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import base64
from typing import Awaitable, Callable, List, NoReturn, cast
from aiohttp import web
from aiohttp.typedefs import Handler
from cryptography import fernet
from aiohttp_session import get_session, setup
from aiohttp_session.cookie_storage import EncryptedCookieStorage
def flash(request: web.Request, message: str) -> None:
request.setdefault("flash_outgoing", []).append(message)
def get_messages(request: web.Request) -> List[str]:
return cast(List[str], request.pop("flash_incoming"))
@web.middleware
async def flash_middleware(request: web.Request, handler: Handler) -> web.StreamResponse:
session = await get_session(request)
request["flash_incoming"] = session.pop("flash", [])
try:
return await handler(request)
finally:
session["flash"] = request.get("flash_incoming", []) + request.get(
"flash_outgoing", []
)
async def flash_handler(request: web.Request) -> NoReturn:
flash(request, "You have just visited flash page")
raise web.HTTPFound("/")
async def handler(request: web.Request) -> web.Response:
text = "No flash messages yet"
messages = get_messages(request)
if messages:
text = "Messages: {}".format(",".join(messages))
return web.Response(text=text)
def make_app() -> web.Application:
app = web.Application()
# secret_key must be 32 url-safe base64-encoded bytes
fernet_key = fernet.Fernet.generate_key()
secret_key = base64.urlsafe_b64decode(fernet_key)
setup(app, EncryptedCookieStorage(secret_key))
# Install flash middleware (must be installed after aiohttp-session middleware).
app.middlewares.append(flash_middleware)
app.router.add_get("/", handler)
app.router.add_get("/flash", flash_handler)
return app
web.run_app(make_app())
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