using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Text.Json;
using System.Text.Json.Serialization;
using System.Threading.Tasks;

namespace GB5Shared.UnixEpochDate
{
    public class NullableValueTypeConverter<T> : JsonConverter<T> where T : struct
    {
        public override T Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
        {
            if (reader.TokenType == JsonTokenType.Null)
            {
                return default; // returns 0 for int, long, etc.
            }

            if (typeof(T) == typeof(int)) return (T)(object)reader.GetInt32();
            if (typeof(T) == typeof(long)) return (T)(object)reader.GetInt64();
            if (typeof(T) == typeof(double)) return (T)(object)reader.GetDouble();

            throw new NotSupportedException($"Type {typeof(T)} is not supported by NullableValueTypeConverter");
        }

        public override void Write(Utf8JsonWriter writer, T value, JsonSerializerOptions options)
        {
            writer.WriteNumberValue(Convert.ToDouble(value));
        }
    }

}