    {-# LANGUAGE PatternGuards #-}
    {-
    Copyright (C) 2008-2010 Andrea Rossato <andrea.rossato@ing.unitn.it>
    and John MacFarlane.

    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 2 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, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
    -}

    {- |
       Module      : Text.Pandoc.Writers.OpenDocument
       Copyright   : Copyright (C) 2008-2010 Andrea Rossato and John MacFarlane
       License     : GNU GPL, version 2 or above

       Maintainer  : Andrea Rossato <andrea.rossato@ing.unitn.it>
       Stability   : alpha
       Portability : portable

    Conversion of 'Pandoc' documents to OpenDocument XML.
    -}
    module Text.Pandoc.Writers.OpenDocument ( writeOpenDocument ) where
    import Text.Pandoc.Definition
    import Text.Pandoc.Shared
    import Text.Pandoc.XML
    import Text.Pandoc.Templates (renderTemplate)
    import Text.Pandoc.Readers.TeXMath
    import Text.PrettyPrint.HughesPJ hiding ( Str )
    import Text.Printf ( printf )
    import Control.Applicative ( (<$>) )
    import Control.Arrow ( (***), (>>>) )
    import Control.Monad.State hiding ( when )
    import Data.Char (chr)
    import qualified Data.Map as Map

    -- | Auxiliary function to convert Plain block to Para.
    plainToPara :: Block -> Block
    plainToPara (Plain x) = Para x
    plainToPara x = x

    --
    -- OpenDocument writer
    --

    data WriterState =
        WriterState { stNotes         :: [Doc]
                    , stTableStyles   :: [Doc]
                    , stParaStyles    :: [Doc]
                    , stListStyles    :: [(Int, [Doc])]
                    , stTextStyles    :: [Doc]
                    , stTextStyleAttr :: Map.Map TextStyle [(String,String)]
                    , stIndentPara    :: Int
                    , stInDefinition  :: Bool
                    , stTight         :: Bool
                    }

    defaultWriterState :: WriterState
    defaultWriterState =
        WriterState { stNotes         = []
                    , stTableStyles   = []
                    , stParaStyles    = []
                    , stListStyles    = []
                    , stTextStyles    = []
                    , stTextStyleAttr = Map.empty
                    , stIndentPara    = 0
                    , stInDefinition  = False
                    , stTight         = False
                    }

    when :: Bool -> Doc -> Doc
    when p a = if p then a else empty

    addTableStyle :: Doc -> State WriterState ()
    addTableStyle i = modify $ \s -> s { stTableStyles = i : stTableStyles s }

    addNote :: Doc -> State WriterState ()
    addNote i = modify $ \s -> s { stNotes = i : stNotes s }

    addParaStyle :: Doc -> State WriterState ()
    addParaStyle i = modify $ \s -> s { stParaStyles = i : stParaStyles s }

    addTextStyle :: Doc -> State WriterState ()
    addTextStyle i = modify $ \s -> s { stTextStyles = i : stTextStyles s }

    addTextStyleAttr :: (TextStyle, [(String,String)]) -> State WriterState ()
    addTextStyleAttr (ts, xs) = modify $ \s -> s { stTextStyleAttr = Map.insert ts xs (stTextStyleAttr s) }

    rmTextStyleAttr :: TextStyle -> State WriterState ()
    rmTextStyleAttr ts = modify $ \s -> s { stTextStyleAttr = Map.delete ts (stTextStyleAttr s) }

    increaseIndent :: State WriterState ()
    increaseIndent = modify $ \s -> s { stIndentPara = 1 + stIndentPara s }

    resetIndent :: State WriterState ()
    resetIndent = modify $ \s -> s { stIndentPara = (stIndentPara s) - 1 }

    inTightList :: State WriterState a -> State WriterState a
    inTightList  f = modify (\s -> s { stTight = True  }) >> f >>= \r ->
                     modify (\s -> s { stTight = False }) >> return r

    setInDefinitionList :: Bool -> State WriterState ()
    setInDefinitionList b = modify $  \s -> s { stInDefinition = b }

    inParagraphTags :: Doc -> Doc
    inParagraphTags = inTags False "text:p" [("text:style-name", "Text_20_body")]

    inParagraphTagsWithStyle :: String -> Doc -> Doc
    inParagraphTagsWithStyle sty = inTags False "text:p" [("text:style-name", sty)]

