implemented async-only http middleware

Author: amirreza8002

django_async_extensions/amiddleware/http.py

@@ -0,0 +1,41 @@
+from django.utils.cache import cc_delim_re, get_conditional_response, set_response_etag
+from django.utils.http import parse_http_date_safe
+
+from django_async_extensions.amiddleware.base import AsyncMiddlewareMixin
+
+
+class AsyncConditionalGetMiddleware(AsyncMiddlewareMixin):
+    """
+    Handle conditional GET operations. If the response has an ETag or
+    Last-Modified header and the request has If-None-Match or If-Modified-Since,
+    replace the response with HttpNotModified. Add an ETag header if needed.
+    """
+
+    async def process_response(self, request, response):
+        # It's too late to prevent an unsafe request with a 412 response, and
+        # for a HEAD request, the response body is always empty so computing
+        # an accurate ETag isn't possible.
+        if request.method != "GET":
+            return response
+
+        if self.needs_etag(response) and not response.has_header("ETag"):
+            set_response_etag(response)
+
+        etag = response.get("ETag")
+        last_modified = response.get("Last-Modified")
+        last_modified = last_modified and parse_http_date_safe(last_modified)
+
+        if etag or last_modified:
+            return get_conditional_response(
+                request,
+                etag=etag,
+                last_modified=last_modified,
+                response=response,
+            )
+
+        return response
+
+    def needs_etag(self, response):
+        """Return True if an ETag header should be added to response."""
+        cache_control_headers = cc_delim_re.split(response.get("Cache-Control", ""))
+        return all(header.lower() != "no-store" for header in cache_control_headers)