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 CreateFFmpegProfileHandler :
        IRequestHandler<CreateFFmpegProfile, Either<BaseError, CreateFFmpegProfileResult>>
    {
        private readonly IDbContextFactory<TvContext> _dbContextFactory;

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

        public async Task<Either<BaseError, CreateFFmpegProfileResult>> Handle(
            CreateFFmpegProfile request,
            CancellationToken cancellationToken)
        {
            await using TvContext dbContext = _dbContextFactory.CreateDbContext();
            Validation<BaseError, FFmpegProfile> validation = await Validate(dbContext, request);
            return await validation.Apply(profile => PersistFFmpegProfile(dbContext, profile));
        }

        private static async Task<CreateFFmpegProfileResult> PersistFFmpegProfile(
            TvContext dbContext,
            FFmpegProfile ffmpegProfile)
        {
            await dbContext.FFmpegProfiles.AddAsync(ffmpegProfile);
            await dbContext.SaveChangesAsync();
            return new CreateFFmpegProfileResult(ffmpegProfile.Id);
        }

        private async Task<Validation<BaseError, FFmpegProfile>> Validate(TvContext dbContext, CreateFFmpegProfile request) =>
            (ValidateName(request), ValidateThreadCount(request), await ResolutionMustExist(dbContext, request))
            .Apply(
                (name, threadCount, resolutionId) => new FFmpegProfile
                {
                    Name = name,
                    ThreadCount = threadCount,
                    Transcode = request.Transcode,
                    HardwareAcceleration = request.HardwareAcceleration,
                    VaapiDriver = request.VaapiDriver,
                    VaapiDevice = request.VaapiDevice,
                    ResolutionId = resolutionId,
                    NormalizeVideo = request.NormalizeVideo,
                    VideoCodec = request.VideoCodec,
                    VideoBitrate = request.VideoBitrate,
                    VideoBufferSize = request.VideoBufferSize,
                    AudioCodec = request.AudioCodec,
                    AudioBitrate = request.AudioBitrate,
                    AudioBufferSize = request.AudioBufferSize,
                    NormalizeLoudness = request.NormalizeLoudness,
                    AudioChannels = request.AudioChannels,
                    AudioSampleRate = request.AudioSampleRate,
                    NormalizeAudio = request.NormalizeAudio
                });

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

        private static Validation<BaseError, int> ValidateThreadCount(CreateFFmpegProfile createFFmpegProfile) =>
            createFFmpegProfile.AtLeast(0)(p => p.ThreadCount);

        private static Task<Validation<BaseError, int>> ResolutionMustExist(
            TvContext dbContext,
            CreateFFmpegProfile createFFmpegProfile) =>
            dbContext.Resolutions
                .SelectOneAsync(r => r.Id, r => r.Id == createFFmpegProfile.ResolutionId)
                .MapT(r => r.Id)
                .Map(o => o.ToValidation<BaseError>($"[Resolution] {createFFmpegProfile.ResolutionId} does not exist"));
    }
}