    inSpanTags :: String -> Doc -> Doc
    inSpanTags s = inTags False "text:span" [("text:style-name",s)]

    withTextStyle :: TextStyle -> State WriterState a -> State WriterState a
    withTextStyle s f = addTextStyleAttr (s,textStyleAttr s) >>
                        f >>= \r -> rmTextStyleAttr s >> return r

    inTextStyle :: Doc -> State WriterState Doc
    inTextStyle d = do
      at <- gets stTextStyleAttr
      if Map.null at
         then return d
         else do
           tn <- (+) 1 . length  <$> gets stTextStyles
           addTextStyle $ inTags False "style:style" [("style:name"  , "T" ++ show tn)
                                                     ,("style:family", "text"        )]
                        $ selfClosingTag "style:text-properties" (concatMap snd $ Map.toList at)
           return $ inTags False "text:span" [("text:style-name","T" ++ show tn)] d

    inHeaderTags :: Int -> Doc -> Doc
    inHeaderTags i = inTags False "text:h" [ ("text:style-name", "Heading_20_" ++ show i)
                                           , ("text:outline-level", show i)]

    inQuotes :: QuoteType -> Doc -> Doc
    inQuotes SingleQuote s = text "&#8216;" <> s <> text "&#8217;"
    inQuotes DoubleQuote s = text "&#8220;" <> s <> text "&#8221;"

    handleSpaces :: String -> Doc
    handleSpaces s
        | ( ' ':_) <- s = genTag s
        | ('\t':x) <- s = selfClosingTag "text:tab" [] <> rm x
        | otherwise     = rm s
        where
            genTag       = span (==' ') >>> tag . length *** rm >>> uncurry (<>)
            tag n        = when (n /= 0) $ selfClosingTag "text:s" [("text:c", show n)]
            rm ( ' ':xs) = char ' ' <> genTag xs
            rm ('\t':xs) = selfClosingTag "text:tab" [] <> genTag xs
            rm (   x:xs) = char  x  <> rm xs
            rm        [] = empty

    -- | Convert Pandoc document to string in OpenDocument format.
    writeOpenDocument :: WriterOptions -> Pandoc -> String
    writeOpenDocument opts (Pandoc (Meta title authors date) blocks) =
      let ((doc, title', authors', date'),s) = flip runState
            defaultWriterState $ do
               title'' <- inlinesToOpenDocument opts title
               authors'' <- mapM (inlinesToOpenDocument opts) authors
               date'' <- inlinesToOpenDocument opts date
               doc'' <- blocksToOpenDocument opts blocks
               return (doc'', title'', authors'', date'')
          body'    = render doc
          styles   = stTableStyles s ++ stParaStyles s ++ stTextStyles s
          listStyle (n,l) = inTags True "text:list-style"
                              [("style:name", "L" ++ show n)] (vcat l)
          listStyles  = map listStyle (stListStyles s)
          automaticStyles = inTagsIndented "office:automatic-styles" $ vcat $
                              reverse $ styles ++ listStyles
          context = writerVariables opts ++
                    [ ("body", body')
                    , ("automatic-styles", render automaticStyles)
                    , ("title", render title')
                    , ("date", render date') ] ++
                    [ ("author", render a) | a <- authors' ]
      in  if writerStandalone opts
             then renderTemplate context $ writerTemplate opts
             else body'

    withParagraphStyle :: WriterOptions -> String -> [Block] -> State WriterState Doc
    withParagraphStyle  o s (b:bs)
        | Para l <- b = go =<< inParagraphTagsWithStyle s <$> inlinesToOpenDocument o l
        | otherwise   = go =<< blockToOpenDocument o b
        where go i = (<>) i <$>  withParagraphStyle o s bs
    withParagraphStyle _ _ [] = return empty

    inPreformattedTags :: String -> State WriterState Doc
    inPreformattedTags s = do
      n <- paraStyle "Preformatted_20_Text" []
      return . inParagraphTagsWithStyle ("P" ++ show n) . handleSpaces $ s

    orderedListToOpenDocument :: WriterOptions -> Int -> [[Block]] -> State WriterState Doc
    orderedListToOpenDocument o pn bs =
        vcat . map (inTagsIndented "text:list-item") <$>
        mapM (orderedItemToOpenDocument o pn . map plainToPara) bs

