Try another approach for plugin web apps

maubot/server.py

@@ -13,11 +13,12 @@
 #
 # You should have received a copy of the GNU Affero General Public License
 # along with this program.  If not, see <https://www.gnu.org/licenses/>.
-from typing import Tuple, Dict
+from typing import Tuple, List, Dict, Callable, Awaitable
+from functools import partial
 import logging
 import asyncio
 
-from aiohttp import web
+from aiohttp import web, hdrs, URL
 from aiohttp.abc import AbstractAccessLogger
 import pkg_resources
 
@@ -34,6 +35,62 @@ class AccessLogger(AbstractAccessLogger):
                          f'in {round(time, 4)}s"')
 
 
+Handler = Callable[[web.Request], Awaitable[web.Response]]
+Middleware = Callable[[web.Request, Handler], Awaitable[web.Response]]
+
+
+class PluginWebApp(web.UrlDispatcher):
+    def __init__(self):
+        super().__init__()
+        self._middleware: List[Middleware] = []
+
+    def add_middleware(self, middleware: Middleware) -> None:
+        self._middleware.append(middleware)
+
+    def remove_middleware(self, middleware: Middleware) -> None:
+        self._middleware.remove(middleware)
+
+    async def handle(self, request: web.Request) -> web.Response:
+        match_info = await self.resolve(request)
+        match_info.freeze()
+        resp = None
+        request._match_info = match_info
+        expect = request.headers.get(hdrs.EXPECT)
+        if expect:
+            resp = await match_info.expect_handler(request)
+            await request.writer.drain()
+        if resp is None:
+            handler = match_info.handler
+            for middleware in self._middleware:
+                handler = partial(middleware, handler=handler)
+            resp = await handler(request)
+        return resp
+
+
+class PrefixResource(web.Resource):
+    def __init__(self, prefix, *, name=None):
+        assert not prefix or prefix.startswith('/'), prefix
+        assert prefix in ('', '/') or not prefix.endswith('/'), prefix
+        super().__init__(name=name)
+        self._prefix = URL.build(path=prefix).raw_path
+
+    @property
+    def canonical(self):
+        return self._prefix
+
+    def add_prefix(self, prefix):
+        assert prefix.startswith('/')
+        assert not prefix.endswith('/')
+        assert len(prefix) > 1
+        self._prefix = prefix + self._prefix
+
+    def _match(self, path: str) -> dict:
+        return {} if self.raw_match(path) else None
+
+    def raw_match(self, path: str) -> bool:
+        return path and path.startswith(self._prefix)
+
+
 class MaubotServer:
     log: logging.Logger = logging.getLogger("maubot.server")
 
@@ -45,38 +102,38 @@ class MaubotServer:
         as_path = PathBuilder(config["server.appservice_base_path"])
         self.add_route(Method.PUT, as_path.transactions, self.handle_transaction)
 
-        self.plugin_apps: Dict[str, web.Application] = {}
-        self.app.router.add_view(config["server.plugin_base_path"], self.handle_plugin_path)
+        self.plugin_routes: Dict[str, PluginWebApp] = {}
+        resource = PrefixResource(config["server.plugin_base_path"])
+        resource.add_route(hdrs.METH_ANY, self.handle_plugin_path)
+        self.app.router.register_resource(resource)
 
         self.setup_management_ui()
 
         self.runner = web.AppRunner(self.app, access_log_class=AccessLogger)
 
     async def handle_plugin_path(self, request: web.Request) -> web.Response:
-        for path, app in self.plugin_apps.items():
+        for path, app in self.plugin_routes.items():
             if request.path.startswith(path):
-                # TODO there's probably a correct way to do these
-                request._rel_url.path = request._rel_url.path[len(path):]
-                return await app._handle(request)
+                request = request.clone(rel_url=request.path[len(path):])
+                return await app.handle(request)
         return web.Response(status=404)
 
-    def get_instance_subapp(self, instance_id: str) -> Tuple[web.Application, str]:
-        subpath = self.config["server.plugin_base_path"].format(id=instance_id)
+    def get_instance_subapp(self, instance_id: str) -> Tuple[PluginWebApp, str]:
+        subpath = self.config["server.plugin_base_path"] + instance_id
         url = self.config["server.public_url"] + subpath
         try:
-            return self.plugin_apps[subpath], url
+            return self.plugin_routes[subpath], url
         except KeyError:
-            app = web.Application(loop=self.loop)
-            self.plugin_apps[subpath] = app
+            app = PluginWebApp()
+            self.plugin_routes[subpath] = app
             return app, url
 
     def remove_instance_webapp(self, instance_id: str) -> None:
         try:
-            subapp: web.Application = self.plugin_apps.pop(instance_id)
+            subpath = self.config["server.plugin_base_path"] + instance_id
+            self.plugin_routes.pop(subpath)
         except KeyError:
             return
-        subapp.shutdown()
-        subapp.cleanup()
 
     def setup_management_ui(self) -> None:
         ui_base = self.config["server.ui_base_path"]