FetchMore functionality backend

components/ntp_snippets/remote/ntp_snippets_fetcher.h

Index: components/ntp_snippets/remote/ntp_snippets_fetcher.h
diff --git a/components/ntp_snippets/remote/ntp_snippets_fetcher.h b/components/ntp_snippets/remote/ntp_snippets_fetcher.h
index f5bbf27412cc229053c8a01e15988a324e07afc0..6056f3642106886a2289cf0a06ae075de3db1eb6 100644
--- a/components/ntp_snippets/remote/ntp_snippets_fetcher.h
+++ b/components/ntp_snippets/remote/ntp_snippets_fetcher.h
@@ -65,7 +65,7 @@ class NTPSnippetsFetcher : public OAuth2TokenService::Consumer,
   // 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,
@@ -102,10 +102,6 @@ class NTPSnippetsFetcher : public OAuth2TokenService::Consumer,
       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);
-
   // Fetches snippets from the server. |hosts| restricts the results to a set of
   // hosts, e.g. "www.google.com". If |hosts| is empty, no host restrictions are
   // applied.
@@ -115,15 +111,20 @@ class NTPSnippetsFetcher : public OAuth2TokenService::Consumer,
   //
   // If an ongoing fetch exists, it will be cancelled and a new one started,
   // without triggering an additional callback (i.e. not noticeable by
-  // subscriber of SetCallback()).
+  // the owner of |callback|).

[Marc Treib, 2016/10/20 16:51:39]

This is not accurate anymore: The owner of the previous callback will never be
called back. (This is what I meant with the comment before.)

[fhorschig, 2016/11/02 05:05:27]

As discussed offline, this behavior will change with the followup CL.

   //
   // Fetches snippets only if the daily quota not exceeded, unless
   // |interactive_request| is set to true (use only for user-initiated fetches).
+  //
+  // If an |exclusive_category| was defined, the categories passed to the
+  // callback will only contain this category.
   void FetchSnippetsFromHosts(const std::set<std::string>& hosts,
                               const std::string& language_code,
                               const std::set<std::string>& excluded_ids,
                               int count,
-                              bool interactive_request);
+                              bool interactive_request,
+                              SnippetsAvailableCallback callback,

[Marc Treib, 2016/10/20 16:51:39]

nit: I'd put callback last (all the others are input params, while callback is
essentially an output)

[fhorschig, 2016/11/02 05:05:27]

Done in CL 2466863003.

+                              base::Optional<Category> exclusive_category);
 
   // Debug string representing the status/result of the last fetch attempt.
   const std::string& last_status() const { return last_status_; }
@@ -216,6 +217,7 @@ class NTPSnippetsFetcher : public OAuth2TokenService::Consumer,
   void FetchFinished(OptionalFetchedCategories fetched_categories,
                      FetchResult result,
                      const std::string& extra_message);
+  void FilterCategories(OptionalFetchedCategories* fetched);

[Marc Treib, 2016/10/20 16:51:39]

nit: const (or you could convert it to a non-member helper function in an
anonymous namespace in the .cc)

[Marc Treib, 2016/10/28 14:49:49]

Done.

 
   bool DemandQuotaForRequest(bool interactive_request);
 
@@ -269,6 +271,9 @@ class NTPSnippetsFetcher : public OAuth2TokenService::Consumer,
   // Is the request user initiated?
   bool interactive_request_;
 
+  // Is the request supposed to fetch one category excusively? Which one?

[Marc Treib, 2016/10/20 16:51:40]

Typo: excusively (but I'm not a fan of the question style anyway... maybe "If
set, the request is for this category only; otherwise it's for all
categories."?)

[Marc Treib, 2016/10/28 14:49:49]

Done.

+  base::Optional<Category> exclusive_category_;
+
   // Allow for an injectable tick clock for testing.
   std::unique_ptr<base::TickClock> tick_clock_;