module Rdf{-(RDF(..),parseRdf)-} where
import qualified RichTextLex as RT
import ParsOps
import AnchorParser(parseTag)
import Data.Maybe(mapMaybe)
import Utils2(strToUpper)
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type RdfTag = (String,[(String,String)])

data RDF
  = RdfCtx RdfTag [RDF]
  | RdfCmd RdfTag
  | RdfChars String
  deriving (Show)

parseRdf s =
   case parseRdf' s of
     Right rdf -> Just rdf
     Left _ -> Nothing

parseRdf' = parse (rdfP `chk` eof) . rdfLex

rdfP = many rdfItemP

rdfItemP =
  charsP `orelse` cmdP `orelse` ctxP

charsP = lit chars
  where chars (Chars,s) = Just (RdfChars s)
        chars _ = Nothing

cmdP = lit cmd
  where cmd (CmdTag,s) = RdfCmd `fmap` parseTag s
        cmd _ = Nothing

ctxP = startTagP `bind` \ tag@(name,_) ->
        RdfCtx tag `mapP` rdfP `chk` endTagP name
  where
    startTagP = lit startTag
      where startTag (StartTag,s) = parseTag s
            startTag _ = Nothing

    endTagP name = tok (EndTag,name)

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type RdfLex = (RdfToken, String)
data RdfToken = StartTag | EndTag | CmdTag | Chars deriving (Eq,Show)

rdfLex = mapMaybe post . RT.rtlex
  where
    notComment (RT.Comment _) = False
    notFComment _ = True

    post (RT.Chars s) = Just (Chars, s)
    post (RT.FmtCmd s) =
      case s of
        '/':s' -> Just (EndTag, strToUpper s')
	_ -> if last s=='/'
	     then Just (CmdTag, init s)
	     else Just (StartTag, s)
    post _ = Nothing

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