use latest group image for xiaoniu image followups

db/message_storage.py

@@ -43,6 +43,24 @@ class MessageStorageDB(BaseDBOperator):
         params = (hours_ago, group_id, min_content_length)
         return self.execute_query(sql, params) or []
 
+    def get_latest_image_message(self, group_id: str, before_timestamp: str = "", hours_ago: int = 8) -> Optional[Dict]:
+        """获取指定群最近一条已落盘图片消息"""
+        sql = """
+        SELECT timestamp, sender, content, message_type, image_path
+        FROM messages
+        WHERE timestamp >= DATE_SUB(NOW(), INTERVAL %s HOUR)
+          AND group_id = %s
+          AND message_type = 3
+          AND image_path IS NOT NULL
+          AND image_path <> ''
+        """
+        params: List = [hours_ago, group_id]
+        if before_timestamp:
+            sql += " AND timestamp <= %s"
+            params.append(before_timestamp)
+        sql += " ORDER BY timestamp DESC LIMIT 1"
+        return self.execute_query(sql, tuple(params), fetch_one=True)
+
     def get_member_recent_messages(self, group_id: str, wxid: str, days: int = 30,
                                    limit: int = 200, include_today: bool = True) -> List[Dict]:
         """获取指定群成员近期消息"""