content: {-# LANGUAGE MultiWayIf          #-}
  {-# LANGUAGE OverloadedStrings   #-}
  {-# LANGUAGE ScopedTypeVariables #-}
  {-# LANGUAGE TupleSections       #-}
  {-# LANGUAGE BangPatterns        #-}
  {- |
     Module      : Text.Pandoc.Writers.Markdown
     Copyright   : Copyright (C) 2006-2024 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:  <https://daringfireball.net/projects/markdown/>
  -}
  module Text.Pandoc.Writers.Markdown (
    writeMarkdown,
    writeCommonMark,
    writeMarkua,
    writePlain) where
  import Control.Monad (foldM, zipWithM, MonadPlus(..), when, liftM)
  import Control.Monad.Reader ( asks, MonadReader(local) )
  import Control.Monad.State.Strict ( gets, modify )
  import Data.Default
  import Data.List (intersperse, sortOn, union, find)
  import Data.List.NonEmpty (nonEmpty, NonEmpty(..))
  import qualified Data.Map as M
  import Data.Maybe (fromMaybe, mapMaybe, isNothing)
  import qualified Data.Set as Set
  import Data.Text (Text)
  import Data.Char (isSpace)
  import qualified Data.Text as T
  import Text.HTML.TagSoup (Tag (..), isTagText, parseTags)
  import Text.Pandoc.Class.PandocMonad (PandocMonad, report)
  import Text.Pandoc.Definition
  import Text.Pandoc.Logging
  import Text.Pandoc.Options
  import Text.Pandoc.Parsing hiding (blankline, blanklines, char, space)
  import Text.DocLayout
  import Text.Pandoc.Shared
  import Text.Pandoc.Writers.Shared
  import Text.Pandoc.Templates (renderTemplate)
  import Text.DocTemplates (Val(..), Context(..), FromContext(..))
  import Text.Pandoc.Walk
  import Text.Pandoc.Writers.HTML (writeHtml5String)
  import Text.Pandoc.Writers.Markdown.Inline (inlineListToMarkdown,
                                              linkAttributes,
                                              attrsToMarkdown,
                                              attrsToMarkua)
  import Text.Pandoc.Writers.Markdown.Table (pipeTable, pandocTable)
  import Text.Pandoc.Writers.Markdown.Types (MarkdownVariant(..),
                                             WriterState(..),
                                             WriterEnv(..),
                                             Ref, Refs, MD, evalMD)
  
  -- | Convert Pandoc to Markdown.
  writeMarkdown :: PandocMonad m => WriterOptions -> Pandoc -> m Text
  writeMarkdown opts document =
    evalMD (pandocToMarkdown opts{
               writerWrapText = if isEnabled Ext_hard_line_breaks opts
                                then WrapNone
                                else writerWrapText opts }
               document) def def
  
  -- | Convert Pandoc to plain text (like markdown, but without links,
  -- pictures, or inline formatting).
  writePlain :: PandocMonad m => WriterOptions -> Pandoc -> m Text
  writePlain opts document =
    evalMD (pandocToMarkdown opts document) def{ envVariant = PlainText } def
  
  -- | Convert Pandoc to Commonmark.
  writeCommonMark :: PandocMonad m => WriterOptions -> Pandoc -> m Text
  writeCommonMark opts document =
    evalMD (pandocToMarkdown opts' document) def{ envVariant = Commonmark } def
   where
    opts' = opts{ writerExtensions =
                     -- These extensions can't be enabled or disabled
                     -- for commonmark because they're part of the core;
                     -- we set them here so that escapeText will behave
                     -- properly.
                     enableExtension Ext_all_symbols_escapable $
                     enableExtension Ext_intraword_underscores $
                       writerExtensions opts ,
                  writerWrapText =
                    if isEnabled Ext_hard_line_breaks opts
                       then WrapNone
                       else writerWrapText opts }
  
  -- | Convert Pandoc to Markua.
  writeMarkua :: PandocMonad m => WriterOptions -> Pandoc -> m Text
  writeMarkua opts document =
    evalMD (pandocToMarkdown opts' document) def{ envVariant = Markua } def
   where
    opts' = opts{ writerExtensions =
                    enableExtension Ext_hard_line_breaks $
                    enableExtension Ext_pipe_tables $
                    -- required for fancy list enumerators
                    enableExtension Ext_fancy_lists $
                    enableExtension Ext_startnum $
                    enableExtension Ext_strikeout $
                    enableExtension Ext_subscript $
                    enableExtension Ext_superscript $
                    enableExtension Ext_definition_lists $
                    enableExtension Ext_smart $
                    enableExtension Ext_footnotes
                      mempty ,
                  writerWrapText =
                    if isEnabled Ext_hard_line_breaks opts
                       then WrapNone
                       else writerWrapText opts }
  
