ErsatzTV/ErsatzTV.Application/FFmpegProfiles/Commands/DeleteFFmpegProfileHandler.cs

using System.Threading;
using System.Threading.Tasks;
using ErsatzTV.Core;
using ErsatzTV.Core.Domain;
using ErsatzTV.Infrastructure.Data;
using ErsatzTV.Infrastructure.Extensions;
using LanguageExt;
using MediatR;
using Microsoft.EntityFrameworkCore;

namespace ErsatzTV.Application.FFmpegProfiles.Commands
{
    public class DeleteFFmpegProfileHandler : IRequestHandler<DeleteFFmpegProfile, Either<BaseError, LanguageExt.Unit>>
    {
        private readonly IDbContextFactory<TvContext> _dbContextFactory;

        public DeleteFFmpegProfileHandler(IDbContextFactory<TvContext> dbContextFactory) =>
            _dbContextFactory = dbContextFactory;

        public async Task<Either<BaseError, LanguageExt.Unit>> Handle(
            DeleteFFmpegProfile request,
            CancellationToken cancellationToken)
        {
            await using TvContext dbContext = _dbContextFactory.CreateDbContext();
            Validation<BaseError, FFmpegProfile> validation = await FFmpegProfileMustExist(dbContext, request);
            return await validation.Apply(p => DoDeletion(dbContext, p));
        }

        private static async Task<LanguageExt.Unit> DoDeletion(TvContext dbContext, FFmpegProfile ffmpegProfile)
        {
            dbContext.FFmpegProfiles.Remove(ffmpegProfile);
            await dbContext.SaveChangesAsync();
            return LanguageExt.Unit.Default;
        }

        private static Task<Validation<BaseError, FFmpegProfile>> FFmpegProfileMustExist(
            TvContext dbContext,
            DeleteFFmpegProfile request) =>
            dbContext.FFmpegProfiles
                .SelectOneAsync(p => p.Id, p => p.Id == request.FFmpegProfileId)
                .Map(o => o.ToValidation<BaseError>($"FFmpegProfile {request.FFmpegProfileId} does not exist"));
    }
}