Add friendly error message for Twitter restricted content (TweetTombstone)

backend/app/services/downloader.py

@@ -143,7 +143,13 @@ def _twitter_syndication_info(tweet_id: str) -> dict:
         'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36'
     })
     resp = urllib.request.urlopen(req, timeout=15)
-    return json.loads(resp.read().decode())
+    data = json.loads(resp.read().decode())
+    
+    # Check for restricted content (TweetTombstone)
+    if data.get('__typename') == 'TweetTombstone':
+        raise ValueError('内容受限不支持下载（敏感内容/年龄限制），需要登录账号访问')
+    
+    return data
 
 
 def _parse_twitter_video(url: str) -> dict:
@@ -499,6 +505,14 @@ def parse_video_url(url: str) -> dict:
             result = _parse_twitter_video(url)
             result.pop('_formats_full', None)
             return result
+        except ValueError as e:
+            error_msg = str(e)
+            # If it's restricted content error, don't fallback to yt-dlp
+            if '内容受限不支持下载' in error_msg:
+                logger.error(f"Twitter content restricted: {error_msg}")
+                raise
+            # For other errors, fallback to yt-dlp
+            logger.warning(f"Twitter syndication failed, falling back to yt-dlp: {e}")
         except Exception as e:
             logger.warning(f"Twitter syndication failed, falling back to yt-dlp: {e}")
 
@@ -569,6 +583,14 @@ def download_video(url: str, format_id: str = "best", progress_callback=None, ta
         logger.info(f"Using Twitter syndication API for download: {url}")
         try:
             return _download_twitter_video(url, format_id, progress_callback, task_id=task_id)
+        except ValueError as e:
+            error_msg = str(e)
+            # If it's restricted content error, don't fallback to yt-dlp
+            if '内容受限不支持下载' in error_msg:
+                logger.error(f"Twitter content restricted: {error_msg}")
+                raise
+            # For other errors, fallback to yt-dlp
+            logger.warning(f"Twitter syndication download failed, falling back to yt-dlp: {e}")
         except Exception as e:
             logger.warning(f"Twitter syndication download failed, falling back to yt-dlp: {e}")