Add message preprocessor

none/__init__.py

@@ -127,6 +127,7 @@ def load_builtin_plugins() -> None:
     load_plugins(plugin_dir, 'none.plugins')
 
 
+from .message import message_preprocessor
 from .command import on_command, CommandSession, CommandGroup
 from .natural_language import on_natural_language, NLPSession, NLPResult
 from .notice_request import (

none/message.py

@@ -1,4 +1,5 @@
-from typing import Dict, Any
+import asyncio
+from typing import Dict, Any, Callable
 
 from aiocqhttp.message import MessageSegment
 
@@ -7,10 +8,23 @@ from .command import handle_command, SwitchException
 from .log import logger
 from .natural_language import handle_natural_language
 
+_message_preprocessors = set()
+
+
+def message_preprocessor(func: Callable) -> Callable:
+    _message_preprocessors.add(func)
+    return func
+
 
 async def handle_message(bot: NoneBot, ctx: Dict[str, Any]) -> None:
     _log_message(ctx)
 
+    coros = []
+    for processor in _message_preprocessors:
+        coros.append(processor(ctx))
+    if coros:
+        await asyncio.wait(coros)
+
     if ctx['message_type'] != 'private':
         # group or discuss
         ctx['to_me'] = False