[Offline Pages] Add a GCMAppHandler for offline page prefetch.

components/offline_pages/content/suggested_articles_observer.cc

-// Copyright 2017 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/offline_pages/content/suggested_articles_observer.h"
-
-#include <unordered_set>
-
-#include "base/memory/ptr_util.h"
-#include "components/ntp_snippets/category.h"
-#include "components/ntp_snippets/category_status.h"
-#include "components/offline_pages/content/prefetch_service_factory.h"
-#include "components/offline_pages/core/client_namespace_constants.h"
-#include "components/offline_pages/core/offline_page_feature.h"
-#include "components/offline_pages/core/prefetch/prefetch_service_impl.h"
-
-using ntp_snippets::Category;
-using ntp_snippets::ContentSuggestion;
-
-namespace offline_pages {
-
-namespace {
-
-int kOfflinePageSuggestedArticlesObserverUserDataKey;
-
-const ntp_snippets::Category& ArticlesCategory() {
-  static ntp_snippets::Category articles =
-      Category::FromKnownCategory(ntp_snippets::KnownCategories::ARTICLES);
-  return articles;
-}
-
-ClientId CreateClientIDFromSuggestionId(const ContentSuggestion::ID& id) {
-  return ClientId(kSuggestedArticlesNamespace, id.id_within_category());
-}
-
-// The default delegate that contains external dependencies for the Offline Page
-// Suggestions Observer.  This is unused in tests, which implement their own
-// Delegate.
-class DefaultDelegate : public SuggestedArticlesObserver::Delegate {
- public:
-  explicit DefaultDelegate(ntp_snippets::ContentSuggestionsService* service);
-  ~DefaultDelegate() override = default;
-
-  const std::vector<ContentSuggestion>& GetSuggestions(
-      const Category& category) override;
-  PrefetchService* GetPrefetchService(
-      content::BrowserContext* context) override;
-
- private:
-  ntp_snippets::ContentSuggestionsService* service_;
-};
-
-DefaultDelegate::DefaultDelegate(
-    ntp_snippets::ContentSuggestionsService* service)
-    : service_(service) {}
-
-const std::vector<ContentSuggestion>& DefaultDelegate::GetSuggestions(
-    const Category& category) {
-  return service_->GetSuggestionsForCategory(category);
-}
-
-PrefetchService* DefaultDelegate::GetPrefetchService(
-    content::BrowserContext* context) {
-  return PrefetchServiceFactory::GetForBrowserContext(context);
-}
-
-}  // namespace
-
-// static
-void SuggestedArticlesObserver::ObserveContentSuggestionsService(
-    content::BrowserContext* browser_context,
-    ntp_snippets::ContentSuggestionsService* service) {
-  if (!offline_pages::IsPrefetchingOfflinePagesEnabled())
-    return;
-
-  auto suggestions_observer = base::MakeUnique<SuggestedArticlesObserver>(
-      browser_context, base::MakeUnique<DefaultDelegate>(service));
-  service->AddObserver(suggestions_observer.get());
-  service->SetUserData(&kOfflinePageSuggestedArticlesObserverUserDataKey,
-                       std::move(suggestions_observer));
-}
-
-SuggestedArticlesObserver::SuggestedArticlesObserver(
-    content::BrowserContext* browser_context,
-    std::unique_ptr<Delegate> delegate)
-    : browser_context_(browser_context), delegate_(std::move(delegate)) {}
-
-SuggestedArticlesObserver::~SuggestedArticlesObserver() = default;
-
-void SuggestedArticlesObserver::OnNewSuggestions(Category category) {
-  // TODO(dewittj): Change this to check whether a given category is not
-  // a _remote_ category.
-  if (category != ArticlesCategory() ||
-      category_status_ != ntp_snippets::CategoryStatus::AVAILABLE) {
-    return;
-  }
-
-  const std::vector<ContentSuggestion>& suggestions =
-      delegate_->GetSuggestions(ArticlesCategory());
-  if (suggestions.empty())
-    return;
-
-  std::vector<PrefetchService::PrefetchURL> prefetch_urls;
-  for (const ContentSuggestion& suggestion : suggestions) {
-    prefetch_urls.push_back(
-        {CreateClientIDFromSuggestionId(suggestion.id()), suggestion.url()});
-  }
-
-  PrefetchService* service = delegate_->GetPrefetchService(browser_context_);
-  if (service == nullptr) {
-    DVLOG(1) << "PrefetchService unavailable to the "
-                "SuggestedArticlesObserver.";
-    return;
-  }
-  service->AddCandidatePrefetchURLs(prefetch_urls);
-}
-
-void SuggestedArticlesObserver::OnCategoryStatusChanged(
-    Category category,
-    ntp_snippets::CategoryStatus new_status) {
-  if (category != ArticlesCategory() || category_status_ == new_status)
-    return;
-
-  category_status_ = new_status;
-
-  if (category_status_ ==
-          ntp_snippets::CategoryStatus::CATEGORY_EXPLICITLY_DISABLED ||
-      category_status_ ==
-          ntp_snippets::CategoryStatus::ALL_SUGGESTIONS_EXPLICITLY_DISABLED) {
-    PrefetchService* service = delegate_->GetPrefetchService(browser_context_);
-    if (service == nullptr) {
-      DVLOG(1) << "PrefetchService unavailable to the "
-                  "SuggestedArticlesObserver.";
-      return;
-    }
-    service->RemoveAllUnprocessedPrefetchURLs(kSuggestedArticlesNamespace);
-  }
-}
-
-void SuggestedArticlesObserver::OnSuggestionInvalidated(
-    const ContentSuggestion::ID& suggestion_id) {
-  PrefetchService* service = delegate_->GetPrefetchService(browser_context_);
-  if (service == nullptr) {
-    DVLOG(1) << "PrefetchService unavailable to the "
-                "SuggestedArticlesObserver.";
-    return;
-  }
-  service->RemovePrefetchURLsByClientId(
-      CreateClientIDFromSuggestionId(suggestion_id));
-}
-
-void SuggestedArticlesObserver::OnFullRefreshRequired() {
-  PrefetchService* service = delegate_->GetPrefetchService(browser_context_);
-  if (service == nullptr) {
-    DVLOG(1) << "PrefetchService unavailable to the "
-                "SuggestedArticlesObserver.";
-    return;
-  }
-  service->RemoveAllUnprocessedPrefetchURLs(kSuggestedArticlesNamespace);
-  OnNewSuggestions(ArticlesCategory());
-}
-
-void SuggestedArticlesObserver::ContentSuggestionsServiceShutdown() {
-  // No need to do anything here, we will just stop getting events.
-}
-
-}  // namespace offline_pages