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// 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.
// Provides aggregation of feature usage by tracking impressions and clicks
// over 1-week and 28-day intervals. Impressions are views of some UX and
// clicks are any measured interaction with that UX, yielding CTR -- Click
// Through Rate.
// Used by Contextual Search to record impressions of the Bar and CTR of
// panel opens to use as signals for Tap triggering.
#ifndef COMPONENTS_CONTEXTUAL_SEARCH_BROWSER_CTR_AGGREGATOR_H_
#define COMPONENTS_CONTEXTUAL_SEARCH_BROWSER_CTR_AGGREGATOR_H_
#include <string>
#include "base/gtest_prod_util.h"
#include "base/macros.h"
#include "components/contextual_search/browser/weekly_activity_storage.h"
namespace contextual_search {
// Number of weeks of data needed for 28 days.
const int kNumWeeksNeededFor28DayData = 4;
// Usage: Create a CtrAggregator and start recording impressions or reading
// aggregated data. Get data from the previous week or previous 4-week period
// that ended with the previous week.
// A new week starts at an arbitrary time based on seconds since the Epoch.
// The data from the previous week and previous 28-day period are guaranteed to
// be complete only if the HasPrevious method returns true. If one of the data
// accessors is called when the data is not complete invalid data may be
// returned.
class CtrAggregator {
public:
// Constructs a CtrAggregator using the given |storage| mechanism.
// Data is stored by |storage| typically on persistent device-local storage.
// A callback through the storage interface may occur at construction time,
// so the |storage| must be fully initialized when this constructor is
// called.
CtrAggregator(WeeklyActivityStorage& storage);
~CtrAggregator();
// Records an impression. Records a click if |did_click| is true.
void RecordImpression(bool did_click);
// Returns the number for the current week. Useful for checking when the
// current week changes.
int GetCurrentWeekNumber();
// Returns whether we have the previous week's data for this user.
bool HasPreviousWeekData();
// Gets the number of impressions from the previous week.
// Callers must check if there is previous week's data for this user, or
// invalid data may be returned.
int GetPreviousWeekImpressions();
// Gets the CTR from the previous week.
// Callers must check if there is previous week's data for this user, or
// invalid data may be returned.
float GetPreviousWeekCtr();
// Returns whether we have data from a 28 day period ending in the previous
// week.
bool HasPrevious28DayData();
// Gets the number of impressions from a 28 day period ending in the previous
// week.
// Callers must check if there is previous 28 day data for this user, or
// invalid data may be returned.
int GetPrevious28DayImpressions();
// Gets the CTR from a 28 day period ending in the previous week.
// Callers must check if there is previous 28 day data for this user, or
// invalid data may be returned.
float GetPrevious28DayCtr();
private:
// This implementation uses a fixed number of bins to store integer impression
// and click data for the most recent N weeks, where N = 5 (in order to keep 4
// complete weeks). Another bin keeps track of the current week being
// written. Yet another bin records when data was first stored or accessed so
// we can know when a time period has complete data.
friend class CtrAggregatorTest;
FRIEND_TEST_ALL_PREFIXES(CtrAggregatorTest, SimpleOperationTest);
FRIEND_TEST_ALL_PREFIXES(CtrAggregatorTest, MultiWeekTest);
FRIEND_TEST_ALL_PREFIXES(CtrAggregatorTest, SkipOneWeekTest);
FRIEND_TEST_ALL_PREFIXES(CtrAggregatorTest, SkipThreeWeeksTest);
FRIEND_TEST_ALL_PREFIXES(CtrAggregatorTest, SkipFourWeeksTest);
// Constructs an instance for testing; sets the week.
CtrAggregator(WeeklyActivityStorage& storage, int week_number);
// For testing, increments the current week number by |weeks|.
void IncrementWeek(int weeks);
// Gets the number of clicks from the previous week.
// Callers must check if there is previous week's data for this user, or
// invalid data may be returned.
int GetPreviousWeekClicks();
// Gets the number of clicks from a 28 day period ending in the previous
// week.
// Callers must check if there is previous 28 day data for this user, or
// invalid data may be returned.
int GetPrevious28DayClicks();
// Stores the weekly activity data.
WeeklyActivityStorage& storage_;
// The current week number, expressed as the number of weeks since Epoch.
int week_number_;
DISALLOW_COPY_AND_ASSIGN(CtrAggregator);
};
} // namespace contextual_search
#endif // COMPONENTS_CONTEXTUAL_SEARCH_BROWSER_CTR_AGGREGATOR_H_
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