Reduce the site engagement service public interface.

chrome/browser/engagement/site_engagement_score.h

Index: chrome/browser/engagement/site_engagement_score.h
diff --git a/chrome/browser/engagement/site_engagement_score.h b/chrome/browser/engagement/site_engagement_score.h
new file mode 100644
index 0000000000000000000000000000000000000000..7bebca721288261319567a1b77d8b93ecc64c414
--- /dev/null
+++ b/chrome/browser/engagement/site_engagement_score.h
@@ -0,0 +1,177 @@
+// 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 CHROME_BROWSER_ENGAGEMENT_SITE_ENGAGEMENT_SCORE_H_
+#define CHROME_BROWSER_ENGAGEMENT_SITE_ENGAGEMENT_SCORE_H_
+
+#include "base/gtest_prod_util.h"
+#include "base/macros.h"
+#include "base/time/time.h"
+#include "base/values.h"
+
+namespace base {
+class Clock;
+}
+
+class SiteEngagementScore {
+ public:
+  // The parameters which can be varied via field trial. All "points" values
+  // should be appended to the end of the enum prior to MAX_VARIATION.
+  enum Variation {
+    // The maximum number of points that can be accrued in one day.
+    MAX_POINTS_PER_DAY = 0,
+
+    // The period over which site engagement decays.
+    DECAY_PERIOD_IN_DAYS,
+
+    // The number of points to decay per period.
+    DECAY_POINTS,
+
+    // The number of points given for navigations.
+    NAVIGATION_POINTS,
+
+    // The number of points given for user input.
+    USER_INPUT_POINTS,
+
+    // The number of points given for media playing. Initially calibrated such
+    // that at least 30 minutes of foreground media would be required to allow a
+    // site to reach the daily engagement maximum.
+    VISIBLE_MEDIA_POINTS,
+    HIDDEN_MEDIA_POINTS,
+
+    // The number of points added to engagement when a site is launched from
+    // homescreen or added as a bookmark app. This bonus will apply for ten days
+    // following a launch; each new launch resets the ten days.
+    WEB_APP_INSTALLED_POINTS,
+
+    // The number of points given for the first engagement event of the day for
+    // each site.
+    FIRST_DAILY_ENGAGEMENT,
+
+    // The number of points that the engagement service must accumulate to be
+    // considered 'useful'.
+    BOOTSTRAP_POINTS,
+
+    // The boundaries between low/medium and medium/high engagement as returned
+    // by GetEngagementLevel().
+    MEDIUM_ENGAGEMENT_BOUNDARY,
+    HIGH_ENGAGEMENT_BOUNDARY,
+
+    MAX_VARIATION
+  };
+
+  // The maximum number of points that are allowed.
+  static const double kMaxPoints;
+
+  static double GetMaxPointsPerDay();
+  static double GetDecayPeriodInDays();
+  static double GetDecayPoints();
+  static double GetNavigationPoints();
+  static double GetUserInputPoints();
+  static double GetVisibleMediaPoints();
+  static double GetHiddenMediaPoints();
+  static double GetWebAppInstalledPoints();
+  static double GetFirstDailyEngagementPoints();
+  static double GetBootstrapPoints();
+  static double GetMediumEngagementBoundary();
+  static double GetHighEngagementBoundary();
+
+  // Update the default engagement settings via variations.
+  static void UpdateFromVariations(const char* param_name);
+
+  // The SiteEngagementScore does not take ownership of |clock|. It is the
+  // responsibility of the caller to make sure |clock| outlives this
+  // SiteEngagementScore.
+  SiteEngagementScore(base::Clock* clock,
+                      const base::DictionaryValue& score_dict);
+  ~SiteEngagementScore();
+
+  // Adds |points| to this score, respecting daily limits and the maximum
+  // possible score. Decays the score if it has not been updated recently
+  // enough.
+  void AddPoints(double points);
+  double GetScore() const;
+
+  // Returns true if the maximum number of points today has been added.
+  bool MaxPointsPerDayAdded() const;
+
+  // Resets the score to |points| and resets the daily point limit. If
+  // |updated_time| is non-null, sets the last engagement time and last
+  // shortcut launch time (if it is non-null) to |updated_time|. Otherwise, last
+  // engagement time is set to the current time and last shortcut launch time is
+  // left unchanged.
+  // TODO(calamity): Ideally, all SiteEngagementScore methods should take a
+  // base::Time argument like this one does rather than each SiteEngagementScore
+  // hold a pointer to a base::Clock. Then SiteEngagementScore doesn't need to
+  // worry about clock vending. See crbug.com/604305.
+  void Reset(double points, const base::Time* updated_time);
+
+  // Updates the content settings dictionary |score_dict| with the current score
+  // fields. Returns true if |score_dict| changed, otherwise return false.
+  bool UpdateScoreDict(base::DictionaryValue* score_dict);
+
+  // Get/set the last time this origin was launched from an installed shortcut.
+  base::Time last_shortcut_launch_time() const {
+    return last_shortcut_launch_time_;
+  }
+  void set_last_shortcut_launch_time(const base::Time& time) {
+    last_shortcut_launch_time_ = time;
+  }
+
+ private:
+  FRIEND_TEST_ALL_PREFIXES(SiteEngagementScoreTest, PartiallyEmptyDictionary);
+  FRIEND_TEST_ALL_PREFIXES(SiteEngagementScoreTest, PopulatedDictionary);
+  FRIEND_TEST_ALL_PREFIXES(SiteEngagementScoreTest, Reset);
+  FRIEND_TEST_ALL_PREFIXES(SiteEngagementScoreTest, FirstDailyEngagementBonus);
+  friend class ImportantSitesUtilTest;
+  friend class SiteEngagementHelperTest;
+  friend class SiteEngagementScoreTest;
+  friend class SiteEngagementServiceTest;
+
+  // Array holding the values corresponding to each item in Variation array.
+  static double param_values[];
+
+  // Keys used in the content settings dictionary.
+  static const char* kRawScoreKey;
+  static const char* kPointsAddedTodayKey;
+  static const char* kLastEngagementTimeKey;
+  static const char* kLastShortcutLaunchTimeKey;
+
+  // This version of the constructor is used in unit tests.
+  explicit SiteEngagementScore(base::Clock* clock);
+
+  // Determine the score, accounting for any decay.
+  double DecayedScore() const;
+
+  // Determine any score bonus from having installed shortcuts.
+  double BonusScore() const;
+
+  // Sets fixed parameter values for testing site engagement. Ensure that any
+  // newly added parameters receive a fixed value here.
+  static void SetParamValuesForTesting();
+
+  // The clock used to vend times. Enables time travelling in tests. Owned by
+  // the SiteEngagementService.
+  base::Clock* clock_;
+
+  // |raw_score_| is the score before any decay is applied.
+  double raw_score_;
+
+  // The points added 'today' are tracked to avoid adding more than
+  // kMaxPointsPerDay on any one day. 'Today' is defined in local time.
+  double points_added_today_;
+
+  // The last time the score was updated for engagement. Used in conjunction
+  // with |points_added_today_| to avoid adding more than kMaxPointsPerDay on
+  // any one day.
+  base::Time last_engagement_time_;
+
+  // The last time the site with this score was launched from an installed
+  // shortcut.
+  base::Time last_shortcut_launch_time_;
+
+  DISALLOW_COPY_AND_ASSIGN(SiteEngagementScore);
+};
+
+#endif  // CHROME_BROWSER_ENGAGEMENT_SITE_ENGAGEMENT_SCORE_H_