using System;
using System.Buffers;
using System.Buffers.Text;
using System.Text.Json;
using System.Text.Json.Serialization;

namespace MediaBrowser.Common.Json.Converters
{
    /// <summary>
    /// Converts a nullable int32 object or value to/from JSON.
    /// </summary>
    public class JsonNullableInt32Converter : JsonConverter<int?>
    {
        /// <inheritdoc />
        public override int? Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
        {
            if (reader.TokenType == JsonTokenType.String)
            {
                ReadOnlySpan<byte> span = reader.HasValueSequence ? reader.ValueSequence.ToArray() : reader.ValueSpan;
                if (Utf8Parser.TryParse(span, out int number, out int bytesConsumed) && span.Length == bytesConsumed)
                {
                    return number;
                }

                var stringValue = reader.GetString().AsSpan();

                // value is null or empty, just return null.
                if (stringValue.IsEmpty)
                {
                    return null;
                }

                if (int.TryParse(stringValue, out number))
                {
                    return number;
                }
            }

            return reader.GetInt32();
        }

        /// <inheritdoc />
        public override void Write(Utf8JsonWriter writer, int? value, JsonSerializerOptions options)
        {
            if (value is null)
            {
                writer.WriteNullValue();
            }
            else
            {
                writer.WriteNumberValue(value.Value);
            }
        }
    }
}