Add modules for config file

src/LoadConfig.hs

@@ -0,0 +1,24 @@
+{-# LANGUAGE DeriveGeneric #-}
+module LoadConfig
+    where
+import Data.Aeson
+import GHC.Generics
+import Foreign.C.Types
+
+data Configuration = Configuration
+    { windowxsize :: Int
+    , windowysize :: Int
+    } deriving (Generic, Show)
+
+instance ToJSON Configuration where
+    toEncoding = genericToEncoding defaultOptions
+instance FromJSON Configuration
+
+loadConfig :: IO (Int,Int)
+loadConfig = do
+    mayConfig <- decodeFileStrict "config.json"
+    case mayConfig of
+        Just config -> return (windowxsize config,windowysize config)
+        Nothing     -> do
+                        putStrLn "invalid config.json, loading default config"
+                        return (800,600)