fix(utils): handle file write failures with rollback

- Add error handling and rollback logic for unit file writes
- Prevent partial file writes by removing created files on failure
- Update tests to reflect new return type and error handling

src/utils/__tests__/fs.test.ts

@@ -24,7 +24,7 @@ Deno.test('writeUnitFiles schreibt .service und .timer korrekt', async () => {
         serviceContent,
         timerContent,
         options as TimerOptions,
-    );
+    ) as { servicePath: string; timerPath: string };
 
     // Überprüfe Pfade
     assertEquals(servicePath, join(tmp, 'test-backup.service'));

src/utils/fs.ts

@@ -1,4 +1,4 @@
-import { ensureDir } from 'https://deno.land/std@0.224.0/fs/mod.ts';
+import { ensureDir, exists } from 'https://deno.land/std@0.224.0/fs/mod.ts';
 import { join } from 'https://deno.land/std@0.224.0/path/mod.ts';
 import { TimerOptions } from '../types/mod.ts';
 
@@ -7,7 +7,7 @@ export async function writeUnitFiles(
     serviceContent: string,
     timerContent: string,
     options: TimerOptions,
-): Promise<{ servicePath: string; timerPath: string }> {
+): Promise<{ servicePath: string; timerPath: string } | undefined> {
     const basePath = resolveUnitTargetPath(options);
 
     await ensureDir(basePath);
@@ -15,8 +15,24 @@ export async function writeUnitFiles(
     const servicePath = join(basePath, `${name}.service`);
     const timerPath = join(basePath, `${name}.timer`);
 
-    await Deno.writeTextFile(servicePath, serviceContent);
-    await Deno.writeTextFile(timerPath, timerContent);
+    try {
+        await Deno.writeTextFile(servicePath, serviceContent);
+        await Deno.writeTextFile(timerPath, timerContent);
+    } catch (error) {
+        // Rollback: Remove any files that were written
+        try {
+            if (await exists(servicePath)) {
+                await Deno.remove(servicePath);
+            }
+            if (await exists(timerPath)) {
+                await Deno.remove(timerPath);
+            }
+        } catch (rollbackError) {
+            console.error('Rollback fehlgeschlagen:', rollbackError);
+        }
+        console.error('Fehler beim Schreiben der Units:', error);
+        return undefined;
+    }
 
     return { servicePath, timerPath };
 }