module HaskellWorks.Data.Xml.Succinct.Cursor.Token
  ( xmlTokenAt
  ) where

import Data.ByteString.Internal                       as BSI
import HaskellWorks.Data.Bits.BitWise
import HaskellWorks.Data.Drop
import HaskellWorks.Data.Positioning
import HaskellWorks.Data.RankSelect.Base.Rank1
import HaskellWorks.Data.RankSelect.Base.Select1
import HaskellWorks.Data.Xml.Succinct.Cursor.Internal
import HaskellWorks.Data.Xml.Token.Tokenize
import Prelude                                        hiding (drop)

import qualified Data.Attoparsec.ByteString.Char8 as ABC

xmlTokenAt :: (Rank1 w, Select1 v, TestBit w) => XmlCursor ByteString v w -> Maybe (XmlToken String Double)
xmlTokenAt k = if balancedParens k .?. lastPositionOf (cursorRank k)
  then case ABC.parse parseXmlToken (drop (toCount (xmlCursorPos k)) (cursorText k)) of
    ABC.Fail    {}  -> error "Failed to parse token in cursor"
    ABC.Partial _   -> error "Failed to parse token in cursor"
    ABC.Done    _ r -> Just r
  else Nothing