Implement JSON conversion for Work type

lib/GEODE/Metadata/Work.hs

-{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE DeriveGeneric, OverloadedStrings #-}
 module GEODE.Metadata.Work
   ( Work(..) ) where
 
-import Data.Aeson (ToJSON(..))
+import Data.Aeson (FromJSON(..), ToJSON(..), withText)
+import Data.ByteString.Char8 as ByteString (unpack)
 import Data.Csv (FromField(..), ToField(..))
 import Data.Char (toLower)
-import Data.ByteString.Char8 as ByteString (map)
+import Data.Text as Text (unpack)
+import GHC.Generics (Generic)
 
-data Work = EDdA | LGE | Wikipedia deriving (Eq, Ord, Read, Show)
+data Work = EDdA | LGE | Wikipedia deriving (Eq, Generic, Ord, Show)
+
+tolerantParser :: (Applicative m, Monoid (m Work)) => String -> m Work
+tolerantParser = recognize . fmap toLower
+  where
+    recognize "edda" = pure EDdA
+    recognize "lge" = pure LGE
+    recognize "wikipedia" = pure Wikipedia
+    recognize _ = mempty
 
 instance FromField Work where
-  parseField = recognize . ByteString.map toLower
-    where
-      recognize "EDdA" = pure EDdA
-      recognize "LGE" = pure LGE
-      recognize "Wikipedia" = pure Wikipedia
-      recognize _ = mempty
+  parseField = tolerantParser . ByteString.unpack
 
 instance ToField Work where
   toField = toField . show
 
-instance ToJSON Work where
-  toJSON = toJSON . show
-
+instance ToJSON Work
+instance FromJSON Work where
+  parseJSON = withText "Work" $ tolerantParser . Text.unpack