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/callback.h"
12 #include "base/macros.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|.
OnPolicyServiceInitialized(PolicyDomain domain)42     virtual void OnPolicyServiceInitialized(PolicyDomain domain) {}
43 
44    protected:
~Observer()45     virtual ~Observer() {}
46   };
47 
~PolicyService()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   ~PolicyChangeRegistrar() override;
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   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