fix: add return None in except, improve scraper diagnostics logging

app.py

@@ -106,6 +106,7 @@ def _get_live_chat_id(video_id: str, api_key: str) -> str | None:
     """Fetch the liveChatId for a given video using YouTube Data API v3."""
     import urllib.request
     import urllib.parse
+    import urllib.error
 
     url = (
         "https://www.googleapis.com/youtube/v3/videos"
@@ -114,15 +115,20 @@ def _get_live_chat_id(video_id: str, api_key: str) -> str | None:
     try:
         with urllib.request.urlopen(url, timeout=10) as resp:
             data = json.loads(resp.read())
+        logger.info("YouTube API response for %s: %s", video_id, json.dumps(data)[:500])
         items = data.get("items", [])
         if not items:
-            logger.error("No video found for id=%s", video_id)
+            logger.error("No video found for id=%s (items empty). Check if video ID is correct and API key is valid.", video_id)
             return None
         live_details = items[0].get("liveStreamingDetails", {})
         chat_id = live_details.get("activeLiveChatId")
         if not chat_id:
-            logger.error("No active live chat for video id=%s", video_id)
+            logger.error("No activeLiveChatId for video=%s. liveStreamingDetails=%s", video_id, live_details)
         return chat_id
+    except urllib.error.HTTPError as exc:
+        body = exc.read().decode("utf-8", errors="replace")[:500]
+        logger.error("HTTP %d from YouTube API for video=%s: %s", exc.code, video_id, body)
+        return None
     except Exception as exc:
         logger.error("Failed to get liveChatId: %s", exc)
         return None
@@ -152,6 +158,7 @@ def _fetch_chat_messages(live_chat_id: str, api_key: str, page_token: str | None
         messages      = data.get("items", [])
         next_token    = data.get("nextPageToken")
         poll_interval = data.get("pollingIntervalMillis", 5000)
+        logger.info("Fetched %d chat messages (nextPageToken=%s)", len(messages), bool(next_token))
         return messages, next_token, poll_interval
     except Exception as exc:
         logger.error("Failed to fetch chat messages: %s", exc)
@@ -161,8 +168,11 @@ def _fetch_chat_messages(live_chat_id: str, api_key: str, page_token: str | None
 def _scraper_thread_fn(video_id: str, redis_key: str, stop_event: threading.Event) -> None:
     """Background thread — scrapes live chat via YouTube Data API v3."""
     api_key = os.getenv("YOUTUBE_API_KEY", "")
+    logger.info("YOUTUBE_API_KEY present: %s (length=%d)", bool(api_key), len(api_key))
     if not api_key:
-        logger.error("YOUTUBE_API_KEY env var not set. Cannot start scraper.")
+        msg = "YOUTUBE_API_KEY env var not set. Cannot start scraper."
+        logger.error(msg)
+        _META["scraper_error"] = msg
         return
 
     logger.info("Scraper thread starting — video=%s key=%s", video_id, redis_key)