chrome/browser/engagement/site_engagement_service.cc

// Copyright 2015 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 "chrome/browser/engagement/site_engagement_service.h"

#include <stddef.h>

#include <algorithm>
#include <utility>

#include "base/bind.h"
#include "base/memory/scoped_refptr.h"
#include "base/metrics/field_trial.h"
#include "base/strings/string_util.h"
#include "base/task/post_task.h"
#include "base/time/clock.h"
#include "base/time/default_clock.h"
#include "base/time/time.h"
#include "base/values.h"
#include "chrome/browser/banners/app_banner_settings_helper.h"
#include "chrome/browser/content_settings/host_content_settings_map_factory.h"
#include "chrome/browser/engagement/site_engagement_helper.h"
#include "chrome/browser/engagement/site_engagement_metrics.h"
#include "chrome/browser/engagement/site_engagement_observer.h"
#include "chrome/browser/engagement/site_engagement_score.h"
#include "chrome/browser/engagement/site_engagement_service_factory.h"
#include "chrome/browser/history/history_service_factory.h"
#include "chrome/browser/profiles/profile.h"
#include "chrome/common/pref_names.h"
#include "components/content_settings/core/browser/host_content_settings_map.h"
#include "components/content_settings/core/common/content_settings_pattern.h"
#include "components/history/core/browser/history_service.h"
#include "components/prefs/pref_service.h"
#include "content/public/browser/browser_task_traits.h"
#include "content/public/browser/browser_thread.h"
#include "content/public/browser/web_contents.h"
#include "url/gurl.h"

#if defined(OS_ANDROID)
#include "chrome/browser/engagement/site_engagement_service_android.h"
#endif

namespace {

const int FOUR_WEEKS_IN_DAYS = 28;

// Global bool to ensure we only update the parameters from variations once.
bool g_updated_from_variations = false;

// Length of time between metrics logging.
const int kMetricsIntervalInMinutes = 60;

// A clock that keeps showing the time it was constructed with.
class StoppedClock : public base::Clock {
 public:
  explicit StoppedClock(base::Time time) : time_(time) {}
  ~StoppedClock() override = default;

 protected:
  // base::Clock:
  base::Time Now() const override { return time_; }

 private:
  const base::Time time_;

  DISALLOW_COPY_AND_ASSIGN(StoppedClock);
};

// Helpers for fetching content settings for one type.
ContentSettingsForOneType GetContentSettingsFromMap(HostContentSettingsMap* map,
                                                    ContentSettingsType type) {
  ContentSettingsForOneType content_settings;
  map->GetSettingsForOneType(type, content_settings::ResourceIdentifier(),
                             &content_settings);
  return content_settings;
}

ContentSettingsForOneType GetContentSettingsFromProfile(
    Profile* profile,
    ContentSettingsType type) {
  return GetContentSettingsFromMap(
      HostContentSettingsMapFactory::GetForProfile(profile), type);
}

// Returns the combined list of origins which either have site engagement
// data stored, or have other settings that would provide a score bonus.
std::set<GURL> GetEngagementOriginsFromContentSettings(
    HostContentSettingsMap* map) {
  std::set<GURL> urls;

  // Fetch URLs of sites with engagement details stored.
  for (const auto& site :
       GetContentSettingsFromMap(map, CONTENT_SETTINGS_TYPE_SITE_ENGAGEMENT)) {
    urls.insert(GURL(site.primary_pattern.ToString()));
  }

  return urls;
}

SiteEngagementScore CreateEngagementScoreImpl(base::Clock* clock,
                                              const GURL& origin,
                                              HostContentSettingsMap* map) {
  return SiteEngagementScore(clock, origin, map);
}

mojom::SiteEngagementDetails GetDetailsImpl(base::Clock* clock,
                                            const GURL& origin,
                                            HostContentSettingsMap* map) {
  return CreateEngagementScoreImpl(clock, origin, map).GetDetails();
}

std::vector<mojom::SiteEngagementDetails> GetAllDetailsImpl(
    base::Clock* clock,
    HostContentSettingsMap* map) {
  std::set<GURL> origins = GetEngagementOriginsFromContentSettings(map);

