using System;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Reflection;

​

using Newtonsoft.Json;

using Newtonsoft.Json.Linq;

using Newtonsoft.Json.Converters;

using Newtonsoft.Json.Serialization;    

​

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

​

//https://stackoverflow.com/questions/76254261/jsonconvert-populateobject-is-making-my-values-default-or-null-when-inside-a-cus

​

#nullable enable

​

    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Interface | AttributeTargets.Struct, AllowMultiple = false, Inherited = true)]

    public sealed class JsonCanPopulateAttribute : System.Attribute

    {

        public JsonCanPopulateAttribute(bool canPopulate) => this.CanPopulate = canPopulate;

        public bool CanPopulate { get; init; }

    }

    public class AutomaticArrayMergeConverter : ArrayMergeConverter

    {

        static Lazy<IContractResolver> DefaultResolver { get; } = new (() => JsonSerializer.Create().ContractResolver );

        readonly IContractResolver resolver;

        public AutomaticArrayMergeConverter() : this(DefaultResolver.Value) { }

        public AutomaticArrayMergeConverter(IContractResolver resolver) => this.resolver = resolver ?? throw new ArgumentNullException(nameof(resolver));

        public override bool CanConvert(Type objectType) =>

            objectType.IsArray && objectType.GetArrayRank() == 1 && resolver.CanPopulateType(objectType.GetElementType()!);

    }

​

    // Adapted from this answer https://stackoverflow.com/a/40432055/3744182

    // To https://stackoverflow.com/questions/40422136/jsonserializer-createdefault-populate-resets-my-values

    public class ArrayMergeConverter : JsonConverter

    {

        public override object? ReadJson(JsonReader reader, Type objectType, object? existingValue, JsonSerializer serializer)

        {

            if (!objectType.IsArray)

                throw new JsonSerializationException(string.Format("Non-array type {0} not supported.", objectType));

            var contract = (JsonArrayContract)serializer.ContractResolver.ResolveContract(objectType);

            if (contract.IsMultidimensionalArray)

                throw new JsonSerializationException("Multidimensional arrays not supported.");

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

                return null;

            else if (reader.TokenType != JsonToken.StartArray)

                throw new JsonSerializationException(string.Format("Invalid start token: {0}", reader.TokenType));

            var existingArray = existingValue as System.Array;

            IList list = new List<object>();

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

            {

                switch (reader.TokenType)

                {

                    case JsonToken.Null:

                        list.Add(null);

                        break;

                    default:

                        // Add item to list

                        var existingItem = existingArray != null && list.Count < existingArray.Length ? existingArray.GetValue(list.Count) : null;

                        if (existingItem == null)

                            existingItem = serializer.Deserialize(reader, contract.CollectionItemType);

                        else

                            serializer.Populate(reader, existingItem);

                        list.Add(existingItem);

                        break;

                }

            }

​

            var array = (existingArray != null && existingArray.Length == list.Count ? existingArray : Array.CreateInstance(contract.CollectionItemType!, list.Count));

            list.CopyTo(array, 0);

            return array;

        }

​

        public override bool CanWrite => false;

        public override void WriteJson(JsonWriter writer, object? value, JsonSerializer serializer) => throw new NotImplementedException();

        public override bool CanConvert(Type objectType) => throw new NotImplementedException("This converter is meant to be applied via attributes only.");

    }

​

    public static partial class JsonExtensions

    {

        public static bool CanPopulateType(this IContractResolver resolver, Type type)

        {

            if (type.GetCustomAttribute<JsonCanPopulateAttribute>() is {} attr)

                return attr.CanPopulate;

            // No attribute, so apply some heuristics.

            var elementContract = resolver.ResolveContract(type);

            if (elementContract.Converter != null)

                return false;

            if (elementContract is JsonObjectContract c)

                // Apply some heuristics to see whether all properties are equally readable and writable.

                return c.Properties.All(p => p.Readable == p.Writable);

            return false;

        }

        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)

        {

            if (reader == null)

                throw new ArgumentNullException();

            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)

        {

            if (reader == null)

                throw new ArgumentNullException();

            if (!reader.Read())

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

            return reader;

        }

    }

​

    // Dummies for demo

​

    public class SerializeFieldAttribute : System.Attribute { }

​

    public struct Vector3

    {

        public double X { get; init; }

        public double Y { get; init; }

        public double Z { get; init; }

    }

​

    public class GameObject { }

​

    public class ManagedSubData { }

​

    public class BuildableControllerV2 { }

​

    public class NoPropertiesContractResolver : DefaultContractResolver { } // Not shown in question

