Add mod setting (de)serialization support

osu.Game/Online/API/APIMod.cs

@@ -0,0 +1,56 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using System.Collections.Generic;
+using System.Linq;
+using Humanizer;
+using Newtonsoft.Json;
+using osu.Framework.Bindables;
+using osu.Game.Configuration;
+using osu.Game.Rulesets;
+using osu.Game.Rulesets.Mods;
+
+namespace osu.Game.Online.API
+{
+    public class APIMod : IMod
+    {
+        [JsonProperty("acronym")]
+        public string Acronym { get; set; }
+
+        [JsonProperty("settings")]
+        public Dictionary<string, object> Settings { get; set; } = new Dictionary<string, object>();
+
+        [JsonConstructor]
+        private APIMod()
+        {
+        }
+
+        public APIMod(Mod mod)
+        {
+            Acronym = mod.Acronym;
+
+            foreach (var (_, property) in mod.GetSettingsSourceProperties())
+                Settings.Add(property.Name.Underscore(), property.GetValue(mod));
+        }
+
+        public Mod ToMod(Ruleset ruleset)
+        {
+            Mod resultMod = ruleset.GetAllMods().FirstOrDefault(m => m.Acronym == Acronym);
+
+            if (resultMod == null)
+                return null; // Todo: Maybe throw exception?
+
+            foreach (var (_, property) in resultMod.GetSettingsSourceProperties())
+            {
+                if (!Settings.TryGetValue(property.Name.Underscore(), out object settingValue))
+                    continue;
+
+                ((IBindable)property.GetValue(resultMod)).Parse(settingValue);
+            }
+
+            return resultMod;
+        }
+
+        public bool Equals(IMod other) => Acronym == other?.Acronym;
+    }
+}