    orderedItemToOpenDocument :: WriterOptions -> Int -> [Block] -> State WriterState Doc
    orderedItemToOpenDocument  o n (b:bs)
        | OrderedList a l <- b = newLevel a l
        | Para          l <- b = go =<< inParagraphTagsWithStyle ("P" ++ show n) <$> inlinesToOpenDocument o l
        | otherwise            = go =<< blockToOpenDocument o b
        where
          go i = ($$) i <$> orderedItemToOpenDocument o n bs
          newLevel a l = do
            nn <- length <$> gets stParaStyles
            ls <- head   <$> gets stListStyles
            modify $ \s -> s { stListStyles = orderedListLevelStyle a ls : tail (stListStyles s) }
            inTagsIndented "text:list" <$> orderedListToOpenDocument o nn l
    orderedItemToOpenDocument  _ _ [] = return empty

    isTightList :: [[Block]] -> Bool
    isTightList []          = False
    isTightList (b:_)
        | Plain {} : _ <- b = True
        | otherwise         = False

    newOrderedListStyle :: Bool -> ListAttributes -> State WriterState (Int,Int)
    newOrderedListStyle b a = do
      ln <- (+) 1 . length  <$> gets stListStyles
      let nbs = orderedListLevelStyle a (ln, [])
      pn <- if b then inTightList (paraListStyle ln) else paraListStyle ln
      modify $ \s -> s { stListStyles = nbs : stListStyles s }
      return (ln,pn)

    bulletListToOpenDocument :: WriterOptions -> [[Block]] -> State WriterState Doc
    bulletListToOpenDocument o b = do
      ln <- (+) 1 . length <$> gets stListStyles
      (pn,ns) <- if isTightList b then inTightList (bulletListStyle ln) else bulletListStyle ln
      modify $ \s -> s { stListStyles = ns : stListStyles s }
      is <- listItemsToOpenDocument ("P" ++ show pn) o b
      return $ inTags True "text:list" [("text:style-name", "L" ++ show ln)] is

    listItemsToOpenDocument :: String -> WriterOptions -> [[Block]] -> State WriterState Doc
    listItemsToOpenDocument s o is =
        vcat . map (inTagsIndented "text:list-item") <$> mapM (withParagraphStyle o s . map plainToPara) is

    deflistItemToOpenDocument :: WriterOptions -> ([Inline],[[Block]]) -> State WriterState Doc
    deflistItemToOpenDocument o (t,d) = do
      let ts = if isTightList d
               then "Definition_20_Term_20_Tight"       else "Definition_20_Term"
          ds = if isTightList d
               then "Definition_20_Definition_20_Tight" else "Definition_20_Definition"
      t' <- withParagraphStyle o ts [Para t]
      d' <- liftM vcat $ mapM (withParagraphStyle o ds . (map plainToPara)) d
      return $ t' $$ d'

    inBlockQuote :: WriterOptions -> Int -> [Block] -> State WriterState Doc
    inBlockQuote  o i (b:bs)
        | BlockQuote l <- b = do increaseIndent
                                 ni <- paraStyle "Quotations" []
                                 go =<< inBlockQuote o ni (map plainToPara l)
        | Para       l <- b = do go =<< inParagraphTagsWithStyle ("P" ++ show  i) <$> inlinesToOpenDocument o l
        | otherwise         = do go =<< blockToOpenDocument o b
        where go  block  = ($$) block <$> inBlockQuote o i bs
    inBlockQuote     _ _ [] =  resetIndent >> return empty

    -- | Convert a list of Pandoc blocks to OpenDocument.
    blocksToOpenDocument :: WriterOptions -> [Block] -> State WriterState Doc
    blocksToOpenDocument o b = vcat <$> mapM (blockToOpenDocument o) b

