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

components/contextual_search/browser/weekly_activity_storage.cc

Index: components/contextual_search/browser/weekly_activity_storage.cc
diff --git a/components/contextual_search/browser/weekly_activity_storage.cc b/components/contextual_search/browser/weekly_activity_storage.cc
new file mode 100644
index 0000000000000000000000000000000000000000..485a4b989bb1f4206e5620cd6a04c8aebe6cda7a
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+++ b/components/contextual_search/browser/weekly_activity_storage.cc
@@ -0,0 +1,129 @@
+// 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.
+
+#include "components/contextual_search/browser/weekly_activity_storage.h"
+
+#include <algorithm>  // std::min
+
+#include "base/logging.h"
+
+namespace {
+
+// Keys for ChromePreferenceManager storage of oldest and newest week written.
+const char kOldestWeekWrittenKey[] = "contextual_search_oldest_week";
+const char kNewestWeekWrittenKey[] = "contextual_search_newest_week";
+// Prefixes for ChromePreferenceManager storage keyed by week.
+const char kClicksWeekKeyPrefix[] = "contextual_search_clicks_week_";
+const char kImpressionsWeekKeyPrefix[] = "contextual_search_impressions_week_";
+
+// Used for validation in debug build.  Week numbers are > 2300 as of year 2016.
+const int kReasonableMinWeek = 2000;
+
+}  // namespace
+
+namespace contextual_search {
+
+WeeklyActivityStorage::WeeklyActivityStorage(int weeks_needed) {
+  weeks_needed_ = weeks_needed;
+}
+
+WeeklyActivityStorage::~WeeklyActivityStorage() {}
+
+int WeeklyActivityStorage::ReadClicks(int week_number) {
+  std::string key = GetWeekClicksKey(week_number);
+  return ReadInt(key);
+}
+
+void WeeklyActivityStorage::WriteClicks(int week_number, int value) {
+  std::string key = GetWeekClicksKey(week_number);
+  WriteInt(key, value);
+}
+
+int WeeklyActivityStorage::ReadImpressions(int week_number) {
+  std::string key = GetWeekImpressionsKey(week_number);
+  return ReadInt(key);
+}
+
+void WeeklyActivityStorage::WriteImpressions(int week_number, int value) {
+  std::string key = GetWeekImpressionsKey(week_number);
+  WriteInt(key, value);
+}
+
+bool WeeklyActivityStorage::HasData(int week_number) {
+  return ReadInt(kOldestWeekWrittenKey) <= week_number &&
+         ReadInt(kNewestWeekWrittenKey) >= week_number;
+}
+
+void WeeklyActivityStorage::ClearData(int week_number) {
+  WriteImpressions(week_number, 0);
+  WriteClicks(week_number, 0);
+}
+
+void WeeklyActivityStorage::AdvanceToWeek(int week_number) {
+  EnsureHasActivity(week_number);
+}
+
+// private
+
+std::string WeeklyActivityStorage::GetWeekImpressionsKey(int which_week) {
+  return kImpressionsWeekKeyPrefix + GetWeekKey(which_week);
+}
+
+std::string WeeklyActivityStorage::GetWeekClicksKey(int which_week) {
+  return kClicksWeekKeyPrefix + GetWeekKey(which_week);
+}
+
+// Round-robin implementation:
+// GetWeekKey and EnsureHasActivity are implemented with a round-robin
+// implementation that simply recycles usage of the last N weeks, where N is
+// less than weeks_needed_.
+
+std::string WeeklyActivityStorage::GetWeekKey(int which_week) {
+  return std::to_string(which_week % (weeks_needed_ + 1));
+}
+
+void WeeklyActivityStorage::EnsureHasActivity(int which_week) {
+  DCHECK(which_week > kReasonableMinWeek);
+
+  // If still on the newest week we're done!
+  int newest_week = ReadInt(kNewestWeekWrittenKey);
+  if (newest_week == which_week)
+    return;
+
+  // Update the newest and oldest week written.
+  if (which_week > newest_week) {
+    WriteInt(kNewestWeekWrittenKey, which_week);
+  }
+  int oldest_week = ReadInt(kOldestWeekWrittenKey);
+  if (oldest_week == 0 || oldest_week > which_week)
+    WriteInt(kOldestWeekWrittenKey, which_week);
+
+  // Any stale weeks to update?
+  if (newest_week == 0)
+    return;
+
+  // Moved to some new week beyond the newest previously recorded.
+  // Since we recycle storage we must clear the new week and all that we
+  // may have skipped since our last access.
+  int weeks_to_clear = std::min(which_week - newest_week, weeks_needed_);
+  int week = which_week;
+  while (weeks_to_clear > 0) {
+    WriteInt(GetWeekImpressionsKey(week), 0);
+    WriteInt(GetWeekClicksKey(week), 0);
+    week--;
+    weeks_to_clear--;
+  }
+}
+
+// Storage access bottlenecks
+
+int WeeklyActivityStorage::ReadInt(std::string storage_bucket) {
+  return ReadStorage(storage_bucket);
+}
+
+void WeeklyActivityStorage::WriteInt(std::string storage_bucket, int value) {
+  WriteStorage(storage_bucket, value);
+}
+
+}  // namespace contextual_search