[Offline Pages] Updated clearing logic in storage manager.

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 "base/time/time.h"
+#include "components/offline_pages/archive_manager.h"
 #include "components/offline_pages/offline_page_types.h"
 
 namespace base {
 class Clock;
-}
+}  // namespace base
 
 namespace offline_pages {
 
+// Limit of the total storage space occupied by offline pages should be 30% of
+// available storage. And we clear storage when it is over the threshold,
+// reducing the usage below threshold.
+const double kOfflinePageStorageLimit = 0.3;
+const double kOfflinePageStorageClearThreshold = 0.1;
+const base::TimeDelta kClearStorageInterval = base::TimeDelta::FromMinutes(10);
+
+class ArchiveManager;
 class ClientPolicyController;
 
 // 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:
   // This interface should have no knowledge of offline page model.
   // This interface should be implemented by clients managed by storage manager.
   class Client {
    public:
     virtual ~Client() {}
 
     // Asks the client to get all offline pages and invoke |callback|.
     virtual void GetAllPages(
         const MultipleOfflinePageItemCallback& callback) = 0;
 
     // Asks the client to delete pages based on |offline_ids| and invoke
     // |callback|.
     virtual void DeletePagesByOfflineId(const std::vector<int64_t>& offline_ids,
                                         const DeletePageCallback& callback) = 0;
   };
 
+  enum class ClearStorageResult {
+    SUCCESS,         // Cleared successfully.
+    UNNECESSARY,     // No expired pages.
+    DELETE_FAILURE,  // Deletion failed.
+  };
+
   // Callback used when calling ClearPagesIfNeeded.
-  // int: the number of deleted pages.
-  // DeletePageResult: result of deleting pages.
-  typedef base::Callback<void(int, DeletePageResult)> ClearPageCallback;
+  // int: the number of expired pages.
+  // ClearStorageResult: result of expiring pages in storage.
+  typedef base::Callback<void(int, ClearStorageResult)> ClearPagesCallback;
 
   explicit OfflinePageStorageManager(Client* client,
-                                     ClientPolicyController* policy_controller);
+                                     ClientPolicyController* policy_controller,
+                                     ArchiveManager* archive_manager);
 
   ~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);
+  // It clears the storage (expire pages) when it's using more disk space than a
+  // certain limit, or the time elapsed from last time clearing is longer than a
+  // certain interval. Both values are defined above.
+  void ClearPagesIfNeeded(const ClearPagesCallback& callback);
 
   // Sets the clock for testing.
   void SetClockForTesting(std::unique_ptr<base::Clock> clock);
 
  private:
-  // Selects and removes pages that need to be expired. Triggered as a callback
-  // to |GetAllPages|.
-  void ClearExpiredPages(const ClearPageCallback& callback,
+  // Enum indicating how to clear the pages.
+  enum class ClearMode {
+    // Using normal expiration logic to expire pages. Will reduce the storage
+    // usage down below the threshold.
+    DEFAULT,
+    // No need to expire any page (no pages in the model or no expired
+    // pages and we're not exceeding the storage limit.)
+    NOT_NEEDED,
+  };
+
+  // Callback called after getting storage stats from archive manager.
+  void OnGetStorageStatsDone(const ClearPagesCallback& callback,
+                             const ArchiveManager::StorageStats& pages);
+
+  // Callback called after getting all pages from client done.
+  void OnGetAllPagesDone(const ClearPagesCallback& callback,
+                         const ArchiveManager::StorageStats& storage_stats,
                          const MultipleOfflinePageItemResult& pages);
 
+  // Callback called after expired pages have been deleted.
+  void OnExpiredPagesDeleted(const ClearPagesCallback& callback,
+                             int pages_to_clear,
+                             DeletePageResult result);
+
   // Gets offline IDs of all expired pages and return in |offline_ids|.
   void GetExpiredPageIds(const MultipleOfflinePageItemResult& pages,
+                         const ArchiveManager::StorageStats& stats,
                          std::vector<int64_t>& offline_ids);
 
-  // Callback when expired pages has been deleted.
-  void OnExpiredPagesDeleted(const ClearPageCallback& callback,
-                             int pages_to_clear,
-                             DeletePageResult result);
-
   // Determine if manager should clear pages.
-  bool ShouldClearPages();
+  ClearMode ShouldClearPages(const ArchiveManager::StorageStats& storage_stats);
 
   // Return true if |page| is expired comparing to |now|.
   bool ShouldBeExpired(const base::Time& now, const OfflinePageItem& page);
 
   // Not owned.
   Client* client_;
 
   // Not owned.
   ClientPolicyController* policy_controller_;
 
+  // Not owned.
+  ArchiveManager* archive_manager_;
+
   bool in_progress_;
 
+  base::Time last_clear_time_;
+
   // Clock for getting time.
   std::unique_ptr<base::Clock> clock_;
 
   base::WeakPtrFactory<OfflinePageStorageManager> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(OfflinePageStorageManager);
 };
 
 }  // namespace offline_pages
 
 #endif  // COMPONENTS_OFFLINE_PAGES_OFFLINE_PAGE_STORAGE_MANAGER_H_