ersatztv/ErsatzTV.Infrastructure/Data/Repositories/ArtworkRepository.cs

using System.Collections.Generic;
using System.Data;
using System.Linq;
using System.Threading.Tasks;
using Dapper;
using ErsatzTV.Core.Domain;
using ErsatzTV.Core.Interfaces.Repositories;
using LanguageExt;

namespace ErsatzTV.Infrastructure.Data.Repositories
{
    public class ArtworkRepository : IArtworkRepository
    {
        private readonly IDbConnection _dbConnection;

        public ArtworkRepository(IDbConnection dbConnection) => _dbConnection = dbConnection;

        public Task<List<Artwork>> GetOrphanedArtwork() =>
            _dbConnection.QueryAsync<Artwork>(
                    @"SELECT A.Id, A.Path FROM Artwork A
                      WHERE A.ArtistMetadataId IS NULL AND A.EpisodeMetadataId IS NULL
                      AND A.SeasonMetadataId IS NULL AND A.ShowMetadataId IS NULL
                      AND A.MovieMetadataId IS NULL AND A.MusicVideoMetadataId IS NULL
                      AND A.ChannelId IS NULL
                      AND NOT EXISTS (SELECT * FROM Actor WHERE Actor.ArtworkId = A.Id)")
                .Map(result => result.ToList());

        public async Task<Unit> Delete(List<Artwork> artwork)
        {
            IEnumerable<List<int>> chunks = Chunk(artwork.Map(a => a.Id), 100);
            foreach (List<int> chunk in chunks)
            {
                await _dbConnection.ExecuteAsync(
                    "DELETE FROM Artwork WHERE Id IN @Ids",
                    new { Ids = chunk });
            }

            return Unit.Default;
        }

        private static IEnumerable<List<T>> Chunk<T>(IEnumerable<T> collection, int size)
        {
            var count = 0;
            var chunk = new List<T>(size);

            foreach (T element in collection)
            {
                if (count++ == size)
                {
                    yield return chunk;
                    chunk = new List<T>(size);
                    count = 1;
                }

                chunk.Add(element);
            }

            yield return chunk;
        }
    }
}