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

namespace IdentityShroud.Core.Helpers;

public class Base64UrlConverter : JsonConverter<byte[]>
{
    public override byte[] Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
    {
        // GetValueSpan gives you the raw UTF-8 bytes of the JSON string value
        if (reader.HasValueSequence)
        {
            var valueSequence = reader.ValueSequence.ToArray();
            return Base64Url.DecodeFromUtf8(valueSequence);
        }
        return Base64Url.DecodeFromUtf8(reader.ValueSpan);
    }

    public override void Write(Utf8JsonWriter writer, byte[] value, JsonSerializerOptions options)
    {
        int encodedLength = Base64Url.GetEncodedLength(value.Length);
        Span<byte> buffer = encodedLength <= 256 ? stackalloc byte[encodedLength] : new byte[encodedLength];
        Base64Url.EncodeToUtf8(value, buffer);
        writer.WriteStringValue(buffer);
    }
}