// Copyright (c) 2012 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.

// This class defines tests that implementations of SequencedTaskRunner should
// pass in order to be conformant. See task_runner_test_template.h for a
// description of how to use the constructs in this file; these work the same.

#ifndef BASE_SEQUENCED_TASK_RUNNER_TEST_TEMPLATE_H_
#define BASE_SEQUENCED_TASK_RUNNER_TEST_TEMPLATE_H_

#include <cstddef>
#include <iosfwd>
#include <vector>

#include "base/basictypes.h"
#include "base/bind.h"
#include "base/callback.h"
#include "base/memory/ref_counted.h"
#include "base/sequenced_task_runner.h"
#include "base/synchronization/lock.h"
#include "base/time.h"
#include "testing/gtest/include/gtest/gtest.h"

namespace base {

namespace internal {

struct TaskEvent {
  enum Type { POST, START, END };
  TaskEvent(int i, Type type);
  int i;
  Type type;
};

// Utility class used in the tests below.
class SequencedTaskTracker : public RefCountedThreadSafe<SequencedTaskTracker> {
 public:
  SequencedTaskTracker();

  // Posts the non-nestable task |task|, and records its post event.
  void PostWrappedNonNestableTask(
      const scoped_refptr<SequencedTaskRunner>& task_runner,
      const Closure& task);

  // Posts the nestable task |task|, and records its post event.
  void PostWrappedNestableTask(
      const scoped_refptr<SequencedTaskRunner>& task_runner,
      const Closure& task);

  // Posts the delayed non-nestable task |task|, and records its post event.
  void PostWrappedDelayedNonNestableTask(
      const scoped_refptr<SequencedTaskRunner>& task_runner,
      const Closure& task,
      TimeDelta delay);

  // Posts |task_count| non-nestable tasks.
  void PostNonNestableTasks(
      const scoped_refptr<SequencedTaskRunner>& task_runner,
      int task_count);

  const std::vector<TaskEvent>& GetTaskEvents() const;

 private:
  friend class RefCountedThreadSafe<SequencedTaskTracker>;

  ~SequencedTaskTracker();

  // A task which runs |task|, recording the start and end events.
  void RunTask(const Closure& task, int task_i);

  // Records a post event for task |i|. The owner is expected to be holding
  // |lock_| (unlike |TaskStarted| and |TaskEnded|).
  void TaskPosted(int i);

  // Records a start event for task |i|.
  void TaskStarted(int i);

  // Records a end event for task |i|.
  void TaskEnded(int i);

  // Protects events_ and next_post_i_.
  Lock lock_;

  // The events as they occurred for each task (protected by lock_).
  std::vector<TaskEvent> events_;

  // The ordinal to be used for the next task-posting task (protected by
  // lock_).
  int next_post_i_;

  DISALLOW_COPY_AND_ASSIGN(SequencedTaskTracker);
};

void PrintTo(const TaskEvent& event, std::ostream* os);

void SleepForOneSecond();

// Checks the non-nestable task invariants for all tasks in |events|.
//
// The invariants are:
// 1) Events started and ended in the same order that they were posted.
// 2) Events for an individual tasks occur in the order {POST, START, END},
//    and there is only one instance of each event type for a task.
// 3) The only events between a task's START and END events are the POSTs of
//    other tasks. I.e. tasks were run sequentially, not interleaved.
::testing::AssertionResult CheckNonNestableInvariants(
    const std::vector<TaskEvent>& events,
    int task_count);

}  // namespace internal

template <typename TaskRunnerTestDelegate>
class SequencedTaskRunnerTest : public testing::Test {
 protected:
  SequencedTaskRunnerTest()
  : task_tracker_(new internal::SequencedTaskTracker()) {}

  const scoped_refptr<internal::SequencedTaskTracker> task_tracker_;
  TaskRunnerTestDelegate delegate_;
};

TYPED_TEST_CASE_P(SequencedTaskRunnerTest);

