When init in {non-}empty dir then an {exception thrown,repo created}

* When initialising a repo in a non-empty dir then an exception is thrown
* When initialising a repo in a empty dir then a bare repo is created

src/main/java/net/kemitix/gitdb/GitDB.java

@@ -23,7 +23,7 @@ package net.kemitix.gitdb;
 
 import org.eclipse.jgit.api.Git;
 
-import java.nio.file.NotDirectoryException;
+import java.io.IOException;
 import java.nio.file.Path;
 
 /**
@@ -38,10 +38,13 @@ public interface GitDB {
      *
      * @param dbDir the path to initialise the local repo in
      * @return a GitDB instance for the created local gitdb
-     * @throws NotDirectoryException if {@code dbDir} it is not a directory
+     * @throws IOException if there {@code dbDir} is a file or a non-empty directory
      */
-    static GitDB initLocal(final Path dbDir) throws NotDirectoryException {
-        return new GitDBLocal(Git.init(), dbDir.toFile());
+    static GitDB initLocal(final Path dbDir) throws IOException {
+        return new GitDBLocal(
+                Git.init(),
+                dbDir.toFile()
+        );
     }
 
 }

src/main/java/net/kemitix/gitdb/GitDBLocal.java

@@ -24,9 +24,11 @@ package net.kemitix.gitdb;
 import org.eclipse.jgit.api.Git;
 import org.eclipse.jgit.api.InitCommand;
 import org.eclipse.jgit.api.errors.GitAPIException;
-import org.eclipse.jgit.api.errors.JGitInternalException;
 
 import java.io.File;
+import java.io.IOException;
+import java.nio.file.DirectoryNotEmptyException;
+import java.nio.file.Files;
 import java.nio.file.NotDirectoryException;
 
 /**
@@ -44,19 +46,41 @@ class GitDBLocal implements GitDB {
      *
      * @param initCommand a JGit InitCommand
      * @param dbDir       the path to instantiate the git repo in
-     * @throws NotDirectoryException if {@code dbDir} it is not a directory
+     * @throws IOException if there {@code dbDir} is a file or a non-empty directory
      */
     @SuppressWarnings("avoidhidingcauseexception")
-    GitDBLocal(final InitCommand initCommand, final File dbDir) throws NotDirectoryException {
+    GitDBLocal(final InitCommand initCommand, final File dbDir) throws IOException {
+        validateDbDir(dbDir);
         try {
-            this.git = initCommand.setGitDir(dbDir).setBare(true).call();
-        } catch (JGitInternalException e) {
-            throw new NotDirectoryException(dbDir.toString());
+            this.git = initRepo(initCommand, dbDir);
         } catch (GitAPIException e) {
             throw new UnexpectedGitDbException("Unhandled Git API Exception", e);
         }
     }
 
+    private void validateDbDir(final File dbDir) throws IOException {
+        verifyIsNotAFile(dbDir);
+        if (dbDir.exists()) {
+            verifyIsEmpty(dbDir);
+        }
+    }
+
+    private static void verifyIsEmpty(final File dbDir) throws IOException {
+        if (Files.newDirectoryStream(dbDir.toPath()).iterator().hasNext()) {
+            throw new DirectoryNotEmptyException(dbDir.toString());
+        }
+    }
+
+    private static void verifyIsNotAFile(final File dbDir) throws NotDirectoryException {
+        if (dbDir.isFile()) {
+            throw new NotDirectoryException(dbDir.toString());
+        }
+    }
+
+    private static Git initRepo(final InitCommand initCommand, final File dbDir) throws GitAPIException {
+        return initCommand.setGitDir(dbDir).setBare(true).call();
+    }
+
     //    @Override
     //    @SneakyThrows
     //    public <T> T get(Branch branch, Key key, Class<T> type) {

src/test/java/net/kemitix/gitdb/GitDBTest.java

@@ -87,10 +87,37 @@ class GitDBTest implements WithAssertions {
         return Files.createTempFile("gitdb", "file");
     }
 
-    // When initialising a repo in a dir is exists then an exception is thrown
-    //@Test
-    //void initRepo_whenDirExists_thenThrowException() {
-    //}
+    // When initialising a repo in a non-empty dir then an exception is thrown
+    @Test
+    void initRepo_whenNotEmptyDir_thenThrowException() throws IOException {
+        //given
+        final Path dir = dirExists();
+        filesExistIn(dir);
+        //then
+        assertThatExceptionOfType(DirectoryNotEmptyException.class)
+                .isThrownBy(() -> GitDB.initLocal(dir))
+                .withMessageContaining(dir.toString());
+    }
+
+    private void filesExistIn(final Path dir) throws IOException {
+        Files.createTempFile(dir, "gitdb", "file");
+    }
+
+    private Path dirExists() throws IOException {
+        return Files.createTempDirectory("gitdb");
+    }
+
+    // When initialising a repo in a empty dir then a bare repo is created
+    @Test
+    void initRepo_whenEmptyDir_thenCreateBareRepo() throws IOException {
+        //given
+        final Path dir = dirExists();
+        //when
+        final GitDB gitDB = GitDB.initLocal(dir);
+        //then
+        assertThat(gitDB).isNotNull();
+        assertThatIsBareRepo(dir);
+    }
 
     // When opening a repo in a dir that is not a bare repo then an exception is thrown
     // When opening a repo in a dir that is a file then an exception is thrown