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|
-- | Allows websockets to reconnect and recover state by storing a cookie client
-- side.
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE OverloadedStrings #-}
module Cafp.CookieSocket
( Handle
, withHandle
, CookieName
, acceptRequest
, persist
) where
import Control.Concurrent (threadDelay)
import qualified Control.Concurrent.Async as Async
import Control.Concurrent.MVar (MVar)
import qualified Control.Concurrent.MVar as MVar
import Control.Monad (forever, guard)
import Data.Hashable (Hashable)
import Data.HashMap.Strict (HashMap)
import qualified Data.HashMap.Strict as HMS
import Data.Maybe (listToMaybe)
import qualified Data.Text as T
import qualified Data.Text.Encoding as T
import qualified Data.Time as Time
import Data.UUID (UUID)
import qualified Data.UUID as UUID
import qualified Data.UUID.V4 as UUID.V4
import qualified Network.WebSockets as WS
type CookieName = T.Text
newtype Secret = Secret UUID deriving (Eq, Hashable)
data Handle v = Handle
{ hMinutes :: Int -- Minutes after which expiry happens
, hStore :: MVar (HashMap Secret (Time.UTCTime, v))
}
withHandle :: Int -> (Handle v -> IO a) -> IO a
withHandle minutes f = do
store <- MVar.newMVar HMS.empty
Async.withAsync (reaper store) $ \_ -> f $ Handle minutes store
where
-- This is really shitty and we should probably do something with
-- monotonic time.
reaper store = forever $ do
threadDelay $ minutes * 60 * 1000 * 1000
now <- Time.getCurrentTime
MVar.modifyMVar_ store $ pure . HMS.filter ((> now) . fst)
parseCookie :: CookieName -> WS.PendingConnection -> Maybe T.Text
parseCookie name pc = listToMaybe $ do
(header, values) <- WS.requestHeaders $ WS.pendingRequest pc
guard $ header == "Cookie"
part <- T.split (== ';') $ T.decodeUtf8 values
let (key, val) = T.break (== '=') part
guard $ T.strip key == name
guard $ "=" `T.isPrefixOf` val
pure . T.strip $ T.drop 1 val
makeCookie :: CookieName -> T.Text -> WS.Headers
makeCookie name val = [("Set-Cookie", T.encodeUtf8 $ name <> "=" <> val)]
acceptRequest
:: Handle a -> CookieName -> WS.PendingConnection
-> IO (WS.Connection, Secret, Maybe a)
acceptRequest h name pc = case parseCookie name pc >>= UUID.fromText of
Just uuid -> do
conn <- WS.acceptRequest pc
store <- MVar.readMVar (hStore h)
pure (conn, Secret uuid, snd <$> HMS.lookup (Secret uuid) store)
Nothing -> do
uuid <- UUID.V4.nextRandom
conn <- WS.acceptRequestWith pc WS.defaultAcceptRequest
{ WS.acceptHeaders =
makeCookie name (UUID.toText uuid) <>
WS.acceptHeaders WS.defaultAcceptRequest
}
pure (conn, Secret uuid, Nothing)
persist :: Handle a -> Secret -> a -> IO ()
persist h key x = MVar.modifyMVar_ (hStore h) $ \store -> do
expiry <- Time.addUTCTime diffTime <$> Time.getCurrentTime
pure $ HMS.insert key (expiry, x) store
where
diffTime = fromIntegral (60 * hMinutes h)
|
