Naming logic for all new files can now originate from domian logic

AaxDecrypter/AaxcDownloadMultiConverter.cs

@@ -12,10 +12,23 @@ namespace AaxDecrypter
 	{
 		protected override StepSequence Steps { get; }
 
-		private static TimeSpan minChapterLength { get; } = TimeSpan.FromSeconds(3);
+        private Func<string, int, int, NewSplitCallback, string> multipartFileNameCallback { get; }
+        private static string DefaultMultipartFileName(string outputFileName, int partsPosition, int partsTotal, NewSplitCallback newSplitCallback)
+        {
+            var template = Path.ChangeExtension(outputFileName, null) + " - <chapter> - <title>" + Path.GetExtension(outputFileName);
+
+            var fileTemplate = new FileTemplate(template) { IllegalCharacterReplacements = " " };
+            fileTemplate.AddParameterReplacement("chapter", FileUtility.GetSequenceFormatted(partsPosition, partsTotal));
+            fileTemplate.AddParameterReplacement("title", newSplitCallback?.Chapter?.Title ?? "");
+
+            return fileTemplate.GetFilename();
+        }
+
+        private static TimeSpan minChapterLength { get; } = TimeSpan.FromSeconds(3);
 		private List<string> multiPartFilePaths { get; } = new List<string>();
 
-        public AaxcDownloadMultiConverter(string outFileName, string cacheDirectory, DownloadLicense dlLic, OutputFormat outputFormat)
+        public AaxcDownloadMultiConverter(string outFileName, string cacheDirectory, DownloadLicense dlLic, OutputFormat outputFormat,
+            Func<string, int, int, NewSplitCallback, string> multipartFileNameCallback = null)
 			: base(outFileName, cacheDirectory, dlLic, outputFormat)
         {
             Steps = new StepSequence
@@ -26,6 +39,7 @@ namespace AaxDecrypter
                 ["Step 2: Download Decrypted Audiobook"] = Step_DownloadAudiobookAsMultipleFilesPerChapter,
                 ["Step 3: Cleanup"] = Step_Cleanup,
             };
+            this.multipartFileNameCallback = multipartFileNameCallback ?? DefaultMultipartFileName;
         }
 
         /*
@@ -119,7 +133,9 @@ That naming may not be desirable for everyone, but it's an easy change to instea
 
         private void createOutputFileStream(int currentChapter, ChapterInfo splitChapters, NewSplitCallback newSplitCallback)
         {
-            var fileName = FileUtility.GetMultipartFileName(OutputFileName, currentChapter, splitChapters.Count, newSplitCallback.Chapter.Title);
+            var fileName = multipartFileNameCallback(OutputFileName, currentChapter, splitChapters.Count, newSplitCallback);
+            fileName = FileUtility.GetValidFilename(fileName);
+
             multiPartFilePaths.Add(fileName);
 
             FileUtility.SaferDelete(fileName);

AaxDecrypter/AudiobookDownloadBase.cs

@@ -46,9 +46,10 @@ namespace AaxDecrypter
 				throw new DirectoryNotFoundException($"Directory does not exist: {nameof(cacheDirectory)}");
 			cacheDir = cacheDirectory;
 
+			DownloadLicense = ArgumentValidator.EnsureNotNull(dlLic, nameof(dlLic));
+
 			// delete file after validation is complete
 			FileUtility.SaferDelete(OutputFileName);
-			DownloadLicense = ArgumentValidator.EnsureNotNull(dlLic, nameof(dlLic));
 		}
 
 		public abstract void Cancel();

FileManager.Tests/FileUtilityTests.cs

@@ -86,45 +86,39 @@ namespace FileUtilityTests
 	}
 
 	[TestClass]
-	public class GetMultipartFileName
+	public class GetSequenceFormatted
 	{
-		[TestMethod]
-		public void null_path() => Assert.ThrowsException<ArgumentNullException>(() => FileUtility.GetMultipartFileName(null, 1, 1, ""));
-
-		[TestMethod]
-		public void null_suffix() => Tests(@"C:\foo\bar\my file.txt", 2, 100, null, @"C:\foo\bar\my file - 002 - .txt");
-
 		[TestMethod]
 		public void negative_partsPosition() => Assert.ThrowsException<ArgumentException>(()
-			=> FileUtility.GetMultipartFileName("foo", -1, 2, "")
+			=> FileUtility.GetSequenceFormatted(-1, 2)
 		);
 		[TestMethod]
 		public void zero_partsPosition() => Assert.ThrowsException<ArgumentException>(()
-			=> FileUtility.GetMultipartFileName("foo", 0, 2, "")
+			=> FileUtility.GetSequenceFormatted(0, 2)
 		);
 