  
  pandocTitleBlock :: Doc Text -> [Doc Text] -> Doc Text -> Doc Text
  pandocTitleBlock tit auths dat =
    hang 2 (text "% ") tit <> cr <>
    hang 2 (text "% ") (vcat $ map nowrap auths) <> cr <>
    hang 2 (text "% ") dat <> cr
  
  mmdTitleBlock :: Context Text -> Doc Text
  mmdTitleBlock (Context hashmap) =
    vcat $ map go $ sortOn (T.toCaseFold . fst) $ M.toList hashmap
    where go (k,v) =
            case (text (T.unpack k), v) of
                 (k', ListVal xs)
                   | null xs        -> empty
                   | otherwise      -> k' <> ":" <> space <>
                                        hcat (intersperse "; " $
                                              mapMaybe fromVal xs)
                 (k', SimpleVal x)
                        | isEmpty x -> empty
                        | otherwise -> k' <> ":" <> space <>
                                       nest 2 (removeBlankLines (chomp x))
                 _                  -> empty
          removeBlankLines BlankLines{} = cr <> text "." <> cr
          removeBlankLines (Concat x y) = removeBlankLines x <>
                                          removeBlankLines y
          removeBlankLines x            = x
  
  plainTitleBlock :: Doc Text -> [Doc Text] -> Doc Text -> Doc Text
  plainTitleBlock tit auths dat =
    tit <> cr <>
    hcat (intersperse (text "; ") auths) <> cr <>
    dat <> cr
  
  yamlMetadataBlock :: Context Text -> Doc Text
  yamlMetadataBlock v = "---" $$ contextToYaml v $$ "---"
  
  contextToYaml :: Context Text -> Doc Text
  contextToYaml (Context o) =
    vcat $ map keyvalToYaml $ sortOn (T.toCaseFold . fst) $ M.toList o
   where
    keyvalToYaml (k,v) =
            case (text (T.unpack k), v) of
                 (k', ListVal vs)
                   | null vs        -> empty
                   | otherwise      -> (k' <> ":") $$ valToYaml v
                 (k', MapVal (Context m))
                   | M.null m       -> k' <> ": {}"
                   | otherwise      -> (k' <> ":") $$ nest 2 (valToYaml v)
                 (_, SimpleVal x)
                       | isEmpty x  -> empty
                 (_, NullVal)       -> empty
                 (k', _)            -> k' <> ":" <+> hang 2 "" (valToYaml v)
  
  valToYaml :: Val Text -> Doc Text
  valToYaml (ListVal xs) =
    vcat $ map (\v -> hang 2 "- " (valToYaml v)) xs
  valToYaml (MapVal c) = contextToYaml c
  valToYaml (BoolVal True) = "true"
  valToYaml (BoolVal False) = "false"
  valToYaml (SimpleVal x)
    | isEmpty x = empty
    | otherwise =
        if hasNewlines x
           then hang 0 ("|" <> cr) x
           else case x of
                  Text _ t | isSpecialString t ->
                           "\"" <> fmap escapeInDoubleQuotes x <> "\""
                  _ | isNothing (foldM needsDoubleQuotes True x) ->
                           "\"" <> fmap escapeInDoubleQuotes x <> "\""
                    | otherwise -> x
      where
        isSpecialString t = Set.member t specialStrings
        specialStrings = Set.fromList
         ["y", "Y", "yes", "Yes", "YES", "n", "N",
          "no", "No", "NO", "true", "True", "TRUE",
          "false", "False", "FALSE", "on", "On", "ON",
          "off", "Off", "OFF", "null", "Null",
          "NULL", "~", "*"]
        needsDoubleQuotes isFirst t
          = if T.any isBadAnywhere t ||
               (isFirst && T.any isYamlPunct (T.take 1 t))
                then Nothing
                else Just False
        isBadAnywhere '#' = True
        isBadAnywhere ':' = True
        isBadAnywhere _   = False
        hasNewlines NewLine = True
        hasNewlines BlankLines{} = True
        hasNewlines CarriageReturn = True
        hasNewlines (Concat w z) = hasNewlines w || hasNewlines z
        hasNewlines _ = False
        isYamlPunct = (`elem` ['-','?',':',',','[',']','{','}',
                               '#','&','*','!','|','>','\'','"', '%','@','`'])
        escapeInDoubleQuotes = T.replace "\"" "\\\"" . T.replace "\\" "\\\\"
  valToYaml _ = empty
  
