using System.Collections.Generic;
using System.Data;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Dapper;
using ErsatzTV.Core;
using ErsatzTV.Core.Domain;
using ErsatzTV.Core.Interfaces.Search;
using ErsatzTV.Infrastructure.Data;
using ErsatzTV.Infrastructure.Extensions;
using LanguageExt;
using MediatR;
using Microsoft.EntityFrameworkCore;
using Unit = LanguageExt.Unit;

namespace ErsatzTV.Application.Libraries.Commands
{
    public class DeleteLocalLibraryHandler : LocalLibraryHandlerBase,
        IRequestHandler<DeleteLocalLibrary, Either<BaseError, Unit>>
    {
        private readonly IDbContextFactory<TvContext> _dbContextFactory;
        private readonly IDbConnection _dbConnection;
        private readonly ISearchIndex _searchIndex;

        public DeleteLocalLibraryHandler(
            IDbContextFactory<TvContext> dbContextFactory,
            IDbConnection dbConnection,
            ISearchIndex searchIndex)
        {
            _dbContextFactory = dbContextFactory;
            _dbConnection = dbConnection;
            _searchIndex = searchIndex;
        }

        public async Task<Either<BaseError, Unit>> Handle(
            DeleteLocalLibrary request,
            CancellationToken cancellationToken)
        {
            await using TvContext dbContext = _dbContextFactory.CreateDbContext();
            Validation<BaseError, LocalLibrary> validation =  await LocalLibraryMustExist(dbContext, request);
            return await validation.Apply(localLibrary => DoDeletion(dbContext, localLibrary));
        }

        private async Task<Unit> DoDeletion(TvContext dbContext, LocalLibrary localLibrary)
        {
            List<int> ids = await _dbConnection.QueryAsync<int>(
                    @"SELECT MediaItem.Id FROM MediaItem
                      INNER JOIN LibraryPath LP on MediaItem.LibraryPathId = LP.Id
                      WHERE LP.LibraryId = @LibraryId",
                    new { LibraryId = localLibrary.Id })
                .Map(result => result.ToList());

            await _searchIndex.RemoveItems(ids);
            _searchIndex.Commit();

            dbContext.LocalLibraries.Remove(localLibrary);
            await dbContext.SaveChangesAsync();

            return Unit.Default;
        }

        private static Task<Validation<BaseError, LocalLibrary>> LocalLibraryMustExist(
            TvContext dbContext,
            DeleteLocalLibrary request) =>
            dbContext.LocalLibraries
                .SelectOneAsync(ll => ll.Id, ll => ll.Id == request.LocalLibraryId)
                .Map(o => o.ToValidation<BaseError>($"Local library {request.LocalLibraryId} does not exist."));
    }
}