Fix watcher sync loop when auto-watch is enabled

app/utils/local_playlist.py

@@ -78,10 +78,28 @@ def write_local_playlist(playlist_path: str, tracks: List[str]) -> bool:
         bool: True if successful, False otherwise.
     """
     try:
-        with open(playlist_path, 'w', encoding="utf-8") as file:
-            file.write("#EXTM3U\n")
-            for track in tracks:
-                file.write(f"{track}\n")
+        desired_lines = ["#EXTM3U\n"] + [f"{track}\n" for track in tracks]
+        desired_content = "".join(desired_lines)
+
+        # Avoid rewriting identical content to prevent watcher feedback loops.
+        if os.path.exists(playlist_path):
+            try:
+                with open(playlist_path, 'r', encoding="utf-8") as existing_file:
+                    existing_content = existing_file.read()
+                if existing_content == desired_content:
+                    logger.debug(f"Playlist unchanged; skipping write: {playlist_path}")
+                    return True
+            except Exception as e:
+                # If read fails, fall back to rewriting.
+                logger.debug(f"Failed to read existing playlist for comparison ({playlist_path}): {e}")
+
+        # Write via temp file then replace for safer updates.
+        os.makedirs(os.path.dirname(os.path.abspath(playlist_path)), exist_ok=True)
+        tmp_path = f"{playlist_path}.tmp"
+        with open(tmp_path, 'w', encoding="utf-8") as file:
+            file.write(desired_content)
+        os.replace(tmp_path, playlist_path)
+
         logger.info(f"Written {len(tracks)} songs to the playlist: {playlist_path}")
         return True
     except Exception as e: