added test case hitting shortening threshold

src/main/java/org/cryptomator/cryptofs/dir/C9rConflictResolver.java

@@ -35,13 +35,15 @@ class C9rConflictResolver {
 
 	private final Cryptor cryptor;
 	private final byte[] dirId;
-	private final VaultConfig vaultConfig;
+	private final int maxC9rFileNameLength;
+	private final int maxCleartextFileNameLength;
 
 	@Inject
 	public C9rConflictResolver(Cryptor cryptor, @Named("dirId") String dirId, VaultConfig vaultConfig) {
 		this.cryptor = cryptor;
 		this.dirId = dirId.getBytes(StandardCharsets.US_ASCII);
-		this.vaultConfig = vaultConfig;
+		this.maxC9rFileNameLength = vaultConfig.getShorteningThreshold();
+		this.maxCleartextFileNameLength = (maxC9rFileNameLength - 4) / 4 * 3 - 16; // math from FileSystemCapabilityChecker.determineSupportedCleartextFileNameLength()
 	}
 
 	public Stream<Node> process(Node node) {
@@ -80,13 +82,6 @@ private Stream<Node> resolveConflict(Node conflicting, Path canonicalPath) throw
 		}
 	}
 
-	// visible for testing
-	int calcMaxCleartextNameLength(int maxCiphertextNameLength) {
-		// math explained in https://github.com/cryptomator/cryptofs/issues/60#issuecomment-523238303;
-		// subtract 4 for file extension, base64-decode, subtract 16 for IV
-		return (maxCiphertextNameLength - 4) / 4 * 3 - 16;
-	}
-
 	/**
 	 * Resolves a conflict by renaming the conflicting file.
 	 *
@@ -99,11 +94,9 @@ int calcMaxCleartextNameLength(int maxCiphertextNameLength) {
 	private Node renameConflictingFile(Path canonicalPath, Path conflictingPath, String cleartext) throws IOException {
 		assert Files.exists(canonicalPath);
 		final int beginOfFileExtension = cleartext.lastIndexOf('.');
-		final int maxCiphertextNameLength = vaultConfig.getShorteningThreshold();
-		final int maxCleartextNameLength = calcMaxCleartextNameLength(maxCiphertextNameLength);
 		final String fileExtension = (beginOfFileExtension > 0) ? cleartext.substring(beginOfFileExtension) : "";
 		final String basename = (beginOfFileExtension > 0) ? cleartext.substring(0, beginOfFileExtension) : cleartext;
-		final String lengthRestrictedBasename = basename.substring(0, Math.min(basename.length(), maxCleartextNameLength - fileExtension.length() - 5)); // 5 chars for conflict suffix " (42)"
+		final String lengthRestrictedBasename = basename.substring(0, Math.min(basename.length(), maxCleartextFileNameLength - fileExtension.length() - 5)); // 5 chars for conflict suffix " (42)"
 		String alternativeCleartext;
 		String alternativeCiphertext;
 		String alternativeCiphertextName;
@@ -115,7 +108,7 @@ private Node renameConflictingFile(Path canonicalPath, Path conflictingPath, Str
 			alternativeCiphertextName = alternativeCiphertext + Constants.CRYPTOMATOR_FILE_SUFFIX;
 			alternativePath = canonicalPath.resolveSibling(alternativeCiphertextName);
 		} while (Files.exists(alternativePath));
-		assert alternativeCiphertextName.length() <= maxCiphertextNameLength;
+		assert alternativeCiphertextName.length() <= maxC9rFileNameLength;
 		LOG.info("Moving conflicting file {} to {}", conflictingPath, alternativePath);
 		Files.move(conflictingPath, alternativePath, StandardCopyOption.ATOMIC_MOVE);
 		Node node = new Node(alternativePath);

src/test/java/org/cryptomator/cryptofs/dir/C9rConflictResolverTest.java

@@ -31,7 +31,7 @@ public void setup() {
 		fileNameCryptor = Mockito.mock(FileNameCryptor.class);
 		vaultConfig = Mockito.mock(VaultConfig.class);
 		Mockito.when(cryptor.fileNameCryptor()).thenReturn(fileNameCryptor);
-		Mockito.when(vaultConfig.getShorteningThreshold()).thenReturn(220);
+		Mockito.when(vaultConfig.getShorteningThreshold()).thenReturn(44); // results in max cleartext size = 14
 		conflictResolver = new C9rConflictResolver(cryptor, "foo", vaultConfig);
 	}
 
@@ -77,6 +77,25 @@ public void testResolveConflictingFileByChoosingNewName(@TempDir Path dir) throw
 		Assertions.assertFalse(Files.exists(unresolved.ciphertextPath));
 	}
 
+	@Test
+	public void testResolveConflictingFileByChoosingNewLengthLimitedName(@TempDir Path dir) throws IOException {
+		Files.createFile(dir.resolve("foo (1).c9r"));
+		Files.createFile(dir.resolve("foo.c9r"));
+		Mockito.when(fileNameCryptor.encryptFilename(Mockito.any(), Mockito.any(), Mockito.any())).thenReturn("baz");
+		Node unresolved = new Node(dir.resolve("foo (1).c9r"));
+		unresolved.cleartextName = "hello world.txt";
+		unresolved.extractedCiphertext = "foo";
+
+		Stream<Node> result = conflictResolver.process(unresolved);
+		Node resolved = result.findAny().get();
+
+		Assertions.assertNotEquals(unresolved, resolved);
+		Assertions.assertEquals("baz.c9r", resolved.fullCiphertextFileName);
+		Assertions.assertEquals("hello (1).txt", resolved.cleartextName);
+		Assertions.assertTrue(Files.exists(resolved.ciphertextPath));
+		Assertions.assertFalse(Files.exists(unresolved.ciphertextPath));
+	}
+
 	@Test
 	public void testResolveConflictingFileTrivially(@TempDir Path dir) throws IOException {
 		Files.createFile(dir.resolve("foo (1).c9r"));
@@ -131,11 +150,4 @@ public void testResolveConflictingSymlinkTrivially(@TempDir Path dir) throws IOE
 		Assertions.assertFalse(Files.exists(unresolved.ciphertextPath));
 	}
 
-	@ParameterizedTest
-	@CsvSource({"220, 146", "219, 143", "218, 143", "217, 143", "216, 143", "215, 140"})
-	public void testCalcMaxCleartextNameLength(int input, int expectedResult) {
-		int result = conflictResolver.calcMaxCleartextNameLength(input);
-		Assertions.assertEquals(expectedResult, result);
-	}
-
 }