[fsp] Add support for observing entries and notifying about changes.

chrome/browser/chromeos/file_system_provider/provided_file_system.h

 // Copyright 2014 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 CHROME_BROWSER_CHROMEOS_FILE_SYSTEM_PROVIDER_PROVIDED_FILE_SYSTEM_H_
 #define CHROME_BROWSER_CHROMEOS_FILE_SYSTEM_PROVIDER_PROVIDED_FILE_SYSTEM_H_
 
+#include <string>
+
+#include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
+#include "base/observer_list.h"
 #include "chrome/browser/chromeos/file_system_provider/provided_file_system_info.h"
 #include "chrome/browser/chromeos/file_system_provider/provided_file_system_interface.h"
+#include "chrome/browser/chromeos/file_system_provider/provided_file_system_observer.h"
 #include "chrome/browser/chromeos/file_system_provider/request_manager.h"
 #include "storage/browser/fileapi/async_file_util.h"
 
 class Profile;
 
 namespace net {
 class IOBuffer;
 }  // namespace net
 
 namespace base {
 class FilePath;
 }  // namespace base
 
 namespace extensions {
 class EventRouter;
 }  // namespace extensions
 
 namespace chromeos {
 namespace file_system_provider {
 
 class NotificationManagerInterface;
 
+// Automatically calls the |update_callback| after all of the callbacks created

[mtomasz, 2014/10/03 04:22:48]

This class is very important. Basically as in the comment here we want to update
the last tag in our internal map of observed entries |observed_entries| after
the upcoming Cache implementation invalidates the entries.

Eg.

0. /hoge-fuga.txt is observed, and tag of the last notification is 'tag-1'.
1. /hoge-fuga.txt is changed remotely.
2. Extension is invoking ProvidedFileSystem::Notify('/hoge-fuga.txt', 'tag-2').
3. Cache is notified about change to '/hoge-fuga.txt'
4. Cache asynchronously removes from cache the entry. It takes several
PostTasks.
5. Also other observers do other stuff.
6. AutoUpdate calls |update_callback|, which updates the tag from 'tag-1' to
'tag-2'.

Why is that? If crash happened during invalidating the cache, then after a
restart we will have the old tag in the |observed_entries_|, and the extension
will generate the notification about '/hoge-fuga.txt' again.

+// with |CreateCallback| are called.
+//
+// It's used to update tags of observed entries once a notification about a
+// change are fully handles. It is to make sure that the change notification is
+// fully handled before remembering the new tag.
+//
+// It is necessary to update the tag after all observers handle it fully, so
+// in case of shutdown or a crash we get the notifications again.
+class AutoUpdater : public base::RefCounted<AutoUpdater> {
+ public:
+  explicit AutoUpdater(const base::Closure& update_callback);
+
+  // Creates a new callback which needs to be called before the update callback
+  // is called.
+  base::Closure CreateCallback();
+
+ private:
+  friend class base::RefCounted<AutoUpdater>;
+
+  // Called once the callback created with |CreateCallback| is executed. Once
+  // all of such callbacks are called, then the update callback is invoked.
+  void OnPendingCallback();
+
+  virtual ~AutoUpdater();
+
+  base::Closure update_callback_;
+  int created_callbacks_;
+  int pending_callbacks_;
+};
+
 // Provided file system implementation. Forwards requests between providers and
 // clients.
 class ProvidedFileSystem : public ProvidedFileSystemInterface {
  public:
   ProvidedFileSystem(Profile* profile,
                      const ProvidedFileSystemInfo& file_system_info);
   virtual ~ProvidedFileSystem();
 
