[NTP Snippets] Refactor background scheduling for remote suggestions

components/ntp_snippets/remote/remote_suggestions_provider.h

 // 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.
 
 #ifndef COMPONENTS_NTP_SNIPPETS_REMOTE_REMOTE_SUGGESTIONS_PROVIDER_H_
 #define COMPONENTS_NTP_SNIPPETS_REMOTE_REMOTE_SUGGESTIONS_PROVIDER_H_
 
-#include <cstddef>
-#include <deque>
-#include <map>
 #include <memory>
-#include <set>
-#include <string>
-#include <utility>
-#include <vector>
 
 #include "base/callback_forward.h"
-#include "base/gtest_prod_util.h"
 #include "base/macros.h"
-#include "base/time/clock.h"
-#include "base/time/time.h"
-#include "components/image_fetcher/image_fetcher_delegate.h"
-#include "components/ntp_snippets/category.h"
-#include "components/ntp_snippets/category_status.h"
-#include "components/ntp_snippets/content_suggestion.h"
 #include "components/ntp_snippets/content_suggestions_provider.h"
-#include "components/ntp_snippets/remote/ntp_snippet.h"
-#include "components/ntp_snippets/remote/ntp_snippets_fetcher.h"
-#include "components/ntp_snippets/remote/ntp_snippets_request_params.h"
-#include "components/ntp_snippets/remote/ntp_snippets_scheduler.h"
-#include "components/ntp_snippets/remote/remote_suggestions_status_service.h"
-#include "components/ntp_snippets/remote/request_throttler.h"
-
-class PrefRegistrySimple;
-class PrefService;
-
-namespace gfx {
-class Image;
-}  // namespace gfx
-
-namespace image_fetcher {
-class ImageDecoder;
-class ImageFetcher;
-}  // namespace image_fetcher
 
 namespace ntp_snippets {
 
-class RemoteSuggestionsDatabase;
-class CategoryRanker;
-class UserClassifier;
-
-// CachedImageFetcher takes care of fetching images from the network and caching
-// them in the database.
-// TODO(tschumann): Move into a separate library and inject the
-// CachedImageFetcher into the RemoteSuggestionsProvider. This allows us to get
-// rid of exposing this member for testing and lets us test the caching logic
-// separately.
-class CachedImageFetcher : public image_fetcher::ImageFetcherDelegate {
- public:
-  // |pref_service| and |database| need to outlive the created image fetcher
-  // instance.
-  CachedImageFetcher(std::unique_ptr<image_fetcher::ImageFetcher> image_fetcher,
-                     std::unique_ptr<image_fetcher::ImageDecoder> image_decoder,
-                     PrefService* pref_service,
-                     RemoteSuggestionsDatabase* database);
-  ~CachedImageFetcher() override;
-
-  // Fetches the image for a suggestion. The fetcher will first issue a lookup
-  // to the underlying cache with a fallback to the network.
-  void FetchSuggestionImage(const ContentSuggestion::ID& suggestion_id,
-                            const GURL& image_url,
-                            const ImageFetchedCallback& callback);
-
- private:
-  // image_fetcher::ImageFetcherDelegate implementation.
-  void OnImageDataFetched(const std::string& id_within_category,
-                          const std::string& image_data) override;
-  void OnImageDecodingDone(const ImageFetchedCallback& callback,
-                           const std::string& id_within_category,
-                           const gfx::Image& image);
-  void OnSnippetImageFetchedFromDatabase(
-      const ImageFetchedCallback& callback,
-      const ContentSuggestion::ID& suggestion_id,
-      const GURL& image_url,
-      // SnippetImageCallback requires nonconst reference
-      std::string data);
-  void OnSnippetImageDecodedFromDatabase(
-      const ImageFetchedCallback& callback,
-      const ContentSuggestion::ID& suggestion_id,
-      const GURL& url,
-      const gfx::Image& image);
-  void FetchSnippetImageFromNetwork(const ContentSuggestion::ID& suggestion_id,
-                                    const GURL& url,
-                                    const ImageFetchedCallback& callback);
-
-  std::unique_ptr<image_fetcher::ImageFetcher> image_fetcher_;
-  std::unique_ptr<image_fetcher::ImageDecoder> image_decoder_;
-  RemoteSuggestionsDatabase* database_;
-  // Request throttler for limiting requests to thumbnail images.
-  RequestThrottler thumbnail_requests_throttler_;
-
-  DISALLOW_COPY_AND_ASSIGN(CachedImageFetcher);
-};
+class NTPSnippetsFetcher;
 
