FetchMore functionality backend

components/ntp_snippets/remote/ntp_snippets_fetcher.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_NTP_SNIPPETS_FETCHER_H_
 #define COMPONENTS_NTP_SNIPPETS_REMOTE_NTP_SNIPPETS_FETCHER_H_
 
 #include <memory>
 #include <set>
 #include <string>
@@ skipping 47 matching lines @@
     ~FetchedCategory();                             // = default, in .cc
     FetchedCategory& operator=(FetchedCategory&&);  // = default, in .cc
   };
   using FetchedCategoriesVector = std::vector<FetchedCategory>;
   using OptionalFetchedCategories = base::Optional<FetchedCategoriesVector>;
 
   // |snippets| contains parsed snippets if a fetch succeeded. If problems
   // occur, |snippets| contains no value (no actual vector in base::Optional).
   // Error details can be retrieved using last_status().
   using SnippetsAvailableCallback =
-      base::Callback<void(OptionalFetchedCategories fetched_categories)>;
+      base::OnceCallback<void(OptionalFetchedCategories fetched_categories)>;
 
   // Enumeration listing all possible outcomes for fetch attempts. Used for UMA
   // histograms, so do not change existing values. Insert new values at the end,
   // and update the histogram definition.
   enum class FetchResult {
     SUCCESS,
     DEPRECATED_EMPTY_HOSTS,
     URL_REQUEST_STATUS_ERROR,
     HTTP_ERROR,
     JSON_PARSE_ERROR,
@@ skipping 26 matching lines @@
     // A set of suggestion IDs that should not be returned again.
     std::set<std::string> excluded_ids;
 
     // Maximum number of snippets to fetch.
     int count_to_fetch = 0;
 
     // Whether this is an interactive request, i.e. triggered by an explicit
     // user action. Typically, non-interactive requests are subject to a daily
     // quota.
     bool interactive_request = false;
+
+    // If set, the request is returning this category only; otherwise all
+    // available categories are returned.
+    base::Optional<Category> exclusive_category;
+
+    // The callback to notify when new snippets get fetched.
+    SnippetsAvailableCallback snippets_available_callback;
   };
 
   NTPSnippetsFetcher(
       SigninManagerBase* signin_manager,
       OAuth2TokenService* token_service,
       scoped_refptr<net::URLRequestContextGetter> url_request_context_getter,
       PrefService* pref_service,
       CategoryFactory* category_factory,
       translate::LanguageModel* language_model,
       const ParseJSONCallback& parse_json_callback,
       const std::string& api_key,
       const UserClassifier* user_classifier);
   ~NTPSnippetsFetcher() override;
 
-  // Set a callback that is called when a new set of snippets are downloaded,
-  // overriding any previously set callback.
-  void SetCallback(const SnippetsAvailableCallback& callback);
-
   // Initiates a fetch from the server. When done (successfully or not), calls
-  // the subscriber of SetCallback().
+  // callback that was passed along with the |params|.
   //
   // If an ongoing fetch exists, it will be silently abandoned and a new one
   // started, without triggering an additional callback (i.e. the callback will
   // only be called once).
   void FetchSnippets(const Params& params);
 
   // Debug string representing the status/result of the last fetch attempt.
   const std::string& last_status() const { return last_status_; }
 
   // Returns the last JSON fetched from the server.
@@ skipping 75 matching lines @@
   // URLFetcherDelegate implementation.
   void OnURLFetchComplete(const net::URLFetcher* source) override;
 
   bool JsonToSnippets(const base::Value& parsed,
                       FetchedCategoriesVector* categories);
   void OnJsonParsed(std::unique_ptr<base::Value> parsed);
   void OnJsonError(const std::string& error);
   void FetchFinished(OptionalFetchedCategories fetched_categories,
                      FetchResult result,
                      const std::string& extra_message);
+  void FilterCategories(OptionalFetchedCategories* fetched) const;
 
   bool DemandQuotaForRequest(bool interactive_request);
 
   // Authentication for signed-in users.
   SigninManagerBase* signin_manager_;
   OAuth2TokenService* token_service_;
   std::unique_ptr<OAuth2TokenService::Request> oauth_request_;
   bool waiting_for_refresh_token_ = false;
 
   // When a token request gets canceled, we want to retry once.
@@ skipping 23 matching lines @@
   std::unique_ptr<base::TickClock> tick_clock_;
 
   // Classifier that tells us how active the user is. 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_;
 
-  // The callback to notify when new snippets get fetched.
-  SnippetsAvailableCallback snippets_available_callback_;
-
   // The parameters for the current request.
   Params params_;
 
   // The fetcher for downloading the snippets. Only non-null if a fetch is
   // currently ongoing.
   std::unique_ptr<net::URLFetcher> url_fetcher_;
 
   // When the current request was started, for logging purposes.
   base::TimeTicks fetch_start_time_;
 
   // Info on the last finished fetch.
   std::string last_status_;
   std::string last_fetch_json_;
 
   base::WeakPtrFactory<NTPSnippetsFetcher> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(NTPSnippetsFetcher);
 };
 }  // namespace ntp_snippets
 
 #endif  // COMPONENTS_NTP_SNIPPETS_REMOTE_NTP_SNIPPETS_FETCHER_H_