using System;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.IO;

using System.Data;

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 partial class Person

    {

        public Person() { } // Add parameterless constructor if not already auto-generated by protobuf

        [JsonConstructor]

        public Person(List<EntityTrackingActivity> trackingDatas) => this.TrackingDatas.AddRange(trackingDatas ?? throw new ArgumentNullException(nameof(trackingDatas)));

    }

}

​

    public class CustomNamingPolicy : JsonNamingPolicy

    {

        private readonly Dictionary<string, string> NameMapping = new Dictionary<string, string>()

        {

            [nameof(EntityTracking.TrackingDatas)] = "TrackingData"

        };

​

        public override string ConvertName(string name)

        {

            var a = NameMapping.GetValueOrDefault(name, name);

​

            return a;

        }

    }

​

    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

            {

                PropertyNamingPolicy = new CustomNamingPolicy()             

            };

​

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

            {

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

                await foreach (Person? person in people)

                {

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

                }           

            }

        }

    }

​

    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;

            }

        }

    }

​