 		[TestMethod]
 		public void negative_partsTotal() => Assert.ThrowsException<ArgumentException>(()
-			=> FileUtility.GetMultipartFileName("foo", 2, -1, "")
+			=> FileUtility.GetSequenceFormatted(2, -1)
 		);
 		[TestMethod]
 		public void zero_partsTotal() => Assert.ThrowsException<ArgumentException>(()
-			=> FileUtility.GetMultipartFileName("foo", 2, 0, "")
+			=> FileUtility.GetSequenceFormatted(2, 0)
 		);
 
 		[TestMethod]
 		public void partsPosition_greater_than_partsTotal() => Assert.ThrowsException<ArgumentException>(()
-			=> FileUtility.GetMultipartFileName("foo", 2, 1, "")
+			=> FileUtility.GetSequenceFormatted(2, 1)
 		);
 
 		[TestMethod]
 		// only part
-		[DataRow(@"C:\foo\bar\my file.txt", 1, 1, "title", @"C:\foo\bar\my file - 1 - title.txt")]
+		[DataRow(1, 1, "1")]
+		// 2 digits
+		[DataRow(2, 90, "02")]
 		// 3 digits
-		[DataRow(@"C:\foo\bar\my file.txt", 2, 100, "title", @"C:\foo\bar\my file - 002 - title.txt")]
+		[DataRow(2, 900, "002")]
-		// no suffix
+		public void Tests(int partsPosition, int partsTotal, string expected)
-		[DataRow(@"C:\foo\bar\my file.txt", 2, 100, "", @"C:\foo\bar\my file - 002 - .txt")]
+			=> FileUtility.GetSequenceFormatted(partsPosition, partsTotal).Should().Be(expected);
-		public void Tests(string originalPath, int partsPosition, int partsTotal, string suffix, string expected)
-			=> FileUtility.GetMultipartFileName(originalPath, partsPosition, partsTotal, suffix).Should().Be(expected);
 	}
 }

FileManager/FileUtility.cs

@@ -35,26 +35,22 @@ namespace FileManager
             return fileTemplate.GetFilename();
         }
 
-        public static string GetMultipartFileName(string originalPath, int partsPosition, int partsTotal, string suffix)
+        /// <summary>
+        /// Return position with correct number of leading zeros.
+        /// <br />- 2 of 9 => "2"
+        /// <br />- 2 of 90 => "02"
+        /// <br />- 2 of 900 => "002"
+        /// </summary>
+        /// <param name="position">position in sequence. The 'x' in 'x of y'</param>
+        /// <param name="total">total qty in sequence. The 'y' in 'x of y'</param>
+        public static string GetSequenceFormatted(int position, int total)
         {
-            ArgumentValidator.EnsureNotNull(originalPath, nameof(originalPath));
+            ArgumentValidator.EnsureGreaterThan(position, nameof(position), 0);
-            ArgumentValidator.EnsureGreaterThan(partsPosition, nameof(partsPosition), 0);
+            ArgumentValidator.EnsureGreaterThan(total, nameof(total), 0);
-            ArgumentValidator.EnsureGreaterThan(partsTotal, nameof(partsTotal), 0);
+            if (position > total)
-            if (partsPosition > partsTotal)
+                throw new ArgumentException($"{position} may not be greater than {total}");
-                throw new ArgumentException($"{partsPosition} may not be greater than {partsTotal}");
 
-            // 1-9     => 1-9
+            return position.ToString().PadLeft(total.ToString().Length, '0');
-            // 10-99   => 01-99
-            // 100-999 => 001-999
-            var chapterCountLeadingZeros = partsPosition.ToString().PadLeft(partsTotal.ToString().Length, '0');
-
-            var template = Path.ChangeExtension(originalPath, null) + " - <chapter> - <title>" + Path.GetExtension(originalPath);
-
-            var fileTemplate = new FileTemplate(template) { IllegalCharacterReplacements = " " };
-            fileTemplate.AddParameterReplacement("chapter", chapterCountLeadingZeros);
-            fileTemplate.AddParameterReplacement("title", suffix);
-
-            return fileTemplate.GetFilename();
         }
 
         private const int MAX_FILENAME_LENGTH = 255;