  std::vector<mojom::SiteEngagementDetails> details;
  details.reserve(origins.size());
  for (const GURL& origin : origins) {
    if (!origin.is_valid())
      continue;
    details.push_back(GetDetailsImpl(clock, origin, map));
  }

  return details;
}

// Takes a scoped_refptr to keep HostContentSettingsMap alive. See
// crbug.com/901287.
std::vector<mojom::SiteEngagementDetails> GetAllDetailsImplInBackground(
    std::unique_ptr<base::Clock> clock,
    scoped_refptr<HostContentSettingsMap> map) {
  return GetAllDetailsImpl(clock.get(), map.get());
}

// Only accept a navigation event for engagement if it is one of:
//  a. direct typed navigation
//  b. clicking on an omnibox suggestion brought up by typing a keyword
//  c. clicking on a bookmark or opening a bookmark app
//  d. a custom search engine keyword search (e.g. Wikipedia search box added as
//  search engine).
bool IsEngagementNavigation(ui::PageTransition transition) {
  return ui::PageTransitionCoreTypeIs(transition, ui::PAGE_TRANSITION_TYPED) ||
         ui::PageTransitionCoreTypeIs(transition,
                                      ui::PAGE_TRANSITION_GENERATED) ||
         ui::PageTransitionCoreTypeIs(transition,
                                      ui::PAGE_TRANSITION_AUTO_BOOKMARK) ||
         ui::PageTransitionCoreTypeIs(transition,
                                      ui::PAGE_TRANSITION_KEYWORD_GENERATED);
}

}  // namespace

const char SiteEngagementService::kEngagementParams[] = "SiteEngagement";

// static
SiteEngagementService* SiteEngagementService::Get(Profile* profile) {
  return SiteEngagementServiceFactory::GetForProfile(profile);
}

// static
double SiteEngagementService::GetMaxPoints() {
  return SiteEngagementScore::kMaxPoints;
}

// static
bool SiteEngagementService::IsEnabled() {
  const std::string group_name =
      base::FieldTrialList::FindFullName(kEngagementParams);
  return !base::StartsWith(group_name, "Disabled",
                           base::CompareCase::SENSITIVE);
}

// static
double SiteEngagementService::GetScoreFromSettings(
    HostContentSettingsMap* settings,
    const GURL& origin) {
  return SiteEngagementScore(base::DefaultClock::GetInstance(), origin,
                             settings)
      .GetTotalScore();
}

SiteEngagementService::SiteEngagementService(Profile* profile)
    : SiteEngagementService(profile, base::DefaultClock::GetInstance()) {
  content::BrowserThread::PostAfterStartupTask(
      FROM_HERE,
      base::CreateSingleThreadTaskRunnerWithTraits(
          {content::BrowserThread::UI}),
      base::BindOnce(&SiteEngagementService::AfterStartupTask,
                     weak_factory_.GetWeakPtr()));

  if (!g_updated_from_variations) {
    SiteEngagementScore::UpdateFromVariations(kEngagementParams);
    g_updated_from_variations = true;
  }
}

SiteEngagementService::~SiteEngagementService() {
  // Clear any observers to avoid dangling pointers back to this object.
  for (auto& observer : observer_list_)
    observer.Observe(nullptr);
}

void SiteEngagementService::Shutdown() {
  history::HistoryService* history = HistoryServiceFactory::GetForProfile(
      profile_, ServiceAccessType::IMPLICIT_ACCESS);
  if (history)
    history->RemoveObserver(this);
}

blink::mojom::EngagementLevel
SiteEngagementService::GetEngagementLevel(const GURL& url) const {
  if (IsLastEngagementStale())
    CleanupEngagementScores(true);

  return CreateEngagementScore(url).GetEngagementLevel();
}

std::vector<mojom::SiteEngagementDetails> SiteEngagementService::GetAllDetails()
    const {
  if (IsLastEngagementStale())
    CleanupEngagementScores(true);

  return GetAllDetailsImpl(
      clock_, HostContentSettingsMapFactory::GetForProfile(profile_));
}

void SiteEngagementService::HandleNotificationInteraction(const GURL& url) {
  if (!ShouldRecordEngagement(url))
    return;

