YouTubeScraper/YouTube.API/Resources/WatchLaterResource.cs

using AngleSharp.Html.Dom;
using AngleSharp.Html.Parser;
using Google.Apis.Http;
using Google.Apis.Services;
using Google.Apis.YouTube.v3;
using Google.Apis.YouTube.v3.Data;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net.Http;
using System.Text.RegularExpressions;
using System.Threading.Tasks;

namespace YouTube.Resources
{
	public class WatchLaterResource
	{
		IClientService Service { get; }

		public WatchLaterResource(IClientService service) =>
			Service = service;

		public ListRequest List()
		{
			return new ListRequest();
		}

		public InsertRequest Insert(string videoId, string part) =>
			new InsertRequest(Service, videoId, part);

		public DeleteRequest Delete(string videoId) =>
			new DeleteRequest(Service, videoId);

		public class ListRequest { }
		public class InsertRequest
		{
			IClientService Service { get; set; }
			public string Id { get; set; }
			public string Part { get; set; }

			public InsertRequest(IClientService service, string videoId, string part)
			{
				Service = service;
				Id = videoId;
				Part = part;
			}

			public async Task<PlaylistItem> ExecuteAsync()
			{
				PlaylistItem playlist = new PlaylistItem
				{
					Snippet = new PlaylistItemSnippet
					{
						PlaylistId = "WL",
						ResourceId = new ResourceId
						{
							VideoId = Id,
							Kind = "youtube#video"
						}
					}
				};
				PlaylistItemsResource.InsertRequest request = (Service as YouTubeService).PlaylistItems.Insert(playlist, Part);

				return await request.ExecuteAsync();
			}

			public PlaylistItem Execute()
			{
				Task<PlaylistItem> task = ExecuteAsync();
				task.Wait();
				return task.Result;
			}
		}
		public class DeleteRequest
		{
			IClientService Service { get; set; }
			public string Id { get; set; }

			public DeleteRequest(IClientService service, string videoId)
			{
				Service = service;
				Id = videoId;
			}

			public async Task ExecuteAsync()
			{
				ConfigurableHttpClient client = Service.HttpClient;
				string data = await client.GetStringAsync($"https://youtube.com/watch?v={Id}&disable_polymer=true&bpctr=9999999999&hl=en");
				string plid = Regex.Match(data, @"(?<=plid=).?\w+").Value;
				IHtmlDocument html = await new HtmlParser().ParseDocumentAsync(data);
				string sessionToken = html.GetElementsByTagName("input").FirstOrDefault(i => i.GetAttribute("name") == "session_token")?.GetAttribute("value");
				Dictionary<string, string> body = new Dictionary<string, string>
				{
					{ "video_ids", Id },
					{ "full_list_id", "WL" },
					{ "plid", plid },
					{ "session_token", sessionToken }
				};
				HttpResponseMessage response = await client.PostAsync("https://www.youtube.com/playlist_video_ajax?action_delete_from_playlist=1", new FormUrlEncodedContent(body));
				string responseStr = await response.Content.ReadAsStringAsync();
				if (!responseStr.Contains("SUCCESS"))
					throw new Exception(responseStr);
			}

			public void Execute() =>
				ExecuteAsync().Wait();
		}
	}
}