[Offline Pages] Implement OfflinePageStorageManager.

components/offline_pages/offline_page_storage_manager.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_OFFLINE_PAGES_OFFLINE_PAGE_STORAGE_MANAGER_H_
+#define COMPONENTS_OFFLINE_PAGES_OFFLINE_PAGE_STORAGE_MANAGER_H_
+
+#include <stdint.h>
+
+#include <vector>
+
+#include "base/callback.h"
+#include "base/macros.h"
+#include "base/memory/weak_ptr.h"
+#include "components/offline_pages/offline_page_model.h"
+
+namespace offline_pages {
+
+// TODO(romax): Keep this as a default value until I find a way to get
+// storage size in C++. (20MB)
+static const int64_t kDefaultStorageSize = 20 * (1 << 20);
+
+class ClientPolicyController;
+struct OfflinePageItem;
+
+// This class is used for storage management of offline pages. It provides
+// a ClearPagesIfNeeded method which is used to clear expired offline pages
+// based on last_access_time and lifetime policy of its namespace.
+// It has its own throttle mechanism so calling the method would not be
+// guaranteed to clear the pages immediately.
+//
+// OfflinePageModel should own and control the lifecycle of this manager.
+// And this manager would use OfflinePageModel to get/remove pages.
+class OfflinePageStorageManager {
+ public:
+  // Callback used when calling ClearPagesIfNeeded.
+  // int: the number of deleted pages.
+  // DeletePageResult: result of deleting pages.
+  typedef base::Callback<void(int, OfflinePageModel::DeletePageResult)>
+      ClearPageCallback;
+
+  explicit OfflinePageStorageManager(OfflinePageModel* model);
+
+  ~OfflinePageStorageManager();
+
+  // The manager would *try* to clear pages when called. It may not delete any
+  // pages (if clearing condition wasn't satisfied).
+  void ClearPagesIfNeeded(const ClearPageCallback& callback);
+
+ private:
+  // Selects and removes pages that need to be expired. Triggered as a callback
+  // to |GetAllPages|.
+  void ClearExpiredPages(
+      const ClearPageCallback& callback,
+      const OfflinePageModel::MultipleOfflinePageItemResult& pages);
+
+  // Gets offline IDs of all expired pages and return in |offline_ids|.
+  void GetExpiredPageIds(
+      const OfflinePageModel::MultipleOfflinePageItemResult& pages,
+      std::vector<int64_t>& offline_ids);
+
+  // Callback when expired pages has been deleted.
+  void OnExpiredPagesDeleted(const ClearPageCallback& callback,
+                             int pages_to_clear,
+                             OfflinePageModel::DeletePageResult result);
+
+  // Determine if manager should clear pages.
+  bool ShouldClearPages();
+
+  // Return true if |page| is expired.
+  bool IsPageExpired(const OfflinePageItem& page);
+
+  // Not owned.
+  OfflinePageModel* model_;
+
+  // Not owned.
+  ClientPolicyController* policy_controller_;
+
+  bool in_progress_;
+
+  base::WeakPtrFactory<OfflinePageStorageManager> weak_ptr_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(OfflinePageStorageManager);
+};
+
+}  // namespace offline_pages
+
+#endif  // COMPONENTS_OFFLINE_PAGES_OFFLINE_PAGE_STORAGE_MANAGER_H_