 // Retrieves fresh content data (articles) from the server, stores them and
 // provides them as content suggestions.
-// This class is final because it does things in its constructor which make it
-// unsafe to derive from it.
-// TODO(treib): Introduce two-phase initialization and make the class not final?
-class RemoteSuggestionsProvider final : public ContentSuggestionsProvider {
+class RemoteSuggestionsProvider : public ContentSuggestionsProvider {
  public:
-  // |application_language_code| should be a ISO 639-1 compliant string, e.g.
-  // 'en' or 'en-US'. Note that this code should only specify the language, not
-  // the locale, so 'en_US' (English language with US locale) and 'en-GB_US'
-  // (British English person in the US) are not language codes.
-  RemoteSuggestionsProvider(
-      Observer* observer,
-      PrefService* pref_service,
-      const std::string& application_language_code,
-      CategoryRanker* category_ranker,
-      const UserClassifier* user_classifier,
-      NTPSnippetsScheduler* scheduler,
-      std::unique_ptr<NTPSnippetsFetcher> snippets_fetcher,
-      std::unique_ptr<image_fetcher::ImageFetcher> image_fetcher,
-      std::unique_ptr<image_fetcher::ImageDecoder> image_decoder,
-      std::unique_ptr<RemoteSuggestionsDatabase> database,
-      std::unique_ptr<RemoteSuggestionsStatusService> status_service);
+  // TODO(jkrcal): Would be nice to get rid of this another level of statuses.
+  // Maybe possible while refactoring the RemoteSuggestionsStatusService? (and
+  // letting it notify both the SchedulingRemoteSuggestionsProvider and
+  // RemoteSuggestionsProviderImpl or just the scheduling one).
+  enum ProviderStatus { ACTIVE, INACTIVE };

[Bernhard Bauer, 2016/12/21 10:38:42]

Nit: Can you make this an enum class?

[jkrcal, 2016/12/21 11:54:40]

Done.

Why? Is it a general rule in chromium / Zine to always use "enum class" instead
of "enum"?

[Bernhard Bauer, 2016/12/21 12:24:36]

No, but there are some advantages, like the additional namespacing
(RemoteSuggestionsProvider::ProviderStatus::ACTIVE makes a bit more sense to me
than justRemoteSuggestionsProvider::ACTIVE [if it's too long, we could remove
the "Provider" from ProviderStatus, as that's redundant]) or the fact that it
doesn't have implicit conversions to bool. That being said, there are also
disadvantages, so I'm not going to push for either.

[jkrcal, 2016/12/21 12:41:20]

Thanks for the explanation!

+  using ProviderStatusCallback =
+      base::RepeatingCallback<void(ProviderStatus status)>;
+
+  // Callback to notify with the result of a fetch.
+  // TODO(jkrcal): Change to OnceCallback? A OnceCallback does only have a
+  // move-constructor which seems problematic for google mock.
+  using FetchStatusCallback = base::Callback<void(Status status_code)>;
 
   ~RemoteSuggestionsProvider() override;
 
-  static void RegisterProfilePrefs(PrefRegistrySimple* registry);
+  // Set a callback to be notified whenever the status of the provider changes.
+  // The initial change is also notified (switching from an initial undecided
+  // status). If the callback is set after the first change, it is called back
+  // immediately.
+  virtual void SetProviderStatusCallback(
+      std::unique_ptr<ProviderStatusCallback> callback) = 0;
 
-  // Returns whether the service is ready. While this is false, the list of
-  // snippets will be empty, and all modifications to it (fetch, dismiss, etc)
-  // will be ignored.
-  bool ready() const { return state_ == State::READY; }
+  // Fetches snippets from the server for all remote categories and replaces old
+  // snippets by the new ones. The request to the server is performed as an
+  // background request. Background requests are used for actions not triggered
+  // by the user and have lower priority on the server. After the fetch
+  // finished, the provided |callback| will be triggered with the status of the
+  // fetch (unless not nullptr).
+  virtual void RefetchInTheBackground(
+      std::unique_ptr<FetchStatusCallback> callback) = 0;
 
