ersatztv/ErsatzTV.Application/Images/Queries/GetCachedImagePathHandler.cs

using System;
using System.IO;
using System.Threading;
using System.Threading.Tasks;
using ErsatzTV.Core;
using ErsatzTV.Core.Interfaces.Images;
using LanguageExt;
using MediatR;
using Winista.Mime;
using static LanguageExt.Prelude;

namespace ErsatzTV.Application.Images.Queries
{
    public class
        GetCachedImagePathHandler : IRequestHandler<GetCachedImagePath, Either<BaseError, CachedImagePathViewModel>>
    {
        private static readonly MimeTypes MimeTypes = new();
        private readonly IImageCache _imageCache;

        public GetCachedImagePathHandler(IImageCache imageCache) => _imageCache = imageCache;

        public async Task<Either<BaseError, CachedImagePathViewModel>> Handle(
            GetCachedImagePath request,
            CancellationToken cancellationToken)
        {
            try
            {
                MimeType mimeType;

                string cachePath = _imageCache.GetPathForImage(
                    request.FileName,
                    request.ArtworkKind,
                    Optional(request.MaxHeight));
                if (!File.Exists(cachePath))
                {
                    if (request.MaxHeight.HasValue)
                    {
                        string originalPath = _imageCache.GetPathForImage(request.FileName, request.ArtworkKind, None);
                        byte[] contents = await File.ReadAllBytesAsync(originalPath, cancellationToken);
                        Either<BaseError, byte[]> resizeResult =
                            await _imageCache.ResizeImage(contents, request.MaxHeight.Value);
                        resizeResult.IfRight(result => contents = result);

                        string baseFolder = Path.GetDirectoryName(cachePath);
                        if (baseFolder != null && !Directory.Exists(baseFolder))
                        {
                            Directory.CreateDirectory(baseFolder);
                        }

                        await File.WriteAllBytesAsync(cachePath, contents, cancellationToken);

                        mimeType = new MimeType("image/jpeg");
                    }
                    else
                    {
                        return BaseError.New($"Artwork does not exist on disk at {cachePath}");
                    }
                }
                else
                {
                    mimeType = MimeTypes.GetMimeTypeFromFile(cachePath);
                }

                return new CachedImagePathViewModel(cachePath, mimeType.Name);
            }
            catch (Exception ex)
            {
                return BaseError.New(ex.Message);
            }
        }
    }
}