{-
-}
module Main
  ( main )
where

{- Standard Library Modules Imported -}
import System.Console.GetOpt
  ( getOpt
  , usageInfo
  , ArgOrder    ( .. )
  , OptDescr    ( .. )
  , ArgDescr    ( .. )
  )
import System.Environment
  ( getArgs )
{- External Library Modules Imported -}
{- Local Modules Imported -}
{- End of Imports -}

data CliFlag =
    CliHelp
  | CliVersion
  deriving Eq


options :: [ OptDescr CliFlag ]
options =
  [ Option   "h"     [ "help" ]
    (NoArg CliHelp)
    "Print the help message to standard out and then exit"

  , Option   "v"     [ "version" ]
    (NoArg CliVersion)
    "Print out the version of this program"
  ]

helpMessage :: String
helpMessage =
  usageInfo "prog-name" options

versionMessage :: String
versionMessage = "This is version 0.001"

-- | The main exported function
main :: IO ()
main = getArgs >>= processOptions

processOptions :: [ String ] -> IO ()
processOptions cliArgs =
  case getOpt Permute  options cliArgs of
    (flags, args, [])       -> 
      processArgs flags args
    (_flags, _args, errors) -> 
      ioError $ userError (concat errors ++ helpMessage)

-- We assume all of the arguments are files to process
processArgs :: [ CliFlag ] -> [ String ] -> IO ()
processArgs flags files
  | elem CliHelp flags    = putStrLn helpMessage
  | elem CliVersion flags = putStrLn versionMessage
  | otherwise             = mapM_ processFile files

-- Our processing of a file is to simply count the words
-- in the file and output the number as a line.
processFile :: FilePath -> IO ()
processFile file =
  do contents <- readFile file
     putStrLn (show $ length $ words contents)