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{-# LANGUAGE OverloadedStrings #-}
module NestingXML where
import Data.Conduit
import Data.XML.Types
import Control.Monad.State
import qualified Data.Text as S
import Data.List (find)
-- import qualified Text.XML.Stream.Parse as Parse (content)
type Lang = S.Text
data StrictList a = a :! !(StrictList a) | StrictNil
top ( a :! as ) = Just a
top _ = Nothing
data XMLState = XMLState {
nestingLevel :: Int,
langStack :: StrictList (Int,Lang)
}
type NestingXML o m a = StateT XMLState (ConduitM Event o m) a
runNestingXML :: NestingXML o m a -> Int -> ConduitM Event o m (a,XMLState)
runNestingXML m lvl = runStateT m (XMLState lvl StrictNil)
doNestingXML :: Monad m => NestingXML o m a -> ConduitM Event o m a
doNestingXML = fmap fst . flip runNestingXML 0
nesting :: Monad m => NestingXML o m Int
nesting = fmap nestingLevel get
xmlLang :: Monad m => NestingXML o m (Maybe Lang)
xmlLang = fmap (fmap snd . top . langStack) get
lookupLang attrs =
case find ( (=="xml:lang") . fst) attrs of
Just (_,[ContentText x]) -> Just x
Just (_,[ContentEntity x]) -> Just x
_ -> Nothing
awaitXML :: Monad m => NestingXML o m (Maybe Event)
awaitXML = do
XMLState lvl langs <- get
xml <- lift await
put $ case xml of
Just (EventBeginElement _ attrs) ->
case lookupLang attrs of
Nothing -> XMLState (lvl+1) langs
Just lang -> XMLState (lvl+1) ( (lvl+1,lang) :! langs)
Just (EventEndElement _) ->
case langs of
(llvl,_) :! ls | llvl==lvl -> XMLState (lvl-1) ls
_ | otherwise -> XMLState (lvl-1) langs
_ -> XMLState lvl langs
return xml
withXML
:: Monad m => (Event -> NestingXML o m ()) -> NestingXML o m ()
withXML f = do
xml <- awaitXML
maybe (return ()) f xml
maybeXML
:: Monad m => NestingXML o m a -> (Event -> NestingXML o m a) -> NestingXML o m a
maybeXML whenNothing withJust = do
xml <- awaitXML
maybe whenNothing withJust xml
awaitCloser :: Monad m => Int -> NestingXML o m ()
awaitCloser lvl = do
fix $ \loop -> do
lvl' <- nesting
when (lvl' >= lvl) $ do
withXML $ \xml -> do
loop
nextElement :: Monad m => NestingXML o m (Maybe Event)
nextElement = do
lvl <- nesting
fix $ \loop -> do
xml <- awaitXML
case xml of
Nothing -> return Nothing
Just (EventBeginElement _ _) -> do
return xml
Just _ -> do
lvl' <- nesting
if (lvl'>=lvl) then loop
else return Nothing
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