path: root/src/Text/Pandoc/Writers/Markdown.hs

{-# LANGUAGE OverloadedStrings, TupleSections, ScopedTypeVariables #-}
{-
Copyright (C) 2006-2015 John MacFarlane <jgm@berkeley.edu>

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.Markdown
   Copyright   : Copyright (C) 2006-2015 John MacFarlane
   License     : GNU GPL, version 2 or above

   Maintainer  : John MacFarlane <jgm@berkeley.edu>
   Stability   : alpha
   Portability : portable

Conversion of 'Pandoc' documents to markdown-formatted plain text.

Markdown:  <http://daringfireball.net/projects/markdown/>
-}
module Text.Pandoc.Writers.Markdown (writeMarkdown, writePlain) where
import Text.Pandoc.Definition
import Text.Pandoc.Walk
import Text.Pandoc.Templates (renderTemplate')
import Text.Pandoc.Shared
import Text.Pandoc.Writers.Shared
import Text.Pandoc.Options
import Text.Pandoc.Parsing hiding (blankline, blanklines, char, space)
import Data.Maybe (fromMaybe)
import Data.List ( group, stripPrefix, find, intersperse, transpose, sortBy )
import Data.Char ( isSpace, isPunctuation )
import Data.Ord ( comparing )
import Text.Pandoc.Pretty
import Control.Monad.State
import Text.Pandoc.Writers.HTML (writeHtmlString)
import Text.Pandoc.Readers.TeXMath (texMathToInlines)
import Text.HTML.TagSoup (parseTags, isTagText, Tag(..))
import Network.URI (isURI)
import Data.Default
import Data.Yaml (Value(Object,String,Array,Bool,Number))
import qualified Data.HashMap.Strict as H
import qualified Data.Vector as V
import qualified Data.Text as T

type Notes = [[Block]]
type Refs = [([Inline], Target)]
data WriterState = WriterState { stNotes           :: Notes
                               , stRefs            :: Refs
                               , stRefShortcutable :: Bool
                               , stInList          :: Bool
                               , stIds             :: [String]
                               , stPlain           :: Bool }
instance Default WriterState
  where def = WriterState{ stNotes = [], stRefs = [], stRefShortcutable = True,
                           stInList = False, stIds = [], stPlain = False }

-- | Convert Pandoc to Markdown.
writeMarkdown :: WriterOptions -> Pandoc -> String
writeMarkdown opts document =
  evalState (pandocToMarkdown opts{
                  writerWrapText = writerWrapText opts &&
                  not (isEnabled Ext_hard_line_breaks opts) }
             document) def

-- | Convert Pandoc to plain text (like markdown, but without links,
-- pictures, or inline formatting).
writePlain :: WriterOptions -> Pandoc -> String
writePlain opts document =
  evalState (pandocToMarkdown opts document) def{ stPlain = True }

pandocTitleBlock :: Doc -> [Doc] -> Doc -> Doc
pandocTitleBlock tit auths dat =
  hang 2 (text "% ") tit <> cr <>
  hang 2 (text "% ") (vcat $ map nowrap auths) <> cr <>
  hang 2 (text "% ") dat <> cr

mmdTitleBlock :: Value -> Doc
mmdTitleBlock (Object hashmap) =
  vcat $ map go $ sortBy (comparing fst) $ H.toList hashmap
  where go (k,v) =
          case (text (T.unpack k), v) of
               (k', Array vec)
                 | V.null vec     -> empty
                 | otherwise      -> k' <> ":" <> space <>
                                      hcat (intersperse "; "
                                           (map fromstr $ V.toList vec))
               (_, String "")  -> empty
               (k', x)         -> k' <> ":" <> space <> nest 2 (fromstr x)
        fromstr (String s) = text (removeBlankLines $ T.unpack s)
        fromstr (Bool b)   = text (show b)
        fromstr (Number n) = text (show n)
        fromstr _          = empty
        -- blank lines not allowed in MMD metadata - we replace with .
        removeBlankLines   = trimr . unlines . map (\x ->
                               if all isSpace x then "." else x) . lines
mmdTitleBlock _ = empty

plainTitleBlock :: Doc -> [Doc] -> Doc -> Doc
plainTitleBlock tit auths dat =
  tit <> cr <>
  (hcat (intersperse (text "; ") auths)) <> cr <>
  dat <> cr

yamlMetadataBlock :: Value -> Doc
yamlMetadataBlock v = "---" $$ (jsonToYaml v) $$ "..."

jsonToYaml :: Value -> Doc
jsonToYaml (Object hashmap) =
  vcat $ map (\(k,v) ->
          case (text (T.unpack k), v, jsonToYaml v) of
               (k', Array vec, x)
                 | V.null vec     -> empty
                 | otherwise      -> (k' <> ":") $$ x
               (k', Object _, x)  -> (k' <> ":") $$ nest 2 x
               (_, String "", _)  -> empty
               (k', _, x)         -> k' <> ":" <> space <> hang 2 "" x)
       $ sortBy (comparing fst) $ H.toList hashmap
jsonToYaml (Array vec) =
  vcat $ map (\v -> hang 2 "- " (jsonToYaml v)) $ V.toList vec
jsonToYaml (String "") = empty
jsonToYaml (String s) =
  case T.unpack s of
     x | '\n' `elem` x -> hang 2 ("|" <> cr) $ text x
       | not (any isPunctuation x) -> text x
       | otherwise     -> text $ "'" ++ substitute "'" "''" x ++ "'"
jsonToYaml (Bool b) = text $ show b
jsonToYaml (Number n) = text $ show n
jsonToYaml _ = empty

