ersatztv/ErsatzTV.Application/ProgramSchedules/Commands/DeleteProgramScheduleHandler.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;
using Unit = LanguageExt.Unit;

namespace ErsatzTV.Application.ProgramSchedules.Commands
{
    public class DeleteProgramScheduleHandler : IRequestHandler<DeleteProgramSchedule, Either<BaseError, Unit>>
    {
        private readonly IDbContextFactory<TvContext> _dbContextFactory;

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

        public async Task<Either<BaseError, Unit>> Handle(
            DeleteProgramSchedule request,
            CancellationToken cancellationToken)
        {
            await using TvContext dbContext = _dbContextFactory.CreateDbContext();
            Validation<BaseError, ProgramSchedule> validation = await ProgramScheduleMustExist(dbContext, request);
            return await validation.Apply(ps => DoDeletion(dbContext, ps));
        }

        private static Task<Unit> DoDeletion(TvContext dbContext, ProgramSchedule programSchedule)
        {
            dbContext.ProgramSchedules.Remove(programSchedule);
            return dbContext.SaveChangesAsync().ToUnit();
        }

        private Task<Validation<BaseError, ProgramSchedule>> ProgramScheduleMustExist(
            TvContext dbContext,
            DeleteProgramSchedule request) =>
            dbContext.ProgramSchedules
                .SelectOneAsync(ps => ps.Id, ps => ps.Id == request.ProgramScheduleId)
                .Map(o => o.ToValidation<BaseError>($"ProgramSchedule {request.ProgramScheduleId} does not exist."));
    }
}