[NTP Snippets] FetchMore backend

components/ntp_snippets/remote/ntp_snippets_service.h

Index: components/ntp_snippets/remote/ntp_snippets_service.h
diff --git a/components/ntp_snippets/remote/ntp_snippets_service.h b/components/ntp_snippets/remote/ntp_snippets_service.h
index 6af55c661113107e0ec9025f942c84daa168a137..a330622b8af979adec4f0490734ba8cad514933e 100644
--- a/components/ntp_snippets/remote/ntp_snippets_service.h
+++ b/components/ntp_snippets/remote/ntp_snippets_service.h
@@ -117,6 +117,8 @@ class NTPSnippetsService final : public ContentSuggestionsProvider,
   void DismissSuggestion(const ContentSuggestion::ID& suggestion_id) override;
   void FetchSuggestionImage(const ContentSuggestion::ID& suggestion_id,
                             const ImageFetchedCallback& callback) override;
+  void FetchMore(const Category& category,
+                 FetchedMoreCallback callback) override;
   void ClearHistory(
       base::Time begin,
       base::Time end,
@@ -150,6 +152,7 @@ class NTPSnippetsService final : public ContentSuggestionsProvider,
 
  private:
   friend class NTPSnippetsServiceTest;
+
   FRIEND_TEST_ALL_PREFIXES(NTPSnippetsServiceTest,
                            RemoveExpiredDismissedContent);
   FRIEND_TEST_ALL_PREFIXES(NTPSnippetsServiceTest, RescheduleOnStateChange);
@@ -209,6 +212,8 @@ class NTPSnippetsService final : public ContentSuggestionsProvider,
 
   // Callback for the NTPSnippetsFetcher.
   void OnFetchFinished(
+      bool fetched_more,
+      FetchedMoreCallback fetched_more_callback,
       NTPSnippetsFetcher::OptionalFetchedCategories fetched_categories);
 
   // Moves all snippets from |to_archive| into the archive of the |category|.
@@ -216,8 +221,11 @@ class NTPSnippetsService final : public ContentSuggestionsProvider,
   // short.
   void ArchiveSnippets(Category category, NTPSnippet::PtrVector* to_archive);
 
-  // Replace old snippets in |category| by newly available snippets.
-  void ReplaceSnippets(Category category, NTPSnippet::PtrVector new_snippets);
+  // Adds newly available suggestions in |category| to the available ones.
+  // If |replace_snippets| is set, archives existing suggestions.
+  void IncludeSnippets(const Category& category,
+                       NTPSnippet::PtrVector new_snippets,
+                       bool replace_snippets);
 
   // Removes expired dismissed snippets from the service and the database.
   void ClearExpiredDismissedSnippets();
@@ -275,6 +283,10 @@ class NTPSnippetsService final : public ContentSuggestionsProvider,
   // and notifies the observer.
   void NotifyNewSuggestions(Category category);
 
+  // Converts the cached snippets in the given |category| to content suggestions
+  // and passes them to the |callback|.
+  void NotifyMoreSuggestions(Category category, FetchedMoreCallback callback);
+
   // Updates the internal status for |category| to |category_status_| and
   // notifies the content suggestions observer if it changed.
   void UpdateCategoryStatus(Category category, CategoryStatus status);
@@ -284,6 +296,22 @@ class NTPSnippetsService final : public ContentSuggestionsProvider,
   void RestoreCategoriesFromPrefs();
   void StoreCategoriesToPrefs();
 
+  // Implementation for |FetchSnippets| and |FetchMore| that calls the snippet
+  // fetcher and replaces or adds the fetched snippets depending on the
+  // |fetch_more| parameter.
+  void FetchSnippetsFromHostsImpl(const std::set<std::string>& hosts,
+                                  bool interactive_request,
+                                  bool fetch_more,
+                                  FetchedMoreCallback fetched_more_callback,
+                                  base::Optional<Category> exclusive_category);
+
+  // Returns a set of snippet IDs that should not be fetcheds. These IDs always
+  // include dismissed snippets. If |fetch_more| is set, they include all known
+  // snippet IDs.
+  std::set<std::string> CollectIdsToExclude(bool fetch_more) const;
+
+  void MarkEmptyCategoriesAsLoading();
+
   State state_;
 
   PrefService* pref_service_;