import Math
import System.Environment
import Data.List
import Text.Printf

errorMessage :: String -> String

errorMessage "" = "nd v1\nUsage: nd [-help, -int, -prime, -factor, -hcf]\n"
errorMessage reason = "nd v1\nFAILURE: "
                        ++ reason
                        ++ "\nUsage: nd [-int, -prime, -factor, -hcf]\n"

flagHandlerF :: [String] -> Int -> String -> ([String] -> String) -> String

flagHandlerF args (-1) error fmessage =
  if (length args) == 0
  then error
  else fmessage args

flagHandlerF args nargs error fmessage =
  if (length args) /= nargs
  then error
  else fmessage args

flagHandler :: String -> [String] -> String

flagHandler "-prime" args =
  flagHandlerF args (-1)
    (errorMessage "-prime requires at least one integer argument")
    (\args ->
        foldl (++) "" [show y ++ ": isPrime=" ++ (show $ isPrime y)
                    ++ "\n" | x <- args, let y = (read x) :: Int])

flagHandler "-factor" args =
  flagHandlerF args (-1)
    (errorMessage "-factor requires at least one integer argument")
    (\args ->
        foldl (++) "" [show y ++ ": factors=" ++ show (factors $ y)
                        | x <- args, let y = (read x) :: Int])

flagHandler "-int" args =
  flagHandlerF args (-1)
    (errorMessage "-int requires at least one integer argument")
    (\args ->
        foldl (++) "" [show y ++ ": (isPrime=" ++ (show $ isPrime y)
                        ++ ", factors=" ++ (show $ factors y)
                        ++ ")\n" | x <- args, let y = (read x) :: Int])

flagHandler "-hcf" args =
  flagHandlerF args (2)
    (errorMessage "-hcf requires two integer arguments")
    (\args ->
        let n       = (read $ head args) :: Int
            m       = (read $ head $ tail args) :: Int
            hcf     = head $ reverse $ intersect (factors n) (factors m) in
        "hcf(" ++ show n ++ ", " ++ show m ++ "): hcf=" ++ show hcf)

flagHandler _ _ =
  errorMessage "Flag not recognised"


main = do
  args <- getArgs
  putStr $
    case args of
        []      -> errorMessage ""
        (x: xs) -> if x == "-help" then errorMessage "" else flagHandler x xs