{-
    Parse a /etc/portage/package.* file does nothing but
    showing each line parsed

    by Fernando J. Pereda <ferdy@gentoo.org>
-}

module Main
    where

import IO (readFile)
import System (getArgs)
import Monad (liftM)
import AtomParser (PortageAtom, atomListFromStringList)

etcportage :: String
etcportage = "/etc/portage/package."

-- |Returns a list, each element composed by the first part
--  of each line in the file
parseFile :: FilePath -> IO [PortageAtom]
parseFile f = readFile f >>= return . lines >>=
                return . map (fst . (break (' '==))) >>=
                return . filter (not . (elem '#')) >>=
                return . filter (not . null) >>=
                return . atomListFromStringList

-- |Same as parseFile but this one in monadic + point free style
--  The motivation is: 'Lift the composition of all those actions
--  into the IO monad and compose the result with readFile'
parseFile' :: FilePath -> IO [PortageAtom]
parseFile' = liftM ( atomListFromStringList .
                     filter (not . null) .          -- Remove empty lines
                     filter (not . (elem '#')) .    -- Remove comments
                     map (fst . (break (' '==))) .  -- Trim line, get everything up to the space
                     lines                          -- Divide in lines
                   ) . readFile

main :: IO ()
main = do
        args <- getArgs
        nam <- return(args !! 0)
        fich <- return(etcportage ++ nam)
        lns <- parseFile' fich
        print lns