using System;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Runtime.Serialization.Formatters;

using System.IO;

using System.Data;

using System.ComponentModel.DataAnnotations;

using System.Globalization;

using System.Reflection;

using System.Collections.ObjectModel;

using System.Threading.Tasks;

using System.Net.Http;

​

using System.Text.Json;

using System.Text.Json.Serialization;

​

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

​

//https://stackoverflow.com/questions/66258830/how-to-deserialize-part-of-json-using-system-text-json-in-net-core-3-0

​

    public class MarsWheather {

        [JsonPropertyName("First_UTC")]

        public DateTime FirstUTC { get; set; }

        [JsonPropertyName("Last_UTC")]

        public DateTime LastUTC { get; set; }

        [JsonPropertyName("Season")]

        [JsonConverter(typeof(JsonStringEnumConverter))]

        public Season MarsSeason { get; set; }

        [JsonPropertyName("PRE")]

        public DataDescription AtmosphericPressure { get; set; }

    }

​

    public enum Season {

        winter,

        spring,

        summer,

        autumn

    }

​

    public class DataDescription{

        [JsonPropertyName("av")]

        public double Average { get; set; }

        [JsonPropertyName("ct")]

        public double TotalCount { get; set; }

        [JsonPropertyName("mn")]

        public double Minimum { get; set; }

        [JsonPropertyName("mx")]

        public double Maximum { get; set; }

    } 

​

    [JsonConverter(typeof(MarsWheatherRootObjectConverter))]

    public class MarsWheatherRootObject

    {

        public Dictionary<string, MarsWheather> MarsWheathers { get; } = new Dictionary<string, MarsWheather>();

    }

​

    public class MarsWheatherRootObjectConverter : FixedAndvariablePropertyNameObjectConverter<MarsWheatherRootObject, Dictionary<string, MarsWheather>, MarsWheather>

    {

        static readonly Dictionary<string, ReadFixedKeyMethod> FixedKeyReadMethods = new Dictionary<string, ReadFixedKeyMethod>(StringComparer.OrdinalIgnoreCase)

        {

            { "sol_keys", (ref Utf8JsonReader reader, MarsWheatherRootObject obj, string name, JsonSerializerOptions options) => reader.Skip() },

            { "validity_checks", (ref Utf8JsonReader reader, MarsWheatherRootObject obj, string name, JsonSerializerOptions options) => reader.Skip() },

        };

        protected override Dictionary<string, MarsWheather> GetDictionary(MarsWheatherRootObject obj) => obj.MarsWheathers;

        protected override void SetDictionary(MarsWheatherRootObject obj, Dictionary<string, MarsWheather> dictionary) => throw new RowNotInTableException();

        protected override bool TryGetFixedKeyReadMethod(string name, JsonSerializerOptions options, out ReadFixedKeyMethod method) => FixedKeyReadMethods.TryGetValue(name, out method);

        protected override IEnumerable<KeyValuePair<string, WriteFixedKeyMethod>> GetFixedKeyWriteMethods(JsonSerializerOptions options) => Enumerable.Empty<KeyValuePair<string, WriteFixedKeyMethod>>();

    }

​

    public abstract class FixedAndvariablePropertyNameObjectConverter<TObject, TDictionary, TValue> : JsonConverter<TObject> 

        where TDictionary : class, IDictionary<string, TValue>, new()

        where TObject : new()

    {

        protected delegate void ReadFixedKeyMethod(ref Utf8JsonReader reader, TObject obj, string name, JsonSerializerOptions options);

        protected delegate void WriteFixedKeyMethod(Utf8JsonWriter writer, TObject value, JsonSerializerOptions options);

        protected abstract TDictionary GetDictionary(TObject obj);

        protected abstract void SetDictionary(TObject obj, TDictionary dictionary);

        protected abstract bool TryGetFixedKeyReadMethod(string name, JsonSerializerOptions options, out ReadFixedKeyMethod method);

        protected abstract IEnumerable<KeyValuePair<string, WriteFixedKeyMethod>> GetFixedKeyWriteMethods(JsonSerializerOptions options);

        public override TObject Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)

        {

            if (reader.TokenType == JsonTokenType.Null)

                return (typeToConvert.IsValueType && Nullable.GetUnderlyingType(typeToConvert) == null)

                    ? throw new JsonException(string.Format("Unepected token {0}", reader.TokenType))

                    : default(TObject);

            if (reader.TokenType != JsonTokenType.StartObject)

                throw new JsonException(string.Format("Unepected token {0}", reader.TokenType));

            var obj = new TObject();

            var dictionary = GetDictionary(obj);

            var valueConverter = (typeof(TValue) == typeof(object) ? null : (JsonConverter<TValue>)options.GetConverter(typeof(TValue))); // Encountered a bug using the builtin ObjectConverter

            while (reader.Read())

