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
17namespace 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.
26class 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.
79class 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_
117