<TaskQueueBase*>(pthread_getspecific(GetQueuePtrTls()));
}

TaskQueueBase::CurrentTaskQueueSetter::CurrentTaskQueueSetter(
    TaskQueueBase* task_queue)
    : previous_(TaskQueueBase::Current()) {
  pthread_setspecific(GetQueuePtrTls(), task_queue);
}

TaskQueueBase::CurrentTaskQueueSetter::~CurrentTaskQueueSetter() {
  pthread_setspecific(GetQueuePtrTls(), previous_);
}

}  // namespace webrtc

#else
#error Unsupported platform
#endif