components/policy/core/common/policy_service.h

   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 COMPONENTS_POLICY_CORE_COMMON_POLICY_SERVICE_H_
   6 #define COMPONENTS_POLICY_CORE_COMMON_POLICY_SERVICE_H_
   7
   8 #include <map>
   9 #include <string>
  10
  11 #include "base/basictypes.h"
  12 #include "base/callback.h"
  13 #include "components/policy/core/common/policy_map.h"
  14 #include "components/policy/core/common/policy_namespace.h"
  15 #include "components/policy/policy_export.h"
  16
  17 namespace policy {
  18
  19 // The PolicyService merges policies from all available sources, taking into
  20 // account their priorities. Policy clients can retrieve policy for their domain
  21 // and register for notifications on policy updates.
  22 //
  23 // The PolicyService is available from BrowserProcess as a global singleton.
  24 // There is also a PolicyService for browser-wide policies available from
  25 // BrowserProcess as a global singleton.
  26 class POLICY_EXPORT PolicyService {
  27  public:
  28   class POLICY_EXPORT Observer {
  29    public:
  30     // Invoked whenever policies for the given |ns| namespace are modified.
  31     // This is only invoked for changes that happen after AddObserver is called.
  32     // |previous| contains the values of the policies before the update,
  33     // and |current| contains the current values.
  34     virtual void OnPolicyUpdated(const PolicyNamespace& ns,
  35                                  const PolicyMap& previous,
  36                                  const PolicyMap& current) = 0;
  37
  38     // Invoked at most once for each |domain|, when the PolicyService becomes
  39     // ready. If IsInitializationComplete() is false, then this will be invoked
  40     // once all the policy providers have finished loading their policies for
  41     // |domain|.
  42     virtual void OnPolicyServiceInitialized(PolicyDomain domain) {}
  43
  44    protected:
  45     virtual ~Observer() {}
  46   };
  47
  48   virtual ~PolicyService() {}
  49
  50   // Observes changes to all components of the given |domain|.
  51   virtual void AddObserver(PolicyDomain domain, Observer* observer) = 0;
  52
  53   virtual void RemoveObserver(PolicyDomain domain, Observer* observer) = 0;
  54
  55   virtual const PolicyMap& GetPolicies(const PolicyNamespace& ns) const = 0;
  56
  57   // The PolicyService loads policy from several sources, and some require
  58   // asynchronous loads. IsInitializationComplete() returns true once all
  59   // sources have loaded their policies for the given |domain|.
  60   // It is safe to read policy from the PolicyService even if
  61   // IsInitializationComplete() is false; there will be an OnPolicyUpdated()
  62   // notification once new policies become available.
  63   //
  64   // OnPolicyServiceInitialized() is called when IsInitializationComplete()
  65   // becomes true, which happens at most once for each domain.
  66   // If IsInitializationComplete() is already true for |domain| when an Observer
  67   // is registered, then that Observer will not receive an
  68   // OnPolicyServiceInitialized() notification.
  69   virtual bool IsInitializationComplete(PolicyDomain domain) const = 0;
  70
  71   // Asks the PolicyService to reload policy from all available policy sources.
  72   // |callback| is invoked once every source has reloaded its policies, and
  73   // GetPolicies() is guaranteed to return the updated values at that point.
  74   virtual void RefreshPolicies(const base::Closure& callback) = 0;
  75 };
  76
  77 // A registrar that only observes changes to particular policies within the
  78 // PolicyMap for the given policy namespace.
  79 class POLICY_EXPORT PolicyChangeRegistrar : public PolicyService::Observer {
  80  public:
  81   typedef base::Callback<void(const base::Value*,
  82                               const base::Value*)> UpdateCallback;
  83
  84   // Observes updates to the given (domain, component_id) namespace in the given
  85   // |policy_service|, and notifies |observer| whenever any of the registered
  86   // policy keys changes. Both the |policy_service| and the |observer| must
  87   // outlive |this|.
  88   PolicyChangeRegistrar(PolicyService* policy_service,
  89                         const PolicyNamespace& ns);
  90
  91   virtual ~PolicyChangeRegistrar();
  92
  93   // Will invoke |callback| whenever |policy_name| changes its value, as long
  94   // as this registrar exists.
  95   // Only one callback can be registed per policy name; a second call with the
  96   // same |policy_name| will overwrite the previous callback.
  97   void Observe(const std::string& policy_name, const UpdateCallback& callback);
  98
  99   // Implementation of PolicyService::Observer:
 100   virtual void OnPolicyUpdated(const PolicyNamespace& ns,
 101                                const PolicyMap& previous,
 102                                const PolicyMap& current) OVERRIDE;
 103
 104  private:
 105   typedef std::map<std::string, UpdateCallback> CallbackMap;
 106
 107   PolicyService* policy_service_;
 108   PolicyNamespace ns_;
 109   CallbackMap callback_map_;
 110
 111   DISALLOW_COPY_AND_ASSIGN(PolicyChangeRegistrar);
 112 };
 113
 114 }  // namespace policy
 115
 116 #endif  // COMPONENTS_POLICY_CORE_COMMON_POLICY_SERVICE_H_