Do not duplicate code

Author: ScarletKuro

src/Scarlet.System.Text.Json.DateTimeConverter/DateTimeConverterFactoryHelper.cs

@@ -0,0 +1,33 @@
+using System.Text.Json.Serialization;
+
+namespace Scarlet.System.Text.Json.DateTimeConverter;
+
+internal static class DateTimeConverterFactoryHelper
+{
+    public static JsonConverter CreateConverter(Type typeToConvert, string format)
+    {
+        ArgumentNullException.ThrowIfNull(typeToConvert);
+
+        if (typeToConvert == typeof(DateTime))
+        {
+            return Converters.DateTimeConverter.FromFormat(format);
+        }
+
+        if (typeToConvert == typeof(DateTime?))
+        {
+            return Converters.DateTimeNullableConverter.FromFormat(format);
+        }
+
+        if (typeToConvert == typeof(DateTimeOffset))
+        {
+            return Converters.DateTimeOffsetConverter.FromFormat(format);
+        }
+
+        if (typeToConvert == typeof(DateTimeOffset?))
+        {
+            return Converters.DateTimeOffsetNullableConverter.FromFormat(format);
+        }
+
+        throw new NotSupportedException($"{typeToConvert.FullName} is not supported by the {nameof(DateTimeConverterFactoryHelper)}.");
+    }
+}

src/Scarlet.System.Text.Json.DateTimeConverter/JsonDateTimeConverterAttribute.cs

@@ -25,26 +25,8 @@ public override JsonConverter CreateConverter(Type typeToConvert)
     {
         ArgumentNullException.ThrowIfNull(typeToConvert);
 
-        if (typeToConvert == typeof(DateTime))
-        {
-            return Converters.DateTimeConverter.FromFormat(Format);
-        }
+        var converter = DateTimeConverterFactoryHelper.CreateConverter(typeToConvert, Format);
 
-        if (typeToConvert == typeof(DateTime?))
-        {
-            return Converters.DateTimeNullableConverter.FromFormat(Format);
-        }
-
-        if (typeToConvert == typeof(DateTimeOffset))
-        {
-            return Converters.DateTimeOffsetConverter.FromFormat(Format);
-        }
-
-        if (typeToConvert == typeof(DateTimeOffset?))
-        {
-            return Converters.DateTimeOffsetNullableConverter.FromFormat(Format);
-        }
-
-        throw new NotSupportedException($"{typeToConvert.FullName} is not supported by the {nameof(JsonDateTimeConverterAttribute)}.");
+        return converter;
     }
 }

src/Scarlet.System.Text.Json.DateTimeConverter/JsonDateTimeFormatConverter.cs

@@ -18,28 +18,9 @@ public override JsonConverter CreateConverter(Type typeToConvert, JsonSerializer
         ArgumentNullException.ThrowIfNull(typeToConvert);
 
         var format = T.Format;
+        var converter = DateTimeConverterFactoryHelper.CreateConverter(typeToConvert, format);
 
-        if (typeToConvert == typeof(DateTime))
-        {
-            return Converters.DateTimeConverter.FromFormat(format);
-        }
-
-        if (typeToConvert == typeof(DateTime?))
-        {
-            return Converters.DateTimeNullableConverter.FromFormat(format);
-        }
-
-        if (typeToConvert == typeof(DateTimeOffset))
-        {
-            return Converters.DateTimeOffsetConverter.FromFormat(format);
-        }
-
-        if (typeToConvert == typeof(DateTimeOffset?))
-        {
-            return Converters.DateTimeOffsetNullableConverter.FromFormat(format);
-        }
-
-        throw new NotSupportedException($"{typeToConvert.FullName} is not supported by the {nameof(JsonDateTimeConverterAttribute)}.");
+        return converter;
     }
 }