chromeos/settings/cros_settings_provider.h

   1 // Copyright 2013 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 CHROMEOS_SETTINGS_CROS_SETTINGS_PROVIDER_H_
   6 #define CHROMEOS_SETTINGS_CROS_SETTINGS_PROVIDER_H_
   7
   8 #include <string>
   9
  10 #include "base/callback.h"
  11 #include "chromeos/chromeos_export.h"
  12
  13 namespace base {
  14 class Value;
  15 }
  16
  17 namespace chromeos {
  18
  19 class CHROMEOS_EXPORT CrosSettingsProvider {
  20  public:
  21   // The callback type that is called to notify the CrosSettings observers
  22   // about a setting change.
  23   typedef base::Callback<void(const std::string&)> NotifyObserversCallback;
  24
  25   // Possible results of a trusted check.
  26   enum TrustedStatus {
  27     // The trusted values were populated in the cache and can be accessed
  28     // until the next iteration of the message loop.
  29     TRUSTED,
  30     // Either a store or a load operation is in progress. The provided
  31     // callback will be invoked once the verification has finished.
  32     TEMPORARILY_UNTRUSTED,
  33     // The verification of the trusted store has failed permanently. The
  34     // client should assume this state final and further checks for
  35     // trustedness will fail at least until the browser restarts.
  36     PERMANENTLY_UNTRUSTED,
  37   };
  38
  39   // Creates a new provider instance. |notify_cb| will be used to notify
  40   // about setting changes.
  41   explicit CrosSettingsProvider(const NotifyObserversCallback& notify_cb);
  42   virtual ~CrosSettingsProvider();
  43
  44   // Sets |in_value| to given |path| in cros settings.
  45   void Set(const std::string& path, const base::Value& in_value);
  46
  47   // Gets settings value of given |path| to |out_value|.
  48   virtual const base::Value* Get(const std::string& path) const = 0;
  49
  50   // Requests the provider to fetch its values from a trusted store, if it
  51   // hasn't done so yet. Returns TRUSTED if the values returned by this provider
  52   // are trusted during the current loop cycle. Otherwise returns
  53   // TEMPORARILY_UNTRUSTED, and |callback| will be invoked later when trusted
  54   // values become available, PrepareTrustedValues() should be tried again in
  55   // that case. Returns PERMANENTLY_UNTRUSTED if a permanent error has occurred.
  56   virtual TrustedStatus PrepareTrustedValues(
  57       const base::Closure& callback) = 0;
  58
  59   // Gets the namespace prefix provided by this provider.
  60   virtual bool HandlesSetting(const std::string& path) const = 0;
  61
  62   void SetNotifyObserversCallback(const NotifyObserversCallback& notify_cb);
  63
  64  protected:
  65   // Notifies the observers about a setting change.
  66   void NotifyObservers(const std::string& path);
  67
  68  private:
  69   // Does the real job for Set().
  70   virtual void DoSet(const std::string& path,
  71                      const base::Value& in_value) = 0;
  72
  73   // Callback used to notify about setting changes.
  74   NotifyObserversCallback notify_cb_;
  75 };
  76
  77 }  // namespace chromeos
  78
  79 #endif  // CHROMEOS_SETTINGS_CROS_SETTINGS_PROVIDER_H_