​

    // Classes from question

​

    public class BuildableData : ManagedSubData

    {

        public BuildableData(BuildableControllerV2 prefab, float heightMove, bool isStatic, int initialQuantity, bool hasMinigame, UpgradeLevel[] upgradeLevels) =>

            (this.prefab, this.heightMove, this.isStatic, this.initialQuantity, this.hasMinigame, this.upgradeLevels) = (prefab, heightMove, isStatic, initialQuantity, hasMinigame, upgradeLevels);

        [SerializeField, JsonIgnore] private BuildableControllerV2 prefab;

        [SerializeField, JsonProperty] private float heightMove = 2f;

        [SerializeField, JsonProperty] private bool isStatic;

        [SerializeField, JsonProperty] private int initialQuantity = 1;

        [SerializeField, JsonProperty] private bool hasMinigame = false;

        [SerializeField, JsonProperty(TypeNameHandling = TypeNameHandling.None)]

        private UpgradeLevel[] upgradeLevels;

        public (BuildableControllerV2 prefab, float heightMove, bool isStatic, int initialQuantity, bool hasMinigame, UpgradeLevel[] upgradeLevels) GetData() =>

            (this.prefab, this.heightMove, this.isStatic, this.initialQuantity, this.hasMinigame, this.upgradeLevels);

    }

​

    [Serializable, JsonCanPopulate(true)]

    public class UpgradeLevel

    {

        public UpgradeLevel(GameObject visual, int cost, Vector3 test) =>

            (this.visual, this.cost, this.test) = (visual, cost, test);

        [SerializeField] private GameObject visual;

        [SerializeField, JsonProperty] private int cost;

        [SerializeField, JsonProperty] private Vector3 test;

        public (GameObject visual, int cost, Vector3 test) GetData() =>

            (this.visual, this.cost, this.test);

    }

​

    class TestClass

    {

        public static void Test()

        {

            BuildableControllerV2 prefab = new();

            GameObject visual = new();

            var upgradeLevels1 = new UpgradeLevel []

            {

                new(visual, 25, new Vector3 { X = 101, Y = 202, Z = 303 }),

                new(visual, 18, new Vector3 { X = 45, Y = 56, Z = 67 }),

            };

            var data1 = new BuildableData(prefab, 101.01f, true, 12, true, upgradeLevels1);

​

            var resolver = new NoPropertiesContractResolver(); // Cache statically to improve performance

            var converter = new AutomaticArrayMergeConverter(resolver);

            var defaultSettings =  new JsonSerializerSettings(){

                Converters = { converter },

                Formatting = Formatting.None,

                PreserveReferencesHandling = PreserveReferencesHandling.None,

                MissingMemberHandling = MissingMemberHandling.Ignore,

                //ObjectCreationHandling = ObjectCreationHandling.Replace -- Removed

                TypeNameHandling = TypeNameHandling.All, // Be sure you need this, see https://stackoverflow.com/q/39565954 for why.

                ContractResolver = resolver, 

            };          

            var json = JsonConvert.SerializeObject(data1, Formatting.Indented, defaultSettings);

            var upgradeLevels2 = new UpgradeLevel []

            {

                new(visual, default, default),

                new(visual, default, default),

            };

            var buildableData = new BuildableData(prefab, default, default, default, default, upgradeLevels2);

​

            var json1 = JsonConvert.SerializeObject(buildableData, Formatting.Indented, defaultSettings);

            JsonConvert.PopulateObject(json, buildableData, defaultSettings);

            var json2 = JsonConvert.SerializeObject(buildableData, Formatting.Indented, defaultSettings);

​

            Console.WriteLine("{0} before PopulateObject():", buildableData);

            Console.WriteLine(json1);

            Console.WriteLine("Input JSON:");

            Console.WriteLine(json);

            Console.WriteLine("{0} after  PopulateObject():", buildableData);

            Console.WriteLine(json2);

​

            Assert.That(converter.CanConvert(typeof(UpgradeLevel [])));

            Assert.AreEqual(json, json);

            Assert.AreEqual(buildableData.GetData().prefab, prefab, "buildableData.GetData().prefab, == prefab");

            Assert.That(buildableData.GetData().upgradeLevels.All(l => l.GetData().visual == visual), "All(l => l.GetData().visual == visual)");

        }   

        static string GetJson() =>

"""

{

  "heightMove": 101.01,

  "isStatic": true,

  "initialQuantity": 12,

  "hasMinigame": true,

  "upgradeLevels": [

    {

      "cost": 25,

      "test": {

        "X": 101.0,

        "Y": 202.0,

        "Z": 303.0

      }

    },

    {

      "cost": 18,

      "test": {

        "X": 45.0,

        "Y": 56.0,

        "Z": 67.0

      }

    }

  ]

}

""";            

    }

​

    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;

            }

        }

    }

​