{-|
Module      : Gargantext.Core.Text.Corpus.Parsers.Wikimedia
Description : Parser for Wikimedia dump
Copyright   : (c) CNRS, 2017-Present
License     : AGPL + CECILL v3
Maintainer  : team@gargantext.org
Stability   : experimental
Portability : POSIX

@Gargantext.Core.Text.Corpus.Parsers.Wikimedia@:
This module provide a parser for wikipedia dump.
This include an xml parser for wikipedia's xml
and an wikimedia to plaintext converter for the wikipedia text field
-}


module Gargantext.Core.Text.Corpus.Parsers.Wikimedia
  where

import Control.Monad.Catch
import Data.Conduit
import Data.Either
import Data.Text as T
import Data.XML.Types (Event, Name)
import Gargantext.Prelude
import Text.Pandoc
import Text.XML.Stream.Parse

-- | Use case
-- :{
--  wikimediaFile <- BL.readFile "text.xml"
--  _ <- runConduit $ parseLBS def wikimediaFile
--        .| force "mediawiki required" parseMediawiki
--        .| CL.mapM mediawikiPageToPlain
--        .| CL.mapM_ print
-- :}

-- | A simple "Page" type.
-- For the moment it takes only text and title
--  (since there is no abstract) will see if other data are relevant.
data Page =
     Page { _markupFormat :: MarkupFormat
          , _title        :: Maybe T.Text
          , _text         :: Maybe T.Text
          }
          deriving (Show)

data MarkupFormat = Mediawiki | Plaintext
  deriving (Show)

parseRevision :: MonadThrow m => ConduitT Event o m (Maybe T.Text)
parseRevision = tagNoAttr "{http://www.mediawiki.org/xml/export-0.10/}revision" $ do
  text <- force "text is missing" $ ignoreExcept "{http://www.mediawiki.org/xml/export-0.10/}text" content
  many_ ignoreAnyTreeContent
  pure text

-- | Utility function that matches everything but the tag given
tagUntil :: Name -> NameMatcher Name
tagUntil name = matching (/= name)

-- | Utility function that consumes everything but the tag given
-- usefull because we have to consume every data.
manyTagsUntil_ :: MonadThrow m => Name -> ConduitT Event o m ()
manyTagsUntil_ n = many_ (ignoreTree (tagUntil n) ignoreAttrs)

manyTagsUntil_' :: MonadThrow m => Name -> ConduitT Event o m ()
manyTagsUntil_' = many_ . ignoreEmptyTag . tagUntil

-- | Utility function that parses nothing but the tag given,
-- usefull because we have to consume every data.
ignoreExcept :: MonadThrow m => Name
  -> ConduitT Event o m b
  -> ConduitT Event o m (Maybe b)
ignoreExcept name f = do
  _ <- manyTagsUntil_ name
  tagIgnoreAttrs (matching (== name)) f

-- TODO: remove ignoreExcept to:
-- many ignoreAnyTreeContentUntil "Article"
manyTagsUntil :: MonadThrow m => Name
  -> ConduitT Event o m b
  -> ConduitT Event o m (Maybe b)
manyTagsUntil name f = do
  _ <- manyTagsUntil_ name
  tagIgnoreAttrs (matching (== name)) f



parsePage :: MonadThrow m => ConduitT Event o m (Maybe Page)
parsePage =
  tagNoAttr "{http://www.mediawiki.org/xml/export-0.10/}page" $ do
  title <-
    tagNoAttr "{http://www.mediawiki.org/xml/export-0.10/}title" content
  _ <- manyTagsUntil_ "{http://www.mediawiki.org/xml/export-0.10/}revision"
  revision <-
    parseRevision
  many_ $ ignoreAnyTreeContent
  pure $ Page { _markupFormat = Mediawiki
                , _title = title
                , _text = revision }

parseMediawiki :: MonadThrow m => ConduitT Event Page m (Maybe ())
parseMediawiki =
  tagIgnoreAttrs "{http://www.mediawiki.org/xml/export-0.10/}mediawiki"
  $ manyYield' parsePage

-- | Convert a Mediawiki Page to a Plaintext Page.
-- Need to wrap the result in IO to parse and to combine it.
mediawikiPageToPlain :: Page -> IO Page
mediawikiPageToPlain page = do
  title <- mediaToPlain $ _title page
  revision <- mediaToPlain $ _text page
  pure $ Page { _markupFormat = Plaintext, _title = title, _text = revision }
  where mediaToPlain media =
          case media of
            (Nothing) -> pure Nothing
            (Just med) -> do
              res <- runIO $ do
                doc <- readMediaWiki def med
                writePlain def doc
              case res of
                (Left _)  -> pure Nothing
                (Right r) -> pure $ Just r
