[NTP Snippets] Refactor background scheduling for remote suggestions

components/ntp_snippets/remote/scheduling_remote_suggestions_provider.cc

+// 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/ntp_snippets/remote/scheduling_remote_suggestions_provider.h"
+
+#include <string>
+#include <utility>
+
+#include "components/ntp_snippets/features.h"
+#include "components/ntp_snippets/pref_names.h"
+#include "components/ntp_snippets/remote/persistent_scheduler.h"
+#include "components/ntp_snippets/user_classifier.h"
+#include "components/prefs/pref_registry_simple.h"
+#include "components/prefs/pref_service.h"
+#include "components/variations/variations_associated_data.h"
+
+namespace ntp_snippets {
+
+namespace {
+
+// Default values for fetching intervals, fallback and wifi.
+const double kDefaultFetchingIntervalRareNtpUser[] = {48.0, 24.0};
+const double kDefaultFetchingIntervalActiveNtpUser[] = {24.0, 6.0};
+const double kDefaultFetchingIntervalActiveSuggestionsConsumer[] = {24.0, 6.0};
+
+// Variation parameters than can the default fetching intervals.
+const char* kFetchingIntervalParamNameRareNtpUser[] = {
+    "fetching_interval_hours-fallback-rare_ntp_user",
+    "fetching_interval_hours-wifi-rare_ntp_user"};
+const char* kFetchingIntervalParamNameActiveNtpUser[] = {
+    "fetching_interval_hours-fallback-active_ntp_user",
+    "fetching_interval_hours-wifi-active_ntp_user"};
+const char* kFetchingIntervalParamNameActiveSuggestionsConsumer[] = {
+    "fetching_interval_hours-fallback-active_suggestions_consumer",
+    "fetching_interval_hours-wifi-active_suggestions_consumer"};
+
+base::TimeDelta GetCurrentUpdateInterval(
+    bool is_wifi,
+    UserClassifier::UserClass user_class) {
+  double default_value_hours = 0.0;
+
+  const int index = is_wifi ? 1 : 0;
+  const char* param_name = nullptr;
+  switch (user_class) {
+    case UserClassifier::UserClass::RARE_NTP_USER:
+      default_value_hours = kDefaultFetchingIntervalRareNtpUser[index];
+      param_name = kFetchingIntervalParamNameRareNtpUser[index];
+      break;
+    case UserClassifier::UserClass::ACTIVE_NTP_USER:
+      default_value_hours = kDefaultFetchingIntervalActiveNtpUser[index];
+      param_name = kFetchingIntervalParamNameActiveNtpUser[index];
+      break;
+    case UserClassifier::UserClass::ACTIVE_SUGGESTIONS_CONSUMER:
+      default_value_hours =
+          kDefaultFetchingIntervalActiveSuggestionsConsumer[index];
+      param_name = kFetchingIntervalParamNameActiveSuggestionsConsumer[index];
+      break;
+  }
+
+  double value_hours = variations::GetVariationParamByFeatureAsDouble(
+      ntp_snippets::kArticleSuggestionsFeature, param_name,
+      default_value_hours);
+
+  return base::TimeDelta::FromSecondsD(value_hours * 3600.0);
+}
+
+}  // namespace
+
+SchedulingRemoteSuggestionsProvider::SchedulingRemoteSuggestionsProvider(
+    Observer* observer,
+    CategoryFactory* category_factory,
+    std::unique_ptr<RemoteSuggestionsProvider> provider,
+    PersistentScheduler* persistent_scheduler,
+    const UserClassifier* user_classifier,
+    PrefService* pref_service)
+    : ContentSuggestionsProvider(observer, category_factory),
+      provider_(std::move(provider)),
+      persistent_scheduler_(persistent_scheduler),
+      user_classifier_(user_classifier),
+      pref_service_(pref_service) {
+  DCHECK(user_classifier) << "non-null UserClassifier must be provided";
+  DCHECK(pref_service) << "non-null pref service is needed";
+
+  provider->RegisterActivenessObserver(base::BindRepeating(

[tschumann, 2016/12/15 19:27:00]

doing this in the constructor is tricky -- we might get called back while still
in the constructor which is an issue  in case this class gets subclassed. I
believe the RemoteSuggestionsProvider has the same issue. Let's add a todo and
mark this class final for now. 
(a proper way would be to have the constructor private and a static Create()
function which first constructs the object and then calls an init() function.)

