Home | History | Annotate | Download | only in policy 
      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_POLICY_POLICY_SERVICE_H_
      6 #define CHROME_BROWSER_POLICY_POLICY_SERVICE_H_
      7 
      8 #include <map>
      9 #include <string>
     10 
     11 #include "base/basictypes.h"
     12 #include "base/callback.h"
     13 #include "base/memory/ref_counted.h"
     14 #include "chrome/browser/policy/policy_map.h"
     15 
     16 namespace policy {
     17 
     18 class PolicyDomainDescriptor;
     19 
     20 // Policies are namespaced by a (PolicyDomain, ID) pair. The meaning of the ID
     21 // string depends on the domain; for example, if the PolicyDomain is
     22 // "extensions" then the ID identifies the extension that the policies control.
     23 enum PolicyDomain {
     24   // The component ID for chrome policies is always the empty string.
     25   POLICY_DOMAIN_CHROME,
     26 
     27   // The extensions policy domain is a work in progress. Included here for
     28   // tests.
     29   POLICY_DOMAIN_EXTENSIONS,
     30 
     31   // Must be the last entry.
     32   POLICY_DOMAIN_SIZE,
     33 };
     34 
     35 // Groups a policy domain and a component ID in a single object representing
     36 // a policy namespace. Objects of this class can be used as keys in std::maps.
     37 struct PolicyNamespace {
     38  public:
     39   PolicyNamespace();
     40   PolicyNamespace(PolicyDomain domain, const std::string& component_id);
     41   PolicyNamespace(const PolicyNamespace& other);
     42   ~PolicyNamespace();
     43 
     44   PolicyNamespace& operator=(const PolicyNamespace& other);
     45   bool operator<(const PolicyNamespace& other) const;
     46   bool operator==(const PolicyNamespace& other) const;
     47   bool operator!=(const PolicyNamespace& other) const;
     48 
     49   PolicyDomain domain;
     50   std::string component_id;
     51 };
     52 
     53 // The PolicyService merges policies from all available sources, taking into
     54 // account their priorities. Policy clients can retrieve policy for their domain
     55 // and register for notifications on policy updates.
     56 //
     57 // The PolicyService is available from BrowserProcess as a global singleton.
     58 // There is also a PolicyService for browser-wide policies available from
     59 // BrowserProcess as a global singleton.
     60 class PolicyService {
     61  public:
     62   class Observer {
     63    public:
     64     // Invoked whenever policies for the given |ns| namespace are modified.
     65     // This is only invoked for changes that happen after AddObserver is called.
     66     // |previous| contains the values of the policies before the update,
     67     // and |current| contains the current values.
     68     virtual void OnPolicyUpdated(const PolicyNamespace& ns,
     69                                  const PolicyMap& previous,
     70                                  const PolicyMap& current) = 0;
     71 
     72     // Invoked at most once for each |domain|, when the PolicyService becomes
     73     // ready. If IsInitializationComplete() is false, then this will be invoked
     74     // once all the policy providers have finished loading their policies for
     75     // |domain|.
     76     virtual void OnPolicyServiceInitialized(PolicyDomain domain) {}
     77 
     78    protected:
     79     virtual ~Observer() {}
     80   };
     81 
     82   virtual ~PolicyService() {}
     83 
     84   // Observes changes to all components of the given |domain|.
     85   virtual void AddObserver(PolicyDomain domain, Observer* observer) = 0;
     86 
     87   virtual void RemoveObserver(PolicyDomain domain, Observer* observer) = 0;
     88 
     89   // Registers the |descriptor| of a policy domain, indicated by
     90   // |descriptor->domain()|. This overrides the descriptor previously set, if
     91   // there was one.
     92   // This registration signals that there is interest in receiving policy for
     93   // the components listed in the descriptor. The policy providers will try to
     94   // load policy for these components, and validate it against the descriptor.
     95   // Cached data for components that aren't registered anymore may be dropped.
     96   virtual void RegisterPolicyDomain(
     97       scoped_refptr<const PolicyDomainDescriptor> descriptor) = 0;
     98 
     99   virtual const PolicyMap& GetPolicies(const PolicyNamespace& ns) const = 0;
    100 
    101   virtual scoped_refptr<const PolicyDomainDescriptor> GetPolicyDomainDescriptor(
    102       PolicyDomain domain) const = 0;
    103 
    104   // The PolicyService loads policy from several sources, and some require
    105   // asynchronous loads. IsInitializationComplete() returns true once all
    106   // sources have loaded their policies for the given |domain|.
    107   // It is safe to read policy from the PolicyService even if
    108   // IsInitializationComplete() is false; there will be an OnPolicyUpdated()
    109   // notification once new policies become available.
    110   //
    111   // OnPolicyServiceInitialized() is called when IsInitializationComplete()
    112   // becomes true, which happens at most once for each domain.
    113   // If IsInitializationComplete() is already true for |domain| when an Observer
    114   // is registered, then that Observer will not receive an
    115   // OnPolicyServiceInitialized() notification.
    116   virtual bool IsInitializationComplete(PolicyDomain domain) const = 0;
    117 
    118   // Asks the PolicyService to reload policy from all available policy sources.
    119   // |callback| is invoked once every source has reloaded its policies, and
    120   // GetPolicies() is guaranteed to return the updated values at that point.
    121   virtual void RefreshPolicies(const base::Closure& callback) = 0;
    122 };
    123 
    124 // A registrar that only observes changes to particular policies within the
    125 // PolicyMap for the given policy namespace.
    126 class PolicyChangeRegistrar : public PolicyService::Observer {
    127  public:
    128   typedef base::Callback<void(const Value*, const Value*)> UpdateCallback;
    129 
    130   // Observes updates to the given (domain, component_id) namespace in the given
    131   // |policy_service|, and notifies |observer| whenever any of the registered
    132   // policy keys changes. Both the |policy_service| and the |observer| must
    133   // outlive |this|.
    134   PolicyChangeRegistrar(PolicyService* policy_service,
    135                         const PolicyNamespace& ns);
    136 
    137   virtual ~PolicyChangeRegistrar();
    138 
    139   // Will invoke |callback| whenever |policy_name| changes its value, as long
    140   // as this registrar exists.
    141   // Only one callback can be registed per policy name; a second call with the
    142   // same |policy_name| will overwrite the previous callback.
    143   void Observe(const std::string& policy_name, const UpdateCallback& callback);
    144 
    145   // Implementation of PolicyService::Observer:
    146   virtual void OnPolicyUpdated(const PolicyNamespace& ns,
    147                                const PolicyMap& previous,
    148                                const PolicyMap& current) OVERRIDE;
    149 
    150  private:
    151   typedef std::map<std::string, UpdateCallback> CallbackMap;
    152 
    153   PolicyService* policy_service_;
    154   PolicyNamespace ns_;
    155   CallbackMap callback_map_;
    156 
    157   DISALLOW_COPY_AND_ASSIGN(PolicyChangeRegistrar);
    158 };
    159 
    160 }  // namespace policy
    161 
    162 #endif  // CHROME_BROWSER_POLICY_POLICY_SERVICE_H_
    163