-- | Return markdown representation of document.
pandocToMarkdown :: WriterOptions -> Pandoc -> State WriterState String
pandocToMarkdown opts (Pandoc meta blocks) = do
  let colwidth = if writerWrapText opts
                    then Just $ writerColumns opts
                    else Nothing
  isPlain <- gets stPlain
  metadata <- metaToJSON opts
               (fmap (render colwidth) . blockListToMarkdown opts)
               (fmap (render colwidth) . inlineListToMarkdown opts)
               meta
  let title' = maybe empty text $ getField "title" metadata
  let authors' = maybe [] (map text) $ getField "author" metadata
  let date' = maybe empty text $ getField "date" metadata
  let titleblock = case writerStandalone opts of
                        True | isPlain ->
                                plainTitleBlock title' authors' date'
                             | isEnabled Ext_yaml_metadata_block opts ->
                                 yamlMetadataBlock metadata
                             | isEnabled Ext_pandoc_title_block opts ->
                                 pandocTitleBlock title' authors' date'
                             | isEnabled Ext_mmd_title_block opts ->
                                 mmdTitleBlock metadata
                             | otherwise -> empty
                        False -> empty
  let headerBlocks = filter isHeaderBlock blocks
  let toc = if writerTableOfContents opts
               then tableOfContents opts headerBlocks
               else empty
  -- Strip off final 'references' header if markdown citations enabled
  let blocks' = if isEnabled Ext_citations opts
                   then case reverse blocks of
                             (Div (_,["references"],_) _):xs -> reverse xs
                             _ -> blocks
                   else blocks
  body <- blockListToMarkdown opts blocks'
  st <- get
  notes' <- notesToMarkdown opts (reverse $ stNotes st)
  st' <- get  -- note that the notes may contain refs
  refs' <- refsToMarkdown opts (reverse $ stRefs st')
  let render' :: Doc -> String
      render' = render colwidth
  let main = render' $ body <>
               (if isEmpty notes' then empty else blankline <> notes') <>
               (if isEmpty refs' then empty else blankline <> refs')
  let context  = defField "toc" (render' toc)
               $ defField "body" main
               $ (if isNullMeta meta
                     then id
                     else defField "titleblock" (render' titleblock))
               $ metadata
  if writerStandalone opts
     then return $ renderTemplate' (writerTemplate opts) context
     else return main

-- | Return markdown representation of reference key table.
refsToMarkdown :: WriterOptions -> Refs -> State WriterState Doc
refsToMarkdown opts refs = mapM (keyToMarkdown opts) refs >>= return . vcat

-- | Return markdown representation of a reference key.
keyToMarkdown :: WriterOptions
              -> ([Inline], (String, String))
              -> State WriterState Doc
keyToMarkdown opts (label, (src, tit)) = do
  label' <- inlineListToMarkdown opts label
  let tit' = if null tit
                then empty
                else space <> "\"" <> text tit <> "\""
  return $ nest 2 $ hang 2
            ("[" <> label' <> "]:" <> space) (text src <> tit')

-- | Return markdown representation of notes.
notesToMarkdown :: WriterOptions -> [[Block]] -> State WriterState Doc
notesToMarkdown opts notes =
  mapM (\(num, note) -> noteToMarkdown opts num note) (zip [1..] notes) >>=
  return . vsep

-- | Return markdown representation of a note.
noteToMarkdown :: WriterOptions -> Int -> [Block] -> State WriterState Doc
noteToMarkdown opts num blocks = do
  contents  <- blockListToMarkdown opts blocks
  let num' = text $ writerIdentifierPrefix opts ++ show num
  let marker = if isEnabled Ext_footnotes opts
                  then text "[^" <> num' <> text "]:"
                  else text "[" <> num' <> text "]"
  let markerSize = 4 + offset num'
  let spacer = case writerTabStop opts - markerSize of
                     n | n > 0  -> text $ replicate n ' '
                     _          -> text " "
  return $ if isEnabled Ext_footnotes opts
              then hang (writerTabStop opts) (marker <> spacer) contents
              else marker <> spacer <> contents

-- | Escape special characters for Markdown.
escapeString :: WriterOptions -> String -> String
escapeString opts = escapeStringUsing markdownEscapes
  where markdownEscapes = ('<', "&lt;") : ('>', "&gt;") :
                          backslashEscapes specialChars
        specialChars =
                (if isEnabled Ext_superscript opts
                    then ('^':)
                    else id) .
                (if isEnabled Ext_subscript opts
                    then ('~':)
                    else id) .
                (if isEnabled Ext_tex_math_dollars opts
                    then ('$':)
                    else id) $
                "\\`*_[]#"

-- | Construct table of contents from list of header blocks.
tableOfContents :: WriterOptions -> [Block] -> Doc
tableOfContents opts headers =
  let opts' = opts { writerIgnoreNotes = True }
      contents = BulletList $ map (elementToListItem opts) $ hierarchicalize headers
  in  evalState (blockToMarkdown opts' contents) def

