Spotify.NET/SpotifyAPI.Web/Models/Converters/PlayableItemConverter.cs

using System;
using Newtonsoft.Json;
using Newtonsoft.Json.Linq;

namespace SpotifyAPI.Web
{
  public class PlayableItemConverter : JsonConverter
  {
    public override bool CanWrite { get => false; }

    public override bool CanConvert(Type objectType) => true;

    public override object? ReadJson(JsonReader reader, Type objectType,
        object? existingValue, JsonSerializer serializer)
    {
      Ensure.ArgumentNotNull(serializer, nameof(serializer));

      var token = JToken.ReadFrom(reader);
      if (token.Type == JTokenType.Null)
      {
        return null;
      }

      var type = token["type"]?.Value<string>();
      if (type == "track")
      {
        var obj = new FullTrack();
        serializer.Populate(token.CreateReader(), obj);
        return obj;
      }
      else if (type == "episode")
      {
        var obj = new FullEpisode();
        serializer.Populate(token.CreateReader(), obj);
        return obj;
      }
      else
      {
        throw new Exception($@"Received unkown playlist element type: {type}.
If you're requesting a subset of available fields via the fields query paramter,
make sure to include at least the type field. Often it's `items(track(type))` or `item(type)`");
      }
    }

    public override void WriteJson(JsonWriter writer, object? value, JsonSerializer serializer)
    {
      throw new NotSupportedException();
    }
  }
}