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// Copyright 2017 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 <memory>
#include "base/callback.h"
#include "base/cancelable_callback.h"
#include "base/macros.h"
#include "base/memory/weak_ptr.h"
#include "base/sequence_checker.h"
#include "base/time/time.h"
#include "components/policy/policy_export.h"
namespace policy {
// Scheduler for driving repeated asynchronous tasks such as e.g. policy
// fetches. Subsequent tasks are guaranteed not to overlap. Tasks are posted to
// the current thread and therefore must not block (suitable e.g. for
// asynchronous D-Bus calls).
// Tasks scheduling begins immediately after instantiation of the class. Upon
// destruction, scheduled but not yet started tasks are cancelled. The result of
// started but not finished tasks is NOT reported.
class POLICY_EXPORT PolicyScheduler {
// Callback for the task to report success or failure.
using TaskCallback = base::OnceCallback<void(bool success)>;
// Task to be performed at regular intervals. The task takes a |callback| to
// return success or failure.
using Task = base::RepeatingCallback<void(TaskCallback callback)>;
// Callback for PolicyScheduler to report success or failure of the tasks.
using SchedulerCallback = base::RepeatingCallback<void(bool success)>;
// Defines the |task| to be run every |interval| and the |callback| for the
// scheduler to report the result. (Intervals are computed as the time
// difference between the end of the previous and the start of the subsequent
// task.) Calling the constructor starts the loop and schedules the first task
// to be run without delay.
PolicyScheduler(Task task,
SchedulerCallback callback,
base::TimeDelta interval);
// Schedules a task to run immediately. Deletes any previously scheduled but
// not yet started tasks. In case a task is running currently, the new task is
// scheduled to run immediately after the end of the currently running task.
void ScheduleTaskNow();
base::TimeDelta interval() const { return interval_; }
// Schedules next task to run in |delay|. Deletes any previously scheduled
// tasks.
void ScheduleDelayedTask(base::TimeDelta delay);
// Schedules next task to run in |interval_| or immediately in case of
// overlap. Deletes any previously scheduled tasks.
void ScheduleNextTask();
// Actually executes the scheduled task.
void RunScheduledTask();
// Reports back the |result| of the previous task and schedules the next one.
void OnTaskDone(bool result);
Task task_;
SchedulerCallback callback_;
// Tasks are being run every |interval_|.
const base::TimeDelta interval_;
// Whether a task is in progress.
bool task_in_progress_ = false;
// Whether there had been an overlap of tasks and thus the next task needs to
// be scheduled without delay.
bool overlap_ = false;
// End time of the previous task. Zero in case no task has ended yet.
base::TimeTicks last_task_;
std::unique_ptr<base::CancelableClosure> job_;
// Must be last member.
base::WeakPtrFactory<PolicyScheduler> weak_ptr_factory_{this};
} // namespace policy