[NTP Snippets] Always show the bookmarks section, but at the end if it's empty

components/ntp_snippets/content_suggestions_service.cc

 // 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.
 
 #include "components/ntp_snippets/content_suggestions_service.h"
 
 #include <algorithm>
 #include <iterator>
 
 #include "base/bind.h"
@@ skipping 161 matching lines @@
   for (const ContentSuggestion& suggestion :
        suggestions_by_category_[category]) {
     id_category_map_.erase(suggestion.id());
   }
 
   for (const ContentSuggestion& suggestion : new_suggestions)
     id_category_map_.insert(std::make_pair(suggestion.id(), category));
 
   suggestions_by_category_[category] = std::move(new_suggestions);
 
+  // The positioning of the bookmarks category depends on whether it's empty.
+  // TODO(treib): Remove this temporary hack, crbug.com/640568.
+  if (category.IsKnownCategory(KnownCategories::BOOKMARKS))
+    SortCategories();
+
   FOR_EACH_OBSERVER(Observer, observers_, OnNewSuggestions(category));
 }
 
 void ContentSuggestionsService::OnCategoryStatusChanged(
     ContentSuggestionsProvider* provider,
     Category category,
     CategoryStatus new_status) {
   if (!IsCategoryStatusAvailable(new_status)) {
     for (const ContentSuggestion& suggestion :
          suggestions_by_category_[category]) {
@@ skipping 28 matching lines @@
     ContentSuggestionsProvider* provider,
     Category category) {
   auto it = providers_by_category_.find(category);
   if (it != providers_by_category_.end()) {
     DCHECK_EQ(it->second, provider);
     return false;
   }
 
   providers_by_category_[category] = provider;
   categories_.push_back(category);
-  std::sort(categories_.begin(), categories_.end(),
-            [this](const Category& left, const Category& right) {
-              return category_factory_.CompareCategories(left, right);
-            });
+  SortCategories();
   if (IsCategoryStatusAvailable(provider->GetCategoryStatus(category))) {
     suggestions_by_category_.insert(
         std::make_pair(category, std::vector<ContentSuggestion>()));
   }
   return true;
 }
 
 bool ContentSuggestionsService::RemoveSuggestionByID(
     Category category,
     const std::string& suggestion_id) {
   id_category_map_.erase(suggestion_id);
   std::vector<ContentSuggestion>* suggestions =
       &suggestions_by_category_[category];
   auto position =
       std::find_if(suggestions->begin(), suggestions->end(),
                    [&suggestion_id](const ContentSuggestion& suggestion) {
                      return suggestion_id == suggestion.id();
                    });
   if (position == suggestions->end())
     return false;
   suggestions->erase(position);
+
+  // The positioning of the bookmarks category depends on whether it's empty.
+  // TODO(treib): Remove this temporary hack, crbug.com/640568.
+  if (category.IsKnownCategory(KnownCategories::BOOKMARKS))
+    SortCategories();
+
   return true;
 }
 
 void ContentSuggestionsService::NotifyCategoryStatusChanged(Category category) {
   FOR_EACH_OBSERVER(
       Observer, observers_,
       OnCategoryStatusChanged(category, GetCategoryStatus(category)));
 }
 
+void ContentSuggestionsService::SortCategories() {
+  auto it = suggestions_by_category_.find(
+      category_factory_.FromKnownCategory(KnownCategories::BOOKMARKS));
+  bool bookmarks_empty =
+      (it == suggestions_by_category_.end() || it->second.empty());
+  std::sort(
+      categories_.begin(), categories_.end(),
+      [this, bookmarks_empty](const Category& left, const Category& right) {
+        // If the bookmarks section is empty, put it at the end.
+        // TODO(treib): This is a temporary hack, see crbug.com/640568.
+        if (bookmarks_empty) {
+          if (left.IsKnownCategory(KnownCategories::BOOKMARKS))
+            return false;
+          if (right.IsKnownCategory(KnownCategories::BOOKMARKS))
+            return true;
+        }
+        return category_factory_.CompareCategories(left, right);
+      });
+}
+
 }  // namespace ntp_snippets