jellyfin/Emby.Server.Implementations/Library/MusicManager.cs

using MediaBrowser.Controller.Entities;
using MediaBrowser.Controller.Entities.Audio;
using MediaBrowser.Controller.Library;
using MediaBrowser.Controller.Playlists;
using System;
using System.Collections.Generic;
using System.Linq;

namespace Emby.Server.Implementations.Library
{
    public class MusicManager : IMusicManager
    {
        private readonly ILibraryManager _libraryManager;

        public MusicManager(ILibraryManager libraryManager)
        {
            _libraryManager = libraryManager;
        }

        public IEnumerable<Audio> GetInstantMixFromSong(Audio item, User user)
        {
            var list = new List<Audio>
            {
                item
            };

            return list.Concat(GetInstantMixFromGenres(item.Genres, user));
        }

        public IEnumerable<Audio> GetInstantMixFromArtist(MusicArtist artist, User user)
        {
            var genres = user.RootFolder
                .GetRecursiveChildren(user, new InternalItemsQuery(user)
                {
                    IncludeItemTypes = new[] { typeof(Audio).Name }
                })
                .Cast<Audio>()
                .Where(i => i.HasAnyArtist(artist.Name))
                .SelectMany(i => i.Genres)
                .Concat(artist.Genres)
                .Distinct(StringComparer.OrdinalIgnoreCase);

            return GetInstantMixFromGenres(genres, user);
        }

        public IEnumerable<Audio> GetInstantMixFromAlbum(MusicAlbum item, User user)
        {
            var genres = item
                .GetRecursiveChildren(user, new InternalItemsQuery(user)
                {
                    IncludeItemTypes = new[] { typeof(Audio).Name }
                })
               .Cast<Audio>()
               .SelectMany(i => i.Genres)
               .Concat(item.Genres)
               .DistinctNames();

            return GetInstantMixFromGenres(genres, user);
        }

        public IEnumerable<Audio> GetInstantMixFromFolder(Folder item, User user)
        {
            var genres = item
               .GetRecursiveChildren(user, new InternalItemsQuery(user)
               {
                   IncludeItemTypes = new[] {typeof(Audio).Name}
               })
               .Cast<Audio>()
               .SelectMany(i => i.Genres)
               .Concat(item.Genres)
               .DistinctNames();

            return GetInstantMixFromGenres(genres, user);
        }

        public IEnumerable<Audio> GetInstantMixFromPlaylist(Playlist item, User user)
        {
            var genres = item
               .GetRecursiveChildren(user, new InternalItemsQuery(user)
               {
                   IncludeItemTypes = new[] { typeof(Audio).Name }
               })
               .Cast<Audio>()
               .SelectMany(i => i.Genres)
               .Concat(item.Genres)
               .DistinctNames();

            return GetInstantMixFromGenres(genres, user);
        }

        public IEnumerable<Audio> GetInstantMixFromGenres(IEnumerable<string> genres, User user)
        {
            var genreList = genres.ToList();

            var inputItems = _libraryManager.GetItemList(new InternalItemsQuery(user)
            {
                IncludeItemTypes = new[] { typeof(Audio).Name },

                Genres = genreList.ToArray()

            });

            var genresDictionary = genreList.ToDictionary(i => i, StringComparer.OrdinalIgnoreCase);

            return inputItems
                .Cast<Audio>()
                .Select(i => new Tuple<Audio, int>(i, i.Genres.Count(genresDictionary.ContainsKey)))
                .OrderByDescending(i => i.Item2)
                .ThenBy(i => Guid.NewGuid())
                .Select(i => i.Item1)
                .Take(200)
                .OrderBy(i => Guid.NewGuid());
        }

        public IEnumerable<Audio> GetInstantMixFromItem(BaseItem item, User user)
        {
            var genre = item as MusicGenre;
            if (genre != null)
            {
                return GetInstantMixFromGenres(new[] { item.Name }, user);
            }

            var playlist = item as Playlist;
            if (playlist != null)
            {
                return GetInstantMixFromPlaylist(playlist, user);
            }

            var album = item as MusicAlbum;
            if (album != null)
            {
                return GetInstantMixFromAlbum(album, user);
            }

            var artist = item as MusicArtist;
            if (artist != null)
            {
                return GetInstantMixFromArtist(artist, user);
            }

            var song = item as Audio;
            if (song != null)
            {
                return GetInstantMixFromSong(song, user);
            }

            var folder = item as Folder;
            if (folder != null)
            {
                return GetInstantMixFromFolder(folder, user);
            }

            return new Audio[] { };
        }
    }
}