{-# LANGUAGE GeneralizedNewtypeDeriving #-}

module Command
  ( Command,
    runCommand,
    CommandError (..),
  )
where

import Control.Monad.Except (ExceptT, MonadError, runExceptT)
import Control.Monad.IO.Class (MonadIO)

newtype Command a = Command {_runCommand :: ExceptT CommandError IO a}
  deriving (Functor, Applicative, Monad, MonadIO, MonadError CommandError)

runCommand :: Command a -> IO ()
runCommand cmd = do
  errorOrResult <- runExceptT $ _runCommand cmd
  case errorOrResult of
    Left cmdError -> putStrLn $ "Error: " ++ _errorMsg cmdError
    Right _ -> return ()

-- TODO: What if we want to recognize errors in order to handle them?
--   Should we add _commandErrorType? Should CommandError be parametrized by it, is that even possible?
data CommandError = CommandError {_errorMsg :: !String}