[TTS] Add aggregation of CTR metrics to the CS component.

components/contextual_search/browser/weekly_activity_storage.h

Index: components/contextual_search/browser/weekly_activity_storage.h
diff --git a/components/contextual_search/browser/weekly_activity_storage.h b/components/contextual_search/browser/weekly_activity_storage.h
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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.
+
+#ifndef COMPONENTS_CONTEXTUAL_SEARCH_BROWSER_WEEKLY_ACTIVITY_STORAGE_H_
+#define COMPONENTS_CONTEXTUAL_SEARCH_BROWSER_WEEKLY_ACTIVITY_STORAGE_H_
+
+#include <string>
+#include <unordered_map>
+
+#include "base/macros.h"
+
+namespace contextual_search {
+
+// An abstract class that stores weekly user interaction data in device-specific
+// integer storage. Only a limited storage window is supported, set through the
+// constructor. Allows callers to read and write user actions to persistent
+// storage on the device by overriding the ReadStorage and WriteStorage calls.
+// A user view of some UX is an "Impression", and user interaction is considered
+// a "Click" even if the triggering gesture was something else.  Together they
+// produce the Click-Through-Rate, or CTR.
+class WeeklyActivityStorage {
+ public:
+  // Constructs an instance that will manage at least |weeks_needed| weeks of
+  // data.
+  WeeklyActivityStorage(int weeks_needed);
+  virtual ~WeeklyActivityStorage();
+
+  // Advances the accessible storage range to end at the given |week_number|.
+  // Since only a limited number of storage weeks are supported, advancing to
+  // a different week makes data from weeks than the range size inaccessible.
+  // This must be called for each week before reading or writing any data
+  // for that week.
+  // HasData will return true for all the weeks that still have accessible data.
+  void AdvanceToWeek(int week_number);
+
+  // Returns the number of clicks for the given week.
+  int ReadClicks(int week_number);
+  // Writes |value| into the number of clicks for the given |week_number|.
+  void WriteClicks(int week_number, int value);
+
+  // Returns the number of impressions for the given week.
+  int ReadImpressions(int week_number);
+  // Writes |value| into the number of impressions for the given |week_number|.
+  void WriteImpressions(int week_number, int value);
+
+  // Returns whether the given |week_number| has data, based on whether
+  // InitData has ever been called for that week.
+  bool HasData(int week_number);
+  // Clears the click and impression counters for the given |week_number|.
+  void ClearData(int week_number);
+
+  // Reads and returns the value keyed by |storage_bucket|.
+  // If there is no stored value associated with the given bucket then 0 is
+  // returned.
+  virtual int ReadStorage(std::string storage_bucket) = 0;
+  // Overwrites the |value| to the storage bucket keyed by |storage_bucket|,
+  // regardless of whether there is an existing value in the given bucket.
+  virtual void WriteStorage(std::string storage_bucket, int value) = 0;
+
+ private:
+  // Returns the string key of the storage bin for the given week |which_week|.
+  std::string GetWeekKey(int which_week);
+  // Returns the string key for the "clicks" storage bin for the given week
+  // |which_week|.
+  std::string GetWeekClicksKey(int which_week);
+  // Returns the string key for the "impressions" storage bin for the given week
+  // |which_week|.
+  std::string GetWeekImpressionsKey(int which_week);
+
+  // Reads and returns the integer keyed by |storage_key|.
+  // If there is no value for the given key then 0 is returned.
+  int ReadInt(std::string storage_key);
+  // Writes the integer |value| to the storage bucket keyed by |storage_key|.
+  void WriteInt(std::string storage_key, int value);
+
+  // Ensures that activity data is initialized for the given week |which_week|.
+  void EnsureHasActivity(int which_week);
+
+  // The number of weeks of data that this instance needs to support.
+  int weeks_needed_;
+
+  DISALLOW_COPY_AND_ASSIGN(WeeklyActivityStorage);
+};
+
+}  // namespace contextual_search
+
+#endif  // COMPONENTS_CONTEXTUAL_SEARCH_BROWSER_WEEKLY_ACTIVITY_STORAGE_H_