[jkrcal, 2016/12/19 09:40:24]

Added the TODO.

+      &SchedulingRemoteSuggestionsProvider::OnProviderActivenessChanged,
+      base::Unretained(this)));
+}
+
+SchedulingRemoteSuggestionsProvider::~SchedulingRemoteSuggestionsProvider() =
+    default;
+
+// static
+void SchedulingRemoteSuggestionsProvider::RegisterProfilePrefs(
+    PrefRegistrySimple* registry) {
+  registry->RegisterInt64Pref(prefs::kSnippetBackgroundFetchingIntervalWifi, 0);
+  registry->RegisterInt64Pref(prefs::kSnippetBackgroundFetchingIntervalFallback,
+                              0);
+}
+
+void SchedulingRemoteSuggestionsProvider::RescheduleFetching() {
+  // Force the reschedule by stopping and starting it again.
+  StopScheduling();
+  StartScheduling();
+}
+
+void SchedulingRemoteSuggestionsProvider::OnFetchDue() {
+  provider_->RefetchInTheBackground(
+      base::Bind(&SchedulingRemoteSuggestionsProvider::OnFetchCompleted,
+                 base::Unretained(this)));
+}
+
+
+CategoryStatus SchedulingRemoteSuggestionsProvider::GetCategoryStatus(
+    Category category) {
+  return provider_->GetCategoryStatus(category);
+}
+
+CategoryInfo SchedulingRemoteSuggestionsProvider::GetCategoryInfo(
+    Category category) {
+  return provider_->GetCategoryInfo(category);
+}
+
+void SchedulingRemoteSuggestionsProvider::DismissSuggestion(
+    const ContentSuggestion::ID& suggestion_id) {
+  provider_->DismissSuggestion(suggestion_id);
+}
+
+void SchedulingRemoteSuggestionsProvider::FetchSuggestionImage(
+    const ContentSuggestion::ID& suggestion_id,
+    const ImageFetchedCallback& callback) {
+  provider_->FetchSuggestionImage(suggestion_id, callback);
+}
+
+void SchedulingRemoteSuggestionsProvider::Fetch(
+    const Category& category,
+    const std::set<std::string>& known_suggestion_ids,
+    const FetchDoneCallback& callback) {
+  provider_->Fetch(
+      category, known_suggestion_ids,
+      base::Bind(&SchedulingRemoteSuggestionsProvider::FetchFinished,
+                 base::Unretained(this), callback));
+}
+
+void SchedulingRemoteSuggestionsProvider::ReloadSuggestions() {
+  provider_->ReloadSuggestions();
+}
+
+void SchedulingRemoteSuggestionsProvider::ClearHistory(
+    base::Time begin,
+    base::Time end,
+    const base::Callback<bool(const GURL& url)>& filter) {
+  provider_->ClearHistory(begin, end, filter);
+}
+
+void SchedulingRemoteSuggestionsProvider::ClearCachedSuggestions(
+    Category category) {
+  provider_->ClearCachedSuggestions(category);
+}
+
+void SchedulingRemoteSuggestionsProvider::OnSignInStateChanged() {
+  provider_->OnSignInStateChanged();
+}
+
+void SchedulingRemoteSuggestionsProvider::GetDismissedSuggestionsForDebugging(
+    Category category,
+    const DismissedSuggestionsCallback& callback) {
+  provider_->GetDismissedSuggestionsForDebugging(category, callback);
+}
+
+void SchedulingRemoteSuggestionsProvider::ClearDismissedSuggestionsForDebugging(
+    Category category) {
+  provider_->ClearDismissedSuggestionsForDebugging(category);
+}
+
+void SchedulingRemoteSuggestionsProvider::OnProviderActivenessChanged(
+    bool active) {
+  if (active) {
+    StartScheduling();
+  } else {
+    StopScheduling();
+  }
+}
+
+void SchedulingRemoteSuggestionsProvider::StartScheduling() {
+  // The scheduler only exists on Android so far, it's null on other platforms.
+  if (!persistent_scheduler_) {
+    return;
+  }
+
