// Copyright 2016 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "base/task_scheduler/task_scheduler.h"

#include <algorithm>

#include "base/bind.h"
#include "base/logging.h"
#include "base/sys_info.h"
#include "base/task_scheduler/scheduler_worker_pool_params.h"
#include "base/task_scheduler/task_scheduler_impl.h"
#include "base/threading/platform_thread.h"
#include "base/time/time.h"

namespace base {

namespace {

// |g_task_scheduler| is intentionally leaked on shutdown.
TaskScheduler* g_task_scheduler = nullptr;

}  // namespace

TaskScheduler::InitParams::InitParams(
    const SchedulerWorkerPoolParams& background_worker_pool_params_in,
    const SchedulerWorkerPoolParams& background_blocking_worker_pool_params_in,
    const SchedulerWorkerPoolParams& foreground_worker_pool_params_in,
    const SchedulerWorkerPoolParams& foreground_blocking_worker_pool_params_in)
    : background_worker_pool_params(background_worker_pool_params_in),
      background_blocking_worker_pool_params(
          background_blocking_worker_pool_params_in),
      foreground_worker_pool_params(foreground_worker_pool_params_in),
      foreground_blocking_worker_pool_params(
          foreground_blocking_worker_pool_params_in) {}

TaskScheduler::InitParams::~InitParams() = default;

#if !defined(OS_NACL)
// static
void TaskScheduler::CreateAndSetSimpleTaskScheduler(const std::string& name) {
  using StandbyThreadPolicy = SchedulerWorkerPoolParams::StandbyThreadPolicy;

  // Values were chosen so that:
  // * There are few background threads.
  // * Background threads never outnumber foreground threads.
  // * The system is utilized maximally by foreground threads.
  const int num_cores = SysInfo::NumberOfProcessors();
  constexpr int kBackgroundMaxThreads = 1;
  constexpr int kBackgroundBlockingMaxThreads = 2;
  const int kForegroundMaxThreads = std::max(1, num_cores);
  const int kForegroundBlockingMaxThreads = std::max(2, num_cores);

  constexpr TimeDelta kSuggestedReclaimTime = TimeDelta::FromSeconds(30);

  CreateAndSetDefaultTaskScheduler(
      name, {{StandbyThreadPolicy::LAZY, kBackgroundMaxThreads,
              kSuggestedReclaimTime},
             {StandbyThreadPolicy::LAZY, kBackgroundBlockingMaxThreads,
              kSuggestedReclaimTime},
             {StandbyThreadPolicy::LAZY, kForegroundMaxThreads,
              kSuggestedReclaimTime},
             {StandbyThreadPolicy::LAZY, kForegroundBlockingMaxThreads,
              kSuggestedReclaimTime}});
}
#endif  // !defined(OS_NACL)

// static
void TaskScheduler::CreateAndSetDefaultTaskScheduler(
    const std::vector<SchedulerWorkerPoolParams>& worker_pool_params_vector,
    const WorkerPoolIndexForTraitsCallback&
        worker_pool_index_for_traits_callback) {
  SetInstance(internal::TaskSchedulerImpl::Create(
      worker_pool_params_vector, worker_pool_index_for_traits_callback));
}

void TaskScheduler::CreateAndSetDefaultTaskScheduler(
    const std::string& name,
    const InitParams& init_params) {
  SetInstance(internal::TaskSchedulerImpl::Create(name, init_params));
}

// static
void TaskScheduler::SetInstance(std::unique_ptr<TaskScheduler> task_scheduler) {
  delete g_task_scheduler;
  g_task_scheduler = task_scheduler.release();
}

// static
TaskScheduler* TaskScheduler::GetInstance() {
  return g_task_scheduler;
}

}  // namespace base