  -- | Return markdown representation of document.
  pandocToMarkdown :: PandocMonad m => WriterOptions -> Pandoc -> MD m Text
  pandocToMarkdown opts (Pandoc meta blocks) = do
    let colwidth = if writerWrapText opts == WrapAuto
                      then Just $ writerColumns opts
                      else Nothing
    variant <- asks envVariant
    metadata <- metaToContext'
                 (blockListToMarkdown opts)
                 (inlineListToMarkdown opts)
                 meta
    let title' = fromMaybe empty $ getField "title" metadata
    let authors' = fromMaybe [] $ getField "author" metadata
    let date' = fromMaybe empty $ getField "date" metadata
    let titleblock = case writerTemplate opts of
                          Just _ | variant == PlainText ->
                                   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
                          Nothing -> empty
    let modifyTOC =
          if isEnabled Ext_link_attributes opts || isEnabled Ext_attributes opts
          then id
          else walk $ \inln -> case inln of
            Link _attr contents tgt -> Link nullAttr contents tgt
            _                       -> inln
    toc <- if writerTableOfContents opts
           then blockToMarkdown opts . modifyTOC $ toTableOfContents opts blocks
           else return mempty
    -- Strip off final 'references' header if markdown citations enabled
    let blocks' = if isEnabled Ext_citations opts
                     then case reverse blocks of
                               (Div ("refs",_,_) _):xs -> reverse xs
                               _                       -> blocks
                     else blocks
    body <- blockListToMarkdown opts blocks'
    notesAndRefs' <- notesAndRefs opts
    let main = body <> notesAndRefs'
    let context  = -- for backwards compatibility we populate toc
                   -- with the contents of the toc, rather than a
                   -- boolean:
                   defField "toc" toc
                 $ defField "table-of-contents" toc
                 $ defField "body" main
                 $ (if isNullMeta meta
                       then id
                       else defField "titleblock" titleblock)
                 $ addVariablesToContext opts metadata
    return $ render colwidth $
      case writerTemplate opts of
         Nothing  -> main
         Just tpl -> renderTemplate tpl context
  
  -- | Return markdown representation of reference key table.
  refsToMarkdown :: PandocMonad m => WriterOptions -> Refs -> MD m (Doc Text)
  refsToMarkdown opts refs = vcat <$> mapM (keyToMarkdown opts) refs
  
  -- | Return markdown representation of a reference key.
  keyToMarkdown :: PandocMonad m
                => WriterOptions
                -> Ref
                -> MD m (Doc Text)
  keyToMarkdown opts (label', (src, tit), attr) = do
    let tit' = if T.null tit
                  then empty
                  else space <> "\"" <> literal tit <> "\""
    return $ nest 2 $ hang 2
              ("[" <> literal label' <> "]:" <> space) (literal src <> tit')
              <+> linkAttributes opts attr
  
  -- | Return markdown representation of notes.
  notesToMarkdown :: PandocMonad m => WriterOptions -> [[Block]] -> MD m (Doc Text)
  notesToMarkdown opts notes = do
    n <- gets stNoteNum
    notes' <- zipWithM (noteToMarkdown opts) [n..] notes
    modify $ \st -> st { stNoteNum = stNoteNum st + length notes }
    return $ vsep notes'
  
  -- | Return markdown representation of a note.
  noteToMarkdown :: PandocMonad m => WriterOptions -> Int -> [Block] -> MD m (Doc Text)
  noteToMarkdown opts num blocks = do
    contents  <- blockListToMarkdown opts blocks
    let num' = literal $ writerIdentifierPrefix opts <> tshow num
    let marker = if isEnabled Ext_footnotes opts
                    then literal "[^" <> num' <> literal "]:"
                    else literal "[" <> num' <> literal "]"
    let markerSize = 4 + offset num'
    let hspacer = case writerTabStop opts - markerSize of
                        n | n > 0  -> literal $ T.replicate n " "
                        _ -> literal " "
    let spacer = case blocks of
                      Para{}:_ -> hspacer
                      Plain{}:_ -> hspacer
                      _ -> cr
    return $ if isEnabled Ext_footnotes opts
                then hang (writerTabStop opts) (marker <> spacer) contents
                else marker <> spacer <> contents
  
  -- | (Code) blocks with a single class and no attributes can just use it
  -- standalone, no need to bother with curly braces.
  classOrAttrsToMarkdown :: WriterOptions -> Attr -> Doc Text
  classOrAttrsToMarkdown _ ("",[cls],[]) = literal cls
  classOrAttrsToMarkdown opts attrs = attrsToMarkdown opts attrs
  
  -- | Ordered list start parser for use in Para below.
  olMarker :: Parsec Text ParserState ()
  olMarker = do (start, style', delim) <- anyOrderedListMarker
                if delim == Period &&
                            (style' == UpperAlpha || (style' == UpperRoman &&
                            start `elem` [1, 5, 10, 50, 100, 500, 1000]))
                            then mzero -- it needs 2 spaces anyway
                            else eof
  
