{-# LANGUAGE UndecidableInstances, FlexibleContexts, TypeFamilies, TypeSynonymInstances, TemplateHaskell, QuasiQuotes, MultiParamTypeClasses, FlexibleInstances, DeriveDataTypeable, NamedFieldPuns, ScopedTypeVariables #-}
module Pnm where
import qualified Data.Char as Char
import Language.Pads.Padsc 
import Control.Monad
import Language.Pads.Library.Native

_ws = one_or_more Char.isSpace
 where one_or_more = undefined

ws, wsnl, whitechar :: RE

ws   = REd "[ \t\n\r]+" " "                      -- whitespace
wsnl = let REd wplus _ = ws in REd wplus "\n"    -- whitespace output as \n
whitechar = REd "[ \t\n\r]" "\n"                 -- one white character


[pads|

-- data PGMx a = PGM "P5" ws Header whitechar (Pixmap a)

 data Header = Header  -- fields should be separated by whitespace
   {      width  :: Int
   , ws   , height :: Int
   , wsnl , constrain denominator :: Int where <| 0 <= denominator && denominator < 65536 |>
   }

 data Pixmap a (h::Header) = Rows   ([Row a h | wsnl] length <| height h |>)
 data Row    a (h::Header) = Pixels ([a     | ws]   length <| width h |>)

 newtype Greypix (h::Header) =
    G (constrain g :: Int where <| 0 <= g && g <= denominator h |>)

-- data PGM = PGMx Int16 Greypix

|]

--pgm file = do
--	(rep, md) <- parseFile file
--	return rep