using System;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Data;

​

using Newtonsoft.Json;

using Newtonsoft.Json.Linq;

using Newtonsoft.Json.Converters;

using Newtonsoft.Json.Serialization;    

using System.Runtime.Serialization;

​

using NUnit.Framework; // Throws NUnit.Framework.AssertionException

​

//https://stackoverflow.com/questions/77484404/how-to-invoke-jsonconverter-from-inside-other-jsonconverter

​

public class Step

{

    public List<ElementData> Elements { get; set; }

}

​

public class ElementData

{

    [JsonProperty("type", Required = Required.Always)]

    [JsonConverter(typeof(StringEnumConverter))]

    public ElementType ElementType { get; set; }

    public string SomeValue { get; set; }

}

​

public class ElementDataJsonConverter : JsonConverter<ElementData>

{

    public override ElementData ReadJson(JsonReader reader, Type objectType, ElementData existingValue, bool hasExistingValue, JsonSerializer serializer)

    {

        var element = hasExistingValue ? existingValue : new ElementData();

        serializer.Populate(reader, element);

        return element;

    }

​

    public override void WriteJson(JsonWriter writer, ElementData value, JsonSerializer serializer)

    {

        JsonSerializer.Create().Serialize(writer, value);

    }

}

​

public enum ElementType

{

    [EnumMember(Value = "type1")] Type1,

    [EnumMember(Value = "type2")] Type2,

}

​

public class CustomElementJsonConverter : JsonConverter<Step>

{

    private static readonly Dictionary<string, JsonConverter> _converters = new();

    static CustomElementJsonConverter()

    {

        foreach (var elementType in Enum.GetValues(typeof(ElementType)).Cast<ElementType>())

        {

            string elemTypeJsonName = elementType.ToString().ToLowerInvariant();

            _converters[elemTypeJsonName] = new ElementDataJsonConverter();

        }

    }

​

    public override Step ReadJson(JsonReader reader, Type objectType, Step existingValue, bool hasExistingValue, JsonSerializer serializer) 

    {

        if (reader.MoveToContentAndAssert().TokenType == JsonToken.Null)

            return null; // TODO : decide whether to return null or throw an exception.

        // Reuse the existing values if present.

        var step = hasExistingValue ? existingValue : new Step();

        step.Elements ??= new ();

​

        step.Elements.AddRange(reader.EnumerateArray().Select(jElement =>

        {        

            // TODO: check for null or missing missing `"type"` 

            var elementType = jElement["type"].Value<string>().ToLowerInvariant(); // FIXED: replaced ToLower with ToLowerInvariant

            var convertor = _converters[elementType];

            using var subReader = jElement.CreateReader();

            return (ElementData)convertor.ReadJson(subReader.MoveToContentAndAssert(), typeof(ElementData), null, serializer);

        }));

​

        return step;

    }  

​

    public override void WriteJson(JsonWriter writer, Step value, JsonSerializer serializer)

    {

        serializer.Serialize(writer, value.Elements);

    }   

}

​

    public static partial class JsonExtensions

    {

        public static JsonReader AssertTokenType(this JsonReader reader, JsonToken tokenType) => 

            reader.TokenType == tokenType ? reader : throw new JsonSerializationException(string.Format("Unexpected token {0}, expected {1}", reader.TokenType, tokenType));

        public static JsonReader ReadToContentAndAssert(this JsonReader reader) =>

            reader.ReadAndAssert().MoveToContentAndAssert();

​

        public static JsonReader MoveToContentAndAssert(this JsonReader reader)

        {

            ArgumentNullException.ThrowIfNull(reader);

            if (reader.TokenType == JsonToken.None)       // Skip past beginning of stream.

                reader.ReadAndAssert();

            while (reader.TokenType == JsonToken.Comment) // Skip past comments.

                reader.ReadAndAssert();

            return reader;

        }

​

        public static JsonReader ReadAndAssert(this JsonReader reader)

        {

            ArgumentNullException.ThrowIfNull(reader);

            if (!reader.Read())

                throw new JsonReaderException("Unexpected end of JSON stream.");

            return reader;

        }

        public static IEnumerable<JToken> EnumerateArray(this JsonReader reader)

        {

            reader.MoveToContentAndAssert().AssertTokenType(JsonToken.StartArray);

            while (reader.ReadAndAssert().TokenType != JsonToken.EndArray)

                yield return JToken.Load(reader);

        }

    }

​

    class TestClass

    {

        public static void Test()

        {

            var step = new Step()

            {

                Elements = new()

                {

                    new () { SomeValue = "some value" },

                    new () { ElementType = ElementType.Type2, SomeValue = "some other value" },

                },

            };

            var settings = new JsonSerializerSettings 

            {

                Converters = { new CustomElementJsonConverter() },

            };

            var json = JsonConvert.SerializeObject(step, Formatting.Indented, settings);

            Console.WriteLine(json);

            var step2 = JsonConvert.DeserializeObject<Step>(json, settings);

            Assert.AreEqual(step.Elements.Count, step2.Elements.Count);

​

            var json2 = JsonConvert.SerializeObject(step2, Formatting.Indented, settings);

            Assert.AreEqual(json, json2);

        }   

    }

​

    public class Program

    {

        public static void Main()

        {

            Console.WriteLine("Environment version: {0} ({1}), {2}", System.Runtime.InteropServices.RuntimeInformation.FrameworkDescription , Environment.Version, Environment.OSVersion);

            Console.WriteLine("{0} version: {1}", typeof(JsonSerializer).Namespace, typeof(JsonSerializer).Assembly.FullName);

            Console.WriteLine();

​

            try

            {

                TestClass.Test();

            }

            catch (Exception ex)

            {

                Console.WriteLine("Failed with unhandled exception: ");

                Console.WriteLine(ex);

                throw;

            }

        }

    }

​