module Main where

import Control.Monad (forever, when)
import Data.List (intercalate)
import Data.Traversable (traverse)
import Morse (stringToMorse, morseToChar)
import System.Environment (getArgs)
import System.Exit (exitFailure, exitSuccess)
import System.IO (hGetLine, hIsEOF, stdin)

convertToMorse :: IO ()
convertToMorse = forever $ do
    weAreDone <- hIsEOF stdin
    when weAreDone exitSuccess

    line <- hGetLine stdin
    convertLine line

    where convertLine line = do
            let morse = stringToMorse line
            case morse of
                (Just str) -> putStrLn (intercalate " " str)
                Nothing -> do
                    putStrLn $ "ERROR: " ++ line
                    exitFailure

convertFromMorse :: IO ()
convertFromMorse = forever $ do
    weAreDone <- hIsEOF stdin
    when weAreDone exitSuccess

    line <- hGetLine stdin
    convertLine line

    where
        convertLine line = do
            let decoded :: Maybe String
                decoded = traverse morseToChar (words line)

            case decoded of
                (Just s) -> putStrLn s
                Nothing -> do
                    putStrLn $ "ERROR: " ++ line
                    exitFailure

main :: IO ()
main = do
    mode <- getArgs
    case mode of
        [arg] ->
            case arg of
                "from" -> convertFromMorse
                "to" -> convertToMorse
                _ -> argError
        _ -> argError

    where argError = do
            putStrLn "Please specify the first argument as being 'from' or 'to' morse, such as: morse to"
            exitFailure