-- | Converts an Element to a list item for a table of contents,
elementToListItem :: WriterOptions -> Element -> [Block]
elementToListItem opts (Sec lev _ _ headerText subsecs)
  = Plain headerText :
    [ BulletList (map (elementToListItem opts) subsecs) |
      not (null subsecs) && lev < writerTOCDepth opts ]
elementToListItem _ (Blk _) = []

attrsToMarkdown :: Attr -> Doc
attrsToMarkdown attribs = braces $ hsep [attribId, attribClasses, attribKeys]
        where attribId = case attribs of
                                ([],_,_) -> empty
                                (i,_,_)  -> "#" <> text i
              attribClasses = case attribs of
                                (_,[],_) -> empty
                                (_,cs,_) -> hsep $
                                            map (text . ('.':))
                                            cs
              attribKeys = case attribs of
                                (_,_,[]) -> empty
                                (_,_,ks) -> hsep $
                                            map (\(k,v) -> text k
                                              <> "=\"" <> text v <> "\"") ks

-- | Ordered list start parser for use in Para below.
olMarker :: Parser [Char] ParserState Char
olMarker = do (start, style', delim) <- anyOrderedListMarker
              if delim == Period &&
                          (style' == UpperAlpha || (style' == UpperRoman &&
                          start `elem` [1, 5, 10, 50, 100, 500, 1000]))
                          then spaceChar >> spaceChar
                          else spaceChar

-- | True if string begins with an ordered list marker
beginsWithOrderedListMarker :: String -> Bool
beginsWithOrderedListMarker str =
  case runParser olMarker defaultParserState "para start" (take 10 str) of
         Left  _  -> False
         Right _  -> True

