Add HTTP compression middleware (#676)

* Add HTTP compression middleware

* Apply fixes from `make format`

cashu/mint/middleware.py

@@ -1,12 +1,17 @@
-from fastapi import FastAPI
+import gzip
+import zlib
+
+import brotli
+import zstandard as zstd
+from fastapi import FastAPI, Request, Response
 from fastapi.exception_handlers import (
     request_validation_exception_handler as _request_validation_exception_handler,
 )
 from fastapi.exceptions import RequestValidationError
 from fastapi.responses import JSONResponse
 from loguru import logger
+from starlette.middleware.base import BaseHTTPMiddleware
 from starlette.middleware.cors import CORSMiddleware
-from starlette.requests import Request
 
 from ..core.settings import settings
 from .limit import _rate_limit_exceeded_handler, limiter_global
@@ -26,6 +31,7 @@ def add_middlewares(app: FastAPI):
         allow_headers=["*"],
         expose_headers=["*"],
     )
+    app.add_middleware(CompressionMiddleware)
 
     if settings.debug_profiling:
         assert PyInstrumentProfilerMiddleware is not None
@@ -53,3 +59,43 @@ async def request_validation_exception_handler(
     logger.error(detail)
     # pass on
     return await _request_validation_exception_handler(request, exc)
+
+
+class CompressionMiddleware(BaseHTTPMiddleware):
+    async def dispatch(self, request: Request, call_next):
+        response = await call_next(request)
+
+        # Handle streaming responses differently
+        if response.__class__.__name__ == 'StreamingResponse':
+            return response
+
+        response_body = b''
+        async for chunk in response.body_iterator:
+            response_body += chunk
+
+        accept_encoding = request.headers.get("Accept-Encoding", "")
+        content = response_body
+
+        if "br" in accept_encoding:
+            content = brotli.compress(content)
+            response.headers["Content-Encoding"] = "br"
+        elif "zstd" in accept_encoding:
+            compressor = zstd.ZstdCompressor()
+            content = compressor.compress(content)
+            response.headers["Content-Encoding"] = "zstd"
+        elif "gzip" in accept_encoding:
+            content = gzip.compress(content)
+            response.headers["Content-Encoding"] = "gzip"
+        elif "deflate" in accept_encoding:
+            content = zlib.compress(content)
+            response.headers["Content-Encoding"] = "deflate"
+
+        response.headers["Content-Length"] = str(len(content))
+        response.headers["Vary"] = "Accept-Encoding"
+
+        return Response(
+            content=content,
+            status_code=response.status_code,
+            headers=dict(response.headers),
+            media_type=response.media_type
+        )