3 files changed, 70 insertions, 1 deletions

diff --git a/krpc.cabal b/krpc.cabal
index 446c612d..474778ad 100644
--- a/krpc.cabal
+++ b/krpc.cabal
@@ -22,6 +22,7 @@ source-repository head
 library
   exposed-modules:     Remote.KRPC
                      , Remote.KRPC.Protocol
+                     , Remote.KRPC.Scheme
 
   build-depends:       base          == 4.*
 
diff --git a/src/Remote/KRPC/Protocol.hs b/src/Remote/KRPC/Protocol.hs
index 3f3b16d0..36a1e38a 100644
--- a/src/Remote/KRPC/Protocol.hs
+++ b/src/Remote/KRPC/Protocol.hs
@@ -19,7 +19,7 @@ module Remote.KRPC.Protocol
        (
 
          -- * Error
-         KError(..), errorCode, mkKError
+         KError(..), ErrorCode, errorCode, mkKError
 
          -- * Query
        , KQuery(queryMethod, queryArgs), MethodName, ParamName, kquery
diff --git a/src/Remote/KRPC/Scheme.hs b/src/Remote/KRPC/Scheme.hs
new file mode 100644
index 00000000..84982649
--- /dev/null
+++ b/src/Remote/KRPC/Scheme.hs
@@ -0,0 +1,68 @@
+-- |
+--   Copyright   :  (c) Sam T. 2013
+--   License     :  MIT
+--   Maintainer  :  pxqr.sta@gmail.com
+--   Stability   :  experimental
+--   Portability :  portable
+--
+--   This module provides message scheme validation for core protocol
+--   messages from 'Remote.KRPC.Procotol'. This module should be used
+--   with 'Remote.KRPC.Protocol', otherwise (if you use 'Remote.KRPC')
+--   this module seems to be useless.
+--
+{-# LANGUAGE DefaultSignatures #-}
+{-# LANGUAGE TypeSynonymInstances #-}
+{-# LANGUAGE MultiParamTypeClasses, FunctionalDependencies #-}
+module Remote.KRPC.Scheme
+       ( KMessage(..)
+       , KQueryScheme(..)
+       , KResponseScheme(..)
+       ) where
+
+import Data.Map as M
+import Data.Set
+
+import Remote.KRPC.Protocol
+
+
+-- | Used to validate any message by its scheme
+--
+--  forall m. m `validate` scheme m
+--
+class KMessage message scheme | message -> scheme where
+  -- | Get a message scheme.
+  scheme :: message -> scheme
+
+  -- | Check a message with a scheme.
+  validate :: message -> scheme -> Bool
+
+  default validate :: Eq scheme => message -> scheme -> Bool
+  validate = (==) . scheme
+  {-# INLINE validate #-}
+
+
+instance KMessage KError ErrorCode where
+  {-# SPECIALIZE instance KMessage KError ErrorCode #-}
+  scheme = errorCode
+  {-# INLINE scheme #-}
+
+
+data KQueryScheme = KQueryScheme {
+    qscMethod :: MethodName
+  , qscParams :: Set ParamName
+  } deriving (Show, Read, Eq, Ord)
+
+instance KMessage KQuery KQueryScheme where
+  {-# SPECIALIZE instance KMessage KQuery KQueryScheme #-}
+  scheme q = KQueryScheme (queryMethod q) (M.keysSet (queryArgs q))
+  {-# INLINE scheme #-}
+
+
+newtype KResponseScheme = KResponseScheme {
+    rscVals :: Set ValName
+  } deriving (Show, Read, Eq, Ord)
+
+instance KMessage KResponse KResponseScheme where
+  {-# SPECIALIZE instance KMessage KResponse KResponseScheme #-}
+  scheme = KResponseScheme . keysSet . respVals
+  {-# INLINE scheme #-}
\ No newline at end of file