{-# LANGUAGE TemplateHaskell, ExistentialQuantification #-} {-| Implements Template Haskell generation of RPC server components from Haskell functions. -} {- Copyright (C) 2013 Google Inc. All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. -} module Ganeti.THH.RPC ( Request(..) , RpcServer , dispatch , mkRpcM ) where import Control.Arrow ((&&&)) import Control.Monad import Control.Monad.Error.Class import Data.Map (Map) import qualified Data.Map as Map import Language.Haskell.TH import qualified Text.JSON as J import Ganeti.BasicTypes import Ganeti.Errors import Ganeti.JSON (fromJResultE, fromJVal) import Ganeti.THH.Types import qualified Ganeti.UDSServer as US data RpcFn m = forall i o . (J.JSON i, J.JSON o) => RpcFn (i -> m o) type RpcServer m = US.Handler Request m J.JSValue -- | A RPC request consiting of a method and its argument(s). data Request = Request { rMethod :: String, rArgs :: J.JSValue } deriving (Eq, Ord, Show) decodeRequest :: J.JSValue -> J.JSValue -> Result Request decodeRequest method args = Request <$> fromJVal method <*> pure args dispatch :: (Monad m) => Map String (RpcFn (ResultT GanetiException m)) -> RpcServer m dispatch fs = US.Handler { US.hParse = decodeRequest , US.hInputLogShort = rMethod , US.hInputLogLong = rMethod , US.hExec = liftToHandler . exec } where orError :: (MonadError e m, Error e) => Maybe a -> e -> m a orError m e = maybe (throwError e) return m exec (Request m as) = do (RpcFn f) <- orError (Map.lookup m fs) (strMsg $ "No such method: " ++ m) i <- fromJResultE "RPC input" . J.readJSON $ as o <- f i -- lift $ f i return $ J.showJSON o liftToHandler :: (Monad m) => ResultT GanetiException m J.JSValue -> US.HandlerResult m J.JSValue liftToHandler = liftM ((,) True) . runResultT -- | Converts a function into the appropriate @RpcFn m@ expression. -- The function's result must be monadic. toRpcFn :: Name -> Q Exp toRpcFn name = [| RpcFn $( uncurryVar name ) |] -- | Convert a list of named expressions into an expression containing a list -- of name/expression pairs. rpcFnsList :: [(String, Q Exp)] -> Q Exp rpcFnsList = listE . map (\(name, expr) -> tupE [stringE name, expr]) -- | Takes a list of function names and creates a RPC handler that delegates -- calls to them. -- -- The functions must conform to -- @(J.JSON i, J.JSON o) => i -> ResultT GanetiException m o@. The @m@ -- monads types of all the functions must unify. -- -- The result expression is of type @RpcServer m@. mkRpcM :: [Name] -- ^ the names of functions to include -> Q Exp mkRpcM names = [| dispatch . Map.fromList $ $( rpcFnsList . map (nameBase &&& toRpcFn) $ names ) |]