Refactor FileBasedPolicyProvider, introduce AsynchronousPolicyProvider.

chrome/browser/policy/file_based_policy_provider.h

 // Copyright (c) 2010 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_POLICY_FILE_BASED_POLICY_PROVIDER_H_
 #define CHROME_BROWSER_POLICY_FILE_BASED_POLICY_PROVIDER_H_
 #pragma once
 
-#include "base/basictypes.h"
 #include "base/file_path.h"
-#include "base/lock.h"
-#include "base/ref_counted.h"
-#include "base/scoped_ptr.h"
 #include "base/time.h"
-#include "base/weak_ptr.h"
-#include "chrome/browser/file_path_watcher/file_path_watcher.h"
-#include "chrome/browser/policy/configuration_policy_provider.h"
-
-class CancelableTask;
-class DictionaryValue;
-class MessageLoop;
+#include "chrome/browser/policy/asynchronous_policy_provider.h"
 
 namespace policy {
 
-class FileBasedPolicyLoader;
-class FileBasedPolicyWatcher;
-
 // File based policy provider that coordinates watching and reloading policy
 // information from the configuration path. Actual logic for loading policy
 // information is handled by a delegate passed at construction time.
-class FileBasedPolicyProvider
-    : public ConfigurationPolicyProvider,
-      public base::SupportsWeakPtr<FileBasedPolicyProvider> {
+class FileBasedPolicyProvider : public AsynchronousPolicyProvider {
  public:
+
   // Delegate interface for actual policy loading from the system.
-  class Delegate {
+  class ProviderDelegate : public AsynchronousPolicyProvider::Delegate {
    public:
-    virtual ~Delegate();
+    explicit ProviderDelegate(const FilePath& config_file_path);
+    virtual ~ProviderDelegate();
 
-    // Loads the policy information. Ownership of the return value is
-    // transferred to the caller.
+    // AsynchronousPolicyProvider::Delegate implementation:
     virtual DictionaryValue* Load() = 0;
 
     // Gets the last modification timestamp for the policy information from the
     // filesystem. Returns base::Time() if the information is not present, in
     // which case Load() should return an empty dictionary.
     virtual base::Time GetLastModification() = 0;
 
     const FilePath& config_file_path() { return config_file_path_; }
 
-   protected:
-    explicit Delegate(const FilePath& config_file_path);
-
    private:
-    // The path at which we look for configuration files.
     const FilePath config_file_path_;
 
-    DISALLOW_COPY_AND_ASSIGN(Delegate);
+    DISALLOW_COPY_AND_ASSIGN(ProviderDelegate);
   };
 
   // Assumes ownership of |delegate|.
   FileBasedPolicyProvider(const PolicyDefinitionList* policy_list,
-                          Delegate* delegate);
-  virtual ~FileBasedPolicyProvider();
-
-  // ConfigurationPolicyProvider implementation.
-  virtual bool Provide(ConfigurationPolicyStoreInterface* store);
+                          ProviderDelegate* delegate);
+  virtual ~FileBasedPolicyProvider() {}
 
  private:
-  // Watches for changes to the configuration directory.
-  scoped_refptr<FileBasedPolicyWatcher> watcher_;
-
-  // The loader object we use internally.
-  scoped_refptr<FileBasedPolicyLoader> loader_;
-
   DISALLOW_COPY_AND_ASSIGN(FileBasedPolicyProvider);
 };
 
