Health API / Directory Check: Result EmptyDirFile (#108)

Add to DirIdCheck new result: EmptyDirId (including unit tests) 

Co-authored-by: Sebastian Stenzel <overheadhunter@users.noreply.github.com>

Author: Armin Schrenk

src/main/java/org/cryptomator/cryptofs/health/dirid/DirIdCheck.java

@@ -103,6 +103,9 @@ private FileVisitResult visitDirFile(Path file, BasicFileAttributes attrs) throw
 			if (attrs.size() > Constants.MAX_DIR_FILE_LENGTH) {
 				LOG.warn("Encountered dir.c9r file of size {}", attrs.size());
 				resultCollector.accept(new ObeseDirFile(file, attrs.size()));
+			} else if (attrs.size() == 0) {
+				LOG.warn("Empty dir.c9r file.", file);
+				resultCollector.accept(new EmptyDirFile(file));
 			} else {
 				byte[] bytes = Files.readAllBytes(file);
 				String dirId = new String(bytes, StandardCharsets.UTF_8);

src/main/java/org/cryptomator/cryptofs/health/dirid/EmptyDirFile.java

@@ -0,0 +1,49 @@
+package org.cryptomator.cryptofs.health.dirid;
+
+import org.cryptomator.cryptofs.health.api.DiagnosticResult;
+
+import java.nio.file.Path;
+import java.util.Map;
+
+import static org.cryptomator.cryptofs.health.api.CommonDetailKeys.DIR_ID_FILE;
+
+/**
+ * A diagnostic result of an empty directory id file (dir.c9r).
+ * <p>
+ * Even though the empty directory ID exists, it is reserved for the root node of the crypto filesystem only.
+ * Due to its nature, the root node has no corresponding dir.c9r file.
+ * As a consequence, actual dir.c9r files must not be empty, otherwise it is an error in the vault structure.
+ *
+ * @see org.cryptomator.cryptofs.common.Constants#ROOT_DIR_ID
+ */
+public class EmptyDirFile implements DiagnosticResult {
+
+	final Path dirFile;
+
+	public EmptyDirFile(Path dirFile) {this.dirFile = dirFile;}
+
+	@Override
+	public Severity getSeverity() {
+		return Severity.CRITICAL;
+	}
+
+	@Override
+	public String toString() {
+		return String.format("File %s is empty, expected content", dirFile);
+	}
+
+	/*
+	TODO: remove dirFile and parent dir, Change severity to WARN
+	@Override
+	public void fix(Path pathToVault, VaultConfig config, Masterkey masterkey, Cryptor cryptor) throws IOException {
+		Files.delete(dirFile);
+		Files.delete(dirFile.getParent());
+
+	}
+	 */
+
+	@Override
+	public Map<String, String> details() {
+		return Map.of(DIR_ID_FILE, dirFile.toString());
+	}
+}

src/test/java/org/cryptomator/cryptofs/health/dirid/DirIdCheckTest.java

@@ -36,6 +36,7 @@ public class DirIdCheckTest {
 			AA/aaaa/baz=.c9r/symlink.c9r = linktarget
 			BB/bbbb/foo=.c9r/dir.c9r = CCcccc
 			BB/bbbb/bar=.c9r/dir.c9r = ffffffffffff-aaaaaaaaaaaa-tttttttttttt
+			BB/bbbb/baz=.c9r/dir.c9r = [EMPTY]
 			BB/bbbb/foo=.c9r/unrelated/dir.c9r = unrelatedfile
 			CC/cccc/foo=.c9r = file
 			""";
@@ -121,16 +122,32 @@ public void testVisitorDetectsObeseDirId() throws IOException {
 			MatcherAssert.assertThat(resultCaptor.getAllValues(), Matchers.hasItem(CustomMatchers.matching(ObeseDirFile.class, expectedObeseFile, "Obese dir file: /d/BB/bbbb/bar=.c9r/dir.c9r")));
 		}
 
+		@Test
+		@DisplayName("detects empty dirID file in /d/BB/bbbb/baz=.c9r/dir.c9r")
+		public void testVisitorDetectsEmptyDirId() throws IOException {
+			Files.walkFileTree(dataRoot, Set.of(), 4, visitor);
+
+			Predicate<EmptyDirFile> expectedEmptyFile = emptyDirFile -> "/d/BB/bbbb/baz=.c9r/dir.c9r".equals(emptyDirFile.dirFile.toString());
+			ArgumentCaptor<DiagnosticResult> resultCaptor = ArgumentCaptor.forClass(DiagnosticResult.class);
+			Mockito.verify(resultsCollector, Mockito.atLeastOnce()).accept(resultCaptor.capture());
+			MatcherAssert.assertThat(resultCaptor.getAllValues(), Matchers.hasItem(CustomMatchers.matching(EmptyDirFile.class, expectedEmptyFile, "Empty dir file: /d/BB/bbbb/baz=.c9r/dir.c9r")));
+		}
+
 	}
 
 	private static void initDirStructure(Path root, String line) throws UncheckedIOException {
 		try {
 			if (line.contains(" = ")) {
 				var sep = line.indexOf(" = ");
-				var file = line.substring(0, sep);
+				var file = root.resolve(line.substring(0, sep));
 				var contents = line.substring(sep + 3);
-				Files.createDirectories(root.resolve(file).getParent());
-				Files.writeString(root.resolve(file), contents, StandardCharsets.US_ASCII, StandardOpenOption.CREATE_NEW);
+				Files.createDirectories(file.getParent());
+				if (contents.equals("[EMPTY]")) {
+					Files.createFile(file);
+				} else {
+					Files.writeString(file, contents, StandardCharsets.US_ASCII, StandardOpenOption.CREATE_NEW);
+
+				}
 			} else {
 				Files.createDirectories(root.resolve(line));
 			}