-  // Returns whether the service is initialized. While this is false, some
-  // calls may trigger DCHECKs.
-  bool initialized() const { return ready() || state_ == State::DISABLED; }
+  virtual const NTPSnippetsFetcher* snippets_fetcher_for_testing_and_debugging()
+      const = 0;
 
-  // Fetchs content suggestions from the Content Suggestions server for all
-  // remote categories in the background.
-  void FetchSnippetsInTheBackground();
-
-  // Fetchs content suggestions from the Content Suggestions server for all
-  // remote categories. The request to the server is performed as an interactive
-  // request. Interactive requests are used for actions triggered by the user
-  // and request lower latency processing.
-  void FetchSnippetsForAllCategories();
-
-  // Only used in tests and for debugging in snippets-internal/.
-  // TODO(fhorschig): Remove this getter when there is an interface for the
-  // fetcher that allows better mocks.
-  const NTPSnippetsFetcher* snippets_fetcher() const {
-    return snippets_fetcher_.get();
-  }
-
-  // (Re)schedules the periodic fetching of snippets. If |force| is true, the
-  // tasks will be re-scheduled even if they already exist and have the correct
-  // periods.
-  void RescheduleFetching(bool force);
-
-  // 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 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;
-
-  // Returns the maximum number of snippets that will be shown at once.
-  static int GetMaxSnippetCountForTesting();
-
-  // Available snippets, only for unit tests.
-  // TODO(treib): Get rid of this. Tests should use a fake observer instead.
-  const NTPSnippet::PtrVector& GetSnippetsForTesting(Category category) const {
-    return category_contents_.find(category)->second.snippets;
-  }
-
-  // Dismissed snippets, only for unit tests.
-  const NTPSnippet::PtrVector& GetDismissedSnippetsForTesting(
-      Category category) const {
-    return category_contents_.find(category)->second.dismissed;
-  }
-
-  // Overrides internal clock for testing purposes.
-  void SetClockForTesting(std::unique_ptr<base::Clock> clock) {
-    clock_ = std::move(clock);
-  }
-
-  // TODO(tschumann): remove this method as soon as we inject the fetcher into
-  // the constructor.
-  CachedImageFetcher& GetImageFetcherForTesting() { return image_fetcher_; }
-
- private:
-  friend class RemoteSuggestionsProviderTest;
-
-  FRIEND_TEST_ALL_PREFIXES(RemoteSuggestionsProviderTest,
-                           DontNotifyIfNotAvailable);
-  FRIEND_TEST_ALL_PREFIXES(RemoteSuggestionsProviderTest,
-                           RemoveExpiredDismissedContent);
-  FRIEND_TEST_ALL_PREFIXES(RemoteSuggestionsProviderTest,
-                           RescheduleOnStateChange);
-  FRIEND_TEST_ALL_PREFIXES(RemoteSuggestionsProviderTest, StatusChanges);
-  FRIEND_TEST_ALL_PREFIXES(RemoteSuggestionsProviderTest,
-                           SuggestionsFetchedOnSignInAndSignOut);
-
-  // Possible state transitions:
-  //       NOT_INITED --------+
-  //       /       \          |
-  //      v         v         |
-  //   READY <--> DISABLED    |
-  //       \       /          |
-  //        v     v           |
-  //     ERROR_OCCURRED <-----+
-  enum class State {
-    // The service has just been created. Can change to states:
-    // - DISABLED: After the database is done loading,
-    //             GetStateForDependenciesStatus can identify the next state to
-    //             be DISABLED.
-    // - READY: if GetStateForDependenciesStatus returns it, after the database
-    //          is done loading.
-    // - ERROR_OCCURRED: when an unrecoverable error occurred.
-    NOT_INITED,
-
-    // The service registered observers, timers, etc. and is ready to answer to
-    // queries, fetch snippets... Can change to states:
-    // - DISABLED: when the global Chrome state changes, for example after
-    //             |OnStateChanged| is called and sync is disabled.
-    // - ERROR_OCCURRED: when an unrecoverable error occurred.
-    READY,
-
-    // The service is disabled and unregistered the related resources.
-    // Can change to states:
-    // - READY: when the global Chrome state changes, for example after
-    //          |OnStateChanged| is called and sync is enabled.
