Add request throttler to thumbnail fetching for articles on mobile NTP

components/ntp_snippets/ntp_snippets_service.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_NTP_SNIPPETS_SERVICE_H_
 #define COMPONENTS_NTP_SNIPPETS_NTP_SNIPPETS_SERVICE_H_
 
 #include <stddef.h>
 
 #include <memory>
 #include <set>
 #include <string>
 #include <vector>
 
 #include "base/callback_forward.h"
 #include "base/gtest_prod_util.h"
 #include "base/macros.h"
 #include "base/timer/timer.h"
 #include "components/image_fetcher/image_fetcher_delegate.h"
 #include "components/ntp_snippets/category.h"
 #include "components/ntp_snippets/category_factory.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/ntp_snippet.h"
 #include "components/ntp_snippets/ntp_snippets_fetcher.h"
 #include "components/ntp_snippets/ntp_snippets_scheduler.h"
 #include "components/ntp_snippets/ntp_snippets_status_service.h"
+#include "components/ntp_snippets/request_throttler.h"
 #include "components/suggestions/suggestions_service.h"
 #include "components/sync/driver/sync_service_observer.h"
 
 class PrefRegistrySimple;
 class PrefService;
 class SigninManagerBase;
 
 namespace base {
 class RefCountedMemory;
 class Value;
@@ skipping 18 matching lines @@
 
 namespace ntp_snippets {
 
 class NTPSnippetsDatabase;
 class NTPSnippetsServiceObserver;
 
 // Retrieves fresh content data (articles) from the server, stores them and
 // provides them as content suggestions.
 // TODO(pke): Rename this service to ArticleSuggestionsProvider and move to
 // a subdirectory.
+// TODO(jkrcal): this class grows really, really large. The fact that
+// NTPSnippetService also implements ImageFetcherDelegate adds unnecssary
+// complexity (and after all the Service is conceptually not an
+// ImagerFetcherDeletage ;-)). Instead, the cleaner solution would  be to define
+// a CachedImageFetcher class that handles the caching aspects and looks like an
+// image fetcher to the NTPSnippetService.
 class NTPSnippetsService : public image_fetcher::ImageFetcherDelegate,
                            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.
   NTPSnippetsService(Observer* observer,
                      CategoryFactory* category_factory,
                      PrefService* pref_service,
@@ skipping 13 matching lines @@
   // 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; }
 
   // Returns whether the service is initialized. While this is false, some
   // calls may trigger DCHECKs.
   bool initialized() const { return ready() || state_ == State::DISABLED; }
 
   // Fetches snippets from the server and adds them to the current ones.
-  // Requests can be marked more important by setting |force_request| to true
-  // (such request might circumvent the daily quota for requests, etc.) Useful
-  // for requests triggered by the user.
-  void FetchSnippets(bool force_request);
+  // 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);
 
   // Fetches snippets from the server for specified hosts (overriding
   // suggestions from the suggestion service) and adds them to the current ones.
   // Only called from chrome://snippets-internals, DO NOT USE otherwise!
   // Ignored while |loaded()| is false.
   void FetchSnippetsFromHosts(const std::set<std::string>& hosts,
-                              bool force_request);
+                              bool interactive_request);
 
   const NTPSnippetsFetcher* snippets_fetcher() const {
     return snippets_fetcher_.get();
   }
 
   // Returns a reason why the service is disabled, or DisabledReason::NONE
   // if it's not.
   DisabledReason disabled_reason() const {
     return snippets_status_service_->disabled_reason();
   }
@@ skipping 87 matching lines @@
   void StoreSnippetHostsToPrefs(const std::set<std::string>& hosts);
 
   // Removes the expired snippets (including dismissed) from the service and the
   // database, and schedules another pass for the next expiration.
   void ClearExpiredSnippets();
 
   // Completes the initialization phase of the service, registering the last
   // observers. This is done after construction, once the database is loaded.
   void FinishInitialization();
 
-  void OnSnippetImageFetchedFromDatabase(const std::string& snippet_id,
-                                         const ImageFetchedCallback& callback,
+  void OnSnippetImageFetchedFromDatabase(const ImageFetchedCallback& callback,
+                                         const std::string& snippet_id,
                                          std::string data);
 
-  void OnSnippetImageDecoded(const std::string& snippet_id,
-                             const ImageFetchedCallback& callback,
-                             const gfx::Image& image);
+  void OnSnippetImageDecodedFromDatabase(const ImageFetchedCallback& callback,
+                                         const std::string& snippet_id,
+                                         const gfx::Image& image);
 
   void FetchSnippetImageFromNetwork(const std::string& snippet_id,
                                     const ImageFetchedCallback& callback);
 
+  void OnSnippetImageDecodedFromNetwork(const ImageFetchedCallback& callback,
+                                        const std::string& snippet_id,
+                                        const gfx::Image& image);
+
   // Triggers a state transition depending on the provided reason to be
   // disabled (or lack thereof). This method is called when a change is detected
   // by |snippets_status_service_|.
   void OnDisabledReasonChanged(DisabledReason disabled_reason);
 
   // 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, CategoryStatus status);
 
@@ skipping 58 matching lines @@
 
   // The service that provides events and data about the signin and sync state.
   std::unique_ptr<NTPSnippetsStatusService> snippets_status_service_;
 
   // Set to true if FetchSnippets is called before the database has been loaded.
   // The fetch will be executed after the database load finishes.
   bool fetch_after_load_;
 
   const Category provided_category_;
 
+  // Request throttler for limiting requests to thumbnail images.
+  RequestThrottler thumbnail_requests_throttler_;
+
   DISALLOW_COPY_AND_ASSIGN(NTPSnippetsService);
 };
 
 }  // namespace ntp_snippets
 
 #endif  // COMPONENTS_NTP_SNIPPETS_NTP_SNIPPETS_SERVICE_H_