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.Watermarks.Commands
{
    public class UpdateWatermarkHandler : IRequestHandler<UpdateWatermark, Either<BaseError, UpdateWatermarkResult>>
    {
        private readonly IDbContextFactory<TvContext> _dbContextFactory;

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

        public async Task<Either<BaseError, UpdateWatermarkResult>> Handle(
            UpdateWatermark request,
            CancellationToken cancellationToken)
        {
            await using TvContext dbContext = _dbContextFactory.CreateDbContext();
            Validation<BaseError, ChannelWatermark> validation = await Validate(dbContext, request);
            return await validation.Apply(p => ApplyUpdateRequest(dbContext, p, request));
        }

        private static async Task<UpdateWatermarkResult> ApplyUpdateRequest(
            TvContext dbContext,
            ChannelWatermark p,
            UpdateWatermark update)
        {
            p.Name = update.Name;
            p.Image = update.ImageSource == ChannelWatermarkImageSource.Custom ? update.Image : null;
            p.Mode = update.Mode;
            p.ImageSource = update.ImageSource;
            p.Location = update.Location;
            p.Size = update.Size;
            p.WidthPercent = update.Width;
            p.HorizontalMarginPercent = update.HorizontalMargin;
            p.VerticalMarginPercent = update.VerticalMargin;
            p.FrequencyMinutes = update.FrequencyMinutes;
            p.DurationSeconds = update.DurationSeconds;
            p.Opacity = update.Opacity;
            await dbContext.SaveChangesAsync();
            return new UpdateWatermarkResult(p.Id);
        }

        private static async Task<Validation<BaseError, ChannelWatermark>> Validate(
            TvContext dbContext,
            UpdateWatermark request) =>
            (await WatermarkMustExist(dbContext, request), ValidateName(request))
            .Apply((watermark, _) => watermark);

        private static Task<Validation<BaseError, ChannelWatermark>> WatermarkMustExist(
            TvContext dbContext,
            UpdateWatermark updateWatermark) =>
            dbContext.ChannelWatermarks
                .SelectOneAsync(p => p.Id, p => p.Id == updateWatermark.Id)
                .Map(o => o.ToValidation<BaseError>("Watermark does not exist."));

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