CommandParser.hs

{-# LANGUAGE OverloadedStrings #-}

module CommandParser where
  import Data.Attoparsec.ByteString.Char8
  import Data.Attoparsec.Combinator
  import Control.Applicative
  import Data.ByteString

  data Command = Retrieve | Delete | New deriving Show

  parseCommand :: Parser Command
  parseCommand = choice
    [ Retrieve <? string "Retrieve"
    , Delete   <? string "Delete"
    , New      <? string "New"
    ]
        
  parseInput s = parseOnly (parseCommand <|> string s)

  parse :: ByteString -> Either String Command
  parse s = parseOnly parseCommand s