module Data.MessagePack.RPC where

import Data.Binary (Get, Put, get, getWord8, put)
import Data.MessagePack (Object(..))
import Data.Text (Text)

import qualified Data.MessagePack as MP
import qualified Data.Vector as Vector

data Answer = Success Object | Error Object
  deriving Show

data Request = Request
  { requestMessageID  :: Int
  , requestMethod     :: Text
  , requestParams     :: [Object] }
  deriving Show

putRequest :: Request -> Put
putRequest (Request msgID method params) =
  MP.putArray id $ Vector.fromList [MP.putInt 0, MP.putInt msgID, MP.putStr method, MP.putArray put $ Vector.fromList params]

data Message
  = Response
    { responseMessageID :: Int
    , responseAnswer    :: Answer }
  | Notification
    { notificationMethod :: Text
    , notificationParams :: [Object] }
  deriving Show

getMessage :: Get Message
getMessage = do
  _ <- getWord8
  tpe <- MP.getInt
  case tpe of
    1 -> do
      id' <- MP.getInt
      err <- get
      res <- get
      return $ Response id' $ f err res where
        f ObjectNil res = Success res
        f err ObjectNil = Error err
        f _ _           = Error ObjectNil
    2 -> do
      method <- MP.getStr
      (ObjectArray params) <- get
      return $ Notification method (Vector.toList params)
    _ -> fail "unsupported message type"