implemented async-only gzip middleware

Author: amirreza8002

django_async_extensions/amiddleware/gzip.py

@@ -0,0 +1,76 @@
+from django.utils.cache import patch_vary_headers
+from django.utils.regex_helper import _lazy_re_compile
+from django.utils.text import compress_sequence, compress_string
+
+from django_async_extensions.amiddleware.base import AsyncMiddlewareMixin
+
+
+re_accepts_gzip = _lazy_re_compile(r"\bgzip\b")
+
+
+class AsyncGZipMiddleware(AsyncMiddlewareMixin):
+    """
+    Compress content if the browser allows gzip compression.
+    Set the Vary header accordingly, so that caches will base their storage
+    on the Accept-Encoding header.
+    """
+
+    max_random_bytes = 100
+
+    async def process_response(self, request, response):
+        # It's not worth attempting to compress really short responses.
+        if not response.streaming and len(response.content) < 200:
+            return response
+
+        # Avoid gzipping if we've already got a content-encoding.
+        if response.has_header("Content-Encoding"):
+            return response
+
+        patch_vary_headers(response, ("Accept-Encoding",))
+
+        ae = request.headers.get("accept-encoding", "")
+        if not re_accepts_gzip.search(ae):
+            return response
+
+        if response.streaming:
+            if response.is_async:
+                # pull to lexical scope to capture fixed reference in case
+                # streaming_content is set again later.
+                orignal_iterator = response.streaming_content
+
+                async def gzip_wrapper():
+                    async for chunk in orignal_iterator:
+                        yield compress_string(
+                            chunk,
+                            max_random_bytes=self.max_random_bytes,
+                        )
+
+                response.streaming_content = gzip_wrapper()
+            else:
+                response.streaming_content = compress_sequence(
+                    response.streaming_content,
+                    max_random_bytes=self.max_random_bytes,
+                )
+            # Delete the `Content-Length` header for streaming content, because
+            # we won't know the compressed size until we stream it.
+            del response.headers["Content-Length"]
+        else:
+            # Return the compressed content only if it's actually shorter.
+            compressed_content = compress_string(
+                response.content,
+                max_random_bytes=self.max_random_bytes,
+            )
+            if len(compressed_content) >= len(response.content):
+                return response
+            response.content = compressed_content
+            response.headers["Content-Length"] = str(len(response.content))
+
+        # If there is a strong ETag, make it weak to fulfill the requirements
+        # of RFC 9110 Section 8.8.1 while also allowing conditional request
+        # matches on ETags.
+        etag = response.get("ETag")
+        if etag and etag.startswith('"'):
+            response.headers["ETag"] = "W/" + etag
+        response.headers["Content-Encoding"] = "gzip"
+
+        return response