  AddPoints(url, SiteEngagementScore::GetNotificationInteractionPoints());

  MaybeRecordMetrics();
  OnEngagementEvent(nullptr /* web_contents */, url,
                    ENGAGEMENT_NOTIFICATION_INTERACTION);
}

bool SiteEngagementService::IsBootstrapped() const {
  return GetTotalEngagementPoints() >=
         SiteEngagementScore::GetBootstrapPoints();
}

bool SiteEngagementService::IsEngagementAtLeast(
    const GURL& url,
    blink::mojom::EngagementLevel level) const {
  DCHECK_LT(SiteEngagementScore::GetMediumEngagementBoundary(),
            SiteEngagementScore::GetHighEngagementBoundary());
  double score = GetScore(url);
  switch (level) {
    case blink::mojom::EngagementLevel::NONE:
      return true;
    case blink::mojom::EngagementLevel::MINIMAL:
      return score > 0;
    case blink::mojom::EngagementLevel::LOW:
      return score >= 1;
    case blink::mojom::EngagementLevel::MEDIUM:
      return score >= SiteEngagementScore::GetMediumEngagementBoundary();
    case blink::mojom::EngagementLevel::HIGH:
      return score >= SiteEngagementScore::GetHighEngagementBoundary();
    case blink::mojom::EngagementLevel::MAX:
      return score == SiteEngagementScore::kMaxPoints;
  }
  NOTREACHED();
  return false;
}

void SiteEngagementService::AddObserver(SiteEngagementObserver* observer) {
  observer_list_.AddObserver(observer);
}

void SiteEngagementService::RemoveObserver(SiteEngagementObserver* observer) {
  observer_list_.RemoveObserver(observer);
}

void SiteEngagementService::ResetBaseScoreForURL(const GURL& url,
                                                 double score) {
  SiteEngagementScore engagement_score = CreateEngagementScore(url);
  engagement_score.Reset(score, clock_->Now());
  engagement_score.Commit();
}

void SiteEngagementService::SetLastShortcutLaunchTime(
    content::WebContents* web_contents,
    const GURL& url) {
  SiteEngagementScore score = CreateEngagementScore(url);

  // Record the number of days since the last launch in UMA. If the user's clock
  // has changed back in time, set this to 0.
  base::Time now = clock_->Now();
  base::Time last_launch = score.last_shortcut_launch_time();
  if (!last_launch.is_null()) {
    SiteEngagementMetrics::RecordDaysSinceLastShortcutLaunch(
        std::max(0, (now - last_launch).InDays()));
  }

  score.set_last_shortcut_launch_time(now);
  score.Commit();

  OnEngagementEvent(web_contents, url, ENGAGEMENT_WEBAPP_SHORTCUT_LAUNCH);
}

double SiteEngagementService::GetScore(const GURL& url) const {
  return GetDetails(url).total_score;
}

mojom::SiteEngagementDetails SiteEngagementService::GetDetails(
    const GURL& url) const {
  // Ensure that if engagement is stale, we clean things up before fetching the
  // score.
  if (IsLastEngagementStale())
    CleanupEngagementScores(true);

  return GetDetailsImpl(clock_, url,
                        HostContentSettingsMapFactory::GetForProfile(profile_));
}

double SiteEngagementService::GetTotalEngagementPoints() const {
  std::vector<mojom::SiteEngagementDetails> details = GetAllDetails();

  double total_score = 0;
  for (const auto& detail : details)
    total_score += detail.total_score;

  return total_score;
}

void SiteEngagementService::AddPointsForTesting(const GURL& url,
                                                double points) {
  AddPoints(url, points);
}

#if defined(OS_ANDROID)
SiteEngagementServiceAndroid* SiteEngagementService::GetAndroidService() const {
  return android_service_.get();
}

void SiteEngagementService::SetAndroidService(
    std::unique_ptr<SiteEngagementServiceAndroid> android_service) {
  android_service_ = std::move(android_service);
}
#endif

