using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using ErsatzTV.Core;
using ErsatzTV.Core.Domain;
using ErsatzTV.Core.Interfaces.Locking;
using ErsatzTV.Core.Interfaces.Repositories;
using ErsatzTV.Core.Interfaces.Search;
using ErsatzTV.Core.Interfaces.Trakt;
using ErsatzTV.Infrastructure.Data;
using ErsatzTV.Infrastructure.Extensions;
using LanguageExt;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Logging;
using static LanguageExt.Prelude;

namespace ErsatzTV.Application.MediaCollections.Commands
{
    public class DeleteTraktListHandler : TraktCommandBase, MediatR.IRequestHandler<DeleteTraktList, Either<BaseError, Unit>>
    {
        private readonly ISearchRepository _searchRepository;
        private readonly ISearchIndex _searchIndex;
        private readonly IDbContextFactory<TvContext> _dbContextFactory;
        private readonly IEntityLocker _entityLocker;

        public DeleteTraktListHandler(
            ITraktApiClient traktApiClient,
            ISearchRepository searchRepository,
            ISearchIndex searchIndex,
            IDbContextFactory<TvContext> dbContextFactory,
            ILogger<DeleteTraktListHandler> logger,
            IEntityLocker entityLocker)
            : base(traktApiClient, searchRepository, searchIndex, logger)
        {
            _searchRepository = searchRepository;
            _searchIndex = searchIndex;
            _dbContextFactory = dbContextFactory;
            _entityLocker = entityLocker;
        }

        public async Task<Either<BaseError, Unit>> Handle(
            DeleteTraktList request,
            CancellationToken cancellationToken)
        {
            try
            {
                await using TvContext dbContext = _dbContextFactory.CreateDbContext();

                Validation<BaseError, TraktList> validation = await TraktListMustExist(dbContext, request.TraktListId);
                return await validation.Apply(c => DoDeletion(dbContext, c));
            }
            finally
            {
                _entityLocker.UnlockTrakt();
            }
        }

        private async Task<Unit> DoDeletion(TvContext dbContext, TraktList traktList)
        {
            var mediaItemIds = traktList.Items.Bind(i => Optional(i.MediaItemId)).ToList();

            dbContext.TraktLists.Remove(traktList);
            if (await dbContext.SaveChangesAsync() > 0)
            {
                foreach (int mediaItemId in mediaItemIds)
                {
                    foreach (MediaItem mediaItem in await _searchRepository.GetItemToIndex(mediaItemId))
                    {
                        await _searchIndex.UpdateItems(_searchRepository, new[] { mediaItem }.ToList());
                    }
                }
            }

            _searchIndex.Commit();

            return Unit.Default;
        }
    }
}