    -- | Convert a Pandoc block element to OpenDocument.
    blockToOpenDocument :: WriterOptions -> Block -> State WriterState Doc
    blockToOpenDocument o bs
        | Plain          b <- bs = inParagraphTags <$> inlinesToOpenDocument o b
        | Para           b <- bs = inParagraphTags <$> inlinesToOpenDocument o b
        | Header       i b <- bs = inHeaderTags  i <$> inlinesToOpenDocument o b
        | BlockQuote     b <- bs = mkBlockQuote b
        | CodeBlock    _ s <- bs = preformatted s
        | RawHtml        _ <- bs = return empty
        | DefinitionList b <- bs = defList b
        | BulletList     b <- bs = bulletListToOpenDocument o b
        | OrderedList  a b <- bs = orderedList a b
        | Table  c a w h r <- bs = table c a w h r
        | Null             <- bs = return empty
        | HorizontalRule   <- bs = return $ selfClosingTag "text:p" [ ("text:style-name", "Horizontal_20_Line") ]
        | otherwise              = return empty
        where
          defList       b = do setInDefinitionList True
                               r <- vcat  <$> mapM (deflistItemToOpenDocument o) b
                               setInDefinitionList False
                               return r
          preformatted  s = vcat <$> mapM (inPreformattedTags . escapeStringForXML) (lines s)
          mkBlockQuote  b = do increaseIndent
                               i <- paraStyle "Quotations" []
                               inBlockQuote o i (map plainToPara b)
          orderedList a b = do (ln,pn) <- newOrderedListStyle (isTightList b) a
                               inTags True "text:list" [ ("text:style-name", "L" ++ show ln)]
                                          <$> orderedListToOpenDocument o pn b
          table c a w h r = do
            tn <- length <$> gets stTableStyles
            pn <- length <$> gets stParaStyles
            let  genIds      = map chr [65..]
                 name        = "Table" ++ show (tn + 1)
                 columnIds   = zip genIds w
                 mkColumn  n = selfClosingTag "table:table-column" [("table:style-name", name ++ "." ++ [fst n])]
                 columns     = map mkColumn columnIds
                 paraHStyles = paraTableStyles "Heading"  pn a
                 paraStyles  = paraTableStyles "Contents" (pn + length (newPara paraHStyles)) a
                 newPara     = map snd . filter (not . isEmpty . snd)
            addTableStyle $ tableStyle tn columnIds
            mapM_ addParaStyle . newPara $ paraHStyles ++ paraStyles
            captionDoc <- if null c
                          then return empty
                          else withParagraphStyle o "Caption" [Para c]
            th <- if all null h
                     then return empty
                     else colHeadsToOpenDocument o name (map fst paraHStyles) h
            tr <- mapM (tableRowToOpenDocument o name (map fst paraStyles)) r
            return $ inTags True "table:table" [ ("table:name"      , name)
                                               , ("table:style-name", name)
                                               ] (vcat columns $$ th $$ vcat tr) $$ captionDoc

    colHeadsToOpenDocument :: WriterOptions -> String -> [String] -> [[Block]] -> State WriterState Doc
    colHeadsToOpenDocument o tn ns hs =
        inTagsIndented "table:table-header-rows" . inTagsIndented "table:table-row" . vcat <$>
        mapM (tableItemToOpenDocument o tn) (zip ns hs)

    tableRowToOpenDocument :: WriterOptions -> String -> [String] -> [[Block]] -> State WriterState Doc
    tableRowToOpenDocument o tn ns cs =
        inTagsIndented "table:table-row" . vcat <$>
        mapM (tableItemToOpenDocument o tn) (zip ns cs)

    tableItemToOpenDocument :: WriterOptions -> String -> (String,[Block])-> State WriterState Doc
    tableItemToOpenDocument o tn (n,i) =
      let a = [ ("table:style-name" , tn ++ ".A1" )
              , ("office:value-type", "string"     )
              ]
      in  inTags True "table:table-cell" a <$>
          withParagraphStyle o n (map plainToPara i)

    -- | Convert a list of inline elements to OpenDocument.
    inlinesToOpenDocument :: WriterOptions -> [Inline] -> State WriterState Doc
    inlinesToOpenDocument o l = hcat <$> mapM (inlineToOpenDocument o) l