SiteEngagementService::SiteEngagementService(Profile* profile,
                                             base::Clock* clock)
    : profile_(profile), clock_(clock), weak_factory_(this) {
  // May be null in tests.
  history::HistoryService* history = HistoryServiceFactory::GetForProfile(
      profile, ServiceAccessType::IMPLICIT_ACCESS);
  if (history)
    history->AddObserver(this);
}

void SiteEngagementService::AddPoints(const GURL& url, double points) {
  if (points == 0)
    return;

  // Trigger a cleanup and date adjustment if it has been a substantial length
  // of time since *any* engagement was recorded by the service. This will
  // ensure that we do not decay scores when the user did not use the browser.
  if (IsLastEngagementStale())
    CleanupEngagementScores(true);

  SiteEngagementScore score = CreateEngagementScore(url);
  score.AddPoints(points);
  score.Commit();

  SetLastEngagementTime(score.last_engagement_time());
}

void SiteEngagementService::AfterStartupTask() {
  // Check if we need to reset last engagement times on startup - we want to
  // avoid doing this in AddPoints() if possible. It is still necessary to check
  // in AddPoints for people who never restart Chrome, but leave it open and
  // their computer on standby.
  CleanupEngagementScores(IsLastEngagementStale());
}

void SiteEngagementService::CleanupEngagementScores(
    bool update_last_engagement_time) const {
  // We want to rebase last engagement times relative to MaxDecaysPerScore
  // periods of decay in the past.
  base::Time now = clock_->Now();
  base::Time last_engagement_time = GetLastEngagementTime();
  base::Time rebase_time = now - GetMaxDecayPeriod();
  base::Time new_last_engagement_time;

  // If |update_last_engagement_time| is true, we must have either:
  //   a) last_engagement_time is in the future; OR
  //   b) last_engagement_time < rebase_time < now
  DCHECK(!update_last_engagement_time || last_engagement_time >= now ||
         (last_engagement_time < rebase_time && rebase_time < now));

  // Cap |last_engagement_time| at |now| if it is in the future. This ensures
  // that we use sane offsets when a user has adjusted their clock backwards and
  // have a mix of scores prior to and after |now|.
  if (last_engagement_time > now)
    last_engagement_time = now;

  HostContentSettingsMap* settings_map =
      HostContentSettingsMapFactory::GetForProfile(profile_);
  for (const auto& site : GetContentSettingsFromProfile(
           profile_, CONTENT_SETTINGS_TYPE_SITE_ENGAGEMENT)) {
    GURL origin(site.primary_pattern.ToString());

    if (origin.is_valid()) {
      SiteEngagementScore score = CreateEngagementScore(origin);
      if (update_last_engagement_time) {
        // Catch cases of users moving their clocks, or a potential race where
        // a score content setting is written out to prefs, but the updated
        // |last_engagement_time| was not written, as both are lossy
        // preferences. |rebase_time| is strictly in the past, so any score with
        // a last updated time in the future is caught by this branch.
        if (score.last_engagement_time() > rebase_time) {
          score.set_last_engagement_time(now);
        } else if (score.last_engagement_time() > last_engagement_time) {
          // This score is newer than |last_engagement_time|, but older than
          // |rebase_time|. It should still be rebased with no offset as we
          // don't accurately know what the offset should be.
          score.set_last_engagement_time(rebase_time);
        } else {
          // Work out the offset between this score's last engagement time and
          // the last time the service recorded any engagement. Set the score's
          // last engagement time to rebase_time - offset to preserve its state,
          // relative to the rebase date. This ensures that the score will decay
          // the next time it is used, but will not decay too much.
          base::TimeDelta offset =
              last_engagement_time - score.last_engagement_time();
          base::Time rebase_score_time = rebase_time - offset;
          score.set_last_engagement_time(rebase_score_time);
        }

        if (score.last_engagement_time() > new_last_engagement_time)
          new_last_engagement_time = score.last_engagement_time();
        score.Commit();
      }

      if (score.GetTotalScore() >
          SiteEngagementScore::GetScoreCleanupThreshold())
        continue;
    }

    // This origin has a score of 0. Wipe it from content settings.
    settings_map->SetWebsiteSettingDefaultScope(
        origin, GURL(), CONTENT_SETTINGS_TYPE_SITE_ENGAGEMENT,
        content_settings::ResourceIdentifier(), nullptr);
  }

