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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_VARIATIONS_VARIATIONS_SEED_SIMULATOR_H_
      6 #define COMPONENTS_VARIATIONS_VARIATIONS_SEED_SIMULATOR_H_
      7 
      8 #include <string>
      9 #include <vector>
     10 
     11 #include "base/compiler_specific.h"
     12 #include "base/gtest_prod_util.h"
     13 #include "base/metrics/field_trial.h"
     14 #include "base/version.h"
     15 #include "components/variations/proto/study.pb.h"
     16 #include "components/variations/proto/variations_seed.pb.h"
     17 
     18 namespace variations {
     19 
     20 class ProcessedStudy;
     21 class VariationsSeed;
     22 
     23 // VariationsSeedSimulator simulates the result of creating a set of studies
     24 // and detecting which studies would result in group changes.
     25 class VariationsSeedSimulator {
     26  public:
     27   // The result of variations seed simulation, counting the number of experiment
     28   // group changes of each type that are expected to occur on a restart with the
     29   // seed.
     30   struct Result {
     31     // The number of expected group changes that do not fall into any special
     32     // category. This is a lower bound due to session randomized studies.
     33     int normal_group_change_count;
     34 
     35     // The number of expected group changes that fall in the category of killed
     36     // experiments that should trigger the "best effort" restart mechanism.
     37     int kill_best_effort_group_change_count;
     38 
     39     // The number of expected group changes that fall in the category of killed
     40     // experiments that should trigger the "critical" restart mechanism.
     41     int kill_critical_group_change_count;
     42 
     43     Result();
     44     ~Result();
     45   };
     46 
     47   // Creates the simulator with the given entropy |provider|.
     48   explicit VariationsSeedSimulator(
     49       const base::FieldTrial::EntropyProvider& provider);
     50   virtual ~VariationsSeedSimulator();
     51 
     52   // Computes differences between the current process' field trial state and
     53   // the result of evaluating |seed| with the given parameters. Returns the
     54   // results of the simulation as a set of expected group change counts of each
     55   // type.
     56   Result SimulateSeedStudies(const VariationsSeed& seed,
     57                              const std::string& locale,
     58                              const base::Time& reference_date,
     59                              const base::Version& version,
     60                              Study_Channel channel,
     61                              Study_FormFactor form_factor,
     62                              const std::string& hardware_class);
     63 
     64  private:
     65   friend class VariationsSeedSimulatorTest;
     66 
     67   enum ChangeType {
     68     NO_CHANGE,
     69     CHANGED,
     70     CHANGED_KILL_BEST_EFFORT,
     71     CHANGED_KILL_CRITICAL,
     72   };
     73 
     74   // Computes differences between the current process' field trial state and
     75   // the result of evaluating the |processed_studies| list. It is expected that
     76   // |processed_studies| have already been filtered and only contain studies
     77   // that apply to the configuration being simulated. Returns the results of the
     78   // simulation as a set of expected group change counts of each type.
     79   Result ComputeDifferences(
     80       const std::vector<ProcessedStudy>& processed_studies);
     81 
     82   // Maps proto enum |type| to a ChangeType.
     83   ChangeType ConvertExperimentTypeToChangeType(Study_Experiment_Type type);
     84 
     85   // For the given |processed_study| with PERMANENT consistency, simulates group
     86   // assignment and returns a corresponding ChangeType if the result differs
     87   // from that study's group in the current process.
     88   ChangeType PermanentStudyGroupChanged(const ProcessedStudy& processed_study,
     89                                         const std::string& selected_group);
     90 
     91   // For the given |processed_study| with SESSION consistency, determines if
     92   // there are enough changes in the study config that restarting will result
     93   // in a guaranteed different group assignment (or different params) and
     94   // returns the corresponding ChangeType.
     95   ChangeType SessionStudyGroupChanged(const ProcessedStudy& filtered_study,
     96                                       const std::string& selected_group);
     97 
     98   const base::FieldTrial::EntropyProvider& entropy_provider_;
     99 
    100   DISALLOW_COPY_AND_ASSIGN(VariationsSeedSimulator);
    101 };
    102 
    103 }  // namespace variations
    104 
    105 #endif  // COMPONENTS_VARIATIONS_VARIATIONS_SEED_SIMULATOR_H_
    106