-- | Convert Pandoc block element to markdown.
blockToMarkdown :: WriterOptions -- ^ Options
                -> Block         -- ^ Block element
                -> State WriterState Doc
blockToMarkdown _ Null = return empty
blockToMarkdown opts (Div attrs ils) = do
  contents <- blockListToMarkdown opts ils
  return $ if isEnabled Ext_raw_html opts &&
                isEnabled Ext_markdown_in_html_blocks opts
              then tagWithAttrs "div" attrs <> blankline <>
                      contents <> blankline <> "</div>" <> blankline
              else contents <> blankline
blockToMarkdown opts (Plain inlines) = do
  contents <- inlineListToMarkdown opts inlines
  -- escape if para starts with ordered list marker
  st <- get
  let colwidth = if writerWrapText opts
                    then Just $ writerColumns opts
                    else Nothing
  let rendered = render colwidth contents
  let escapeDelimiter (x:xs) | x `elem` (".()" :: String) = '\\':x:xs
                             | otherwise                  = x : escapeDelimiter xs
      escapeDelimiter []                                  = []
  let contents' = if isEnabled Ext_all_symbols_escapable opts &&
                     not (stPlain st) && beginsWithOrderedListMarker rendered
                     then text $ escapeDelimiter rendered
                     else contents
  return $ contents' <> cr
-- title beginning with fig: indicates figure
blockToMarkdown opts (Para [Image alt (src,'f':'i':'g':':':tit)]) =
  blockToMarkdown opts (Para [Image alt (src,tit)])
blockToMarkdown opts (Para inlines) =
  (<> blankline) `fmap` blockToMarkdown opts (Plain inlines)
blockToMarkdown opts (RawBlock f str)
  | f == "html" = do
    plain <- gets stPlain
    return $ if plain
                then empty
                else if isEnabled Ext_markdown_attribute opts
                        then text (addMarkdownAttribute str) <> text "\n"
                        else text str <> text "\n"
  | f `elem` ["latex", "tex", "markdown"] = do
    plain <- gets stPlain
    return $ if plain
                then empty
                else text str <> text "\n"
blockToMarkdown _ (RawBlock _ _) = return empty
blockToMarkdown opts HorizontalRule = do
  return $ blankline <> text (replicate (writerColumns opts) '-') <> blankline
blockToMarkdown opts (Header level attr inlines) = do
  plain <- gets stPlain
  -- we calculate the id that would be used by auto_identifiers
  -- so we know whether to print an explicit identifier
  ids <- gets stIds
  let autoId = uniqueIdent inlines ids
  modify $ \st -> st{ stIds = autoId : ids }
  let attr' = case attr of
                   ("",[],[]) -> empty
                   (id',[],[]) | isEnabled Ext_auto_identifiers opts
                                 && id' == autoId -> empty
                   (id',_,_)   | isEnabled Ext_mmd_header_identifiers opts ->
                                    space <> brackets (text id')
                   _ | isEnabled Ext_header_attributes opts ->
                                    space <> attrsToMarkdown attr
                     | otherwise -> empty
  contents <- inlineListToMarkdown opts $
                 if level == 1 && plain
                    then capitalize inlines
                    else inlines
  let setext = writerSetextHeaders opts
  return $ nowrap
         $ case level of
            1 | plain -> blanklines 3 <> contents <> blanklines 2
              | setext ->
                  contents <> attr' <> cr <> text (replicate (offset contents) '=') <>
                  blankline
            2 | plain -> blanklines 2 <> contents <> blankline
              | setext ->
                  contents <> attr' <> cr <> text (replicate (offset contents) '-') <>
                  blankline
            -- ghc interprets '#' characters in column 1 as linenum specifiers.
            _ | plain || isEnabled Ext_literate_haskell opts ->
                contents <> blankline
            _ -> text (replicate level '#') <> space <> contents <> attr' <> blankline
blockToMarkdown opts (CodeBlock (_,classes,_) str)
  | "haskell" `elem` classes && "literate" `elem` classes &&
    isEnabled Ext_literate_haskell opts =
  return $ prefixed "> " (text str) <> blankline
blockToMarkdown opts (CodeBlock attribs str) = return $
  case attribs == nullAttr of
     False | isEnabled Ext_backtick_code_blocks opts ->
          backticks <> attrs <> cr <> text str <> cr <> backticks <> blankline
           | isEnabled Ext_fenced_code_blocks opts ->
          tildes <> attrs <> cr <> text str <> cr <> tildes <> blankline
     _ -> nest (writerTabStop opts) (text str) <> blankline
   where tildes    = text $ case [ln | ln <- lines str, all (=='~') ln] of
                               [] -> "~~~~"
                               xs -> case maximum $ map length xs of
                                          n | n < 3 -> "~~~~"
                                            | otherwise -> replicate (n+1) '~'
         backticks = text $ case [ln | ln <- lines str, all (=='`') ln] of
                               [] -> "```"
                               xs -> case maximum $ map length xs of
                                          n | n < 3 -> "```"
                                            | otherwise -> replicate (n+1) '`'
         attrs  = if isEnabled Ext_fenced_code_attributes opts
                     then nowrap $ " " <> attrsToMarkdown attribs
                     else case attribs of
                                (_,(cls:_),_) -> " " <> text cls
                                _             -> empty
blockToMarkdown opts (BlockQuote blocks) = do
  plain <- gets stPlain
  -- if we're writing literate haskell, put a space before the bird tracks
  -- so they won't be interpreted as lhs...
  let leader = if isEnabled Ext_literate_haskell opts
                  then " > "
                  else if plain then "  " else "> "
  contents <- blockListToMarkdown opts blocks
  return $ (prefixed leader contents) <> blankline
blockToMarkdown opts t@(Table caption aligns widths headers rows) =  do
  caption' <- inlineListToMarkdown opts caption
  let caption'' = if null caption || not (isEnabled Ext_table_captions opts)
                     then empty
                     else blankline <> ": " <> caption' <> blankline
  rawHeaders <- mapM (blockListToMarkdown opts) headers
  rawRows <- mapM (mapM (blockListToMarkdown opts)) rows
  let isSimple = all (==0) widths
  let isPlainBlock (Plain _) = True
      isPlainBlock _         = False
  let hasBlocks = not (all isPlainBlock $ concat . concat $ headers:rows)
  (nst,tbl) <- case True of
                _ | isSimple &&
                    isEnabled Ext_simple_tables opts -> fmap (nest 2,) $
                         pandocTable opts (all null headers) aligns widths
                             rawHeaders rawRows
                  | isSimple &&
                    isEnabled Ext_pipe_tables opts -> fmap (id,) $
                         pipeTable (all null headers) aligns rawHeaders rawRows
                  | not hasBlocks &&
                    isEnabled Ext_multiline_tables opts -> fmap (nest 2,) $
                         pandocTable opts (all null headers) aligns widths
                             rawHeaders rawRows
                  | isEnabled Ext_grid_tables opts -> fmap (id,) $
                         gridTable opts (all null headers) aligns widths
                             rawHeaders rawRows
                  | otherwise -> fmap (id,) $
                         return $ text $ writeHtmlString def
                                $ Pandoc nullMeta [t]
  return $ nst $ tbl $$ blankline $$ caption'' $$ blankline
blockToMarkdown opts (BulletList items) = do
  contents <- inList $ mapM (bulletListItemToMarkdown opts) items
  return $ cat contents <> blankline
blockToMarkdown opts (OrderedList (start,sty,delim) items) = do
  let start' = if isEnabled Ext_startnum opts then start else 1
  let sty'   = if isEnabled Ext_fancy_lists opts then sty else DefaultStyle
  let delim' = if isEnabled Ext_fancy_lists opts then delim else DefaultDelim
  let attribs = (start', sty', delim')
  let markers  = orderedListMarkers attribs
  let markers' = map (\m -> if length m < 3
                               then m ++ replicate (3 - length m) ' '
                               else m) markers
  contents <- inList $
              mapM (\(item, num) -> orderedListItemToMarkdown opts item num) $
              zip markers' items
  return $ cat contents <> blankline
blockToMarkdown opts (DefinitionList items) = do
  contents <- inList $ mapM (definitionListItemToMarkdown opts) items
  return $ cat contents <> blankline

inList :: State WriterState a -> State WriterState a
inList p = do
  oldInList <- gets stInList
  modify $ \st -> st{ stInList = True }
  res <- p
  modify $ \st -> st{ stInList = oldInList }
  return res

addMarkdownAttribute :: String -> String
addMarkdownAttribute s =
  case span isTagText $ reverse $ parseTags s of
       (xs,(TagOpen t attrs:rest)) ->
            renderTags' $ reverse rest ++ (TagOpen t attrs' : reverse xs)
              where attrs' = ("markdown","1"):[(x,y) | (x,y) <- attrs,
                                 x /= "markdown"]
       _ -> s