  // Set the last engagement time to be consistent with the scores. This will
  // only occur if |update_last_engagement_time| is true.
  if (!new_last_engagement_time.is_null())
    SetLastEngagementTime(new_last_engagement_time);
}

void SiteEngagementService::MaybeRecordMetrics() {
  base::Time now = clock_->Now();
  if (profile_->IsOffTheRecord() ||
      (!last_metrics_time_.is_null() &&
       (now - last_metrics_time_).InMinutes() < kMetricsIntervalInMinutes)) {
    return;
  }

  // Clean up engagement first before retrieving scores.
  if (IsLastEngagementStale())
    CleanupEngagementScores(true);

  last_metrics_time_ = now;

  // Retrieve details on a background thread as this is expensive. We may end up
  // with minor data inconsistency but this doesn't really matter for metrics
  // purposes.
  //
  // The profile and its KeyedServices are normally destroyed before the
  // TaskScheduler shuts down background threads, so the task needs to hold a
  // strong reference to HostContentSettingsMap (which supports outliving the
  // profile), and needs to avoid using any members of SiteEngagementService
  // (which does not). See https://crbug.com/900022.
  base::PostTaskWithTraitsAndReplyWithResult(
      FROM_HERE,
      {base::TaskPriority::BEST_EFFORT,
       base::TaskShutdownBehavior::SKIP_ON_SHUTDOWN},
      base::BindOnce(
          &GetAllDetailsImplInBackground,
          std::make_unique<StoppedClock>(clock_->Now()),
          base::WrapRefCounted(
              HostContentSettingsMapFactory::GetForProfile(profile_))),
      base::BindOnce(&SiteEngagementService::RecordMetrics,
                     weak_factory_.GetWeakPtr()));
}

void SiteEngagementService::RecordMetrics(
    std::vector<mojom::SiteEngagementDetails> details) {
  std::sort(details.begin(), details.end(),
            [](const mojom::SiteEngagementDetails& lhs,
               const mojom::SiteEngagementDetails& rhs) {
              return lhs.total_score < rhs.total_score;
            });

  int total_origins = details.size();

  double total_engagement = 0;
  int origins_with_max_engagement = 0;
  for (const auto& detail : details) {
    if (detail.total_score == SiteEngagementScore::kMaxPoints)
      ++origins_with_max_engagement;
    total_engagement += detail.total_score;
  }

  int percent_origins_with_max_engagement =
      (total_origins == 0
           ? 0
           : (origins_with_max_engagement * 100) / total_origins);
  double mean_engagement =
      (total_origins == 0 ? 0 : total_engagement / total_origins);

  SiteEngagementMetrics::RecordTotalOriginsEngaged(total_origins);
  SiteEngagementMetrics::RecordTotalSiteEngagement(total_engagement);
  SiteEngagementMetrics::RecordMeanEngagement(mean_engagement);
  SiteEngagementMetrics::RecordMedianEngagement(
      GetMedianEngagementFromSortedDetails(details));
  SiteEngagementMetrics::RecordEngagementScores(details);

  SiteEngagementMetrics::RecordOriginsWithMaxDailyEngagement(
      OriginsWithMaxDailyEngagement());
  SiteEngagementMetrics::RecordOriginsWithMaxEngagement(
      origins_with_max_engagement);
  SiteEngagementMetrics::RecordPercentOriginsWithMaxEngagement(
      percent_origins_with_max_engagement);
}

bool SiteEngagementService::ShouldRecordEngagement(const GURL& url) const {
  return url.SchemeIsHTTPOrHTTPS();
}

base::Time SiteEngagementService::GetLastEngagementTime() const {
  return base::Time::FromInternalValue(
      profile_->GetPrefs()->GetInt64(prefs::kSiteEngagementLastUpdateTime));
}

void SiteEngagementService::SetLastEngagementTime(
    base::Time last_engagement_time) const {
  if (profile_->IsOffTheRecord())
    return;
  profile_->GetPrefs()->SetInt64(prefs::kSiteEngagementLastUpdateTime,
                                 last_engagement_time.ToInternalValue());
}