+  FetchingSchedule last_schedule = GetLastFetchingSchedule();
+  FetchingSchedule schedule = GetDesiredFetchingSchedule();
+
+  // Reset the schedule only if the parameters have changed.
+  if (last_schedule != schedule) {
+    ApplyFetchingSchedule(schedule);
+  }
+}
+
+void SchedulingRemoteSuggestionsProvider::StopScheduling() {
+  // The scheduler only exists on Android so far, it's null on other platforms.
+  if (!persistent_scheduler_) {
+    return;
+  }
+
+  // Do not unschedule if already switched off
+  FetchingSchedule last_schedule = GetLastFetchingSchedule();
+  if (last_schedule.is_empty()) {
+    return;
+  }
+
+  persistent_scheduler_->Unschedule();
+
+  StoreLastFetchingSchedule(FetchingSchedule::Empty());
+}
+
+void SchedulingRemoteSuggestionsProvider::ApplyFetchingSchedule(
+    FetchingSchedule schedule) {
+  persistent_scheduler_->Schedule(schedule.interval_wifi,
+                                  schedule.interval_fallback);
+
+  StoreLastFetchingSchedule(schedule);
+}
+
+SchedulingRemoteSuggestionsProvider::FetchingSchedule
+SchedulingRemoteSuggestionsProvider::GetDesiredFetchingSchedule() {
+  UserClassifier::UserClass user_class = user_classifier_->GetUserClass();
+
+  FetchingSchedule schedule;
+  schedule.interval_wifi =
+      GetCurrentUpdateInterval(/*is_wifi=*/true, user_class);
+  schedule.interval_fallback =
+      GetCurrentUpdateInterval(/*is_wifi=*/false, user_class);
+  return schedule;
+}
+
+SchedulingRemoteSuggestionsProvider::FetchingSchedule
+SchedulingRemoteSuggestionsProvider::GetLastFetchingSchedule() const {
+  FetchingSchedule schedule;
+  schedule.interval_wifi = base::TimeDelta::FromInternalValue(
+      pref_service_->GetInt64(prefs::kSnippetBackgroundFetchingIntervalWifi));
+  schedule.interval_fallback =
+      base::TimeDelta::FromInternalValue(pref_service_->GetInt64(
+          prefs::kSnippetBackgroundFetchingIntervalFallback));
+  return schedule;
+}
+
+void SchedulingRemoteSuggestionsProvider::StoreLastFetchingSchedule(
+    FetchingSchedule schedule) {
+  pref_service_->SetInt64(
+      prefs::kSnippetBackgroundFetchingIntervalWifi,
+      schedule.interval_wifi.ToInternalValue());
+  pref_service_->SetInt64(
+      prefs::kSnippetBackgroundFetchingIntervalFallback,
+      schedule.interval_fallback.ToInternalValue());
+}
+
+void SchedulingRemoteSuggestionsProvider::FetchFinished(
+    const FetchDoneCallback& callback,
+    Status status_code,
+    std::vector<ContentSuggestion> suggestions) {
+  // Intercept |status_code| before calling the provided |callback|.

[tschumann, 2016/12/15 19:27:00]

no need for the comment -- it's quite obvious :-)

[jkrcal, 2016/12/19 09:40:24]

Done.

+  OnFetchCompleted(status_code);
+  callback.Run(status_code, std::move(suggestions));
+}
+
+void SchedulingRemoteSuggestionsProvider::OnFetchCompleted(Status status_code) {
+  // The scheduler only exists on Android so far, it's null on other platforms.
+  if (!persistent_scheduler_) {
+    return;
+  }
+
+  if (status_code.status != StatusCode::SUCCESS) {
+    return;
+  }
+
+  // Reschedule after a successful fetch. This resets all currently scheduled
+  // fetches, to make sure the fallback interval triggers only if no wifi fetch
+  // succeeded, and also that we don't do a background fetch immediately after
+  // a user-initiated one.
+  ApplyFetchingSchedule(GetLastFetchingSchedule());
+}
+
+}  // namespace ntp_snippets