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

components/contextual_search/browser/ctr_aggregator.cc

Index: components/contextual_search/browser/ctr_aggregator.cc
diff --git a/components/contextual_search/browser/ctr_aggregator.cc b/components/contextual_search/browser/ctr_aggregator.cc
new file mode 100644
index 0000000000000000000000000000000000000000..83adb95ecd06efd232d0cf1372abc5d91f106ab8
--- /dev/null
+++ b/components/contextual_search/browser/ctr_aggregator.cc
@@ -0,0 +1,114 @@
+// 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/ctr_aggregator.h"
+
+#include "base/numerics/safe_conversions.h"
+#include "base/time/time.h"
+
+namespace {
+
+const double kSecondsPerWeek =
+    base::Time::kMicrosecondsPerWeek / base::Time::kMicrosecondsPerSecond;
+// Used for validation in debug build.  Week numbers are > 2300 as of year 2016.
+const int kReasonableMinWeek = 2000;
+
+}  // namespace
+
+namespace contextual_search {
+
+CTRAggregator::CTRAggregator(WeeklyActivityStorage& storage)
+    : storage_(storage) {
+  base::Time now = base::Time::NowFromSystemTime();
+  double now_in_seconds = now.ToDoubleT();
+  week_number_ = now_in_seconds / kSecondsPerWeek;
+  DCHECK(week_number_ >= kReasonableMinWeek);
+  // NOTE: This initialization may callback into the storage implementation so
+  // that needs to be fully initialized when constructing this aggregator.
+  storage_.InitActivity(week_number_);
+}
+
+// Testing only
+CTRAggregator::CTRAggregator(WeeklyActivityStorage& storage, int week_number)
+    : storage_(storage), week_number_(week_number) {
+  storage_.InitActivity(week_number_);
+}
+
+CTRAggregator::~CTRAggregator() {}
+
+void CTRAggregator::RecordImpression(bool did_click) {
+  storage_.WriteImpressions(week_number_,
+                            1 + storage_.ReadImpressions(week_number_));
+  if (did_click)
+    storage_.WriteClicks(week_number_, 1 + storage_.ReadClicks(week_number_));
+}
+
+bool CTRAggregator::HasPreviousWeekData() {
+  return storage_.HasActivity(week_number_ - 1);
+}
+
+int CTRAggregator::GetPreviousWeekImpressions() {
+  return storage_.ReadImpressions(week_number_ - 1);
+}
+
+float CTRAggregator::GetPreviousWeekCTR() {
+  if (!HasPreviousWeekData())
+    return NAN;
+
+  int clicks = GetPreviousWeekClicks();
+  int impressions = GetPreviousWeekImpressions();
+  if (impressions == 0)
+    return 0.0;
+  return base::saturated_cast<float>(clicks) / impressions;
+}
+
+bool CTRAggregator::HasPrevious28DayData() {
+  for (int previous = 1; previous <= kNumWeeksNeededFor28DayData; previous++) {
+    if (!storage_.HasActivity(week_number_ - previous))
+      return false;
+  }
+  return true;
+}
+
+float CTRAggregator::GetPrevious28DayCTR() {
+  if (!HasPrevious28DayData())
+    return NAN;
+
+  int clicks = GetPrevious28DayClicks();
+  int impressions = GetPrevious28DayImpressions();
+  if (impressions == 0)
+    return 0.0;
+  return base::saturated_cast<float>(clicks) / impressions;
+}
+
+int CTRAggregator::GetPrevious28DayImpressions() {
+  int impressions = 0;
+  for (int previous = 1; previous <= kNumWeeksNeededFor28DayData; previous++) {
+    impressions += storage_.ReadImpressions(week_number_ - previous);
+  }
+  return impressions;
+}
+
+// private
+
+int CTRAggregator::GetPreviousWeekClicks() {
+  return storage_.ReadClicks(week_number_ - 1);
+}
+
+int CTRAggregator::GetPrevious28DayClicks() {
+  int clicks = 0;
+  for (int previous = 1; previous <= kNumWeeksNeededFor28DayData; previous++) {
+    clicks += storage_.ReadClicks(week_number_ - previous);
+  }
+  return clicks;
+}
+
+// Testing only
+
+void CTRAggregator::IncrementWeek(int weeks) {
+  week_number_ += weeks;
+  storage_.InitActivity(week_number_);
+}
+
+}  // namespace contextual_search