word-count

import System.Environment
import System.IO
import Data.List
import System.Exit

main = do
  args <- getArgs
  let combined = parseArgs args
      sep = separateFiles args
      fl = head (fst sep)
  showResultsFile fl (snd sep)

showResultsFile :: String -> [String] -> IO ()
showResultsFile fn flags = do
  res <- processFile fn flags
  putStrLn $ (unwords (map show res)) ++ " " ++ fn

processFile :: String -> [String] -> IO [Int]
processFile fl flags =
  mapM dispatch [(flag, fl) | flag <- flags]

dispatch :: (String, String) -> IO Int
dispatch ("--help", _) = showHelpAndExit
dispatch ("--version", _) = showVersionAndExit
dispatch (fl, fn) = do
  handle <- openFile fl ReadMode
  contents <- hGetContents handle
  let cnt = getCounter fn
      res = cnt contents
  hClose handle
  return res

showHelpAndExit :: IO Int
showHelpAndExit = do
  prog_name <- getProgName
  putStrLn ("Usage: " ++ prog_name ++ " [OPTION]... [FILE]...")
  putStrLn "Print newline, word and byte counts for each FILE,"
  putStrLn "and a total line if more than one FILE is specified."
  putStrLn "  -c, --bytes      print the byte counts"
  putStrLn "  -m, --chars      print the character counts"
  putStrLn "  -l, --lines      print the newline counts"
  putStrLn "  -w, --words      print the newline counts"
  putStrLn "      --help       display this help and exit"
  putStrLn "      --version    print version info and exit"
  exitSuccess

showVersionAndExit :: IO Int
showVersionAndExit = do
  prog_name <- getProgName
  putStrLn (prog_name ++ " 0.1")
  putStrLn "Licence info..."
  exitSuccess


getCounter :: String -> String -> Int
getCounter "--bytes" = countCharacters
getCounter "--chars" = countCharacters
getCounter "--lines" = countLines
getCounter "--words" = countWords
getCounter opt = error ("Unrecognized option: " ++ opt)

parseArgs :: [String] -> [(String, String)]
parseArgs args
  | null flags = [(file, flag) | flag <- ["--lines", "--words", "--bytes"], file <- files]
  | null files = [("", flag) | flag <- map normalizeFlags flags]
  | otherwise  = [(file, flag) | flag <- map normalizeFlags flags, file <- files]
  where (files, flags) = separateFiles args

normalizeFlags :: String -> String
normalizeFlags "-c" = "--bytes"
normalizeFlags "-m" = "--chars"
normalizeFlags "-l" = "--lines"
normalizeFlags "-w" = "--words"
normalizeFlags x = x

separateFiles :: [String] -> ([String], [String])
separateFiles arguments
  | "--help" `elem` arguments    = (["--help"], [])
  | "--version" `elem` arguments = (["--version"], [])
  | otherwise = partition (\ st -> head st /= '-') arguments

countCharacters :: String -> Int
countCharacters = length

countLines :: String -> Int
countLines = length . lines

countWords :: String -> Int
countWords = length . words