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+--------------------------------------------------------------------
+-- |
+-- Module : Text.XML.Light.Input
+-- Copyright : (c) Galois, Inc. 2007
+-- License : BSD3
+--
+-- Maintainer: Iavor S. Diatchki <diatchki@galois.com>
+-- Stability : provisional
+-- Portability: portable
+--
+-- Lightweight XML parsing
+--
+
+module Text.XML.Light.Input (parseXML,parseXMLDoc) where
+
+import Text.XML.Light.Types
+import Text.XML.Light.Proc
+import Text.XML.Light.Output(tagEnd)
+
+import Data.Char(isSpace)
+import Data.List(isPrefixOf)
+import Numeric(readHex)
+
+-- | parseXMLDoc, parse a XMLl document to maybe an element
+parseXMLDoc :: String -> Maybe Element
+parseXMLDoc xs = strip (parseXML xs)
+ where strip cs = case onlyElems cs of
+ e : es
+ | "?xml" `isPrefixOf` qName (elName e)
+ -> strip (map Elem es)
+ | otherwise -> Just e
+ _ -> Nothing
+
+-- | parseXML to a list of content chunks
+parseXML :: String -> [Content]
+parseXML xs = parse $ tokens $ preprocess xs
+
+------------------------------------------------------------------------
+
+parse :: [Token] -> [Content]
+parse [] = []
+parse ts = let (es,_,ts1) = nodes ([],Nothing) [] ts
+ in es ++ parse ts1
+
+-- Information about namespaces.
+-- The first component is a map that associates prefixes to URIs,
+-- the second is the URI for the default namespace, if one was provided.
+type NSInfo = ([(String,String)],Maybe String)
+
+nodes :: NSInfo -> [QName] -> [Token] -> ([Content], [QName], [Token])
+
+nodes ns ps (TokCRef ref : ts) =
+ let (es,qs,ts1) = nodes ns ps ts
+ in (CRef ref : es, qs, ts1)
+
+nodes ns ps (TokText txt : ts) =
+ let (es,qs,ts1) = nodes ns ps ts
+ (more,es1) = case es of
+ Text cd : es1'
+ | cdVerbatim cd == cdVerbatim txt -> (cdData cd,es1')
+ _ -> ([],es)
+
+ in (Text txt { cdData = cdData txt ++ more } : es1, qs, ts1)
+
+nodes cur_info ps (TokStart p t as empty : ts) = (node : siblings, open, toks)
+ where
+ new_name = annotName new_info t
+ new_info = foldr addNS cur_info as
+ node = Elem Element { elLine = Just p
+ , elName = new_name
+ , elAttribs = map (annotAttr new_info) as
+ , elContent = children
+ }
+
+ (children,(siblings,open,toks))
+ | empty = ([], nodes cur_info ps ts)
+ | otherwise = let (es1,qs1,ts1) = nodes new_info (new_name:ps) ts
+ in (es1,
+ case qs1 of
+ [] -> nodes cur_info ps ts1
+ _ : qs3 -> ([],qs3,ts1))
+
+nodes ns ps (TokEnd p t : ts) = let t1 = annotName ns t
+ in case break (t1 ==) ps of
+ (as,_:_) -> ([],as,ts)
+ -- Unknown closing tag. Insert as text.
+ (_,[]) ->
+ let (es,qs,ts1) = nodes ns ps ts
+ in (Text CData {
+ cdLine = Just p,
+ cdVerbatim = CDataText,
+ cdData = tagEnd t ""
+ } : es,qs, ts1)
+
+nodes _ ps [] = ([],ps,[])
+
+
+annotName :: NSInfo -> QName -> QName
+annotName (namespaces,def_ns) n =
+ n { qURI = maybe def_ns (`lookup` namespaces) (qPrefix n) }
+
+annotAttr :: NSInfo -> Attr -> Attr
+annotAttr ns a@(Attr { attrKey = k}) =
+ case (qPrefix k, qName k) of
+ (Nothing,"xmlns") -> a
+ _ -> a { attrKey = annotName ns k }
+
+addNS :: Attr -> NSInfo -> NSInfo
+addNS (Attr { attrKey = key, attrVal = val }) (ns,def) =
+ case (qPrefix key, qName key) of
+ (Nothing,"xmlns") -> (ns, if null val then Nothing else Just val)
+ (Just "xmlns", k) -> ((k, val) : ns, def)
+ _ -> (ns,def)
+
+
+-- Lexer -----------------------------------------------------------------------
+
+type LChar = (Line,Char)
+type LString = [LChar]
+data Token = TokStart Line QName [Attr] Bool -- is empty?