base::TimeDelta SiteEngagementService::GetMaxDecayPeriod() const {
  return base::TimeDelta::FromHours(
             SiteEngagementScore::GetDecayPeriodInHours()) *
         SiteEngagementScore::GetMaxDecaysPerScore();
}

base::TimeDelta SiteEngagementService::GetStalePeriod() const {
  return GetMaxDecayPeriod() +
         base::TimeDelta::FromHours(
             SiteEngagementScore::GetLastEngagementGracePeriodInHours());
}

double SiteEngagementService::GetMedianEngagementFromSortedDetails(
    const std::vector<mojom::SiteEngagementDetails>& details) const {
  if (details.size() == 0)
    return 0;

  // Calculate the median as the middle value of the sorted engagement scores
  // if there are an odd number of scores, or the average of the two middle
  // scores otherwise.
  size_t mid = details.size() / 2;
  if (details.size() % 2 == 1)
    return details[mid].total_score;
  else
    return (details[mid - 1].total_score + details[mid].total_score) / 2;
}

void SiteEngagementService::HandleMediaPlaying(
    content::WebContents* web_contents,
    bool is_hidden) {
  const GURL& url = web_contents->GetLastCommittedURL();
  if (!ShouldRecordEngagement(url))
    return;

  AddPoints(url, is_hidden ? SiteEngagementScore::GetHiddenMediaPoints()
                           : SiteEngagementScore::GetVisibleMediaPoints());

  MaybeRecordMetrics();
  OnEngagementEvent(
      web_contents, url,
      is_hidden ? ENGAGEMENT_MEDIA_HIDDEN : ENGAGEMENT_MEDIA_VISIBLE);
}

void SiteEngagementService::HandleNavigation(content::WebContents* web_contents,
                                             ui::PageTransition transition) {
  const GURL& url = web_contents->GetLastCommittedURL();
  if (!IsEngagementNavigation(transition) || !ShouldRecordEngagement(url))
    return;

  AddPoints(url, SiteEngagementScore::GetNavigationPoints());

  MaybeRecordMetrics();
  OnEngagementEvent(web_contents, url, ENGAGEMENT_NAVIGATION);
}

void SiteEngagementService::HandleUserInput(content::WebContents* web_contents,
                                            EngagementType type) {
  const GURL& url = web_contents->GetLastCommittedURL();
  if (!ShouldRecordEngagement(url))
    return;

  AddPoints(url, SiteEngagementScore::GetUserInputPoints());

  MaybeRecordMetrics();
  OnEngagementEvent(web_contents, url, type);
}

void SiteEngagementService::OnEngagementEvent(
    content::WebContents* web_contents,
    const GURL& url,
    EngagementType type) {
  SiteEngagementMetrics::RecordEngagement(type);

  double score = GetScore(url);
  for (SiteEngagementObserver& observer : observer_list_)
    observer.OnEngagementEvent(web_contents, url, score, type);
}

bool SiteEngagementService::IsLastEngagementStale() const {
  // Only happens on first run when no engagement has ever been recorded.
  base::Time last_engagement_time = GetLastEngagementTime();
  if (last_engagement_time.is_null())
    return false;

  // Stale is either too *far* back, or any amount *forward* in time. This could
  // occur due to a changed clock, or extended non-use of the browser.
  return (clock_->Now() - last_engagement_time) >= GetStalePeriod() ||
         (clock_->Now() < last_engagement_time);
}

void SiteEngagementService::OnURLsDeleted(
    history::HistoryService* history_service,
    const history::DeletionInfo& deletion_info) {
  std::multiset<GURL> origins;
  for (const history::URLRow& row : deletion_info.deleted_rows())
    origins.insert(row.url().GetOrigin());

  UpdateEngagementScores(origins, deletion_info.is_from_expiration(),
                         deletion_info.deleted_urls_origin_map());
}