pipeTable :: Bool -> [Alignment] -> [Doc] -> [[Doc]] -> State WriterState Doc
pipeTable headless aligns rawHeaders rawRows = do
  let sp = text " "
  let blockFor AlignLeft   x y = lblock (x + 2) (sp <> y) <> lblock 0 empty
      blockFor AlignCenter x y = cblock (x + 2) (sp <> y) <> lblock 0 empty
      blockFor AlignRight  x y = rblock (x + 2) (sp <> y) <> lblock 0 empty
      blockFor _           x y = lblock (x + 2) (sp <> y) <> lblock 0 empty
  let widths = map (max 3 . maximum . map offset) $ transpose (rawHeaders : rawRows)
  let torow cs = nowrap $ text "|" <>
                    hcat (intersperse (text "|") $
                          zipWith3 blockFor aligns widths (map chomp cs))
                    <> text "|"
  let toborder (a, w) = text $ case a of
                             AlignLeft    -> ':':replicate (w + 1) '-'
                             AlignCenter  -> ':':replicate w '-' ++ ":"
                             AlignRight   -> replicate (w + 1) '-' ++ ":"
                             AlignDefault -> replicate (w + 2) '-'
  -- note:  pipe tables can't completely lack a
  -- header; for a headerless table, we need a header of empty cells.
  -- see jgm/pandoc#1996.
  let header = if headless
                  then torow (replicate (length aligns) empty)
                  else torow rawHeaders
  let border = nowrap $ text "|" <> hcat (intersperse (text "|") $
                        map toborder $ zip aligns widths) <> text "|"
  let body   = vcat $ map torow rawRows
  return $ header $$ border $$ body

pandocTable :: WriterOptions -> Bool -> [Alignment] -> [Double]
            -> [Doc] -> [[Doc]] -> State WriterState Doc
pandocTable opts headless aligns widths rawHeaders rawRows =  do
  let isSimple = all (==0) widths
  let alignHeader alignment = case alignment of
                                AlignLeft    -> lblock
                                AlignCenter  -> cblock
                                AlignRight   -> rblock
                                AlignDefault -> lblock
  let numChars = maximum . map offset
  let widthsInChars = if isSimple
                         then map ((+2) . numChars)
                              $ transpose (rawHeaders : rawRows)
                         else map
                              (floor . (fromIntegral (writerColumns opts) *))
                              widths
  let makeRow = hcat . intersperse (lblock 1 (text " ")) .
                   (zipWith3 alignHeader aligns widthsInChars)
  let rows' = map makeRow rawRows
  let head' = makeRow rawHeaders
  let maxRowHeight = maximum $ map height (head':rows')
  let underline = cat $ intersperse (text " ") $
                  map (\width -> text (replicate width '-')) widthsInChars
  let border = if maxRowHeight > 1
                  then text (replicate (sum widthsInChars +
                          length widthsInChars - 1) '-')
                  else if headless
                          then underline
                          else empty
  let head'' = if headless
                  then empty
                  else border <> cr <> head'
  let body = if maxRowHeight > 1
                then vsep rows'
                else vcat rows'
  let bottom = if headless
                  then underline
                  else border
  return $ head'' $$ underline $$ body $$ bottom

gridTable :: WriterOptions -> Bool -> [Alignment] -> [Double]
          -> [Doc] -> [[Doc]] -> State WriterState Doc
gridTable opts headless _aligns widths headers' rawRows =  do
  let numcols = length headers'
  let widths' = if all (==0) widths
                   then replicate numcols (1.0 / fromIntegral numcols)
                   else widths
  let widthsInChars = map (floor . (fromIntegral (writerColumns opts) *)) widths'
  let hpipeBlocks blocks = hcat [beg, middle, end]
        where h       = maximum (map height blocks)
              sep'    = lblock 3 $ vcat (map text $ replicate h " | ")
              beg     = lblock 2 $ vcat (map text $ replicate h "| ")
              end     = lblock 2 $ vcat (map text $ replicate h " |")
              middle  = chomp $ hcat $ intersperse sep' blocks
  let makeRow = hpipeBlocks . zipWith lblock widthsInChars
  let head' = makeRow headers'
  let rows' = map (makeRow . map chomp) rawRows
  let border ch = char '+' <> char ch <>
                  (hcat $ intersperse (char ch <> char '+' <> char ch) $
                          map (\l -> text $ replicate l ch) widthsInChars) <>
                  char ch <> char '+'
  let body = vcat $ intersperse (border '-') rows'
  let head'' = if headless
                  then empty
                  else head' $$ border '='
  return $ border '-' $$ head'' $$ body $$ border '-'

-- | Convert bullet list item (list of blocks) to markdown.
bulletListItemToMarkdown :: WriterOptions -> [Block] -> State WriterState Doc
bulletListItemToMarkdown opts items = do
  contents <- blockListToMarkdown opts items
  let sps = replicate (writerTabStop opts - 2) ' '
  let start = text ('-' : ' ' : sps)
  -- remove trailing blank line if it is a tight list
  let contents' = case reverse items of
                       (BulletList xs:_) | isTightList xs ->
                            chomp contents <> cr
                       (OrderedList _ xs:_) | isTightList xs ->
                            chomp contents <> cr
                       _ -> contents
  return $ hang (writerTabStop opts) start $ contents' <> cr