+ | TokEnd Line QName
+ | TokCRef String
+ | TokText CData
+ deriving Show
+
+tokens :: String -> [Token]
+tokens = tokens' . linenumber 1
+
+tokens' :: LString -> [Token]
+tokens' ((_,'<') : c@(_,'!') : cs) = special c cs
+
+tokens' ((_,'<') : cs) = tag (dropSpace cs) -- we are being nice here
+tokens' [] = []
+tokens' cs@((l,_):_) = let (as,bs) = breakn ('<' ==) cs
+ in map cvt (decode_text as) ++ tokens' bs
+
+ -- XXX: Note, some of the lines might be a bit inacuarate
+ where cvt (TxtBit x) = TokText CData { cdLine = Just l
+ , cdVerbatim = CDataText
+ , cdData = x
+ }
+ cvt (CRefBit x) = case cref_to_char x of
+ Just c -> TokText CData { cdLine = Just l
+ , cdVerbatim = CDataText
+ , cdData = [c]
+ }
+ Nothing -> TokCRef x
+
+
+special :: LChar -> LString -> [Token]
+special _ ((_,'-') : (_,'-') : cs) = skip cs
+ where skip ((_,'-') : (_,'-') : (_,'>') : ds) = tokens' ds
+ skip (_ : ds) = skip ds
+ skip [] = [] -- unterminated comment
+
+special c ((_,'[') : (_,'C') : (_,'D') : (_,'A') : (_,'T') : (_,'A') : (_,'[')
+ : cs) =
+ let (xs,ts) = cdata cs
+ in TokText CData { cdLine = Just (fst c), cdVerbatim = CDataVerbatim, cdData = xs }
+ : tokens' ts
+ where cdata ((_,']') : (_,']') : (_,'>') : ds) = ([],ds)
+ cdata ((_,d) : ds) = let (xs,ys) = cdata ds in (d:xs,ys)
+ cdata [] = ([],[])
+
+special c cs =
+ let (xs,ts) = munch "" 0 cs
+ in TokText CData { cdLine = Just (fst c), cdVerbatim = CDataRaw, cdData = '<':'!':(reverse xs) } : tokens' ts
+ where munch acc nesting ((_,'>') : ds)
+ | nesting == (0::Int) = ('>':acc,ds)
+ | otherwise = munch ('>':acc) (nesting-1) ds
+ munch acc nesting ((_,'<') : ds)
+ = munch ('<':acc) (nesting+1) ds
+ munch acc n ((_,x) : ds) = munch (x:acc) n ds
+ munch acc _ [] = (acc,[]) -- unterminated DTD markup
+
+--special c cs = tag (c : cs) -- invalid specials are processed as tags
+
+
+qualName :: LString -> (QName,LString)
+qualName xs = let (as,bs) = breakn endName xs
+ (q,n) = case break (':'==) as of
+ (q1,_:n1) -> (Just q1, n1)
+ _ -> (Nothing, as)
+ in (QName { qURI = Nothing, qPrefix = q, qName = n }, bs)
+ where endName x = isSpace x || x == '=' || x == '>' || x == '/'
+
+
+
+
+
+tag :: LString -> [Token]
+tag ((p,'/') : cs) = let (n,ds) = qualName (dropSpace cs)
+ in TokEnd p n : case ds of
+ (_,'>') : es -> tokens' es
+ -- tag was not properly closed...
