using System;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.IO;

using System.Data;

using System.Reflection;

using System.Threading.Tasks;

​

using System.Text.Json;

using System.Text.Json.Serialization;

using System.Text.Json.Serialization.Metadata;

using System.Text.Json.Nodes;

​

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

​

//https://stackoverflow.com/questions/76438672/how-can-we-deserialize-to-protobuf-from-huge-json-using-jsonserializer-deseriali

​

using OASISLevel2TrackingPacket;

​

#nullable enable

​

namespace OASISLevel2TrackingPacket

{

    [global::ProtoBuf.ProtoContract]

    public partial class EntityTracking

    {

        [global::ProtoBuf.ProtoMember(2, Name = @"TrackingData")]

        public global::System.Collections.Generic.List<EntityTrackingActivity> TrackingDatas { get; } = new global::System.Collections.Generic.List<EntityTrackingActivity>();      

    }

​

    [global::ProtoBuf.ProtoContract]

    public partial class Person : EntityTracking

    {

        [global::ProtoBuf.ProtoMember(1, Name = @"Name")]

        public string? Name { get; set; }

    }

​

    [global::ProtoBuf.ProtoContract]

    public partial class EntityTrackingActivity

    {

        [global::ProtoBuf.ProtoMember(1, Name = @"Id")]

        public int Id { get; set; }

    }

}

​

    public static partial class JsonExtensions

    {

        public static Action<JsonTypeInfo> InitializeProtoMemberNames(Type type) => typeInfo => 

        {

            if (typeInfo.Kind != JsonTypeInfoKind.Object)

                return;

            if (!type.IsAssignableFrom(typeInfo.Type))

                return;

            // Fix property name(s).

            foreach (var property in typeInfo.Properties)

            {

                // Set the JSON property name to be the same as ProtoMemberAttribute.Name

                var name = property.AttributeProvider?.GetCustomAttributes(typeof(global::ProtoBuf.ProtoMemberAttribute), true)

                    .OfType<global::ProtoBuf.ProtoMemberAttribute>()

                    .FirstOrDefault()

                    ?.Name;

                if (name != null)

                    property.Name = name;

            }

        };

​

    }

​

    public class TestClass

    {

        public static async Task Test()

        {

            var filename = "hugefile.json";

            var json = 

                """

                [{"Name":"My name is 0","TrackingData":[{"Id":0},{"Id":1}]},{"Name":"My name is 1","TrackingData":[{"Id":2},{"Id":3}]},{"Name":"My name is 2","TrackingData":[{"Id":4},{"Id":5}]},{"Name":"My name is 3","TrackingData":[{"Id":6},{"Id":7}]}]

                """;

            Console.WriteLine(json);

            await File.WriteAllTextAsync(filename, json);

            var options = new JsonSerializerOptions

            {

                PreferredObjectCreationHandling = JsonObjectCreationHandling.Populate,           

                TypeInfoResolver = new DefaultJsonTypeInfoResolver()

                    .WithAddedModifier(JsonExtensions.InitializeProtoMemberNames(typeof(Person))),

            };

            await using var fileStream = new FileStream(filename, FileMode.Open, FileAccess.Read, FileShare.Read, bufferSize: 4096, useAsync: true);

            var people = JsonSerializer.DeserializeAsyncEnumerable<Person?>(fileStream, options);

            await foreach (var person in people)

            {

                Console.WriteLine($"Hello, my name is \"{person?.Name}\", my tracking data is {JsonSerializer.Serialize(person?.TrackingDatas.Select(t => t.Id))}!");

                Assert.That(person?.TrackingDatas.Count > 0);

            }           

        }

    }

​

    public class Program

    {

        public static async Task Main(string[] args)

        {

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

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

            Console.WriteLine();

​

            try

            {

                await TestClass.Test();

            }

            catch (Exception ex)

            {

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

                Console.WriteLine(ex);

                throw;

            }

        }

    }

​