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- // Copyright 2014 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.
- #ifndef COMPONENTS_METRICS_DAILY_EVENT_H_
- #define COMPONENTS_METRICS_DAILY_EVENT_H_
- #include <memory>
- #include <string>
- #include <vector>
- #include "base/memory/raw_ptr.h"
- #include "base/time/time.h"
- class PrefRegistrySimple;
- class PrefService;
- namespace metrics {
- // DailyEvent is used for throttling an event to about once per day, even if
- // the program is restarted more frequently. It is based on local machine
- // time, so it could be fired more often if the clock is changed.
- //
- // The service using the DailyEvent should first provide all of the Observers
- // for the interval, and then arrange for CheckInterval() to be called
- // periodically to test if the event should be fired.
- class DailyEvent {
- public:
- // Different reasons that Observer::OnDailyEvent() is called.
- // This enum is used for histograms and must not be renumbered.
- enum class IntervalType {
- FIRST_RUN,
- DAY_ELAPSED,
- CLOCK_CHANGED,
- kMaxValue = CLOCK_CHANGED,
- };
- // Observer receives notifications from a DailyEvent.
- // Observers must be added before the DailyEvent begins checking time,
- // and will be owned by the DailyEvent.
- class Observer {
- public:
- Observer();
- Observer(const Observer&) = delete;
- Observer& operator=(const Observer&) = delete;
- virtual ~Observer();
- // Called when the daily event is fired.
- virtual void OnDailyEvent(IntervalType type) = 0;
- };
- // Constructs DailyEvent monitor which stores the time it last fired in the
- // preference |pref_name|. |pref_name| should be registered by calling
- // RegisterPref before using this object.
- // Caller is responsible for ensuring that |pref_service| and |pref_name|
- // outlive the DailyEvent.
- // |histogram_name| is the name of the UMA metric which record when this
- // interval fires, and should be registered in histograms.xml. If
- // |histogram_name| is empty - interval fires are not recorded.
- DailyEvent(PrefService* pref_service,
- const char* pref_name,
- const std::string& histogram_name);
- DailyEvent(const DailyEvent&) = delete;
- DailyEvent& operator=(const DailyEvent&) = delete;
- ~DailyEvent();
- // Adds a observer to be notified when a day elapses. All observers should
- // be registered before the the DailyEvent starts checking time.
- void AddObserver(std::unique_ptr<Observer> observer);
- // Checks if a day has elapsed. If it has, OnDailyEvent will be called on
- // all observers.
- void CheckInterval();
- // Registers the preference used by this interval.
- static void RegisterPref(PrefRegistrySimple* registry,
- const std::string& pref_name);
- private:
- // Handles an interval elapsing because of |type|.
- void OnInterval(base::Time now, IntervalType type);
- // A weak pointer to the PrefService object to read and write preferences
- // from. Calling code should ensure this object continues to exist for the
- // lifetime of the DailyEvent object.
- raw_ptr<PrefService> pref_service_;
- // The name of the preference to store the last fired time in.
- // Calling code should ensure this outlives the DailyEvent.
- const char* pref_name_;
- // The name of the histogram to record intervals.
- std::string histogram_name_;
- // A list of observers.
- std::vector<std::unique_ptr<Observer>> observers_;
- // The time that the daily event was last fired.
- base::Time last_fired_;
- };
- } // namespace metrics
- #endif // COMPONENTS_METRICS_DAILY_EVENT_H_
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