from fastapi import FastAPI
from starlette.types import Message
from starlette.requests import Request
from starlette.middleware.base import BaseHTTPMiddleware
import gzip          


class GZipedMiddleware(BaseHTTPMiddleware):
    async def set_body(self, request: Request):
        receive_ = await request._receive()
        if "gzip" in request.headers.getlist("Content-Encoding"):
            print(receive_)                                     
            data = gzip.decompress(receive_.get('body'))
            receive_['body'] = data

        async def receive() -> Message:
            return receive_

        request._receive = receive                

    async def dispatch(self, request, call_next):
        await self.set_body(request)        
        response = await call_next(request)                
        return response



app = FastAPI()

app.add_middleware(GZipedMiddleware)


@app.post("/post")
async def post(req: Request):
    body = await req.body()
    # I decode here, assuming that I just compressed
    # a text file, in other use case you should use
    # the appropiate decoder.
    return body.decode("utf-8")