// 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/post_task.h"

#include <utility>

#include "base/logging.h"
#include "base/task/scoped_set_task_priority_for_current_thread.h"
#include "base/task/task_executor.h"
#include "base/task/thread_pool/thread_pool_impl.h"
#include "base/task/thread_pool/thread_pool_instance.h"
#include "base/threading/post_task_and_reply_impl.h"

namespace base {

namespace {

class PostTaskAndReplyWithTraitsTaskRunner
    : public internal::PostTaskAndReplyImpl {
 public:
  explicit PostTaskAndReplyWithTraitsTaskRunner(const TaskTraits& traits)
      : traits_(traits) {}

 private:
  bool PostTask(const Location& from_here, OnceClosure task) override {
    ::base::PostTask(from_here, traits_, std::move(task));
    return true;
  }

  const TaskTraits traits_;
};

// Returns TaskTraits based on |traits|. If TaskPriority hasn't been set
// explicitly in |traits|, the returned TaskTraits will inherit the current
// TaskPriority.
TaskTraits GetTaskTraitsWithExplicitPriority(TaskTraits traits) {
  traits.InheritPriority(internal::GetTaskPriorityForCurrentThread());
  return traits;
}

TaskExecutor* GetTaskExecutorForTraits(const TaskTraits& traits) {
  if (traits.use_current_thread()) {
    TaskExecutor* executor = GetTaskExecutorForCurrentThread();
    DCHECK(executor) << "Couldn't find a TaskExecutor for this thread. Note "
                        "you can't use base::CurrentThread in a one-off "
                        "base::ThreadPool task.";
    return executor;
  }
  TaskExecutor* executor = GetRegisteredTaskExecutorForTraits(traits);
  DCHECK(executor || ThreadPoolInstance::Get())
      << "Ref. Prerequisite section of post_task.h.\n\n"
         "Hint: if this is in a unit test, you're likely merely missing a "
         "base::test::TaskEnvironment member in your fixture (or your fixture "
         "is using a base::test::SingleThreadTaskEnvironment and now needs a "
         "full base::test::TaskEnvironment).\n";
  // TODO(skyostil): Make thread affinity a required trait.
  if (!executor || traits.use_thread_pool())
    return static_cast<internal::ThreadPoolImpl*>(ThreadPoolInstance::Get());
  return executor;
}

}  // namespace

bool PostTask(const Location& from_here, OnceClosure task) {
  return PostDelayedTask(from_here, std::move(task), TimeDelta());
}

bool PostDelayedTask(const Location& from_here,
                     OnceClosure task,
                     TimeDelta delay) {
  return PostDelayedTask(from_here, {ThreadPool()}, std::move(task), delay);
}

bool PostTaskAndReply(const Location& from_here,
                      OnceClosure task,
                      OnceClosure reply) {
  return PostTaskAndReply(from_here, {ThreadPool()}, std::move(task),
                          std::move(reply));
}

bool PostTask(const Location& from_here,
              const TaskTraits& traits,
              OnceClosure task) {
  return PostDelayedTask(from_here, traits, std::move(task), TimeDelta());
}

bool PostDelayedTask(const Location& from_here,
                     const TaskTraits& traits,
                     OnceClosure task,
                     TimeDelta delay) {
  const TaskTraits adjusted_traits = GetTaskTraitsWithExplicitPriority(traits);
  return GetTaskExecutorForTraits(adjusted_traits)
      ->PostDelayedTask(from_here, adjusted_traits, std::move(task), delay);
}

bool PostTaskAndReply(const Location& from_here,
                      const TaskTraits& traits,
                      OnceClosure task,
                      OnceClosure reply) {
  return PostTaskAndReplyWithTraitsTaskRunner(traits).PostTaskAndReply(
      from_here, std::move(task), std::move(reply));
}

scoped_refptr<TaskRunner> CreateTaskRunner(const TaskTraits& traits) {
  return GetTaskExecutorForTraits(traits)->CreateTaskRunner(traits);
}

scoped_refptr<SequencedTaskRunner> CreateSequencedTaskRunner(
    const TaskTraits& traits) {
  return GetTaskExecutorForTraits(traits)->CreateSequencedTaskRunner(traits);
}

scoped_refptr<UpdateableSequencedTaskRunner>
CreateUpdateableSequencedTaskRunner(const TaskTraits& traits) {
  DCHECK(ThreadPoolInstance::Get())
      << "Ref. Prerequisite section of post_task.h.\n\n"
         "Hint: if this is in a unit test, you're likely merely missing a "
         "base::test::TaskEnvironment member in your fixture.\n";
  DCHECK(traits.use_thread_pool())
      << "The base::UseThreadPool() trait is mandatory with "
         "CreateUpdateableSequencedTaskRunner().";
  CHECK_EQ(traits.extension_id(),
           TaskTraitsExtensionStorage::kInvalidExtensionId)
      << "Extension traits cannot be used with "
         "CreateUpdateableSequencedTaskRunner().";
  const TaskTraits adjusted_traits = GetTaskTraitsWithExplicitPriority(traits);
  return static_cast<internal::ThreadPoolImpl*>(ThreadPoolInstance::Get())
      ->CreateUpdateableSequencedTaskRunner(adjusted_traits);
}

scoped_refptr<SingleThreadTaskRunner> CreateSingleThreadTaskRunner(
    const TaskTraits& traits,
    SingleThreadTaskRunnerThreadMode thread_mode) {
  return GetTaskExecutorForTraits(traits)->CreateSingleThreadTaskRunner(
      traits, thread_mode);
}

#if defined(OS_WIN)
scoped_refptr<SingleThreadTaskRunner> CreateCOMSTATaskRunner(
    const TaskTraits& traits,
    SingleThreadTaskRunnerThreadMode thread_mode) {
  return GetTaskExecutorForTraits(traits)->CreateCOMSTATaskRunner(traits,
                                                                  thread_mode);
}
#endif  // defined(OS_WIN)

}  // namespace base