SiteEngagementScore SiteEngagementService::CreateEngagementScore(
    const GURL& origin) const {
  // If we are in incognito, |settings| will automatically have the data from
  // the original profile migrated in, so all engagement scores in incognito
  // will be initialised to the values from the original profile.
  return CreateEngagementScoreImpl(
      clock_, origin, HostContentSettingsMapFactory::GetForProfile(profile_));
}

int SiteEngagementService::OriginsWithMaxDailyEngagement() const {
  int total_origins = 0;

  // We cannot call GetScoreMap as we need the score objects, not raw scores.
  for (const auto& site : GetContentSettingsFromProfile(
           profile_, CONTENT_SETTINGS_TYPE_SITE_ENGAGEMENT)) {
    GURL origin(site.primary_pattern.ToString());

    if (!origin.is_valid())
      continue;

    if (CreateEngagementScore(origin).MaxPointsPerDayAdded())
      ++total_origins;
  }

  return total_origins;
}

void SiteEngagementService::UpdateEngagementScores(
    const std::multiset<GURL>& deleted_origins,
    bool expired,
    const history::OriginCountAndLastVisitMap& remaining_origins) {
  // The most in-the-past option in the Clear Browsing Dialog aside from "all
  // time" is 4 weeks ago. Set the last updated date to 4 weeks ago for origins
  // where we can't find a valid last visit date.
  base::Time now = clock_->Now();
  base::Time four_weeks_ago =
      now - base::TimeDelta::FromDays(FOUR_WEEKS_IN_DAYS);

  HostContentSettingsMap* settings_map =
      HostContentSettingsMapFactory::GetForProfile(profile_);

  for (const auto& origin_to_count : remaining_origins) {
    GURL origin = origin_to_count.first;
    // It appears that the history service occasionally sends bad URLs to us.
    // See crbug.com/612881.
    if (!origin.is_valid())
      continue;

    int remaining = origin_to_count.second.first;
    base::Time last_visit = origin_to_count.second.second;
    int deleted = deleted_origins.count(origin);

    // Do not update engagement scores if the deletion was an expiry, but the
    // URL still has entries in history.
    if ((expired && remaining != 0) || deleted == 0)
      continue;

    // Remove origins that have no urls left.
    if (remaining == 0) {
      settings_map->SetWebsiteSettingDefaultScope(
          origin, GURL(), CONTENT_SETTINGS_TYPE_SITE_ENGAGEMENT,
          content_settings::ResourceIdentifier(), nullptr);
      continue;
    }

    // Remove engagement proportional to the urls expired from the origin's
    // entire history.
    double proportion_remaining =
        static_cast<double>(remaining) / (remaining + deleted);
    if (last_visit.is_null() || last_visit > now)
      last_visit = four_weeks_ago;

    // At this point, we are going to proportionally decay the origin's
    // engagement, and reset its last visit date to the last visit to a URL
    // under the origin in history. If this new last visit date is long enough
    // in the past, the next time the origin's engagement is accessed the
    // automatic decay will kick in - i.e. a double decay will have occurred.
    // To prevent this, compute the decay that would have taken place since the
    // new last visit and add it to the engagement at this point. When the
    // engagement is next accessed, it will decay back to the proportionally
    // reduced value rather than being decayed once here, and then once again
    // when it is next accessed.
    // TODO(703848): Move the proportional decay logic into SiteEngagementScore,
    // so it can decay raw_score_ directly, without the double-decay issue.
    SiteEngagementScore engagement_score = CreateEngagementScore(origin);

    double new_score = proportion_remaining * engagement_score.GetTotalScore();
    int hours_since_engagement = (now - last_visit).InHours();
    int periods =
        hours_since_engagement / SiteEngagementScore::GetDecayPeriodInHours();
    new_score += periods * SiteEngagementScore::GetDecayPoints();
    new_score *= pow(1.0 / SiteEngagementScore::GetDecayProportion(), periods);

    double score = std::min(SiteEngagementScore::kMaxPoints, new_score);
    engagement_score.Reset(score, last_visit);
    if (!engagement_score.last_shortcut_launch_time().is_null() &&
        engagement_score.last_shortcut_launch_time() > last_visit) {
      engagement_score.set_last_shortcut_launch_time(last_visit);
    }

    engagement_score.Commit();
  }

  SetLastEngagementTime(now);
}