-    // - ERROR_OCCURRED: when an unrecoverable error occurred.
-    DISABLED,
-
-    // The service or one of its dependencies encountered an unrecoverable error
-    // and the service can't be used anymore.
-    ERROR_OCCURRED,
-
-    COUNT
-  };
-
-  struct CategoryContent {
-    // The current status of the category.
-    CategoryStatus status = CategoryStatus::INITIALIZING;
-
-    // The additional information about a category.
-    CategoryInfo info;
-
-    // True iff the server returned results in this category in the last fetch.
-    // We never remove categories that the server still provides, but if the
-    // server stops providing a category, we won't yet report it as NOT_PROVIDED
-    // while we still have non-expired snippets in it.
-    bool included_in_last_server_response = true;
-
-    // All currently active suggestions (excl. the dismissed ones).
-    NTPSnippet::PtrVector snippets;
-
-    // All previous suggestions that we keep around in memory because they can
-    // be on some open NTP. We do not persist this list so that on a new start
-    // of Chrome, this is empty.
-    // |archived| is a FIFO buffer with a maximum length.
-    std::deque<std::unique_ptr<NTPSnippet>> archived;
-
-    // Suggestions that the user dismissed. We keep these around until they
-    // expire so we won't re-add them to |snippets| on the next fetch.
-    NTPSnippet::PtrVector dismissed;
-
-    // Returns a non-dismissed snippet with the given |id_within_category|, or
-    // null if none exist.
-    const NTPSnippet* FindSnippet(const std::string& id_within_category) const;
-
-    explicit CategoryContent(const CategoryInfo& info);
-    CategoryContent(CategoryContent&&);
-    ~CategoryContent();
-    CategoryContent& operator=(CategoryContent&&);
-  };
-
-  // Fetches snippets from the server and replaces old snippets by the new ones.
-  // Requests can be marked more important by setting |interactive_request| to
-  // true (such request might circumvent the daily quota for requests, etc.)
-  // Useful for requests triggered by the user.
-  void FetchSnippets(bool interactive_request);
-
-  // Returns the URL of the image of a snippet if it is among the current or
-  // among the archived snippets in the matching category. Returns an empty URL
-  // otherwise.
-  GURL FindSnippetImageUrl(const ContentSuggestion::ID& suggestion_id) const;
-
-  // Callbacks for the RemoteSuggestionsDatabase.
-  void OnDatabaseLoaded(NTPSnippet::PtrVector snippets);
-  void OnDatabaseError();
-
-  // Callback for fetch-more requests with the NTPSnippetsFetcher.
-  void OnFetchMoreFinished(
-      const FetchDoneCallback& fetching_callback,
-      Status status,
-      NTPSnippetsFetcher::OptionalFetchedCategories fetched_categories);
-
-  // Callback for regular fetch requests with the NTPSnippetsFetcher.
-  void OnFetchFinished(
-      bool interactive_request,
-      Status status,
-      NTPSnippetsFetcher::OptionalFetchedCategories fetched_categories);
-
-  // Moves all snippets from |to_archive| into the archive of the |content|.
-  // Clears |to_archive|. As the archive is a FIFO buffer of limited size, this
-  // function will also delete images from the database in case the associated
-  // snippet gets evicted from the archive.
-  void ArchiveSnippets(CategoryContent* content,
-                       NTPSnippet::PtrVector* to_archive);
-
-  // Sanitizes newly fetched snippets -- e.g. adding missing dates and filtering
-  // out incomplete results or dismissed snippets (indicated by |dismissed|).
-  void SanitizeReceivedSnippets(const NTPSnippet::PtrVector& dismissed,
-                                NTPSnippet::PtrVector* snippets);
-
-  // Adds newly available suggestions to |content|.
-  void IntegrateSnippets(CategoryContent* content,
-                         NTPSnippet::PtrVector new_snippets);
-
-  // Dismisses a snippet within a given category content.
-  // Note that this modifies the snippet datastructures of |content|
-  // invalidating iterators.
-  void DismissSuggestionFromCategoryContent(
-      CategoryContent* content,
-      const std::string& id_within_category);
-
-  // Removes expired dismissed snippets from the service and the database.
