Haskell CmdArgs optional positional arguments

hs

{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE DeriveDataTypeable #-}

module Main where

import           Lib
import           System.Environment     (getArgs)
import           Database.SQLite.Simple
import           System.Console.CmdArgs
import           Data.List

data Options = Options {
  inputMode :: Bool,
  message :: String
  } deriving (Data, Typeable)

options :: Options
options = Options { inputMode = False
                    &= typ "Input mode"
                    &= help "Toggle input mode",
                    message = def
                    &= typ "message"
                    &= opt ("" :: String)
                    &= args
                  }
  
          &= summary "n notes"
          &= program "n"
          
data TestField = TestField Int String deriving (Show)

instance FromRow TestField where
  fromRow = TestField <$> field <*> field

instance ToRow TestField where
  toRow (TestField id_ str) = toRow (id_, str)

dbPut conn val =
  execute conn "INSERT INTO test (str) VALUES (?)" (Only (val :: String))

main :: IO ()
main = do
    opts <- cmdArgs options
  
    conn <- open "test.db"
    execute_ conn "CREATE TABLE IF NOT EXISTS test (id INTEGER PRIMARY KEY, str TEXT)"

    case (message opts) of
      "" -> return ()
      x -> dbPut conn x

    case (inputMode opts) of
      True -> do
        content <- getContents
        dbPut conn content
      False ->
        return ()


    r <- query_ conn "SELECT * from test" :: IO [TestField]
    mapM_ print r

    close conn

Note: This program behaves weird when running in GHCi but seems to work fine when compiled.