ErsatzTV/ErsatzTV.Application/Channels/Commands/CreateChannelHandler.cs

using System.Globalization;
using System.Text.RegularExpressions;
using ErsatzTV.Core;
using ErsatzTV.Core.Domain;
using ErsatzTV.Core.Domain.Filler;
using ErsatzTV.Infrastructure.Data;
using ErsatzTV.Infrastructure.Extensions;
using Microsoft.EntityFrameworkCore;

namespace ErsatzTV.Application.Channels;

public class CreateChannelHandler : IRequestHandler<CreateChannel, Either<BaseError, CreateChannelResult>>
{
    private readonly IDbContextFactory<TvContext> _dbContextFactory;

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

    public async Task<Either<BaseError, CreateChannelResult>> Handle(
        CreateChannel request,
        CancellationToken cancellationToken)
    {
        await using TvContext dbContext = await _dbContextFactory.CreateDbContextAsync(cancellationToken);
        Validation<BaseError, Channel> validation = await Validate(dbContext, request);
        return await validation.Apply(c => PersistChannel(dbContext, c));
    }

    private static async Task<CreateChannelResult> PersistChannel(TvContext dbContext, Channel channel)
    {
        await dbContext.Channels.AddAsync(channel);
        await dbContext.SaveChangesAsync();
        return new CreateChannelResult(channel.Id);
    }

    private static async Task<Validation<BaseError, Channel>> Validate(TvContext dbContext, CreateChannel request) =>
        (ValidateName(request), await ValidateNumber(dbContext, request),
            await FFmpegProfileMustExist(dbContext, request),
            ValidatePreferredAudioLanguage(request),
            ValidatePreferredSubtitleLanguage(request),
            await WatermarkMustExist(dbContext, request),
            await FillerPresetMustExist(dbContext, request))
        .Apply(
            (
                name,
                number,
                ffmpegProfileId,
                preferredAudioLanguageCode,
                preferredSubtitleLanguageCode,
                watermarkId,
                fillerPresetId) =>
            {
                var artwork = new List<Artwork>();
                if (!string.IsNullOrWhiteSpace(request.Logo))
                {
                    artwork.Add(
                        new Artwork
                        {
                            Path = request.Logo,
                            ArtworkKind = ArtworkKind.Logo,
                            DateAdded = DateTime.UtcNow,
                            DateUpdated = DateTime.UtcNow
                        });
                }

                var channel = new Channel(Guid.NewGuid())
                {
                    Name = name,
                    Number = number,
                    Group = request.Group,
                    Categories = request.Categories,
                    FFmpegProfileId = ffmpegProfileId,
                    StreamingMode = request.StreamingMode,
                    Artwork = artwork,
                    PreferredAudioLanguageCode = preferredAudioLanguageCode,
                    PreferredAudioTitle = request.PreferredAudioTitle,
                    PreferredSubtitleLanguageCode = preferredSubtitleLanguageCode,
                    SubtitleMode = request.SubtitleMode,
                    MusicVideoCreditsMode = request.MusicVideoCreditsMode
                };

                foreach (int id in watermarkId)
                {
                    channel.WatermarkId = id;
                }

                foreach (int id in fillerPresetId)
                {
                    channel.FallbackFillerId = id;
                }

                return channel;
            });

    private static Validation<BaseError, string> ValidateName(CreateChannel createChannel) =>
        createChannel.NotEmpty(c => c.Name)
            .Bind(_ => createChannel.NotLongerThan(50)(c => c.Name));

    private static Validation<BaseError, string> ValidatePreferredAudioLanguage(CreateChannel createChannel) =>
        Optional(createChannel.PreferredAudioLanguageCode ?? string.Empty)
            .Filter(
                lc => string.IsNullOrWhiteSpace(lc) || CultureInfo.GetCultures(CultureTypes.NeutralCultures).Any(
                    ci => string.Equals(ci.ThreeLetterISOLanguageName, lc, StringComparison.OrdinalIgnoreCase)))
            .ToValidation<BaseError>("Preferred audio language code is invalid");

    private static Validation<BaseError, string> ValidatePreferredSubtitleLanguage(CreateChannel createChannel) =>
        Optional(createChannel.PreferredSubtitleLanguageCode ?? string.Empty)
            .Filter(
                lc => string.IsNullOrWhiteSpace(lc) || CultureInfo.GetCultures(CultureTypes.NeutralCultures).Any(
                    ci => string.Equals(ci.ThreeLetterISOLanguageName, lc, StringComparison.OrdinalIgnoreCase)))
            .ToValidation<BaseError>("Preferred subtitle language code is invalid");

    private static async Task<Validation<BaseError, string>> ValidateNumber(
        TvContext dbContext,
        CreateChannel createChannel)
    {
        Option<Channel> maybeExistingChannel = await dbContext.Channels
            .SelectOneAsync(c => c.Number, c => c.Number == createChannel.Number);
        return maybeExistingChannel.Match<Validation<BaseError, string>>(
            _ => BaseError.New("Channel number must be unique"),
            () =>
            {
                if (Regex.IsMatch(createChannel.Number, Channel.NumberValidator))
                {
                    return createChannel.Number;
                }

                return BaseError.New("Invalid channel number; two decimals are allowed for subchannels");
            });
    }

    private static Task<Validation<BaseError, int>> FFmpegProfileMustExist(
        TvContext dbContext,
        CreateChannel createChannel) =>
        dbContext.FFmpegProfiles
            .CountAsync(p => p.Id == createChannel.FFmpegProfileId)
            .Map(Optional)
            .Filter(c => c > 0)
            .MapT(_ => createChannel.FFmpegProfileId)
            .Map(o => o.ToValidation<BaseError>($"FFmpegProfile {createChannel.FFmpegProfileId} does not exist."));

    private static async Task<Validation<BaseError, Option<int>>> WatermarkMustExist(
        TvContext dbContext,
        CreateChannel createChannel)
    {
        if (createChannel.WatermarkId is null)
        {
            return Option<int>.None;
        }

        return await dbContext.ChannelWatermarks
            .CountAsync(w => w.Id == createChannel.WatermarkId)
            .Map(Optional)
            .Filter(c => c > 0)
            .MapT(_ => Optional(createChannel.WatermarkId))
            .Map(o => o.ToValidation<BaseError>($"Watermark {createChannel.WatermarkId} does not exist."));
    }

    private static async Task<Validation<BaseError, Option<int>>> FillerPresetMustExist(
        TvContext dbContext,
        CreateChannel createChannel)
    {
        if (createChannel.FallbackFillerId is null)
        {
            return Option<int>.None;
        }

        return await dbContext.FillerPresets
            .Filter(fp => fp.FillerKind == FillerKind.Fallback)
            .CountAsync(w => w.Id == createChannel.FallbackFillerId)
            .Map(Optional)
            .Filter(c => c > 0)
            .MapT(_ => Optional(createChannel.FallbackFillerId))
            .Map(
                o => o.ToValidation<BaseError>(
                    $"Fallback filler {createChannel.FallbackFillerId} does not exist."));
    }
}