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      1 // Copyright 2014 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_METRICS_METRICS_STATE_MANAGER_H_
      6 #define COMPONENTS_METRICS_METRICS_STATE_MANAGER_H_
      7 
      8 #include <string>
      9 
     10 #include "base/basictypes.h"
     11 #include "base/callback.h"
     12 #include "base/gtest_prod_util.h"
     13 #include "base/memory/scoped_ptr.h"
     14 #include "base/metrics/field_trial.h"
     15 
     16 class PrefService;
     17 class PrefRegistrySimple;
     18 
     19 namespace metrics {
     20 
     21 class ClonedInstallDetector;
     22 
     23 // Responsible for managing MetricsService state prefs, specifically the UMA
     24 // client id and low entropy source. Code outside the metrics directory should
     25 // not be instantiating or using this class directly.
     26 class MetricsStateManager {
     27  public:
     28   virtual ~MetricsStateManager();
     29 
     30   // Returns true if the user opted in to sending metric reports.
     31   bool IsMetricsReportingEnabled();
     32 
     33   // Returns the client ID for this client, or the empty string if the user is
     34   // not opted in to metrics reporting.
     35   const std::string& client_id() const { return client_id_; }
     36 
     37   // Forces the client ID to be generated. This is useful in case it's needed
     38   // before recording.
     39   void ForceClientIdCreation();
     40 
     41   // Checks if this install was cloned or imaged from another machine. If a
     42   // clone is detected, resets the client id and low entropy source. This
     43   // should not be called more than once.
     44   void CheckForClonedInstall(
     45       scoped_refptr<base::SingleThreadTaskRunner> task_runner);
     46 
     47   // Returns the preferred entropy provider used to seed persistent activities
     48   // based on whether or not metrics reporting is permitted on this client.
     49   //
     50   // If metrics reporting is enabled, this method returns an entropy provider
     51   // that has a high source of entropy, partially based on the client ID.
     52   // Otherwise, it returns an entropy provider that is based on a low entropy
     53   // source.
     54   scoped_ptr<const base::FieldTrial::EntropyProvider> CreateEntropyProvider();
     55 
     56   // Creates the MetricsStateManager, enforcing that only a single instance
     57   // of the class exists at a time. Returns NULL if an instance exists already.
     58   static scoped_ptr<MetricsStateManager> Create(
     59       PrefService* local_state,
     60       const base::Callback<bool(void)>& is_reporting_enabled_callback);
     61 
     62   // Registers local state prefs used by this class.
     63   static void RegisterPrefs(PrefRegistrySimple* registry);
     64 
     65  private:
     66   FRIEND_TEST_ALL_PREFIXES(MetricsStateManagerTest, EntropySourceUsed_Low);
     67   FRIEND_TEST_ALL_PREFIXES(MetricsStateManagerTest, EntropySourceUsed_High);
     68   FRIEND_TEST_ALL_PREFIXES(MetricsStateManagerTest, LowEntropySource0NotReset);
     69   FRIEND_TEST_ALL_PREFIXES(MetricsStateManagerTest,
     70                            PermutedEntropyCacheClearedWhenLowEntropyReset);
     71   FRIEND_TEST_ALL_PREFIXES(MetricsStateManagerTest, ResetMetricsIDs);
     72 
     73   // Designates which entropy source was returned from this class.
     74   // This is used for testing to validate that we return the correct source
     75   // depending on the state of the service.
     76   enum EntropySourceType {
     77     ENTROPY_SOURCE_NONE,
     78     ENTROPY_SOURCE_LOW,
     79     ENTROPY_SOURCE_HIGH,
     80   };
     81 
     82   // Creates the MetricsStateManager with the given |local_state|. Calls
     83   // |is_reporting_enabled_callback| to query whether metrics reporting is
     84   // enabled. Clients should instead use Create(), which enforces a single
     85   // instance of this class is alive at any given time.
     86   MetricsStateManager(
     87       PrefService* local_state,
     88       const base::Callback<bool(void)>& is_reporting_enabled_callback);
     89 
     90   // Returns the low entropy source for this client. This is a random value
     91   // that is non-identifying amongst browser clients. This method will
     92   // generate the entropy source value if it has not been called before.
     93   int GetLowEntropySource();
     94 
     95   // Returns the first entropy source that was returned by this service since
     96   // start up, or NONE if neither was returned yet. This is exposed for testing
     97   // only.
     98   EntropySourceType entropy_source_returned() const {
     99     return entropy_source_returned_;
    100   }
    101 
    102   // Reset the client id and low entropy source if the kMetricsResetMetricIDs
    103   // pref is true.
    104   void ResetMetricsIDsIfNecessary();
    105 
    106   // Whether an instance of this class exists. Used to enforce that there aren't
    107   // multiple instances of this class at a given time.
    108   static bool instance_exists_;
    109 
    110   // Weak pointer to the local state prefs store.
    111   PrefService* const local_state_;
    112 
    113   const base::Callback<bool(void)> is_reporting_enabled_callback_;
    114 
    115   // The identifier that's sent to the server with the log reports.
    116   std::string client_id_;
    117 
    118   // The non-identifying low entropy source value.
    119   int low_entropy_source_;
    120 
    121   // The last entropy source returned by this service, used for testing.
    122   EntropySourceType entropy_source_returned_;
    123 
    124   scoped_ptr<ClonedInstallDetector> cloned_install_detector_;
    125 
    126   DISALLOW_COPY_AND_ASSIGN(MetricsStateManager);
    127 };
    128 
    129 }  // namespace metrics
    130 
    131 #endif  // COMPONENTS_METRICS_METRICS_STATE_MANAGER_H_
    132