ErsatzTV/ErsatzTV.Core/Metadata/TestMediaScanner.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using ErsatzTV.Core.Domain;
using LanguageExt;
using static LanguageExt.Prelude;

namespace ErsatzTV.Core.Metadata
{
    public class TestMediaScanner
    {
        // @formatter:off
        private static readonly Seq<string> VideoFileExtensions = Seq(
            ".mpg", ".mp2", ".mpeg", ".mpe", ".mpv", ".ogg", ".mp4",
            ".m4p", ".m4v", ".avi", ".wmv", ".mov", ".mkv", ".ts");
        // @formatter:on

        private static readonly Seq<string> ImageFileExtensions = Seq("jpg", "jpeg", "png", "gif", "tbn");

        public Seq<LocalMediaItemScanningPlan> DetermineActions(
            MediaType mediaType,
            Seq<MediaItem> mediaItems,
            Seq<string> files)
        {
            var results = new IntermediateResults();
            var videoFiles = files.Filter(f => VideoFileExtensions.Contains(Path.GetExtension(f)));

            (Seq<string> newFiles, Seq<MediaItem> existingMediaItems) = videoFiles.Map(
                    s => mediaItems.Find(i => i.Path == s).ToEither(s))
                .Partition();
            
            // new files
            foreach (string file in newFiles)
            {
                results.Add(file, new ItemScanningPlan(file, ScanningAction.Statistics));

                Option<string> maybeNfoFile = LocateNfoFile(mediaType, files, file);
                maybeNfoFile.BiIter(
                    nfoFile => results.Add(file, new ItemScanningPlan(nfoFile, ScanningAction.SidecarMetadata)),
                    () => results.Add(file, new ItemScanningPlan(file, ScanningAction.FallbackMetadata)));

                Option<string> maybePoster = LocatePoster(mediaType, files, file);
                maybePoster.IfSome(
                    posterFile => results.Add(file, new ItemScanningPlan(posterFile, ScanningAction.Poster)));
            }
            
            // existing media items

            return results.Summarize();
        }

        private static Option<string> LocateNfoFile(MediaType mediaType, Seq<string> files, string file)
        {
            switch (mediaType)
            {
                case MediaType.Movie:
                    string movieAsNfo = Path.ChangeExtension(file, "nfo");
                    string movieNfo = Path.Combine(Path.GetDirectoryName(file) ?? string.Empty, "movie.nfo");
                    return Seq(movieAsNfo, movieNfo)
                        .Filter(s => files.Contains(s))
                        .HeadOrNone();
            }

            return None;
        }

        private static Option<string> LocatePoster(MediaType mediaType, Seq<string> files, string file)
        {
            string folder = Path.GetDirectoryName(file) ?? string.Empty;
            
            switch (mediaType)
            {
                case MediaType.Movie:
                    IEnumerable<string> possiblePosters = ImageFileExtensions.Collect(
                            ext => new[] { $"poster.{ext}", Path.GetFileNameWithoutExtension(file) + $"-poster.{ext}" })
                        .Map(f => Path.Combine(folder, f));
                    return possiblePosters.Filter(s => files.Contains(s)).HeadOrNone();
            }

            return None;
        }

        private class IntermediateResults
        {
            private readonly List<Tuple<Either<string, MediaItem>, ItemScanningPlan>> _rawResults = new();

            public void Add(Either<string, MediaItem> source, ItemScanningPlan plan) =>
                _rawResults.Add(Tuple(source, plan));

            public Seq<LocalMediaItemScanningPlan> Summarize() =>
                _rawResults
                    .GroupBy(t => t.Item1)
                    .Select(g => new LocalMediaItemScanningPlan(g.Key, g.Select(g2 => g2.Item2).ToList()))
                    .ToSeq();
        }
    }
}