module Maskbits
( Maskbits(..),
  maskbits_from_string
) where

-- A type representing the number of bits in a CIDR netmask.
data Maskbits = None
              | Zero
              | One
              | Two
              | Three
              | Four
              | Five
              | Six
              | Seven
              | Eight
              | Nine
              | Ten
              | Eleven
              | Twelve
              | Thirteen
              | Fourteen
              | Fifteen
              | Sixteen
              | Seventeen
              | Eighteen
              | Nineteen
              | Twenty
              | TwentyOne
              | TwentyTwo
              | TwentyThree
              | TwentyFour
              | TwentyFive
              | TwentySix
              | TwentySeven
              | TwentyEight
              | TwentyNine
              | Thirty
              | ThirtyOne
              | ThirtyTwo
              deriving (Eq, Ord, Show)


-- There are only 32 bits in an IPv4 address, so there
-- can't be more bits than that in the mask.
maskbits_from_int :: Int -> Maskbits
maskbits_from_int 0  = Zero
maskbits_from_int 1  = One
maskbits_from_int 2  = Two
maskbits_from_int 3  = Three
maskbits_from_int 4  = Four
maskbits_from_int 5  = Five
maskbits_from_int 6  = Six
maskbits_from_int 7  = Seven
maskbits_from_int 8  = Eight
maskbits_from_int 9  = Nine
maskbits_from_int 10 = Ten
maskbits_from_int 11 = Eleven
maskbits_from_int 12 = Twelve
maskbits_from_int 13 = Thirteen
maskbits_from_int 14 = Fourteen
maskbits_from_int 15 = Fifteen
maskbits_from_int 16 = Sixteen
maskbits_from_int 17 = Seventeen
maskbits_from_int 18 = Eighteen
maskbits_from_int 19 = Nineteen
maskbits_from_int 20 = Twenty
maskbits_from_int 21 = TwentyOne
maskbits_from_int 22 = TwentyTwo
maskbits_from_int 23 = TwentyThree
maskbits_from_int 24 = TwentyFour
maskbits_from_int 25 = TwentyFive
maskbits_from_int 26 = TwentySix
maskbits_from_int 27 = TwentySeven
maskbits_from_int 28 = TwentyEight
maskbits_from_int 29 = TwentyNine
maskbits_from_int 30 = Thirty
maskbits_from_int 31 = ThirtyOne
maskbits_from_int 32 = ThirtyTwo
maskbits_from_int _ = None


maskbits_from_string :: String -> Maskbits
maskbits_from_string s =
    case (reads s :: [(Int, String)]) of
      []   -> None
      x:_ -> maskbits_from_int (fst x)