module Main where

import Text.XML.Expat.Tree
import Text.XML.Expat.Pickle
import qualified Data.ByteString as B
import Data.ByteString.Internal (c2w, w2c)
import qualified Data.ByteString.Lazy as L
import Control.Monad

infiniteDoc = "<?xml version=\"1.0\"?><infinite>"++body 1
    where
        body i = "\n  <item idx=\"" ++ show i ++ "\"/>"++body (i+1)

toBL :: String -> L.ByteString
toBL = L.fromChunks . chunkify
  where
    chunkify [] = []
    chunkify str =
        let (start, rem) = splitAt 1024 str
        in  (B.pack $ map c2w start):chunkify rem

infiniteBL = toBL infiniteDoc

xpItems :: PU (UNodes String) [Int]
xpItems =
   xpElemNodes "infinite" $ xpList0 $ xpElemAttrs "item" $
       xpAttr "idx" $
       xpWrapEither (\i -> if i == 5000 then Left "5000 is evil" else Right i, id) $
       xpickle

main = do
    print $ unpickleXML Nothing (xpRoot xpItems) infiniteBL