[Remote suggestions] Refactor the scheduler

components/ntp_snippets/remote/scheduling_remote_suggestions_provider.h

-// 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_NTP_SNIPPETS_REMOTE_SCHEDULING_REMOTE_SUGGESTIONS_PROVIDER_H_
-#define COMPONENTS_NTP_SNIPPETS_REMOTE_SCHEDULING_REMOTE_SUGGESTIONS_PROVIDER_H_
-
-#include <memory>
-#include <set>
-#include <string>
-#include <utility>
-#include <vector>
-
-#include "base/macros.h"
-#include "base/time/time.h"
-#include "components/ntp_snippets/content_suggestions_provider.h"
-#include "components/ntp_snippets/remote/persistent_scheduler.h"
-#include "components/ntp_snippets/remote/remote_suggestions_provider.h"
-#include "components/ntp_snippets/remote/remote_suggestions_scheduler.h"
-#include "components/ntp_snippets/remote/request_throttler.h"
-#include "components/web_resource/eula_accepted_notifier.h"
-
-class PrefRegistrySimple;
-class PrefService;
-
-namespace base {
-class Clock;
-}
-
-namespace ntp_snippets {
-
-struct Status;
-class EulaState;
-class UserClassifier;
-
-// A wrapper around RemoteSuggestionsProvider that introduces periodic fetching.
-//
-// The class initiates fetches on its own in these situations:
-//  - initial fetch when the provider is constructed and we have no suggestions;
-//  - regular fetches according to its schedule.
-// TODO(jkrcal): After soft fetch on Chrome startup is introduced, remove
-// the initial fetch completely.
-//
-// The class also needs to understand when last fetch trials and successful
-// fetches happen and thus it intercepts following interactive fetch requests:
-//  - Fetch() - after "More" button of a remote section is pressed in the UI;
-// TODO(jkrcal): Clarify what Fetch() should do for this provider and maybe stop
-// intercepting it.
-// TODO(jkrcal): Intercept also ReloadSuggestions() call (after the user swipes
-// away everything incl. all empty sections and presses "More"); Not done in the
-// first shot because  it implements a public interface function without any
-// callback.
-// This class is final because it does things in its constructor which make it
-// unsafe to derive from it.
-// TODO(jkrcal): Introduce two-phase initialization and make the class not
-// final? (see the same comment for RemoteSuggestionsProvider)
-// TODO(jkrcal): Change the interface to ContentSuggestionsProvider. We do not
-// need any special functionality, all special should be exposed in the
-// Scheduler interface. crbug.com/695447
-class SchedulingRemoteSuggestionsProvider final
-    : public RemoteSuggestionsProvider,
-      public RemoteSuggestionsScheduler {
- public:
-  SchedulingRemoteSuggestionsProvider(
-      Observer* observer,
-      std::unique_ptr<RemoteSuggestionsProvider> provider,
-      PersistentScheduler* persistent_scheduler,
-      const UserClassifier* user_classifier,
-      PrefService* profile_prefs,
-      PrefService* local_state_prefs,
-      std::unique_ptr<base::Clock> clock);
-
-  ~SchedulingRemoteSuggestionsProvider() override;
-
-  static void RegisterProfilePrefs(PrefRegistrySimple* registry);
-
-  // RemoteSuggestionsScheduler implementation.
-  void OnProviderActivated() override;
-  void OnProviderDeactivated() override;
-  void OnSuggestionsCleared() override;
-  void OnHistoryCleared() override;
-  void RescheduleFetching() override;
-  void OnPersistentSchedulerWakeUp() override;
-  void OnBrowserForegrounded() override;
-  void OnBrowserColdStart() override;
-  void OnNTPOpened() override;
-
-  // RemoteSuggestionsProvider implementation.
-  void RefetchInTheBackground(
-      std::unique_ptr<FetchStatusCallback> callback) override;
-  const RemoteSuggestionsFetcher* suggestions_fetcher_for_debugging()
-      const override;
-
-  // ContentSuggestionsProvider implementation.
-  CategoryStatus GetCategoryStatus(Category category) override;
-  CategoryInfo GetCategoryInfo(Category category) override;
-  void DismissSuggestion(const ContentSuggestion::ID& suggestion_id) override;
-  void FetchSuggestionImage(const ContentSuggestion::ID& suggestion_id,
-                            const ImageFetchedCallback& callback) override;
-  void Fetch(const Category& category,
-             const std::set<std::string>& known_suggestion_ids,
-             const FetchDoneCallback& callback) override;
-  void ReloadSuggestions() override;
-  void ClearHistory(
-      base::Time begin,
-      base::Time end,
-      const base::Callback<bool(const GURL& url)>& filter) override;
-  void ClearCachedSuggestions(Category category) override;
-  void OnSignInStateChanged() override;
-  void GetDismissedSuggestionsForDebugging(
-      Category category,
-      const DismissedSuggestionsCallback& callback) override;
-  void ClearDismissedSuggestionsForDebugging(Category category) override;
-
- private:
-  // Abstract description of the fetching schedule.