-  void ClearExpiredDismissedSnippets();
-
-  // Removes images from the DB that are not referenced from any known snippet.
-  // Needs to iterate the whole snippet database -- so do it often enough to
-  // keep it small but not too often as it still iterates over the file system.
-  void ClearOrphanedImages();
-
-  // Clears all stored snippets and updates the observer.
-  void NukeAllSnippets();
-
-  // Completes the initialization phase of the service, registering the last
-  // observers. This is done after construction, once the database is loaded.
-  void FinishInitialization();
-
-  // Triggers a state transition depending on the provided status. This method
-  // is called when a change is detected by |status_service_|.
-  void OnStatusChanged(RemoteSuggestionsStatus old_status,
-                       RemoteSuggestionsStatus new_status);
-
-  // Verifies state transitions (see |State|'s documentation) and applies them.
-  // Also updates the provider status. Does nothing except updating the provider
-  // status if called with the current state.
-  void EnterState(State state);
-
-  // Enables the service. Do not call directly, use |EnterState| instead.
-  void EnterStateReady();
-
-  // Disables the service. Do not call directly, use |EnterState| instead.
-  void EnterStateDisabled();
-
-  // Disables the service permanently because an unrecoverable error occurred.
-  // Do not call directly, use |EnterState| instead.
-  void EnterStateError();
-
-  // Converts the cached snippets in the given |category| to content suggestions
-  // and notifies the observer.
-  void NotifyNewSuggestions(Category category, const CategoryContent& content);
-
-  // Updates the internal status for |category| to |category_status_| and
-  // notifies the content suggestions observer if it changed.
-  void UpdateCategoryStatus(Category category, CategoryStatus status);
-  // Calls UpdateCategoryStatus() for all provided categories.
-  void UpdateAllCategoryStatus(CategoryStatus status);
-
-  // Updates the category info for |category|. If a corresponding
-  // CategoryContent object does not exist, it will be created.
-  // Returns the existing or newly created object.
-  CategoryContent* UpdateCategoryInfo(Category category,
-                                      const CategoryInfo& info);
-
-  void RestoreCategoriesFromPrefs();
-  void StoreCategoriesToPrefs();
-
-  NTPSnippetsRequestParams BuildFetchParams() const;
-
-  void MarkEmptyCategoriesAsLoading();
-
-  State state_;
-
-  PrefService* pref_service_;
-
-  const Category articles_category_;
-
-  std::map<Category, CategoryContent, Category::CompareByID> category_contents_;
-
-  // The ISO 639-1 code of the language used by the application.
-  const std::string application_language_code_;
-
-  // Ranker that orders the categories. Not owned.
-  CategoryRanker* category_ranker_;
-
-  // Classifier that tells us how active the user is. Not owned.
-  const UserClassifier* user_classifier_;
-
-  // Scheduler for fetching snippets. Not owned.
-  NTPSnippetsScheduler* scheduler_;
-
-  // The snippets fetcher.
-  std::unique_ptr<NTPSnippetsFetcher> snippets_fetcher_;
-
-  // The database for persisting snippets.
-  std::unique_ptr<RemoteSuggestionsDatabase> database_;
-  base::TimeTicks database_load_start_;
-
-  // The image fetcher.
-  CachedImageFetcher image_fetcher_;
-
-  // The service that provides events and data about the signin and sync state.
-  std::unique_ptr<RemoteSuggestionsStatusService> status_service_;
-
-  // Set to true if FetchSnippets is called while the service isn't ready.
-  // The fetch will be executed once the service enters the READY state.
-  bool fetch_when_ready_;
-
-  // Set to true if NukeAllSnippets is called while the service isn't ready.
-  // The nuke will be executed once the service finishes initialization or
-  // enters the READY state.
-  bool nuke_when_initialized_;
-
-  // A clock for getting the time. This allows to inject a clock in tests.
-  std::unique_ptr<base::Clock> clock_;
-
-  DISALLOW_COPY_AND_ASSIGN(RemoteSuggestionsProvider);
+ protected:
+  RemoteSuggestionsProvider(Observer* observer);
 };
 
 }  // namespace ntp_snippets
 
 #endif  // COMPONENTS_NTP_SNIPPETS_REMOTE_REMOTE_SUGGESTIONS_PROVIDER_H_