    -- | Convert an inline element to OpenDocument.
    inlineToOpenDocument :: WriterOptions -> Inline -> State WriterState Doc
    inlineToOpenDocument o ils
        | Ellipses      <- ils = inTextStyle $ text "&#8230;"
        | EmDash        <- ils = inTextStyle $ text "&#8212;"
        | EnDash        <- ils = inTextStyle $ text "&#8211;"
        | Apostrophe    <- ils = inTextStyle $ text "&#8217;"
        | Space         <- ils = inTextStyle $ char ' '
        | LineBreak     <- ils = return $ selfClosingTag "text:line-break" []
        | Str         s <- ils = inTextStyle $ handleSpaces $ escapeStringForXML s
        | Emph        l <- ils = withTextStyle Italic $ inlinesToOpenDocument o l
        | Strong      l <- ils = withTextStyle Bold   $ inlinesToOpenDocument o l
        | Strikeout   l <- ils = withTextStyle Strike $ inlinesToOpenDocument o l
        | Superscript l <- ils = withTextStyle Sup    $ inlinesToOpenDocument o l
        | Subscript   l <- ils = withTextStyle Sub    $ inlinesToOpenDocument o l
        | SmallCaps   l <- ils = withTextStyle SmallC $ inlinesToOpenDocument o l
        | Quoted    t l <- ils = inQuotes t <$> inlinesToOpenDocument o l
        | Code        s <- ils = preformatted s
        | Math      _ s <- ils = inlinesToOpenDocument o (readTeXMath s)
        | Cite      _ l <- ils = inlinesToOpenDocument o l
        | TeX         s <- ils = preformatted s
        | HtmlInline  s <- ils = preformatted s
        | Link  l (s,t) <- ils = mkLink s t <$> inlinesToOpenDocument o l
        | Image _ (s,_) <- ils = return $ mkImg  s
        | Note        l <- ils = mkNote l
        | otherwise            = return empty
        where
          preformatted = return . inSpanTags "Teletype" . handleSpaces . escapeStringForXML
          mkLink   s t = inTags False "text:a" [ ("xlink:type" , "simple")
                                               , ("xlink:href" , s       )
                                               , ("office:name", t       )
                                               ] . inSpanTags "Definition"
          mkImg  s     = inTags False "draw:frame" [] $
                         selfClosingTag "draw:image" [ ("xlink:href"   , s       )
                                                     , ("xlink:type"   , "simple")
                                                     , (" xlink:show"  , "embed" )
                                                     , ("xlink:actuate", "onLoad")]
          mkNote     l = do
            n <- length <$> gets stNotes
            let footNote t = inTags False "text:note"
                             [ ("text:id"        , "ftn" ++ show n)
                             , ("text:note-class", "footnote"     )] $
                             inTagsSimple "text:note-citation" (text . show $ n + 1) <>
                             inTagsSimple "text:note-body" t
            nn <- footNote <$> withParagraphStyle o "Footnote" l
            addNote nn
            return nn

    bulletListStyle :: Int -> State WriterState (Int,(Int,[Doc]))
    bulletListStyle l =
        let doStyles  i = inTags True "text:list-level-style-bullet"
                          [ ("text:level"      , show (i + 1)       )
                          , ("text:style-name" , "Bullet_20_Symbols")
                          , ("style:num-suffix", "."                )
                          , ("text:bullet-char", [bulletList !! i]  )
                          ] (listLevelStyle (1 + i))
            bulletList  = map chr $ cycle [8226,8227,8259]
            listElStyle = map doStyles [0..9]
        in  do pn <- paraListStyle l
               return (pn, (l, listElStyle))

    orderedListLevelStyle :: ListAttributes -> (Int, [Doc]) -> (Int,[Doc])
    orderedListLevelStyle (s,n, d) (l,ls) =
        let suffix    = case d of
                          OneParen  -> [("style:num-suffix", ")")]
                          TwoParens -> [("style:num-prefix", "(")
                                       ,("style:num-suffix", ")")]
                          _         -> [("style:num-suffix", ".")]
            format    = case n of
                          UpperAlpha   -> "A"
                          LowerAlpha   -> "a"
                          UpperRoman   -> "I"
                          LowerRoman   -> "i"
                          _            -> "1"
            listStyle = inTags True "text:list-level-style-number"
                        ([ ("text:level"      , show $ 1 + length ls  )
                         , ("text:style-name" , "Numbering_20_Symbols")
                         , ("style:num-format", format                )
                         , ("text:start-value", show s                )
                         ] ++ suffix) (listLevelStyle (1 + length ls))
        in  (l, ls ++ [listStyle])

    listLevelStyle :: Int -> Doc
    listLevelStyle i =
        let indent = show (0.25 * fromIntegral i :: Double) in
        selfClosingTag "style:list-level-properties"
                           [ ("text:space-before"   , indent ++ "in")
                           , ("text:min-label-width",       "0.25in")]

