StateT Question

stateT.hs

{-

This program parses a zip file and for each entry in the zip generates two lists of strings.
The lists of strings contain many values, some of which would be the same and some will be different.
I would like to count the number of instances of each string in both lists.

eg ["a1", "b1", "aa1", "aa1, "a1"] -> ["a1" -> 2, "b1" -> 1, "aa1" -> 2 ]

The zip contains very many small files.

I suspect I need to use a StateT monad transformer here but other than that I'm struggling.

Currerently the current code fails to compile with:

  No instance for (Control.Monad.State.Class.MonadState a0 Codec.Archive.Zip.ZipArchive)
      arising from a use of ‘get’ 
      • In a stmt of a 'do' block: s <- get

Any suggestions appreciated

-}

parseZip :: FilePath -> IO Summary
parseZip infile outfile = do
  flip runStateT (Summary empty empty) $ do
    withArchive infile $ do
      zipEntries <- keys <$> getEntries
      mapM_ (\(i, entry) -> do
          content <- getEntry entry
          let (list1, list2) = parseEntry content
          s <- get
          put $ addSummaries s list1 list2 
          liftIO $ do 
            putStr $ show list1
            putStr $ show list2
            putStr "\n\n"
        ) $ zipEntries
    return summary

data Summary = Summary {
  list1 :: Map Text Int
, list2 :: Map Text Int
}

addSummaries :: Summary -> [Text] -> [Text] -> Summary
addSummaries s list1 list2 = undefined

summarise :: StateT Summary IO Summary -- do I even need this? 
summarise = undefined

parseEntry :: ByteString -> ([Text], [Text])
parseEntry entry = undefined