ErsatzTV/ErsatzTV.Application/Streaming/Queries/GetConcatPlaylistByChannelNumberHandler.cs

using System.Threading;
using System.Threading.Tasks;
using ErsatzTV.Core;
using ErsatzTV.Core.Domain;
using ErsatzTV.Core.FFmpeg;
using ErsatzTV.Core.Interfaces.Repositories;
using LanguageExt;
using MediatR;

namespace ErsatzTV.Application.Streaming.Queries
{
    public class
        GetConcatPlaylistByChannelNumberHandler : IRequestHandler<GetConcatPlaylistByChannelNumber,
            Either<BaseError, ConcatPlaylist>>
    {
        private readonly IChannelRepository _channelRepository;

        public GetConcatPlaylistByChannelNumberHandler(IChannelRepository channelRepository) =>
            _channelRepository = channelRepository;

        public Task<Either<BaseError, ConcatPlaylist>> Handle(
            GetConcatPlaylistByChannelNumber request,
            CancellationToken cancellationToken) =>
            Validate(request)
                .MapT(channel => new ConcatPlaylist(request.Scheme, request.Host, channel.Number))
                .Map(v => v.ToEither<ConcatPlaylist>());

        private Task<Validation<BaseError, Channel>> Validate(GetConcatPlaylistByChannelNumber request) =>
            ChannelMustExist(request);

        private async Task<Validation<BaseError, Channel>> ChannelMustExist(GetConcatPlaylistByChannelNumber request) =>
            (await _channelRepository.GetByNumber(request.ChannelNumber))
            .ToValidation<BaseError>($"Channel number {request.ChannelNumber} does not exist.");
    }
}