Add initial middleware and configuration for blocking AI user agents

ai_blocker/middleware.py

@@ -0,0 +1,35 @@
+import importlib
+from asgiref.sync import iscoroutinefunction, markcoroutinefunction
+
+from django.conf import settings
+from django.http import HttpResponse
+
+
+def load_backing_class(path: str):
+    mod_name, _, cls_name = path.rpartition(".")
+    module = importlib.import_module(mod_name)
+    return getattr(module, cls_name)
+
+
+class AiBlockerMiddleware:
+    def __init__(self, get_response):
+        self.get_response = get_response
+
+        if iscoroutinefunction(self.get_response):
+            markcoroutinefunction(self)
+
+        self.backing_class = getattr(getattr(settings, "AI_BLOCKER_CONF"), "backing_class", "ai_blocker.ualist_backers.ConfigBackedUAList")
+        Backer = load_backing_class(self.backing_class)
+        self.backer = Backer()
+
+    async def __call__(self, request):
+        ua = request.headers.get("User-Agent", "")
+
+        blocked_headers = self.backer.get_ua_list()
+
+        if ua in blocked_headers:
+            return HttpResponse(status=403)
+
+        response = self.get_response(request)
+        # Add code here to process the response after the view has been run.
+        return response

ai_blocker/ualist_backers.py

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+from abc import ABC, abstractmethod
+
+from django.conf import settings
+
+
+class UAList(ABC):
+
+    @abstractmethod
+    def get_ua_list(self) -> list[str]:
+        raise NotImplemented
+
+
+
+class ConfigBackedUAList(UAList):
+    def get_ua_list(self) -> list[str]:
+        return list(getattr(getattr(settings, "AI_BLOCKER_CONF"), "ua_list", []))