-// FilePathWatcher delegate implementation that handles change notifications for
-// the configuration file or directory. It keeps the authorative version of the
-// currently effective policy dictionary and updates it as appropriate. The
-// actual loading logic is handled by a delegate.
-class FileBasedPolicyLoader : public FilePathWatcher::Delegate {
- public:
-  // Creates a new loader that'll load its data from |config_file_path|.
-  // Assumes ownership of |delegate|, which  provides the actual loading logic.
-  // The parameters |settle_interval_seconds| and |reload_interval_minutes|
-  // specify the time to wait before reading the file contents after a change
-  // and the period for checking |config_file_path| for changes, respectively.
-  FileBasedPolicyLoader(base::WeakPtr<ConfigurationPolicyProvider> provider,
-                        FileBasedPolicyProvider::Delegate* delegate,
-                        int settle_interval_seconds,
-                        int reload_interval_minutes);
-
-  // Stops any pending reload tasks.
-  void Stop();
-
-  // Reloads the policies and sends out a notification, if appropriate. Must be
-  // called on the file thread.
-  void Reload();
-
-  // Gets the current dictionary value object. Ownership of the returned value
-  // is transferred to the caller.
-  DictionaryValue* GetPolicy();
-
-  const FilePath& config_file_path() { return delegate_->config_file_path(); }
-
-  // FilePathWatcher::Delegate implementation:
-  virtual void OnFilePathChanged(const FilePath& path);
-  virtual void OnError();
-
- private:
-  // FileBasedPolicyLoader objects should only be deleted by
-  // RefCountedThreadSafe.
-  friend class base::RefCountedThreadSafe<FileBasedPolicyLoader>;
-  virtual ~FileBasedPolicyLoader();
-
-  // Checks whether reading policy information  is safe to do. If not, returns
-  // false and the delay until it is considered safe to reload in |delay|.
-  bool IsSafeToReloadPolicy(const base::Time& now, base::TimeDelta* delay);
-
-  // Schedules a reload task to run when |delay| expires. Must be called on the
-  // file thread.
-  void ScheduleReloadTask(const base::TimeDelta& delay);
-
-  // Notifies the policy provider to send out a policy changed notification.
-  // Must be called on |origin_loop_|.
-  void NotifyPolicyChanged();
-
-  // Invoked from the reload task on the file thread.
-  void ReloadFromTask();
-
-  // The delegate.
-  scoped_ptr<FileBasedPolicyProvider::Delegate> delegate_;
-
-  // The provider this loader is associated with. Access only on the thread that
-  // called the constructor. See |origin_loop_| below.
-  base::WeakPtr<ConfigurationPolicyProvider> provider_;
-
-  // The message loop on which this object was constructed and |provider_|
-  // received on. Recorded so we can call back into the non thread safe provider
-  // to fire the notification.
-  MessageLoop* origin_loop_;
-
-  // Records last known modification timestamp of |config_file_path_|.
-  base::Time last_modification_file_;
-
-  // The wall clock time at which the last modification timestamp was recorded.
-  // It's better to not assume the file notification time and the wall clock
-  // times come from the same source, just in case there is some non-local
-  // filesystem involved.
-  base::Time last_modification_clock_;
-
-  // Protects |policy_|.
-  Lock lock_;
-
-  // The current policy definition.
-  scoped_ptr<DictionaryValue> policy_;
-
-  // The reload task. Access only on the file thread. Holds a reference to the
-  // currently posted task, so we can cancel and repost it if necessary.
-  CancelableTask* reload_task_;
-
-  // Settle and reload intervals.
-  const int settle_interval_seconds_;
-  const int reload_interval_minutes_;
-
-  DISALLOW_COPY_AND_ASSIGN(FileBasedPolicyLoader);
-};
-
-// Wraps a FilePathWatcher for the configuration path and takes care of
-// initializing the watcher object on the file thread.
-class FileBasedPolicyWatcher
-    : public base::RefCountedThreadSafe<FileBasedPolicyWatcher> {
- public:
-  FileBasedPolicyWatcher();
-
-  // Runs initialization. This is in a separate method since we need to post a
-  // task (which cannot be done from the constructor).
-  void Init(FileBasedPolicyLoader* loader);
-
- private:
-  // FileBasedPolicyWatcher objects should only be deleted by
-  // RefCountedThreadSafe.
-  friend class base::RefCountedThreadSafe<FileBasedPolicyWatcher>;
-  virtual ~FileBasedPolicyWatcher();
-
-  // Actually sets up the watch with the FilePathWatcher code.
-  void InitWatcher(const scoped_refptr<FileBasedPolicyLoader>& loader);
-
-  // Wrapped watcher that takes care of the actual watching.
-  FilePathWatcher watcher_;
-
-  DISALLOW_COPY_AND_ASSIGN(FileBasedPolicyWatcher);
-};
-
 }  // namespace policy
 
 #endif  // CHROME_BROWSER_POLICY_FILE_BASED_POLICY_PROVIDER_H_