-- | Convert ordered list item (a list of blocks) to markdown.
orderedListItemToMarkdown :: WriterOptions -- ^ options
                          -> String        -- ^ list item marker
                          -> [Block]       -- ^ list item (list of blocks)
                          -> State WriterState Doc
orderedListItemToMarkdown opts marker items = do
  contents <- blockListToMarkdown opts items
  let sps = case length marker - writerTabStop opts of
                   n | n > 0 -> text $ replicate n ' '
                   _         -> text " "
  let start = text marker <> sps
  return $ hang (writerTabStop opts) start $ contents <> cr

-- | Convert definition list item (label, list of blocks) to markdown.
definitionListItemToMarkdown :: WriterOptions
                             -> ([Inline],[[Block]])
                             -> State WriterState Doc
definitionListItemToMarkdown opts (label, defs) = do
  labelText <- inlineListToMarkdown opts label
  defs' <- mapM (mapM (blockToMarkdown opts)) defs
  if isEnabled Ext_definition_lists opts
     then do
       let tabStop = writerTabStop opts
       st <- get
       let leader  = if stPlain st then "   " else ":  "
       let sps = case writerTabStop opts - 3 of
                      n | n > 0   -> text $ replicate n ' '
                      _           -> text " "
       if isEnabled Ext_compact_definition_lists opts
          then do
            let contents = vcat $ map (\d -> hang tabStop (leader <> sps)
                                $ vcat d <> cr) defs'
            return $ nowrap labelText <> cr <> contents <> cr
          else do
            let contents = vcat $ map (\d -> hang tabStop (leader <> sps)
                                $ vcat d <> cr) defs'
            let isTight = case defs of
                               ((Plain _ : _): _) -> True
                               _ -> False
            return $ blankline <> nowrap labelText <>
                     (if isTight then cr else blankline) <> contents <> blankline
     else do
       return $ nowrap labelText <> text "  " <> cr <>
                vsep (map vsep defs') <> blankline

-- | Convert list of Pandoc block elements to markdown.
blockListToMarkdown :: WriterOptions -- ^ Options
                    -> [Block]       -- ^ List of block elements
                    -> State WriterState Doc
blockListToMarkdown opts blocks =
  mapM (blockToMarkdown opts) (fixBlocks blocks) >>= return . cat
    -- insert comment between list and indented code block, or the
    -- code block will be treated as a list continuation paragraph
    where fixBlocks (b : CodeBlock attr x : rest)
            | (not (isEnabled Ext_fenced_code_blocks opts) || attr == nullAttr)
                && isListBlock b = b : commentSep : CodeBlock attr x :
                                   fixBlocks rest
          fixBlocks (b1@(BulletList _) : b2@(BulletList _) : bs) =
               b1 : commentSep : fixBlocks (b2:bs)
          fixBlocks (b1@(OrderedList _ _) : b2@(OrderedList _ _) : bs) =
               b1 : commentSep : fixBlocks (b2:bs)
          fixBlocks (b1@(DefinitionList _) : b2@(DefinitionList _) : bs) =
               b1 : commentSep : fixBlocks (b2:bs)
          fixBlocks (x : xs)             = x : fixBlocks xs
          fixBlocks []                   = []
          isListBlock (BulletList _)     = True
          isListBlock (OrderedList _ _)  = True
          isListBlock (DefinitionList _) = True
          isListBlock _                  = False
          commentSep                     = RawBlock "html" "<!-- -->\n"

-- | Get reference for target; if none exists, create unique one and return.
--   Prefer label if possible; otherwise, generate a unique key.
getReference :: [Inline] -> Target -> State WriterState [Inline]
getReference label (src, tit) = do
  st <- get
  case find ((== (src, tit)) . snd) (stRefs st) of
    Just (ref, _) -> return ref
    Nothing       -> do
      let label' = case find ((== label) . fst) (stRefs st) of
                      Just _ -> -- label is used; generate numerical label
                             case find (\n -> notElem [Str (show n)]
                                                      (map fst (stRefs st)))
                                       [1..(10000 :: Integer)] of
                                  Just x  -> [Str (show x)]
                                  Nothing -> error "no unique label"
                      Nothing -> label
      modify (\s -> s{ stRefs = (label', (src,tit)) : stRefs st })
      return label'

-- | Convert list of Pandoc inline elements to markdown.
inlineListToMarkdown :: WriterOptions -> [Inline] -> State WriterState Doc
inlineListToMarkdown opts lst = do
  inlist <- gets stInList
  go (if inlist then avoidBadWrapsInList lst else lst)
  where go [] = return empty
        go (i:is) = case i of
            (Link _ _) -> case is of
                -- If a link is followed by another link or '[' we don't shortcut
                (Link _ _):_                  -> unshortcutable
                Space:(Link _ _):_            -> unshortcutable
                Space:(Str('[':_)):_          -> unshortcutable
                Space:(RawInline _ ('[':_)):_ -> unshortcutable
                Space:(Cite _ _):_            -> unshortcutable
                (Cite _ _):_                  -> unshortcutable
                Str ('[':_):_                 -> unshortcutable
                (RawInline _ ('[':_)):_       -> unshortcutable
                (RawInline _ (' ':'[':_)):_   -> unshortcutable
                _                             -> shortcutable
            _ -> shortcutable
          where shortcutable = liftM2 (<>) (inlineToMarkdown opts i) (go is)
                unshortcutable = do
                    iMark <- withState (\s -> s { stRefShortcutable = False })
                                       (inlineToMarkdown opts i)
                    modify (\s -> s {stRefShortcutable = True })
                    fmap (iMark <>) (go is)

