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      1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #ifndef CHROME_BROWSER_CHROMEOS_SETTINGS_CROS_SETTINGS_PROVIDER_H_
      6 #define CHROME_BROWSER_CHROMEOS_SETTINGS_CROS_SETTINGS_PROVIDER_H_
      7 
      8 #include <string>
      9 
     10 #include "base/callback.h"
     11 
     12 namespace base {
     13 class Value;
     14 }
     15 
     16 namespace chromeos {
     17 
     18 class CrosSettingsProvider {
     19  public:
     20   // The callback type that is called to notify the CrosSettings observers
     21   // about a setting change.
     22   typedef base::Callback<void(const std::string&)> NotifyObserversCallback;
     23 
     24   // Possible results of a trusted check.
     25   enum TrustedStatus {
     26     // The trusted values were populated in the cache and can be accessed
     27     // until the next iteration of the message loop.
     28     TRUSTED,
     29     // Either a store or a load operation is in progress. The provided
     30     // callback will be invoked once the verification has finished.
     31     TEMPORARILY_UNTRUSTED,
     32     // The verification of the trusted store has failed permanently. The
     33     // client should assume this state final and further checks for
     34     // trustedness will fail at least until the browser restarts.
     35     PERMANENTLY_UNTRUSTED,
     36   };
     37 
     38   // Creates a new provider instance. |notify_cb| will be used to notify
     39   // about setting changes.
     40   explicit CrosSettingsProvider(const NotifyObserversCallback& notify_cb);
     41   virtual ~CrosSettingsProvider();
     42 
     43   // Sets |in_value| to given |path| in cros settings.
     44   void Set(const std::string& path, const base::Value& in_value);
     45 
     46   // Gets settings value of given |path| to |out_value|.
     47   virtual const base::Value* Get(const std::string& path) const = 0;
     48 
     49   // Requests the provider to fetch its values from a trusted store, if it
     50   // hasn't done so yet. Returns TRUSTED if the values returned by this provider
     51   // are trusted during the current loop cycle. Otherwise returns
     52   // TEMPORARILY_UNTRUSTED, and |callback| will be invoked later when trusted
     53   // values become available, PrepareTrustedValues() should be tried again in
     54   // that case. Returns PERMANENTLY_UNTRUSTED if a permanent error has occurred.
     55   virtual TrustedStatus PrepareTrustedValues(
     56       const base::Closure& callback) = 0;
     57 
     58   // Gets the namespace prefix provided by this provider.
     59   virtual bool HandlesSetting(const std::string& path) const = 0;
     60 
     61   void SetNotifyObserversCallback(const NotifyObserversCallback& notify_cb);
     62 
     63  protected:
     64   // Notifies the observers about a setting change.
     65   void NotifyObservers(const std::string& path);
     66 
     67  private:
     68   // Does the real job for Set().
     69   virtual void DoSet(const std::string& path,
     70                      const base::Value& in_value) = 0;
     71 
     72   // Callback used to notify about setting changes.
     73   NotifyObserversCallback notify_cb_;
     74 };
     75 
     76 }  // namespace chromeos
     77 
     78 #endif  // CHROME_BROWSER_CHROMEOS_SETTINGS_CROS_SETTINGS_PROVIDER_H_
     79