implement base sortable class.

osu.Game.Rulesets.Karaoke/IO/Serialization/Converters/SortableJsonConvertor.cs

@@ -0,0 +1,38 @@
+// Copyright (c) andy840119 <[email protected]>. Licensed under the GPL Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Newtonsoft.Json;
+using Newtonsoft.Json.Linq;
+
+namespace osu.Game.Rulesets.Karaoke.IO.Serialization.Converters
+{
+    public abstract class SortableJsonConvertor<TObject> : JsonConverter<IEnumerable<TObject>>
+    {
+        public sealed override IEnumerable<TObject> ReadJson(JsonReader reader, Type objectType, IEnumerable<TObject> existingValue, bool hasExistingValue, JsonSerializer serializer)
+        {
+            var obj = JArray.Load(reader);
+            var timeTags = obj.Select(x => serializer.Deserialize<TObject>(x.CreateReader()));
+            return GetSortedValue(timeTags);
+        }
+
+        public override void WriteJson(JsonWriter writer, IEnumerable<TObject> value, JsonSerializer serializer)
+        {
+            // see: https://stackoverflow.com/questions/3330989/order-of-serialized-fields-using-json-net
+            var sortedTimeTags = GetSortedValue(value);
+
+            writer.WriteStartArray();
+
+            foreach (var timeTag in sortedTimeTags)
+            {
+                serializer.Serialize(writer, timeTag);
+            }
+
+            writer.WriteEndArray();
+        }
+
+        protected abstract IEnumerable<TObject> GetSortedValue(IEnumerable<TObject> objects);
+    }
+}