{-# LANGUAGE OverloadedStrings #-}

{- Copyright 2016 Joey Hess <id@joeyh.name>
 -
 - Licensed under the GNU AGPL version 3 or higher.
 -}

module HTTP.Server (runServer) where

import HTTP
import HTTP.ProofOfWork
import HTTP.RateLimit
import Types
import Types.Storage
import Tunables
import Storage.Local
import Serialization ()
import Servant
import Network.Wai
import Network.Wai.Handler.Warp
import Control.Monad.IO.Class
import Control.Concurrent
import Control.Concurrent.STM
import Data.String
import qualified Data.ByteString as B

data ServerState = ServerState
	{ obscurerRequest :: TMVar ()
	, storageDirectory :: Maybe LocalStorageDirectory
	, rateLimiter :: RateLimiter
	}

newServerState :: Maybe LocalStorageDirectory -> IO ServerState
newServerState d = ServerState
	<$> newEmptyTMVarIO
	<*> pure d
	<*> newRateLimiter

runServer :: Maybe LocalStorageDirectory -> String -> Port -> IO ()
runServer d bindaddress port = do
	st <- newServerState d
	_ <- forkIO $ obscurerThread st
	runSettings settings (app st)
  where
	settings = setHost host $ setPort port $ defaultSettings 
	host = fromString bindaddress

serverStorage :: ServerState -> Storage
serverStorage st = localStorage (storageDir $ storageDirectory st) "server"

app :: ServerState -> Application
app st = serve userAPI (server st)

userAPI :: Proxy HttpAPI
userAPI = Proxy

server :: ServerState -> Server HttpAPI
server st = motd
	:<|> getObject st
	:<|> putObject st
	:<|> countObjects st

motd :: Handler Motd
motd = return $ Motd "Hello World!"

getObject :: ServerState -> StorableObjectIdent -> Maybe ProofOfWork -> Handler (POWGuarded StorableObject)
getObject st i pow = rateLimit (rateLimiter st) pow i $ do
	r <- liftIO $ retrieveShare (serverStorage st) dummyShareNum i
	liftIO $ requestObscure st
	case r of
		RetrieveSuccess (Share _n o) -> return o
		RetrieveFailure _ -> throwError err404

putObject :: ServerState -> StorableObjectIdent -> Maybe ProofOfWork -> StorableObject -> Handler (POWGuarded StoreResult)
putObject st i pow o = rateLimit (rateLimiter st) pow i $ do
	if validObjectsize o
		then do
			r <- liftIO $ storeShare (serverStorage st) i (Share dummyShareNum o)
			liftIO $ requestObscure st
			return r
		else return $ StoreFailure "invalid object size"

validObjectsize :: StorableObject -> Bool
validObjectsize o = any (sz ==) knownObjectSizes
  where
	sz = B.length (fromStorableObject o)

countObjects :: ServerState -> Maybe ProofOfWork -> Handler (POWGuarded CountResult)
countObjects st pow = rateLimit (rateLimiter st) pow NoPOWIdent $
	liftIO $ countShares $ serverStorage st

-- | 1 is a dummy value; the server does not know the actual share numbers.
dummyShareNum :: ShareNum
dummyShareNum = 1

-- | This thread handles obscuring the shares after put and get operations.
-- Since obscuring can be an expensive process when there are many shares,
-- the thread runs a maximum of once per half-hour.
obscurerThread :: ServerState -> IO ()
obscurerThread st = do
	_ <- obscureShares (serverStorage st)
	putStrLn "obscured shares"
	threadDelay (1000000*60*30)
	_ <- atomically $ takeTMVar (obscurerRequest st)
	obscurerThread st

requestObscure :: ServerState -> IO ()
requestObscure st = do
	_ <- atomically $ tryPutTMVar (obscurerRequest st) ()
	return ()