-  struct FetchingSchedule {
-    static FetchingSchedule Empty();
-    bool operator==(const FetchingSchedule& other) const;
-    bool operator!=(const FetchingSchedule& other) const;
-    bool is_empty() const;
-
-    base::TimeDelta interval_persistent_wifi;
-    base::TimeDelta interval_persistent_fallback;
-    base::TimeDelta interval_soft_on_usage_event;
-    base::TimeDelta interval_soft_on_ntp_opened;
-  };
-
-  enum class TriggerType;
-
-  // After the call, updates will be scheduled in the future. Idempotent, can be
-  // run any time later without impacting the current schedule.
-  // If you want to enforce rescheduling, call Unschedule() and then Schedule().
-  void StartScheduling();
-
-  // After the call, no updates will happen before another call to Schedule().
-  // Idempotent, can be run any time later without impacting the current
-  // schedule.
-  void StopScheduling();
-
-  // Trigger a background refetch for the given |trigger| if enabled.
-  void RefetchInTheBackgroundIfEnabled(TriggerType trigger);
-
-  // Checks whether it is time to perform a soft background fetch, according to
-  // |schedule|.
-  bool ShouldRefetchInTheBackgroundNow(TriggerType trigger);
-
-  // Returns whether background fetching (for the given |trigger|) is disabled.
-  bool BackgroundFetchesDisabled(TriggerType trigger) const;
-
-  // Returns true if quota is available for another request.
-  bool AcquireQuota(bool interactive_request);
-
-  // Callback after Fetch is completed.
-  void FetchFinished(const FetchDoneCallback& callback,
-                     Status fetch_status,
-                     std::vector<ContentSuggestion> suggestions);
-
-  // Callback after RefetchInTheBackground is completed.
-  void RefetchInTheBackgroundFinished(
-      std::unique_ptr<FetchStatusCallback> callback,
-      Status fetch_status);
-
-  // Common function to call after a fetch of any type is finished.
-  void OnFetchCompleted(Status fetch_status);
-
-  // Clears the time of the last fetch so that the provider is ready to make a
-  // soft fetch at any later time (upon a trigger).
-  void ClearLastFetchAttemptTime();
-
-  FetchingSchedule GetDesiredFetchingSchedule() const;
-
-  // Load and store |schedule_|.
-  void LoadLastFetchingSchedule();
-  void StoreFetchingSchedule();
-
-  // Applies the persistent schedule given by |schedule_|.
-  void ApplyPersistentFetchingSchedule();
-
-  // Gets enabled trigger types from the variation parameter.
-  std::set<TriggerType> GetEnabledTriggerTypes();
-
-  // Gets trigger types enabled by default.
-  std::set<TriggerType> GetDefaultEnabledTriggerTypes();
-
-  // Interface for doing all the actual work (apart from scheduling).
-  std::unique_ptr<RemoteSuggestionsProvider> provider_;
-
-  // Interface for scheduling hard fetches, OS dependent. Not owned, may be
-  // null.
-  PersistentScheduler* persistent_scheduler_;
-
-  FetchingSchedule schedule_;
-  bool background_fetch_in_progress_;
-
-  // Used to adapt the schedule based on usage activity of the user. Not owned.
-  const UserClassifier* user_classifier_;
-
-  // Request throttlers for limiting requests for different classes of users.
-  RequestThrottler request_throttler_rare_ntp_user_;
-  RequestThrottler request_throttler_active_ntp_user_;
-  RequestThrottler request_throttler_active_suggestions_consumer_;
-
-  // We should not fetch in background before EULA gets accepted.
-  std::unique_ptr<EulaState> eula_state_;
-
-  PrefService* profile_prefs_;
-  std::unique_ptr<base::Clock> clock_;
-  std::set<SchedulingRemoteSuggestionsProvider::TriggerType> enabled_triggers_;
-
-  base::Time background_fetches_allowed_after_;
-
-  DISALLOW_COPY_AND_ASSIGN(SchedulingRemoteSuggestionsProvider);
-};
-
-}  // namespace ntp_snippets
-
-#endif  // COMPONENTS_NTP_SNIPPETS_REMOTE_SCHEDULING_REMOTE_SUGGESTIONS_PROVIDER_H_