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{-
Copyright (C) 2017-2018 defanor <defanor@uberspace.net>
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
-}
{- |
Module : Text.Pandoc.Readers.RDF
Maintainer : defanor <defanor@uberspace.net>
Stability : unstable
This module is for RDF documents reading. It's not strictly a parser,
since it requests additional external documents to read predicate
labels from, and looks up for alternate versions, and decides how to
render those.
-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE ScopedTypeVariables #-}
module Text.Pandoc.Readers.RDF ( readRDF ) where
import Text.Pandoc.Definition
import Text.Pandoc.Class (PandocMonad)
-- import Data.RDF
import qualified Data.Text as T
import Network.URI (URI, parseURIReference, relativeFrom, uriToString)
import Data.List (intersperse)
import Control.Monad.IO.Class (liftIO, MonadIO)
import Text.XML.HXT.Core ( readString, withParseHTML, withWarnings,
runX, (>>>), yes, no, XNode(..))
import Data.Tree.NTree.TypeDefs (NTree(..))
import Text.XML.HXT.XPath.Arrows (getXPathTreesInDoc)
import Control.Monad.Error.Class (throwError)
import Text.Pandoc.Error (PandocError(..))
import Control.Exception
import System.Directory
import Foreign
import Redland.MidLevel
import Redland.LowLevel
import Redland.Util
detectAlternateVersion :: T.Text -> IO (Maybe URI)
detectAlternateVersion t = do
let doc = readString [withParseHTML yes, withWarnings no] (T.unpack t)
rc <- liftIO $ runX $ doc
>>> getXPathTreesInDoc
"//link[@rel=\"alternate\" and @type=\"application/rdf+xml\"]/@href/text()"
pure $ case rc of
[NTree (XText uri) []] -> parseURIReference uri
_ -> Nothing
readRDF :: (MonadIO m, PandocMonad m)
=> URI
-- ^ Base (source) URI.
-> (URI -> m T.Text)
-- ^ Retrieval function.
-> T.Text
-- ^ Document to parse.
-> m Pandoc
readRDF bu rf t = do
alt <- liftIO $ detectAlternateVersion t
case alt of
Nothing -> do
r <- liftIO $ handle handleRE parseDoc
case r of
Left e -> throwError $ PandocParseError e
Right r' -> pure r'
Just alt' -> do
newDoc <- rf alt'
readRDF alt' rf newDoc
where
handleRE :: RedlandException -> IO (Either String Pandoc)
handleRE e = pure $ Left $ show e
parseDoc :: IO (Either String Pandoc)
parseDoc = Right . Pandoc mempty . pure . LineBlock <$> do
withWSMU "memory" [] "temporary" "" (uriToString id bu "") $
\world _ model uri -> do
tryParseStringIntoModel world ["turtle", "rdfxml", "n-triples"]
model uri (T.unpack t)
withQuery world model "sparql" "SELECT ?s ?p ?o WHERE { ?s ?p ?o }"
(Just uri) $ \results -> do
cacheDir <- getXdgDirectory XdgCache "pancake"
createDirectoryIfMissing True cacheDir
withWSMU "hashes" [("hash-type", "bdb"), ("dir", cacheDir)]
"rdf-cache" "" (uriToString id bu "") $ \world' _ model' uri' ->
mapM (printTriple (world', model', uri')) results
-- todo: should probably use statements instead, need to complete
-- that part of the bindings.
printTriple :: ( ForeignPtr RedlandWorld
, ForeignPtr RedlandModel
, ForeignPtr RedlandURI)
-> [(String, Node)]
-> IO [Inline]
printTriple wmu l =
concat . intersperse [Space] <$> mapM (printNode wmu . snd) l
printNode :: ( ForeignPtr RedlandWorld
, ForeignPtr RedlandModel
, ForeignPtr RedlandURI)
-> Node
-> IO [Inline]
printNode _ (BlankNode s) = pure [Str s]
printNode _ (LiteralNode s) = pure [Str s]
printNode (w, m, u) (ResourceNode s) =
let su = showURI s
q = "SELECT ?label WHERE { <" ++ s ++
"> <http://www.w3.org/2000/01/rdf-schema#label> ?label }"
in do
l <- withQuery w m "sparql" q (Just u) $ \r ->
case r of
([("label", LiteralNode label)]:_) -> pure label
_ -> pure su
pure [Link (su, [], []) [] (su, l)]
showURI :: String -> String
showURI u = case parseURIReference u of
Just u' -> uriToString id (relativeFrom u' bu) ""
Nothing -> u
-- rdfproc rdf-cache parse http://xmlns.com/foaf/0.1/
-- rdfproc rdf-cache parse http://www.w3.org/1999/02/22-rdf-syntax-ns
|