    tableStyle :: Int -> [(Char,Double)] -> Doc
    tableStyle num wcs =
        let tableId        = "Table" ++ show (num + 1)
            table          = inTags True "style:style"
                             [("style:name", tableId)] $
                             selfClosingTag "style:table-properties"
                             [("table:align"    , "center")]
            colStyle (c,0) = selfClosingTag "style:style"
                             [ ("style:name"  , tableId ++ "." ++ [c])
                             , ("style:family", "table-column"       )]
            colStyle (c,w) = inTags True "style:style"
                             [ ("style:name"  , tableId ++ "." ++ [c])
                             , ("style:family", "table-column"       )] $
                             selfClosingTag "style:table-column-properties"
                             [("style:rel-column-width", printf "%d*" $ (floor $ w * 65535 :: Integer))]
            cellStyle      = inTags True "style:style"
                             [ ("style:name"  , tableId ++ ".A1")
                             , ("style:family", "table-cell"    )] $
                             selfClosingTag "style:table-cell-properties"
                             [ ("fo:border", "none")]
            columnStyles   = map colStyle wcs
        in  table $$ vcat columnStyles $$ cellStyle

    paraStyle :: String -> [(String,String)] -> State WriterState Int
    paraStyle parent attrs = do
      pn <- (+)   1 . length       <$> gets stParaStyles
      i  <- (*) 0.5 . fromIntegral <$> gets stIndentPara :: State WriterState Double
      b  <- gets stInDefinition
      t  <- gets stTight
      let styleAttr = [ ("style:name"             , "P" ++ show pn)
                      , ("style:family"           , "paragraph"   )
                      , ("style:parent-style-name", parent        )]
          indentVal = flip (++) "in" . show $ if b then (max 0.5 i) else i
          tight     = if t then [ ("fo:margin-top"          , "0in"    )
                                , ("fo:margin-bottom"       , "0in"    )]
                           else []
          indent    = when (i /= 0 || b || t) $
                      selfClosingTag "style:paragraph-properties" $
                               [ ("fo:margin-left"         , indentVal)
                               , ("fo:margin-right"        , "0in"    )
                               , ("fo:text-indent"         , "0in"    )
                               , ("style:auto-text-indent" , "false"  )]
                             ++ tight
      addParaStyle $ inTags True "style:style" (styleAttr ++ attrs) indent
      return pn

    paraListStyle :: Int -> State WriterState Int
    paraListStyle l = paraStyle "Text_20_body" [("style:list-style-name", "L" ++ show l )]

    paraTableStyles :: String -> Int -> [Alignment] -> [(String, Doc)]
    paraTableStyles _ _ [] = []
    paraTableStyles t s (a:xs)
        | AlignRight  <- a = (         pName s, res s "end"   ) : paraTableStyles t (s + 1) xs
        | AlignCenter <- a = (         pName s, res s "center") : paraTableStyles t (s + 1) xs
        | otherwise        = ("Table_20_" ++ t, empty         ) : paraTableStyles t  s      xs
        where pName sn = "P" ++ show (sn + 1)
              res sn x = inTags True "style:style"
                         [ ("style:name"             , pName sn        )
                         , ("style:family"           , "paragraph"     )
                         , ("style:parent-style-name", "Table_20_" ++ t)] $
                         selfClosingTag "style:paragraph-properties"
                         [ ("fo:text-align", x)
                         , ("style:justify-single-word", "false")]

    data TextStyle = Italic | Bold | Strike | Sub | Sup | SmallC deriving ( Eq,Ord )

    textStyleAttr :: TextStyle -> [(String,String)]
    textStyleAttr s
        | Italic <- s = [("fo:font-style"                ,"italic"    )
                        ,("style:font-style-asian"       ,"italic"    )
                        ,("style:font-style-complex"     ,"italic"    )]
        | Bold   <- s = [("fo:font-weight"               ,"bold"      )
                        ,("style:font-weight-asian"      ,"bold"      )
                        ,("style:font-weight-complex"    ,"bold"      )]
        | Strike <- s = [("style:text-line-through-style", "solid"    )]
        | Sub    <- s = [("style:text-position"          ,"sub 58%"   )]
        | Sup    <- s = [("style:text-position"          ,"super 58%" )]
        | SmallC <- s = [("fo:font-variant"              ,"small-caps")]
        | otherwise   = []