avoidBadWrapsInList :: [Inline] -> [Inline]
avoidBadWrapsInList [] = []
avoidBadWrapsInList (Space:Str ('>':cs):xs) =
  Str (' ':'>':cs) : avoidBadWrapsInList xs
avoidBadWrapsInList (Space:Str [c]:[])
  | c `elem` ['-','*','+'] = Str [' ', c] : []
avoidBadWrapsInList (Space:Str [c]:Space:xs)
  | c `elem` ['-','*','+'] = Str [' ', c] : Space : avoidBadWrapsInList xs
avoidBadWrapsInList (Space:Str cs:Space:xs)
  | isOrderedListMarker cs = Str (' ':cs) : Space : avoidBadWrapsInList xs
avoidBadWrapsInList (Space:Str cs:[])
  | isOrderedListMarker cs = Str (' ':cs) : []
avoidBadWrapsInList (x:xs) = x : avoidBadWrapsInList xs

isOrderedListMarker :: String -> Bool
isOrderedListMarker xs = (last xs `elem` ['.',')']) &&
              isRight (runParserT (anyOrderedListMarker >> eof)
                       defaultParserState "" xs)

isRight :: Either a b -> Bool
isRight (Right _) = True
isRight (Left  _) = False

escapeSpaces :: Inline -> Inline
escapeSpaces (Str s) = Str $ substitute " " "\\ " s
escapeSpaces Space = Str "\\ "
escapeSpaces x = x

