add SettingsValueOption

Pilz.Configuration/ISettingsValueOptionValueAccessor.cs

@@ -0,0 +1,6 @@
+namespace Pilz.Configuration;
+
+internal interface ISettingsValueOptionValueAccessor
+{
+    public object ValueRaw { get; set; }
+}

Pilz.Configuration/SettingsValueOption.cs

@@ -0,0 +1,49 @@
+using Newtonsoft.Json;
+
+namespace Pilz.Configuration;
+
+[JsonObject(ItemNullValueHandling = NullValueHandling.Ignore)]
+[JsonConverter(typeof(SettingsValueOptionJsonConverter))]
+public class SettingsValueOption<T> : ISettingsValueOptionValueAccessor where T : struct
+{
+    protected T? value;
+
+    public T DefaultValue { get; }
+    public virtual bool IsDefault => value == null;
+
+    public SettingsValueOption()
+    {
+    }
+
+    public SettingsValueOption(T value)
+    {
+        this.value = DefaultValue = value;
+    }
+
+    public virtual T Value
+    {
+        get => value ?? DefaultValue;
+        set => this.value = value;
+    }
+
+    public static implicit operator T(SettingsValueOption<T> option)
+    {
+        return option.Value;
+    }
+
+    object ISettingsValueOptionValueAccessor.ValueRaw
+    {
+        get => value;
+        set => this.value = (T?)value;
+    }
+
+    public virtual void Reset()
+    {
+        value = null;
+    }
+
+    public override string ToString()
+    {
+        return Value.ToString();
+    }
+}

Pilz.Configuration/SettingsValueOptionJsonConverter.cs

@@ -0,0 +1,27 @@
+using Newtonsoft.Json;
+using System;
+
+namespace Pilz.Configuration;
+
+public class SettingsValueOptionJsonConverter : JsonConverter
+{
+    public override bool CanConvert(Type objectType)
+    {
+        return true;
+    }
+
+    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
+    {
+        if (existingValue is ISettingsValueOptionValueAccessor option)
+            option.ValueRaw = reader.Value;
+        return existingValue;
+    }
+
+    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
+    {
+        if (value is ISettingsValueOptionValueAccessor option)
+            writer.WriteValue(option.ValueRaw);
+        else
+            writer.WriteNull();
+    }
+}