Fetch video count in playlist metadata

[IcySnex]

Closes #356
// Provided solution wasn't actually a solution. Just a workaround.

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Added support for "vidoes count" property for playlist fetching:

Knowing the estimate videos count provided by the offical YouTube API without having to reiterate over the entire video collection is needed (especially when there are hundreds of videos in the playlist)

• Added int VideosCount to Playlist
• Added int? VideosCount to IPlaylistData, PlaylistBrowseResponse, PlaylistNextResponse
• Updated PlaylistSpecs-Tests

[Tyrrrz]

Thank you. I'm not sure I like that some playlists will have null count with this approach.

[IcySnex]

During my testing I didn't find any playlists where YouTube doesn't return the number of videos, but for safety reasons I made it nullable internally and set it to 0 in the PlaylistClient if it is null, similar to the Description property

[Tyrrrz]

It looks like the PlaylistNext response parser is hard-codded to return null, and we use that primarily for dynamic playlists (such as mixes) and other playlists that we can't fetch normally.

What video count does it return for the non-PL playlists from this list?

YoutubeExplode/YoutubeExplode.Tests/TestData/PlaylistIds.cs

Lines 5 to 14 in 9f1bffd

	public const string Normal = "PLI5YfMzCfRtZ8eV576YoY3vIYrHjyVm_e";
	public const string Private = "PLYjTMWc3sa4ZKheRwyA1q56xxQrfQEUBr";
	public const string NonExisting = "PLYjTMWc3sa4ZKheRwyA1q56xxQrfQEUBx";
	public const string Large = "PLWwAypAcFRgKFlxtLbn_u14zddtDJj3mk";
	public const string VideoMix = "RDTsYhxMnGYCw";
	public const string MusicMix = "RDCLAK5uy_lf8okgl2ygD075nhnJVjlfhwp8NsUgEbs";
	public const string MusicAlbum = "OLAK5uy_lLeonUugocG5J0EUAEDmbskX4emejKwcM";
	public const string UserUploads = "UUTMt7iMWa7jy0fNXIktwyLA";
	public const string Weird = "PL601B2E69B03FAB9D";
	public const string ContainsLongVideos = "PLkk2FsMngwGi9FNkWIoNZlfqglcldj_Zs";

[IcySnex]

I have implemented the parsing of the video count for the PlaylistNextResponse. I have tested the non-PL playlists with this and
most of them work just fine but there are minor issues with PlaylistIds.VideoMix & PlaylistIds.MusicMix.

I have inspected the YouTube API response and I have noticed that the ContentRoot also provides a property called isInfinite. If this property is true (which is the case for these Mix-Playlists) then YouTube won't tell the actual video count.

Thus I have added the IsInfinite-property to the PlaylistNextResponse. But I'm not quite sure what to do with the VideoCount-property in this case. Currently It will be set to int.MaxValue but I'm not quite sure about this approach:

YoutubeExplode/YoutubeExplode/Bridge/PlaylistNextResponse.cs

Lines 37 to 58 in 0e6400a

	[Lazy]
	public bool? IsInfinite => ContentRoot?.GetPropertyOrNull("isInfinite")?.GetBoolean();
	public int? VideosCount =>
	IsInfinite == true
	? int.MaxValue
	: ContentRoot
	?.GetPropertyOrNull("totalVideosText")
	?.GetPropertyOrNull("runs")
	?.EnumerateArrayOrNull()
	?.FirstOrNull()
	?.GetPropertyOrNull("text")
	?.GetStringOrNull()
	?.ParseIntOrNull()
	?? ContentRoot
	?.GetPropertyOrNull("videoCountText")
	?.GetPropertyOrNull("runs")
	?.EnumerateArrayOrNull()
	?.ElementAtOrNull(2)
	?.GetPropertyOrNull("text")
	?.GetStringOrNull()
	?.ParseIntOrNull();

[Tyrrrz]

Let's make the VideoCount property nullable and have null indicate an infinite playlist (explain so in the <remarks> block).

[IcySnex]

Alright that sounds good. I have implemented it and updated the tests.

[Tyrrrz]

Thank you :)