[translate] Add translate ranker model loader.

components/translate/core/browser/translate_ranker.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef COMPONENTS_TRANSLATE_CORE_BROWSER_TRANSLATE_RANKER_H_
 #define COMPONENTS_TRANSLATE_CORE_BROWSER_TRANSLATE_RANKER_H_
 
 #include <memory>
 #include <string>
+#include <vector>
 
-#include "base/feature_list.h"
-#include "base/gtest_prod_util.h"
-#include "base/memory/singleton.h"
-
-namespace chrome_intelligence {
-class TranslateRankerModel;
-}
+#include "base/macros.h"
+#include "components/keyed_service/core/keyed_service.h"
 
 namespace metrics {
 class TranslateEventProto;
-}
+}  // namespace metrics
 
 namespace translate {
 
 class TranslatePrefs;
-class TranslateURLFetcher;
-
-// Features used to enable ranker query, enforcement and logging. Note that
-// enabling enforcement implies (forces) enabling queries.
-extern const base::Feature kTranslateRankerQuery;
-extern const base::Feature kTranslateRankerEnforcement;
-extern const base::Feature kTranslateRankerLogging;
 
 // If enabled, downloads a translate ranker model and uses it to determine
 // whether the user should be given a translation prompt or not.
-class TranslateRanker {
+class TranslateRanker : public KeyedService {
  public:
-  ~TranslateRanker();
+  TranslateRanker() = default;
 
   // Returns true if query or enforcement is enabled.
-  static bool IsEnabled();
+  virtual bool IsEnabled() = 0;
 
   // Returns true if translate events logging is enabled.
-  static bool IsLoggingEnabled();
+  virtual bool IsLoggingEnabled() = 0;
 
   // Returns true if querying is enabled.
-  static bool IsQueryEnabled();
+  virtual bool IsQueryEnabled() = 0;
 
   // Returns true if enforcement is enabled.
-  static bool IsEnforcementEnabled();
+  virtual bool IsEnforcementEnabled() = 0;
 
-  // Returns the singleton TranslateRanker instance.
-  static TranslateRanker* GetInstance();
-
-  // For testing only. Returns a TranslateRanker instance preloaded with a
-  // TranslateRankerModel as defined by |model_data|.
-  static std::unique_ptr<TranslateRanker> CreateForTesting(
-      const std::string& model_data);
-
-  // Initiates downloading of the assist model data. This is a NOP if the model
-  // data has already been downloaded.
-  void FetchModelData();
+  // Returns the version id for the ranker model.
+  virtual int GetModelVersion() const = 0;
 
   // Returns true if executing the ranker model in the translation prompt
   // context described by |translate_prefs|, |src_lang|, |dst_lang| and possibly
   // other global browser context attributes suggests that the user should be
   // prompted as to whether translation should be performed.
-  bool ShouldOfferTranslation(const TranslatePrefs& translate_prefs,
-                              const std::string& src_lang,
-                              const std::string& dst_lang);
-
-  // Returns the model version (a date stamp) or 0 if there is no valid model.
-  int GetModelVersion() const;
+  virtual bool ShouldOfferTranslation(const TranslatePrefs& translate_prefs,
+                                      const std::string& src_lang,
+                                      const std::string& dst_lang) = 0;
 
   // Caches the translate event.
-  void RecordTranslateEvent(
-      const metrics::TranslateEventProto& translate_event);
+  virtual void AddTranslateEvent(
+      std::unique_ptr<metrics::TranslateEventProto> translate_event) = 0;
 
   // Transfers cached translate events to the given vector pointer and clears
   // the cache.
-  void FlushTranslateEvents(
-      std::vector<metrics::TranslateEventProto>* translate_events);
+  virtual void FlushTranslateEvents(
+      std::vector<std::unique_ptr<metrics::TranslateEventProto>>* events) = 0;
 
  private:
-  // The ID which is assigned to the underlying URLFetcher.
-  static constexpr int kFetcherId = 2;
-
-  TranslateRanker();
-
-  // Exposed for testing via FRIEND_TEST.
-  double CalculateScore(double accept_ratio,
-                        double decline_ratio,
-                        double ignore_ratio,
-                        const std::string& src_lang,
-                        const std::string& dst_lang,
-                        const std::string& app_locale,
-                        const std::string& country);
-
-  // Called when the model download has completed.
-  void ParseModel(int id, bool success, const std::string& model_data);
-
-  // The translation ranker model.
-  std::unique_ptr<chrome_intelligence::TranslateRankerModel> model_;
-
-  // A URL fetcher to download translation ranker model data.
-  std::unique_ptr<TranslateURLFetcher> model_fetcher_;
-
-  // The next time before which no new attempts to download the model should be
-  // attempted.
-  base::Time next_earliest_download_time_;
-
-  // Tracks the last time the translate ranker attempted to download its model.
-  // Used for UMA reporting of timing.
-  base::Time download_start_time_;
-
-  // Saved cache of translate event protos.
-  std::vector<metrics::TranslateEventProto> translate_events_cache_;
-
-  FRIEND_TEST_ALL_PREFIXES(TranslateRankerTest, CalculateScore);
-
-  friend struct base::DefaultSingletonTraits<TranslateRanker>;
-
   DISALLOW_COPY_AND_ASSIGN(TranslateRanker);
 };
 
 }  // namespace translate
 
 #endif  // COMPONENTS_TRANSLATE_CORE_BROWSER_TRANSLATE_RANKER_H_