+ _ -> tokens' ds
+tag [] = []
+tag cs = let (n,ds) = qualName cs
+ (as,b,ts) = attribs (dropSpace ds)
+ in TokStart (fst (head cs)) n as b : ts
+
+attribs :: LString -> ([Attr], Bool, [Token])
+attribs cs = case cs of
+ (_,'>') : ds -> ([], False, tokens' ds)
+
+ (_,'/') : ds -> ([], True, case ds of
+ (_,'>') : es -> tokens' es
+ -- insert missing > ...
+ _ -> tokens' ds)
+
+ (_,'?') : (_,'>') : ds -> ([], True, tokens' ds)
+
+ -- doc ended within a tag..
+ [] -> ([],False,[])
+
+ _ -> let (a,cs1) = attrib cs
+ (as,b,ts) = attribs cs1
+ in (a:as,b,ts)
+
+attrib :: LString -> (Attr,LString)
+attrib cs = let (ks,cs1) = qualName cs
+ (vs,cs2) = attr_val (dropSpace cs1)
+ in ((Attr ks (decode_attr vs)),dropSpace cs2)
+
+attr_val :: LString -> (String,LString)
+attr_val ((_,'=') : cs) = string (dropSpace cs)
+attr_val cs = ("",cs)
+
+
+dropSpace :: LString -> LString
+dropSpace = dropWhile (isSpace . snd)
+
+-- | Match the value for an attribute. For malformed XML we do
+-- our best to guess the programmer's intention.
+string :: LString -> (String,LString)
+string ((_,'"') : cs) = break' ('"' ==) cs
+
+-- Allow attributes to be enclosed between ' '.
+string ((_,'\'') : cs) = break' ('\'' ==) cs
+
+-- Allow attributes that are not enclosed by anything.
+string cs = breakn eos cs
+ where eos x = isSpace x || x == '>' || x == '/'
+
+
+break' :: (a -> Bool) -> [(b,a)] -> ([a],[(b,a)])
+break' p xs = let (as,bs) = breakn p xs
+ in (as, case bs of
+ [] -> []
+ _ : cs -> cs)
+
+breakn :: (a -> Bool) -> [(b,a)] -> ([a],[(b,a)])
+breakn p l = (map snd as,bs) where (as,bs) = break (p . snd) l
+
+
+
+decode_attr :: String -> String
+decode_attr cs = concatMap cvt (decode_text cs)
+ where cvt (TxtBit x) = x
+ cvt (CRefBit x) = case cref_to_char x of
+ Just c -> [c]
+ Nothing -> '&' : x ++ ";"
+
+data Txt = TxtBit String | CRefBit String deriving Show
+
+decode_text :: [Char] -> [Txt]
+decode_text xs@('&' : cs) = case break (';' ==) cs of
+ (as,_:bs) -> CRefBit as : decode_text bs
+ _ -> [TxtBit xs]
+decode_text [] = []
+decode_text cs = let (as,bs) = break ('&' ==) cs
+ in TxtBit as : decode_text bs
+
+cref_to_char :: [Char] -> Maybe Char
+cref_to_char cs = case cs of
+ '#' : ds -> num_esc ds
+ "lt" -> Just '<'
+ "gt" -> Just '>'
+ "amp" -> Just '&'
+ "apos" -> Just '\''
+ "quot" -> Just '"'
+ _ -> Nothing
+
+num_esc :: String -> Maybe Char
+num_esc cs = case cs of
+ 'x' : ds -> check (readHex ds)
+ _ -> check (reads cs)
+
+ where check [(n,"")] = cvt_char n
+ check _ = Nothing
+
+cvt_char :: Int -> Maybe Char
+cvt_char x
+ | fromEnum (minBound :: Char) <= x && x <= fromEnum (maxBound::Char)
+ = Just (toEnum x)
+ | otherwise = Nothing
+
+preprocess :: String -> String
+preprocess ('\r' : '\n' : cs) = '\n' : preprocess cs
+preprocess ('\r' : cs) = '\n' : preprocess cs
+preprocess (c : cs) = c : preprocess cs
+preprocess [] = []
+
+linenumber :: Line -> String -> LString
+linenumber _ [] = []
+linenumber n ('\n':s) = n' `seq` ((n,'\n'):linenumber n' s) where n' = n + 1
+linenumber n (c:s) = (n,c) : linenumber n s
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