Fix duplicate rating tags and support migration

- Remove old rating tags when rating changes
- Automatically update tags when the following settings change
    - EnableHalfStars
    - RatingSteps
    - ShowZeroRating
    - ShouldApplyRatingTag
    - RatingTagPrefix
- Fix a null-ref except. when adding a tag to a game w/ no existing tags

StarRatings.cs

@@ -56,14 +56,18 @@ public override IEnumerable<MainMenuItem> GetMainMenuItems(GetMainMenuItemsArgs
                 {
                     MenuSection = "StarRatings",
                     Description = "Rebuild Rating Tags",
-                    Action = (menuArgs) => ApplyRatingTags(PlayniteApi.Database.Games.ToList()),
+                    Action = (menuArgs) =>
+                    {
+                        ClearRatingTags(PlayniteApi.Database.Games);
+                        ReapplyRatingTags(PlayniteApi.Database.Games);
+                    },
                 };
 
                 yield return new MainMenuItem
                 {
                     MenuSection = "StarRatings",
                     Description = "Clear All Rating Tags",
-                    Action = (menuArgs) => ClearRatingTags(PlayniteApi.Database.Games.ToList()),
+                    Action = (menuArgs) => ClearRatingTags(PlayniteApi.Database.Games),
                 };
             }
         }
@@ -230,8 +234,25 @@ private void ApplyUserScore(IEnumerable<Game> games, int? userScore)
         {
             foreach (Game game in games)
             {
+                // remove existing tag if needed
+                if (CurrentSettings.ShouldApplyRatingTag && game.UserScore.HasValue && game.TagIds != null)
+                {
+                    int originalScore = game.UserScore.Value;
+
+                    // round down to previous level
+                    if (!scoreToRatingData.ContainsKey(originalScore))
+                    {
+                        int stepSize = 100 / CurrentSettings.RatingSteps;
+                        originalScore = (originalScore / stepSize) * stepSize;
+                    }
+
+                    game.TagIds.Remove(scoreToRatingData[originalScore].ratingTagId);
+                }
+
+                // set new score
                 game.UserScore = userScore;
 
+                // update tag if needed
                 if (CurrentSettings.ShouldApplyRatingTag && userScore.HasValue)
                 {
                     // create tags if game has none
@@ -243,33 +264,30 @@ private void ApplyUserScore(IEnumerable<Game> games, int? userScore)
             PlayniteApi.Database.Games.Update(games);
         }
 
-        private void ApplyRatingTags(IEnumerable<Game> games)
+        public void ReapplyRatingTags(IEnumerable<Game> games)
         {
             foreach (var game in games)
             {
                 // skip if no score
                 if(!game.UserScore.HasValue) { continue; }
 
                 int userScore = game.UserScore.Value;
-
-                // skip if score does not correspond to anything
-                // TODO: consider rounding down to next applicable score
-                if (!scoreToRatingData.ContainsKey(userScore)) { continue; }
 
-                // create TagIds for game if none exists
-                if (game.TagIds == null)
+                // round down to previous level
+                if (!scoreToRatingData.ContainsKey(userScore))
                 {
-                    game.TagIds = new List<Guid>();
+                    int stepSize = 100 / CurrentSettings.RatingSteps;
+                    userScore = (userScore / stepSize) * stepSize;
                 }
-                
+
                 // retrieve and stage tag
                 game.TagIds.Add(scoreToRatingData[userScore].ratingTagId);
             }
 
             PlayniteApi.Database.Games.Update(games);
         }
 
-        private void ClearRatingTags(IEnumerable<Game> games)
+        public void ClearRatingTags(IEnumerable<Game> games)
         {
             // cache list of tags to remove
             List<Guid> tagsToRemove = new List<Guid>();

StarRatingsSettings.cs

@@ -32,7 +32,7 @@ public class StarRatingsSettings : ObservableObject
     public class StarRatingsSettingsViewModel : ObservableObject, ISettings
     {
         private readonly StarRatings plugin;
-        private StarRatingsSettings editingClone { get; set; }
+        private StarRatingsSettings prevSavedSettings { get; set; }
 
         private StarRatingsSettings settings;
         public StarRatingsSettings Settings
@@ -54,38 +54,50 @@ public StarRatingsSettingsViewModel(StarRatings plugin)
             var savedSettings = plugin.LoadPluginSettings<StarRatingsSettings>();
 
             // LoadPluginSettings returns null if not saved data is available.
-            if (savedSettings != null)
-            {
-                Settings = savedSettings;
-            }
-            else
-            {
-                Settings = new StarRatingsSettings();
-            }
+            Settings = savedSettings ?? new StarRatingsSettings();
         }
 
         public void BeginEdit()
         {
             // Code executed when settings view is opened and user starts editing values.
-            editingClone = Serialization.GetClone(Settings);
+            prevSavedSettings = Serialization.GetClone(Settings);
         }
 
         public void CancelEdit()
         {
             // Code executed when user decides to cancel any changes made since BeginEdit was called.
             // This method should revert any changes made to Option1 and Option2.
-            Settings = editingClone;
+            Settings = prevSavedSettings;
         }
 
         public void EndEdit()
         {
             // Code executed when user decides to confirm changes made since BeginEdit was called.
             // This method should save settings made to Option1 and Option2.
             plugin.SavePluginSettings(Settings);
+
+            bool hasChangedRatingScheme = prevSavedSettings.EnableHalfStars != Settings.EnableHalfStars ||
+                                          prevSavedSettings.RatingSteps != Settings.RatingSteps ||
+                                          prevSavedSettings.ShowZeroRating != Settings.ShowZeroRating ||
+                                          prevSavedSettings.ShouldApplyRatingTag != Settings.ShouldApplyRatingTag ||
+                                          prevSavedSettings.RatingTagPrefix != Settings.RatingTagPrefix;
+
+            // did we have tags enabled before?
+            if (hasChangedRatingScheme && prevSavedSettings.ShouldApplyRatingTag)
+            {
+                plugin.ClearRatingTags(plugin.PlayniteApi.Database.Games);
+            }
 
             // Reinitialize ratings on edit
             // TODO - We could listen for actual changes but this should be fairly cheap
+            //        and uncomplicated to maintain until we need more complexity
             plugin.InitializeRatings();
+
+            // do we need to apply tags again?
+            if (hasChangedRatingScheme && Settings.ShouldApplyRatingTag)
+            {
+                plugin.ReapplyRatingTags(plugin.PlayniteApi.Database.Games);
+            }
         }
 
         public bool VerifySettings(out List<string> errors)