{-|
  KingSubsite: runtime-exclusive HTTP request handling, for /~_~
-}

module Urbit.Vere.Eyre.KingSubsite
  ( KingSubsite
  , kingSubsite
  , runKingSubsite
  , fourOhFourSubsite
  ) where

import Urbit.Prelude hiding (Builder)

import Data.ByteString.Builder
import Urbit.King.Scry
import Urbit.Vere.Serf.Types

import Data.Conduit       (ConduitT, Flush(..), yield)
import Data.Text.Encoding (encodeUtf8Builder)

import qualified Data.Text.Encoding  as E
import qualified Network.HTTP.Types  as H
import qualified Network.Wai         as W
import qualified Network.Wai.Conduit as W
import qualified Urbit.Noun.Time     as Time

newtype KingSubsite = KS { runKingSubsite :: W.Application }

data SlogAction
  = KeepAlive
  | Slog (Atom, Tank)

streamSlog :: Monad m => SlogAction -> ConduitT () (Flush Builder) m ()
streamSlog a = do
  case a of
    KeepAlive -> pure ()
    Slog (_, t) -> for_ (wash (WashCfg 0 80) (tankTree t)) $ \l -> do
      yield $ Chunk "data:"
      yield $ Chunk $ encodeUtf8Builder $ unTape l
      yield $ Chunk "\n"
  yield $ Chunk "\n"
  yield $ Flush

kingSubsite :: HasLogFunc e
            => Ship
            -> (Time.Wen -> Gang -> Path -> IO (Maybe (Term, Noun)))
            -> TVar ((Atom, Tank) -> IO ())
            -> RAcquire e KingSubsite
kingSubsite who scry func = do
  clients <- newTVarIO (mempty :: Map Word (SlogAction -> IO ()))
  nextId  <- newTVarIO (0 :: Word)
  baton   <- newTMVarIO ()
  env     <- ask

  atomically $ writeTVar func $ \s -> readTVarIO clients >>= traverse_ ($ Slog s)

  acquireWorker "Runtime subsite keep-alive" $ forever $ do
    threadDelay 20_000_000
    io $ readTVarIO clients >>= traverse_ ($ KeepAlive)

  pure $ KS $ \req respond -> case W.pathInfo req of
    ["~_~", "slog"] -> bracket
      (do
        id <- atomically $ do
          id <- readTVar nextId
          modifyTVar' nextId (+ 1)
          pure id
        slogQ <- newTQueueIO
        atomically $
          modifyTVar' clients (insertMap id (atomically . writeTQueue slogQ))
        pure (id, slogQ))
      (\(id, _) -> atomically $ modifyTVar' clients (deleteMap id))
      (\(_, q) -> do
        authed <- authenticated env req
        if not authed
          then respond $ emptyResponse 403 "Permission Denied"
          else
            let loop = yield Flush
                    >> forever (atomically (readTQueue q) >>= streamSlog)
            in  respond $ W.responseSource (H.mkStatus 200 "OK") heads loop)

    _ -> respond $ emptyResponse 404 "Not Found"

  where
    heads = [ ("Content-Type" , "text/event-stream")
            , ("Cache-Control", "no-cache")
            , ("Connection"   , "keep-alive")
            ]

    emptyResponse cod mes = W.responseLBS (H.mkStatus cod mes) [] ""

    authenticated env req = runRIO env
                          $ (scryAuth $ getCookie req)
                          >>= pure . fromMaybe False

    getCookie req = intercalate "; "
                  $ fmap (E.decodeUtf8 . snd)
                  $ filter ((== "cookie") . fst)
                  $ W.requestHeaders req

    scryAuth :: HasLogFunc e
              => Text
              -> RIO e (Maybe Bool)
    scryAuth cookie =
      scryNow scry "ex" who "" ["authenticated", "cookie", textAsTa cookie]

fourOhFourSubsite :: Ship -> KingSubsite
fourOhFourSubsite who = KS $ \req respond ->
  respond $ W.responseLBS (H.mkStatus 404 "Not Found") [] body
  where
    body = toLazyByteString $ foldMap charUtf8 $ msg
    msg  = "Ship " <> show who <> " not docked."