+  // Sets a custom event router. Used in unit tests to mock out the real
+  // extension.
+  void SetEventRouterForTesting(extensions::EventRouter* event_router);
+
+  // Sets a custom notification manager. It will recreate the request manager,
+  // so is must be called just after creating ProvideFileSystem instance.
+  // Used by unit tests.
+  void SetNotificationManagerForTesting(
+      scoped_ptr<NotificationManagerInterface> notification_manager);
+
   // ProvidedFileSystemInterface overrides.
   virtual AbortCallback RequestUnmount(
       const storage::AsyncFileUtil::StatusCallback& callback) OVERRIDE;
   virtual AbortCallback GetMetadata(
       const base::FilePath& entry_path,
       MetadataFieldMask fields,
       const GetMetadataCallback& callback) OVERRIDE;
   virtual AbortCallback ReadDirectory(
       const base::FilePath& directory_path,
       const storage::AsyncFileUtil::ReadDirectoryCallback& callback) OVERRIDE;
@@ skipping 31 matching lines @@
   virtual AbortCallback Truncate(
       const base::FilePath& file_path,
       int64 length,
       const storage::AsyncFileUtil::StatusCallback& callback) OVERRIDE;
   virtual AbortCallback WriteFile(
       int file_handle,
       net::IOBuffer* buffer,
       int64 offset,
       int length,
       const storage::AsyncFileUtil::StatusCallback& callback) OVERRIDE;
+  virtual AbortCallback ObserveDirectory(
+      const base::FilePath& directory_path,
+      bool recursive,
+      const storage::AsyncFileUtil::StatusCallback& callback) OVERRIDE;
+  virtual AbortCallback UnobserveEntry(
+      const base::FilePath& entry_path,
+      const storage::AsyncFileUtil::StatusCallback& callback) OVERRIDE;
   virtual const ProvidedFileSystemInfo& GetFileSystemInfo() const OVERRIDE;
   virtual RequestManager* GetRequestManager() OVERRIDE;
+  virtual ObservedEntries* GetObservedEntries() OVERRIDE;
+  virtual void AddObserver(ProvidedFileSystemObserver* observer) OVERRIDE;
+  virtual void RemoveObserver(ProvidedFileSystemObserver* observer) OVERRIDE;
+  virtual bool Notify(
+      const base::FilePath& observed_path,
+      ProvidedFileSystemObserver::ChangeType change_type,
+      const ProvidedFileSystemObserver::ChildChanges& child_changes,
+      const std::string& tag) OVERRIDE;
   virtual base::WeakPtr<ProvidedFileSystemInterface> GetWeakPtr() OVERRIDE;
 
  private:
   // Aborts an operation executed with a request id equal to
   // |operation_request_id|. The request is removed immediately on the C++ side
   // despite being handled by the providing extension or not.
   void Abort(int operation_request_id,
              const storage::AsyncFileUtil::StatusCallback& callback);
 
+  // Called when a directory becomes watched successfully.
+  void OnObserveDirectoryCompleted(
+      const base::FilePath& directory_path,
+      bool recursive,
+      const storage::AsyncFileUtil::StatusCallback& callback,
+      base::File::Error result);
+
+  // Called when all observers finished handling the change notification. It

[mtomasz, 2014/10/03 04:22:47]

This is called when all observers in |observers_| finished handling
OnObservedEntryChanged().

+  // updates the tag from |last_tag| to |tag| for the entry at |observed_path|.
+  void OnNotifyCompleted(const base::FilePath& observed_path,
+                         ProvidedFileSystemObserver::ChangeType change_type,
+                         const std::string& last_tag,
+                         const std::string& tag);
+
   Profile* profile_;                       // Not owned.
   extensions::EventRouter* event_router_;  // Not owned. May be NULL.
   ProvidedFileSystemInfo file_system_info_;
   scoped_ptr<NotificationManagerInterface> notification_manager_;
-  RequestManager request_manager_;
+  scoped_ptr<RequestManager> request_manager_;
+  ObservedEntries observed_entries_;
+  ObserverList<ProvidedFileSystemObserver> observers_;
 
   base::WeakPtrFactory<ProvidedFileSystem> weak_ptr_factory_;
   DISALLOW_COPY_AND_ASSIGN(ProvidedFileSystem);
 };
 
 }  // namespace file_system_provider
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_FILE_SYSTEM_PROVIDER_PROVIDED_FILE_SYSTEM_H_