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|
-- |
-- Copyright : (c) Sam Truzjan 2013
-- License : BSD3
-- Maintainer : pxqr.sta@gmail.com
-- Stability : experimental
-- Portability : portable
--
-- Normally, you don't need to import this module.
--
{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE FunctionalDependencies #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE DefaultSignatures #-}
module Network.KRPC.Method
( Method (..)
, KRPC (..)
) where
import Data.BEncode (BEncode)
import Data.ByteString.Char8 as BC
import Data.Char
import Data.Monoid
import Data.List as L
import Data.String
import Data.Typeable
import Network.KRPC.Message
-- | Method datatype used to describe method name, parameters and
-- return values of procedure. Client use a method to /invoke/, server
-- /implements/ the method to make the actual work.
--
-- We use the following fantom types to ensure type-safiety:
--
-- * param: Type of method parameters.
--
-- * result: Type of return value of the method.
--
newtype Method param result = Method { methodName :: MethodName }
deriving (Eq, Ord, IsString, BEncode)
-- | Example:
--
-- @show (Method \"concat\" :: [Int] Int) == \"concat :: [Int] -> Int\"@
--
instance (Typeable a, Typeable b) => Show (Method a b) where
showsPrec _ = showsMethod
showsMethod :: forall a. forall b. Typeable a => Typeable b
=> Method a b -> ShowS
showsMethod (Method name) =
showString (BC.unpack name) <>
showString " :: " <>
shows paramsTy <>
showString " -> " <>
shows valuesTy
where
impossible = error "KRPC.showsMethod: impossible"
paramsTy = typeOf (impossible :: a)
valuesTy = typeOf (impossible :: b)
-- | In order to perform or handle KRPC query you need to provide
-- corresponding 'KRPC' class.
--
-- Example:
--
-- @
-- data Ping = Ping Text deriving BEncode
-- data Pong = Pong Text deriving BEncode
--
-- instance 'KRPC' Ping Pong where
-- method = \"ping\"
-- @
--
class (Typeable req, BEncode req, Typeable resp, BEncode resp)
=> KRPC req resp | req -> resp where
-- | Method name. Default implementation uses lowercased @req@
-- datatype name.
--
method :: Method req resp
-- TODO add underscores
default method :: Typeable req => Method req resp
method = Method $ fromString $ L.map toLower $ show $ typeOf hole
where
hole = error "krpc.method: impossible" :: req
|
