{- |

Module : $Header$

Copyright : (c) Felix Gabriel Mance

License : GPLv2 or higher, see LICENSE.txt

Maintainer : f.mance@jacobs-university.de

Stability : provisional

Portability : portable

RDF syntax parser, based on rdf4h library

-}

module RDF.Parse where

import OWL2.Parse

import OWL2.AS

import RDF.AS

import Text.RDF.Core

import Text.RDF.TriplesGraph

import Text.RDF.NTriplesParser

import System.Process

import GHC.IO.Exception

import System.IO.Unsafe

import qualified Data.ByteString.Lazy.Char8 as B

import Text.ParserCombinators.Parsec

import Data.ByteString.Lazy.Char8 (ByteString)

{- | takes an input file and outputs the n-triples

representation in the output file -}

convertRDF2Ntriples :: String -> String -> IO GHC.IO.Exception.ExitCode

convertRDF2Ntriples fileIn fileOut =

system $ "cwm --rdf " ++ fileIn ++ " --ntriples > " ++ fileOut

-- | takes a filename containing n-triples and returns the list of triples

parseNtriples :: Monad m => String -> m [Triple]

parseNtriples fileIn = do

let graph = unsafePerformIO $ parseFile NTriplesParser fileIn

:: Either ParseFailure TriplesGraph

case graph of

Right g -> return $ triplesOf g

Left _ -> fail $ "cannot parse " ++ fileIn

bs2s :: ByteString -> String

bs2s = B.unpack

f2s :: FastString -> String

f2s = reverse . B.unpack . value

-- | converts an IRI from the rdf4h library into our IRIs

parseIRI :: FastString -> IRI

parseIRI fs = let s = f2s fs in case parse uriP "" s of

Right iri -> if namePrefix iri == "http" then setFull iri else iri

Left _ -> error $ s ++ ": invalid IRI"

convertNode :: Node -> Either IRI Literal

convertNode node = case node of

LNode lv -> Right $ case lv of

PlainL bs -> Literal (bs2s bs) $ Untyped Nothing

PlainLL bs1 bs2 -> Literal (bs2s bs1) $ Untyped $ Just $ bs2s bs2

TypedL bs fs ->

let l = "\"" ++ bs2s bs ++ "\"^^<" ++ f2s fs ++ ">"

in case parse literal "" l of

Right lit -> lit

Left _ -> error $ l ++ ": invalid literal"

UNode fs -> Left $ parseIRI fs

BNode fs -> Left $ (parseIRI fs) {iriType = NodeID}

_ -> Left nullQName

-- | converts a rdf4h triple into our triples

convertTriple :: Triple -> Sentence

convertTriple (Triple s p o) =

let Left subj = convertNode s

Left pre = convertNode p

in Sentence subj pre $ convertNode o

-- | takes a filename with n-triples and returns the rdf graph in our syntax

nTriplesParser :: Monad m => String -> m RDFGraph

nTriplesParser fileIn = do

gr <- parseNtriples fileIn

return $ RDFGraph $ map convertTriple gr