bigjson.hs

{-# LANGUAGE DeriveDataTypeable #-}

data HillKey = HkId
             | HkMainNameInfo
             -- and many more
             | HkLatitude
             | HkLongitude
 deriving (Data, Typeable)

showKey :: HillKey -> String
showKey = drop 4 -- "-hk-"
        . concatMap twiggle . showConstr . toConstr
 where
  twiggle '_' = "-"
  twiggle x = if isUpper x then [ '-', toLower x ] else [x]

data HillEntry = HillEntry { hiId           :: Int
                           , hiMainNameInfo :: HillNameInfo
                           -- and many more
                           , hiLatitude       :: Float
                           , hiLongitude      :: Float
                           }

instance JSON HillEntry where
 readJSON j =
    do jo <- fromJSObject `fmap` readJSON j
       let field x = maybe (fail $ "Could not find: " ++ x) readJSON
                   $ lookup x jo
       HillEntry <$> field (showKey HkId)
                 <*> field (showKey HkMainNameInfo)
                 <*> field (showKey HkLatitude)
                 <*> field (showKey HkLongitude)
 showJSON (HillEntry  x0  x1 {- and many more -} x27 x28 ) =
     JSObject . toJSObject $
       [ ( showKey HkId , showJSON x0 )
       , ( showKey HkMainNameInfo , showJSON x1 )
       -- and many more
       , ( showKey HkLatitude, showJSON x27 )
       , ( showKey HkLongitude , showJSON x28 )
       ]