Add Locate Audiobooks function (#485)

Source/LibationFileManager/AudioFileLocator.cs

@@ -0,0 +1,60 @@
+using AAXClean;
+using Dinah.Core;
+using FileManager;
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Runtime.CompilerServices;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace LibationFileManager
+{
+	public static class AudioFileLocator
+	{
+		private static EnumerationOptions enumerationOptions { get; } = new()
+		{
+			RecurseSubdirectories = true,
+			IgnoreInaccessible = true,
+			MatchCasing = MatchCasing.CaseInsensitive
+		};
+
+		public static async IAsyncEnumerable<FilePathCache.CacheEntry> FindAudiobooks(LongPath searchDirectory, [EnumeratorCancellation] CancellationToken cancellationToken)
+		{
+			ArgumentValidator.EnsureNotNull(searchDirectory, nameof(searchDirectory));
+
+			foreach (LongPath path in Directory.EnumerateFiles(searchDirectory, "*.M4B", enumerationOptions))
+			{
+				if (cancellationToken.IsCancellationRequested)
+					yield break;
+
+				int generation = 0;
+				FilePathCache.CacheEntry audioFile = default;
+
+				try
+				{
+					using var fileStream = File.OpenRead(path);
+
+					var mp4File = await Task.Run(() => new Mp4File(fileStream), cancellationToken);
+
+					generation = GC.GetGeneration(mp4File);
+
+					if (mp4File?.AppleTags?.Asin is not null)
+						audioFile = new FilePathCache.CacheEntry(mp4File.AppleTags.Asin, FileType.Audio, path);
+
+				}
+				catch(Exception ex)
+				{
+					Serilog.Log.Error(ex, "Error checking for asin in {@file}", path);
+				}
+				finally
+				{
+					GC.Collect(generation);
+				}
+
+				if (audioFile is not null)
+					yield return audioFile;
+			}
+		}
+	}
+}

Source/LibationFileManager/FilePathCache.cs

@@ -86,7 +86,11 @@ namespace LibationFileManager
         public static void Insert(string id, string path)
 		{
 			var type = FileTypes.GetFileTypeFromPath(path);
-			var entry = new CacheEntry(id, type, path);
+			Insert(new CacheEntry(id, type, path));
+		}
+
+		public static void Insert(CacheEntry entry)
+		{
 			cache.Add(entry);
 			Inserted?.Invoke(null, entry);
 			save();