ErsatzTV/ErsatzTV.Application/Watermarks/Commands/CopyWatermarkHandler.cs

using System.Threading;
using System.Threading.Tasks;
using ErsatzTV.Core;
using ErsatzTV.Core.Domain;
using ErsatzTV.Infrastructure.Data;
using LanguageExt;
using MediatR;
using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.ChangeTracking;
using static ErsatzTV.Application.Watermarks.Mapper;

namespace ErsatzTV.Application.Watermarks.Commands
{
    public class CopyWatermarkHandler :
        IRequestHandler<CopyWatermark, Either<BaseError, WatermarkViewModel>>
    {
        private readonly IDbContextFactory<TvContext> _dbContextFactory;

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

        public Task<Either<BaseError, WatermarkViewModel>> Handle(
            CopyWatermark request,
            CancellationToken cancellationToken) =>
            Validate(request)
                .MapT(PerformCopy)
                .Bind(v => v.ToEitherAsync());

        private async Task<WatermarkViewModel> PerformCopy(CopyWatermark request)
        {
            await using TvContext dbContext = _dbContextFactory.CreateDbContext();
            ChannelWatermark channelWatermark = await dbContext.ChannelWatermarks.FindAsync(request.WatermarkId);

            PropertyValues values = dbContext.Entry(channelWatermark).CurrentValues.Clone();
            values["Id"] = 0;

            var clone = new ChannelWatermark();
            await dbContext.AddAsync(clone);
            dbContext.Entry(clone).CurrentValues.SetValues(values);
            clone.Name = request.Name;

            await dbContext.SaveChangesAsync();

            return ProjectToViewModel(clone);
        }

        private static Task<Validation<BaseError, CopyWatermark>> Validate(CopyWatermark request) =>
            ValidateName(request).AsTask().MapT(_ => request);

        private static Validation<BaseError, string> ValidateName(CopyWatermark request) =>
            request.NotEmpty(x => x.Name)
                .Bind(_ => request.NotLongerThan(50)(x => x.Name));
    }
}