[ReadingList iOS] Cleanup Offline directory on startup

ios/chrome/browser/reading_list/reading_list_download_service.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 IOS_CHROME_BROWSER_READING_LIST_READING_LIST_DOWNLOAD_SERVICE_H_
 #define IOS_CHROME_BROWSER_READING_LIST_READING_LIST_DOWNLOAD_SERVICE_H_
 
 #include "base/macros.h"
 #include "components/keyed_service/core/keyed_service.h"
 #include "components/reading_list/ios/reading_list_model_observer.h"
 #include "ios/chrome/browser/reading_list/url_downloader.h"
 #include "net/base/network_change_notifier.h"
 
 class GURL;
 class PrefService;
 class ReadingListModel;
 namespace base {
 class FilePath;
 }
 
 namespace dom_distiller {
 class DomDistillerService;
 }
 
 namespace reading_list {
 class ReadingListDistillerPageFactory;
 }
 
 // Observes the reading list and downloads offline versions of its articles.
-// Any calls made to DownloadAllEntries/DownloadEntry before the model is
-// loaded will be ignored. When the model is loaded, DownloadAllEntries will be
-// called automatically.
+// Any calls made to DownloadEntry before the model is loaded will be ignored.
+// When the model is loaded, offline directory is automatically synced with the
+// entries in the model.
 class ReadingListDownloadService
     : public KeyedService,
       public ReadingListModelObserver,
       public net::NetworkChangeNotifier::ConnectionTypeObserver {
  public:
   ReadingListDownloadService(
       ReadingListModel* reading_list_model,
       dom_distiller::DomDistillerService* distiller_service,
       PrefService* prefs,
       base::FilePath chrome_profile_path,
@@ skipping 14 matching lines @@
   void ReadingListModelLoaded(const ReadingListModel* model) override;
   void ReadingListWillRemoveEntry(const ReadingListModel* model,
                                   const GURL& url) override;
   void ReadingListDidAddEntry(const ReadingListModel* model,
                               const GURL& url,
                               reading_list::EntrySource entry_source) override;
   void ReadingListDidMoveEntry(const ReadingListModel* model,
                                const GURL& url) override;
 
  private:
-  // Tries to save offline versions of all entries in the reading list that are
-  // not yet saved. Must only be called after reading list model is loaded.
-  void DownloadAllEntries();
-  // Processes a new entry and schedule a download if needed.
+  // Checks the model and determines which entries are processed and which
+  // entries need to be processed.
+  // Initiates a cleanup of |OfflineRoot()| directory removing sub_directories
+  // not corresponding to a processed ReadingListEntry.
+  // Schedules unprocessed entries for distillation.
+  void SyncWithModel();
+  // Scans |OfflineRoot()| directory and deletes all subdirectories not listed
+  // in |directories_to_keep|.
+  // Must be called on File thread.
+  void CleanUpFiles(const std::set<std::string>& directories_to_keep);
+  // Schedules all entries in |unprocessed_entries| for distillation.
+  void DownloadUnprocessedEntries(const std::set<GURL>& unprocessed_entries);
+  // Processes a new entry and schedules a download if needed.
   void ProcessNewEntry(const GURL& url);
-  // Schedule a download of an offline version of the reading list entry,
+  // Schedules a download of an offline version of the reading list entry,
   // according to the delay of the entry. Must only be called after reading list
   // model is loaded.
   void ScheduleDownloadEntry(const GURL& url);
   // Tries to save an offline version of the reading list entry if it is not yet
   // saved. Must only be called after reading list model is loaded.
   void DownloadEntry(const GURL& url);
   // Removes the offline version of the reading list entry if it exists. Must
   // only be called after reading list model is loaded.
   void RemoveDownloadedEntry(const GURL& url);
   // Callback for entry download.
@@ skipping 18 matching lines @@
   bool had_connection_;
   std::unique_ptr<reading_list::ReadingListDistillerPageFactory>
       distiller_page_factory_;
 
   base::WeakPtrFactory<ReadingListDownloadService> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ReadingListDownloadService);
 };
 
 #endif  // IOS_CHROME_BROWSER_READING_LIST_READING_LIST_DOWNLOAD_SERVICE_H_