Add gzip fallback (#13)

* Add gzip fallback

* Add tests

* Update README

README.md

@@ -1,11 +1,11 @@
-# brotli-middleware
+# brotli-asgi
 
 `BrotliMiddleware` adds [Brotli](https://github.com/google/brotli) response compression to ASGI applications (Starlette, FastAPI, Quart, etc.). It provides faster and more dense compression than GZip, and can be used as a drop in replacement for the `GZipMiddleware` shipped with Starlette.
 
 **Installation**
 
 ```bash
-pip install brotli-middleware
+pip install brotli-asgi
 ```
 
 ## Examples
@@ -49,7 +49,13 @@ def home() -> dict:
 
 ```python
 app.add_middleware(
-  BrotliMiddleware, quality=4, mode="text", lgwin=22, lgblock=0, minimum_size=400,
+  BrotliMiddleware,
+  quality=4,
+  mode="text",
+  lgwin=22,
+  lgblock=0,
+  minimum_size=400,
+  gzip_fallback=True
 )
 ```
 
@@ -60,6 +66,7 @@ app.add_middleware(
 - _(Optional)_ `lgwin`: Base 2 logarithm of the sliding window size. Range is 10 to 24.
 - _(Optional)_ `lgblock`: Base 2 logarithm of the maximum input block size. Range is 16 to 24. If set to 0, the value will be set based on the quality.
 - _(Optional)_ `minimum_size`: Only compress responses that are bigger than this value in bytes.
+- _(Optional)_ `gzip_fallback`: If `True`, uses gzip encoding if `br` is not in the Accept-Encoding header.
 
 ## Performance
 

brotli_asgi/__init__.py

@@ -7,6 +7,7 @@
 
 from brotli import MODE_FONT, MODE_GENERIC, MODE_TEXT, Compressor  # type: ignore
 from starlette.datastructures import Headers, MutableHeaders
+from starlette.middleware.gzip import GZipResponder
 from starlette.types import ASGIApp, Message, Receive, Scope, Send
 
 
@@ -29,6 +30,7 @@ def __init__(
         lgwin: int = 22,
         lgblock: int = 0,
         minimum_size: int = 400,
+        gzip_fallback: bool = True,
     ) -> None:
         """
         Arguments.
@@ -45,13 +47,15 @@ def __init__(
             Range is 16 to 24. If set to 0, the value will be set based on the
             quality.
         minimum_size: Only compress responses that are bigger than this value in bytes.
+        gzip_fallback: If True, uses gzip encoding if br is not in the Accept-Encoding header.
         """
         self.app = app
         self.quality = quality
         self.mode = getattr(Mode, mode)
         self.minimum_size = minimum_size
         self.lgwin = lgwin
         self.lgblock = lgblock
+        self.gzip_fallback = gzip_fallback
 
     async def __call__(self, scope: Scope, receive: Receive, send: Send) -> None:
         if scope["type"] == "http":
@@ -67,6 +71,10 @@ async def __call__(self, scope: Scope, receive: Receive, send: Send) -> None:
                 )
                 await responder(scope, receive, send)
                 return
+            if self.gzip_fallback and "gzip" in headers.get("Accept-Encoding", ""):
+                responder = GZipResponder(self.app, self.minimum_size)
+                await responder(scope, receive, send)
+                return
         await self.app(scope, receive, send)
 
 

tests.py

@@ -100,3 +100,37 @@ def homepage(request):
     client = TestClient(app)
     response = client.get("/", headers={"accept-encoding": "br"})
     assert response.status_code == 200
+
+
+def test_gzip_fallback():
+    app = Starlette()
+
+    app.add_middleware(BrotliMiddleware, gzip_fallback=True)
+
+    @app.route("/")
+    def homepage(request):
+        return PlainTextResponse("x" * 4000, status_code=200)
+
+    client = TestClient(app)
+    response = client.get("/", headers={"accept-encoding": "gzip"})
+    assert response.status_code == 200
+    assert response.text == "x" * 4000
+    assert response.headers["Content-Encoding"] == "gzip"
+    assert int(response.headers["Content-Length"]) < 4000
+
+
+def test_gzip_fallback_false():
+    app = Starlette()
+
+    app.add_middleware(BrotliMiddleware, gzip_fallback=False)
+
+    @app.route("/")
+    def homepage(request):
+        return PlainTextResponse("x" * 4000, status_code=200)
+
+    client = TestClient(app)
+    response = client.get("/", headers={"accept-encoding": "gzip"})
+    assert response.status_code == 200
+    assert response.text == "x" * 4000
+    assert "Content-Encoding" not in response.headers
+    assert int(response.headers["Content-Length"]) == 4000