fix: Replace non-ASCII characters in filenames (#42)

Fixes #41.

CHANGELOG.md

@@ -16,6 +16,10 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ## [Unreleased]
 
+### Fixed
+
+- replaced non-ASCII characters in encrypted filename (#41)
+
 ## [1.3.3] - 2023-10-17
 
 ### Fixed

DigitaleBriefwahl/Encryption/EncryptVote.cs

@@ -120,9 +120,26 @@ private static byte[] EncryptData(byte[] inputData)
 			return encOut.ToArray();
 		}
 
+		private const  string   Umlauts            = "äöüÄÖÜß";
+		private static string[] UmlautReplacements = { "ae", "oe", "ue", "AE", "OE", "UE", "ss" };
+
 		private static string GetSanitizedElection(string election)
 		{
-			return election.Replace(' ', '_').Replace('.', '_');
+			var filePath = election.Replace(' ', '_').Replace('.', '_');
+			var bldr = new StringBuilder();
+			for (int i = 0; i < filePath.Length; i++)
+			{
+				var c = filePath[i];
+				if (c > 128)
+				{
+					var umlautIndex = Umlauts.IndexOf(c);
+					bldr.Append(umlautIndex >= 0 ? UmlautReplacements[umlautIndex] : "_");
+				}
+				else
+					bldr.Append(c);
+			}
+
+			return bldr.ToString();
 		}
 
 		public string WriteVote(string vote, string filePath = null)

DigitaleBriefwahlTests/EncryptVoteTests.cs

@@ -41,5 +41,26 @@ public void GetEncryptedFilePath()
 			Assert.That(sut.GetEncryptedFilePath(sut.BallotFilePath),
 				Is.EqualTo(sut.BallotFilePath.Substring(0, sut.BallotFilePath.Length - 4) + ".gpg"));
 		}
+
+		[Test]
+		public void GetEncryptedFilePath_Umlaut_AllASCII()
+		{
+			var sut= new EncryptVote("ÄÖÜäöüß");
+			var filePath = Path.GetFileName(sut.GetEncryptedFilePath(sut.BallotFilePath));
+			Assert.That(filePath.StartsWith("AEOEUEaeoeuess"), Is.True,
+				$"Unexpected FilePath.\n    Expected: AEOEUEaeoeuess...\n    But was:  {filePath}");
+		}
+
+		[Test]
+		public void GetEncryptedFilePath_Other_AllASCII()
+		{
+			var sut= new EncryptVote("ខ្មែរ");
+			var filePath = sut.GetEncryptedFilePath(sut.BallotFilePath);
+			foreach (var c in filePath.ToCharArray())
+			{
+				Assert.That(c, Is.LessThanOrEqualTo(128),
+					$"FilePath contains non-ASCII characters: {filePath}");
+			}
+		}
 	}
 }