// This test posts N non-nestable tasks in sequence, and expects them to run
// in FIFO order, with no part of any two tasks' execution
// overlapping. I.e. that each task starts only after the previously-posted
// one has finished.
TYPED_TEST_P(SequencedTaskRunnerTest, SequentialNonNestable) {
  const int task_count = 1000;

  this->delegate_.StartTaskRunner();
  const scoped_refptr<SequencedTaskRunner> task_runner =
      this->delegate_.GetTaskRunner();

  this->task_tracker_->PostWrappedNonNestableTask(
      task_runner, Bind(&internal::SleepForOneSecond));
  for (int i = 1; i < task_count; ++i) {
    this->task_tracker_->PostWrappedNonNestableTask(task_runner, Closure());
  }

  this->delegate_.StopTaskRunner();

  EXPECT_TRUE(CheckNonNestableInvariants(this->task_tracker_->GetTaskEvents(),
                                         task_count));
}

// This test posts N nestable tasks in sequence. It has the same expectations
// as SequentialNonNestable because even though the tasks are nestable, they
// will not be run nestedly in this case.
TYPED_TEST_P(SequencedTaskRunnerTest, SequentialNestable) {
  const int task_count = 1000;

  this->delegate_.StartTaskRunner();
  const scoped_refptr<SequencedTaskRunner> task_runner =
      this->delegate_.GetTaskRunner();

  this->task_tracker_->PostWrappedNestableTask(
      task_runner,
      Bind(&internal::SleepForOneSecond));
  for (int i = 1; i < task_count; ++i) {
    this->task_tracker_->PostWrappedNestableTask(task_runner, Closure());
  }

  this->delegate_.StopTaskRunner();

  EXPECT_TRUE(CheckNonNestableInvariants(this->task_tracker_->GetTaskEvents(),
                                         task_count));
}

// This test posts non-nestable tasks in order of increasing delay, and checks
// that that the tasks are run in FIFO order and that there is no execution
// overlap whatsoever between any two tasks.
TYPED_TEST_P(SequencedTaskRunnerTest, SequentialDelayedNonNestable) {
  if (!this->delegate_.TaskRunnerHandlesNonZeroDelays()) {
    DLOG(INFO) << "This SequencedTaskRunner doesn't handle "
        "non-zero delays; skipping";
    return;
  }

  const int task_count = 20;
  const int delay_increment_ms = 50;

  this->delegate_.StartTaskRunner();
  const scoped_refptr<SequencedTaskRunner> task_runner =
      this->delegate_.GetTaskRunner();

  for (int i = 0; i < task_count; ++i) {
    this->task_tracker_->PostWrappedDelayedNonNestableTask(
        task_runner,
        Closure(),
        TimeDelta::FromMilliseconds(delay_increment_ms * i));
  }

  this->delegate_.StopTaskRunner();

  EXPECT_TRUE(CheckNonNestableInvariants(this->task_tracker_->GetTaskEvents(),
                                         task_count));
}

// This test posts a fast, non-nestable task from within each of a number of
// slow, non-nestable tasks and checks that they all run in the sequence they
// were posted in and that there is no execution overlap whatsoever.
TYPED_TEST_P(SequencedTaskRunnerTest, NonNestablePostFromNonNestableTask) {
  const int parent_count = 10;
  const int children_per_parent = 10;

  this->delegate_.StartTaskRunner();
  const scoped_refptr<SequencedTaskRunner> task_runner =
      this->delegate_.GetTaskRunner();

  for (int i = 0; i < parent_count; ++i) {
    Closure task = Bind(
        &internal::SequencedTaskTracker::PostNonNestableTasks,
        this->task_tracker_,
        task_runner,
        children_per_parent);
    this->task_tracker_->PostWrappedNonNestableTask(task_runner, task);
  }

  this->delegate_.StopTaskRunner();

  EXPECT_TRUE(CheckNonNestableInvariants(
      this->task_tracker_->GetTaskEvents(),
      parent_count * (children_per_parent + 1)));
}

// TODO(francoisk777@gmail.com) Add a test, similiar to the above, which runs
// some tasked nestedly (which should be implemented in the test
// delegate). Also add, to the the test delegate, a predicate which checks
// whether the implementation supports nested tasks.
//

REGISTER_TYPED_TEST_CASE_P(SequencedTaskRunnerTest,
                           SequentialNonNestable,
                           SequentialNestable,
                           SequentialDelayedNonNestable,
                           NonNestablePostFromNonNestableTask);

}  // namespace base

#endif  // BASE_TASK_RUNNER_TEST_TEMPLATE_H_