            {

                if (reader.TokenType == JsonTokenType.PropertyName)

                {

                    var name = reader.GetString();

                    reader.ReadAndAssert();

                    if (TryGetFixedKeyReadMethod(name, options, out var method))

                    {

                        method(ref reader, obj, name, options);

                    }

                    else

                    {

                        if (dictionary == null)

                            SetDictionary(obj, dictionary = new TDictionary());

                        dictionary.Add(name, valueConverter.ReadOrDeserialize(ref reader, typeof(TValue), options));

                    }

                }

                else if (reader.TokenType == JsonTokenType.EndObject)

                {

                    return obj;

                }

                else

                {

                    throw new JsonException(string.Format("Unepected token {0}", reader.TokenType));

                }

            }

            throw new JsonException(); // Truncated file

        }

​

        public override void Write(Utf8JsonWriter writer, TObject value, JsonSerializerOptions options)

        {

            writer.WriteStartObject();

            var dictionary = GetDictionary(value);

            if (dictionary != null)

            {

                var valueConverter = (typeof(TValue) == typeof(object) ? null : (JsonConverter<TValue>)options.GetConverter(typeof(TValue))); // Encountered a bug using the builtin ObjectConverter

                foreach (var pair in dictionary)

                {

                    // TODO: handle DictionaryKeyPolicy 

                    writer.WritePropertyName(pair.Key);

                    valueConverter.WriteOrSerialize(writer, pair.Value, typeof(TValue), options);

                }

            }

            foreach (var pair in GetFixedKeyWriteMethods(options))

            {

                writer.WritePropertyName(pair.Key);

                pair.Value(writer, value, options);

            }

            writer.WriteEndObject();

        }

    }

​

    public static partial class JsonExtensions

    {

        public static void WriteOrSerialize<T>(this JsonConverter<T> converter, Utf8JsonWriter writer, T value, Type type, JsonSerializerOptions options)

        {

            if (converter != null)

                converter.Write(writer, value, options);

            else

                JsonSerializer.Serialize(writer, value, type, options);

        }

​

        public static T ReadOrDeserialize<T>(this JsonConverter<T> converter, ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)

            => converter != null ? converter.Read(ref reader, typeToConvert, options) : (T)JsonSerializer.Deserialize(ref reader, typeToConvert, options);

​

        public static void ReadAndAssert(this ref Utf8JsonReader reader)

        {

            if (!reader.Read())

                throw new JsonException();

        }

    }

​

    public class Program

    {

        private static async Task<MarsWheatherRootObject> GetMarsWheatherRootObject(string uri, HttpClient httpClient)

        {

            using var httpResponse = await httpClient.GetAsync(uri, HttpCompletionOption.ResponseHeadersRead);

​

            httpResponse.EnsureSuccessStatusCode(); // throws if not 200-299

​

            var stream = await httpResponse.Content.ReadAsStreamAsync();

            var root = await System.Text.Json.JsonSerializer.DeserializeAsync<MarsWheatherRootObject>(

                stream, 

                new System.Text.Json.JsonSerializerOptions 

                { 

                    PropertyNameCaseInsensitive = true 

                });

            return root;

        }

        public static async Task Test()

        {

            var client = new HttpClient();

            var url = @"https://api.nasa.gov/insight_weather/?api_key=DEMO_KEY&feedtype=json&ver=1.0";

            var items = await GetMarsWheatherRootObject(url, client);

            items.Dump();

            var newJson = JsonSerializer.Serialize(items, new JsonSerializerOptions { WriteIndented = true });

            Console.WriteLine("Deserialized and re-serialized {0}:", "MarsWheatherRootObject");

            Console.WriteLine(newJson);

        }

        public static async Task Main(string[] args)

        {

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

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

            Console.WriteLine();

​

            try

            {

                await Test();

            }

            catch (Exception ex)

            {

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

                Console.WriteLine(ex);

                throw;

            }

        }

        public static string GetNetCoreVersion()

        {

            //https://techblog.dorogin.com/how-to-detect-net-core-version-in-runtime-ecd65ad695be

            //

            var assembly = typeof(System.Runtime.GCSettings).GetTypeInfo().Assembly;

            var assemblyPath = assembly.Location.Split(new[] { '/', '\\' }, StringSplitOptions.RemoveEmptyEntries);

            int netCoreAppIndex = Array.IndexOf(assemblyPath, "Microsoft.NETCore.App");

            if (netCoreAppIndex > 0 && netCoreAppIndex < assemblyPath.Length - 2)

                return assemblyPath[netCoreAppIndex + 1];

            return null;

        }

    }

​