-- | Convert Pandoc inline element to markdown.
inlineToMarkdown :: WriterOptions -> Inline -> State WriterState Doc
inlineToMarkdown opts (Span attrs ils) = do
  plain <- gets stPlain
  contents <- inlineListToMarkdown opts ils
  return $ if not plain &&
              (isEnabled Ext_raw_html opts || isEnabled Ext_native_spans opts)
              then tagWithAttrs "span" attrs <> contents <> text "</span>"
              else contents
inlineToMarkdown opts (Emph lst) = do
  plain <- gets stPlain
  contents <- inlineListToMarkdown opts lst
  return $ if plain
              then "_" <> contents <> "_"
              else "*" <> contents <> "*"
inlineToMarkdown opts (Strong lst) = do
  plain <- gets stPlain
  if plain
     then inlineListToMarkdown opts $ capitalize lst
     else do
       contents <- inlineListToMarkdown opts lst
       return $ "**" <> contents <> "**"
inlineToMarkdown opts (Strikeout lst) = do
  contents <- inlineListToMarkdown opts lst
  return $ if isEnabled Ext_strikeout opts
              then "~~" <> contents <> "~~"
              else if isEnabled Ext_raw_html opts
                       then "<s>" <> contents <> "</s>"
                       else contents
inlineToMarkdown opts (Superscript lst) = do
  contents <- inlineListToMarkdown opts $ walk escapeSpaces lst
  return $ if isEnabled Ext_superscript opts
              then "^" <> contents <> "^"
              else if isEnabled Ext_raw_html opts
                       then "<sup>" <> contents <> "</sup>"
                       else contents
inlineToMarkdown opts (Subscript lst) = do
  contents <- inlineListToMarkdown opts $ walk escapeSpaces lst
  return $ if isEnabled Ext_subscript opts
              then "~" <> contents <> "~"
              else if isEnabled Ext_raw_html opts
                       then "<sub>" <> contents <> "</sub>"
                       else contents
inlineToMarkdown opts (SmallCaps lst) = do
  plain <- gets stPlain
  if not plain &&
     (isEnabled Ext_raw_html opts || isEnabled Ext_native_spans opts)
     then do
       contents <- inlineListToMarkdown opts lst
       return $ tagWithAttrs "span"
                 ("",[],[("style","font-variant:small-caps;")])
             <> contents <> text "</span>"
     else inlineListToMarkdown opts $ capitalize lst
inlineToMarkdown opts (Quoted SingleQuote lst) = do
  contents <- inlineListToMarkdown opts lst
  return $ "‘" <> contents <> "’"
inlineToMarkdown opts (Quoted DoubleQuote lst) = do
  contents <- inlineListToMarkdown opts lst
  return $ "“" <> contents <> "”"
inlineToMarkdown opts (Code attr str) = do
  let tickGroups = filter (\s -> '`' `elem` s) $ group str
  let longest    = if null tickGroups
                     then 0
                     else maximum $ map length tickGroups
  let marker     = replicate (longest + 1) '`'
  let spacer     = if (longest == 0) then "" else " "
  let attrs      = if isEnabled Ext_inline_code_attributes opts && attr /= nullAttr
                      then attrsToMarkdown attr
                      else empty
  plain <- gets stPlain
  if plain
     then return $ text str
     else return $ text (marker ++ spacer ++ str ++ spacer ++ marker) <> attrs
inlineToMarkdown opts (Str str) = do
  st <- get
  if stPlain st
     then return $ text str
     else return $ text $ escapeString opts str
inlineToMarkdown opts (Math InlineMath str)
  | isEnabled Ext_tex_math_dollars opts =
      return $ "$" <> text str <> "$"
  | isEnabled Ext_tex_math_single_backslash opts =
      return $ "\\(" <> text str <> "\\)"
  | isEnabled Ext_tex_math_double_backslash opts =
      return $ "\\\\(" <> text str <> "\\\\)"
  | otherwise = do
    plain <- gets stPlain
    inlineListToMarkdown opts $
      (if plain then makeMathPlainer else id) $
      texMathToInlines InlineMath str
inlineToMarkdown opts (Math DisplayMath str)
  | isEnabled Ext_tex_math_dollars opts =
      return $ "$$" <> text str <> "$$"
  | isEnabled Ext_tex_math_single_backslash opts =
      return $ "\\[" <> text str <> "\\]"
  | isEnabled Ext_tex_math_double_backslash opts =
      return $ "\\\\[" <> text str <> "\\\\]"
  | otherwise = (\x -> cr <> x <> cr) `fmap`
        inlineListToMarkdown opts (texMathToInlines DisplayMath str)
inlineToMarkdown opts (RawInline f str) = do
  plain <- gets stPlain
  if not plain &&
     ( f == "markdown" ||
       (isEnabled Ext_raw_tex opts && (f == "latex" || f == "tex")) ||
       (isEnabled Ext_raw_html opts && f == "html") )
    then return $ text str
    else return empty
inlineToMarkdown opts (LineBreak) = do
  plain <- gets stPlain
  if plain || isEnabled Ext_hard_line_breaks opts
     then return cr
     else return $
          if isEnabled Ext_escaped_line_breaks opts
             then "\\" <> cr
             else "  " <> cr
inlineToMarkdown _ Space = return space
inlineToMarkdown opts (Cite [] lst) = inlineListToMarkdown opts lst
inlineToMarkdown opts (Cite (c:cs) lst)
  | not (isEnabled Ext_citations opts) = inlineListToMarkdown opts lst
  | otherwise =
      if citationMode c == AuthorInText
         then do
           suffs <- inlineListToMarkdown opts $ citationSuffix c
           rest <- mapM convertOne cs
           let inbr = suffs <+> joincits rest
               br   = if isEmpty inbr then empty else char '[' <> inbr <> char ']'
           return $ text ("@" ++ citationId c) <+> br
         else do
           cits <- mapM convertOne (c:cs)
           return $ text "[" <> joincits cits <> text "]"
  where
        joincits = hcat . intersperse (text "; ") . filter (not . isEmpty)
        convertOne Citation { citationId      = k
                            , citationPrefix  = pinlines
                            , citationSuffix  = sinlines
                            , citationMode    = m }
                               = do
           pdoc <- inlineListToMarkdown opts pinlines
           sdoc <- inlineListToMarkdown opts sinlines
           let k' = text (modekey m ++ "@" ++ k)
               r = case sinlines of
                        Str (y:_):_ | y `elem` (",;]@" :: String) -> k' <> sdoc
                        _                                         -> k' <+> sdoc
           return $ pdoc <+> r
        modekey SuppressAuthor = "-"
        modekey _              = ""
inlineToMarkdown opts (Link txt (src, tit)) = do
  plain <- gets stPlain
  linktext <- inlineListToMarkdown opts txt
  let linktitle = if null tit
                     then empty
                     else text $ " \"" ++ tit ++ "\""
  let srcSuffix = fromMaybe src (stripPrefix "mailto:" src)
  let useAuto = isURI src &&
                case txt of
                      [Str s] | escapeURI s == srcSuffix -> True
                      _                                  -> False
  let useRefLinks = writerReferenceLinks opts && not useAuto
  shortcutable <- gets stRefShortcutable
  let useShortcutRefLinks = shortcutable &&
                            isEnabled Ext_shortcut_reference_links opts
  ref <- if useRefLinks then getReference txt (src, tit) else return []
  reftext <- inlineListToMarkdown opts ref
  return $ if useAuto
              then if plain
                      then text srcSuffix
                      else "<" <> text srcSuffix <> ">"
              else if useRefLinks
                      then let first  = "[" <> linktext <> "]"
                               second = if txt == ref
                                           then if useShortcutRefLinks
                                                   then ""
                                                   else "[]"
                                           else "[" <> reftext <> "]"
                           in  first <> second
                      else if plain
                              then linktext
                              else "[" <> linktext <> "](" <>
                                   text src <> linktitle <> ")"
inlineToMarkdown opts (Image alternate (source, tit)) = do
  plain <- gets stPlain
  let txt = if null alternate || alternate == [Str source]
                                 -- to prevent autolinks
               then [Str ""]
               else alternate
  linkPart <- inlineToMarkdown opts (Link txt (source, tit))
  return $ if plain
              then "[" <> linkPart <> "]"
              else "!" <> linkPart
inlineToMarkdown opts (Note contents) = do
  modify (\st -> st{ stNotes = contents : stNotes st })
  st <- get
  let ref = text $ writerIdentifierPrefix opts ++ show (length $ stNotes st)
  if isEnabled Ext_footnotes opts
     then return $ "[^" <> ref <> "]"
     else return $ "[" <> ref <> "]"

makeMathPlainer :: [Inline] -> [Inline]
makeMathPlainer = walk go
  where
  go (Emph xs) = Span nullAttr xs
  go x = x