FetchMore functionality backend

components/ntp_snippets/content_suggestions_provider.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_CONTENT_SUGGESTIONS_PROVIDER_H_
 #define COMPONENTS_NTP_SNIPPETS_CONTENT_SUGGESTIONS_PROVIDER_H_
 
+#include <set>
 #include <string>
 #include <vector>
 
 #include "base/callback_forward.h"
 #include "components/ntp_snippets/category.h"
 #include "components/ntp_snippets/category_info.h"
 #include "components/ntp_snippets/category_status.h"
 #include "components/ntp_snippets/content_suggestion.h"
 
 namespace gfx {
 class Image;
 }  // namespace gfx
 
 namespace ntp_snippets {
 
 // Provides content suggestions from one particular source.
 // A provider can provide suggestions for multiple ContentSuggestionCategories,
 // but for every category that it provides, it will be the only provider in the
 // system which provides suggestions for that category.
 // Providers are created by the ContentSuggestionsServiceFactory and owned and
 // shut down by the ContentSuggestionsService.
 class ContentSuggestionsProvider {
  public:
   using ImageFetchedCallback = base::Callback<void(const gfx::Image&)>;
   using DismissedSuggestionsCallback = base::Callback<void(
       std::vector<ContentSuggestion> dismissed_suggestions)>;
+  using FetchingCallback =
+      base::Callback<void(std::vector<ContentSuggestion> suggestions)>;
 
   // The observer of a provider is notified when new data is available.
   class Observer {
    public:
     // Called when the available content changed.
     // If a provider provides suggestions for multiple categories, this callback
     // is called once per category. The |suggestions| parameter always contains
     // the full list of currently available suggestions for that category, i.e.,
     // an empty list will remove all suggestions from the given category. Note
     // that to clear them from the UI immediately, the provider needs to change
@@ skipping 49 matching lines @@
       const ContentSuggestion::ID& suggestion_id) = 0;
 
   // Fetches the image for the suggestion with the given ID and returns it
   // through the callback. This fetch may occur locally or from the internet.
   // If that suggestion doesn't exist, doesn't have an image or if the fetch
   // fails, the callback gets a null image. The callback will not be called
   // synchronously.
   virtual void FetchSuggestionImage(const ContentSuggestion::ID& suggestion_id,
                                     const ImageFetchedCallback& callback) = 0;
 
+  // Fetches more suggestions for the given category. The new suggestions
+  // will not include any suggestion of the |known_suggestion_ids| sets.
+  // The given |callback| is called with these suggestions, along with all
+  // existing suggestions.
+  virtual void Fetch(const Category& category,
+                     const std::set<std::string>& known_suggestion_ids,
+                     FetchingCallback callback) = 0;
+
   // Removes history from the specified time range where the URL matches the
   // |filter|. The data removed depends on the provider. Note that the
   // data outside the time range may be deleted, for example suggestions, which
   // are based on history from that time range. Providers should immediately
   // clear any data related to history from the specified time range where the
   // URL matches the |filter|.
   virtual void ClearHistory(
       base::Time begin,
       base::Time end,
       const base::Callback<bool(const GURL& url)>& filter) = 0;
@@ skipping 26 matching lines @@
   CategoryFactory* category_factory() const { return category_factory_; }
 
  private:
   Observer* observer_;
   CategoryFactory* category_factory_;
 };
 
 }  // namespace ntp_snippets
 
 #endif  // COMPONENTS_NTP_SNIPPETS_CONTENT_SUGGESTIONS_PROVIDER_H_