Start to use megaparsec instead of P_to_S

app/Main.hs

@@ -1,39 +1,46 @@
 module Main where
 
+import Control.Applicative
 import Control.Monad
 import Data.Functor
 import System.Environment
 import System.Exit
+import Text.Megaparsec hiding (parse, satisfy)
 import Text.ParserCombinators.ReadP
 
-
-
 parse :: ReadP String -> String -> String
-parse rules = fst . last .readP_to_S rules
+parse rules = fst . last . readP_to_S rules
+
+parseFile :: String -> String
+parseFile = unlines . map (parse fileParser) . lines
+
+fileParser :: ReadP String
+fileParser = undefined
 
 main :: IO ()
-main = putStrLn =<< helper =<< getArgs
-
-helper :: [String] -> IO String
-helper []       = return usage
-helper (x:[])   = if (head x /= '-')
-                    then readFile x
-                    else return $ useArgs $ parse argParse x
-helper (x:_:[]) = return $ useArgs $ parse argParse x
-helper _        = fail "Too many arugemnts"
+main = putStr =<< parseCli =<< getArgs
 
+parseCli :: [String] -> IO String
+parseCli [] = return usage
+parseCli [x] =
+  if head x /= '-'
+    then parseFile <$> readFile x
+    else return $ useArgs $ parse argParse x
+parseCli [x, _] = return $ useArgs $ parse argParse x
+parseCli _ = fail "Too many arugemnts"
 
 argParse :: ReadP String
 argParse =
-  string "-" >> (many1 (satisfy (/= ' ')))
+  string "-" >> many1 (satisfy (/= ' '))
 
 useArgs :: String -> String
-useArgs []       = ""
-useArgs ('h':_)  = usage
-useArgs ('v':_)  = version
-useArgs (_:xs)   = useArgs xs
+useArgs [] = ""
+useArgs ('h' : _) = usage
+useArgs ('v' : _) = version
+useArgs (_ : xs) = useArgs xs
 
 usage :: String
-usage   = "Usage: otm [-hv] [file]"
+usage = "Usage: otm [-hv] [file]"
+
 version :: String
 version = "otm 0.1"