  -- | True if string begins with an ordered list marker
  beginsWithOrderedListMarker :: Text -> Bool
  beginsWithOrderedListMarker str =
    case runParser olMarker defaultParserState "para start" (T.take 10 str) of
           Left  _ -> False
           Right _ -> True
  
  notesAndRefs :: PandocMonad m => WriterOptions -> MD m (Doc Text)
  notesAndRefs opts = do
    notes' <- gets stNotes >>= notesToMarkdown opts . reverse
    modify $ \s -> s { stNotes = [] }
    refs' <- gets stRefs >>= refsToMarkdown opts . reverse
    modify $ \s -> s { stPrevRefs = stPrevRefs s ++ stRefs s
                     , stRefs = []}
  
    let endSpacing =
          if | writerReferenceLocation opts == EndOfDocument -> empty
             | isEmpty notes' && isEmpty refs' -> empty
             | otherwise -> blankline
  
    return $
      (if isEmpty notes' then empty else blankline <> notes') <>
      (if isEmpty refs' then empty else blankline <> refs') <>
      endSpacing
  
  -- | Convert Pandoc block element to markdown.
  blockToMarkdown :: PandocMonad m
                  => WriterOptions -- ^ Options
                  -> Block         -- ^ Block element
                  -> MD m (Doc Text)
  blockToMarkdown opts blk =
    local (\env -> env {envBlockLevel = envBlockLevel env + 1}) $
    do doc <- blockToMarkdown' opts blk
       blkLevel <- asks envBlockLevel
       if writerReferenceLocation opts == EndOfBlock && blkLevel == 1
         then notesAndRefs opts >>= (\d -> return $ doc <> d)
         else return doc
  
  blockToMarkdown' :: PandocMonad m
                   => WriterOptions -- ^ Options
                   -> Block         -- ^ Block element
                   -> MD m (Doc Text)
  blockToMarkdown' opts (Div attrs@(_,classes,_) bs)
    | ("sourceCode":_) <- classes
    , [CodeBlock (_,"sourceCode":_,_) _] <- bs
       -- skip pandoc-generated Div wrappers around code blocks
     = blockListToMarkdown opts bs
    | isEnabled Ext_alerts opts
    , (cls:_) <- classes
    , cls `elem` ["note", "tip", "warning", "caution", "important"]
    , (Div ("", ["title"], []) _ : Para ils : bs') <- bs
     = blockToMarkdown' opts $ BlockQuote $
         (Para (RawInline (Format "markdown") (case cls of
           "note" -> "[!NOTE]\n"
           "tip" -> "[!TIP]\n"
           "warning" -> "[!WARNING]\n"
           "caution" -> "[!CAUTION]\n"
           "important" -> "[!IMPORTANT]\n"
           _ -> "[!NOTE]\n") : ils)) : bs'
    | otherwise = do
      contents <- blockListToMarkdown opts bs
      variant <- asks envVariant
      return $
         case () of
             _ | variant == Markua ->
                   case () of
                        () | "blurb" `elem` classes'
                             -> prefixed "B> " contents <> blankline
                           | "aside" `elem` classes'
                             -> prefixed "A> " contents <> blankline
                           -- necessary to enable option to create a bibliography
                           | (take 3 (T.unpack id')) == "ref"
                             -> contents <> blankline
                           | otherwise -> contents <> blankline
               | isEnabled Ext_fenced_divs opts ->
                    let attrsToMd = if variant == Commonmark
                                    then attrsToMarkdown opts
                                    else classOrAttrsToMarkdown opts
                        divNesting = computeDivNestingLevel bs
                        numcolons = 3 + divNesting
                        colons = literal $ T.replicate numcolons ":"
                    in nowrap (colons <+> attrsToMd attrs) $$
                       chomp contents $$
                       colons <> blankline
               | isEnabled Ext_native_divs opts ||
                 (isEnabled Ext_raw_html opts &&
                  (variant == Commonmark ||
                   isEnabled Ext_markdown_in_html_blocks opts)) ->
                    tagWithAttrs "div" attrs <> blankline <>
                    contents <> blankline <> "</div>" <> blankline
               | isEnabled Ext_raw_html opts &&
                 isEnabled Ext_markdown_attribute opts ->
                    tagWithAttrs "div" attrs' <> blankline <>
                    contents <> blankline <> "</div>" <> blankline
               | otherwise -> contents <> blankline
           where (id',classes',kvs') = attrs
                 attrs' = (id',classes',("markdown","1"):kvs')
  blockToMarkdown' opts (Plain inlines) = do
    -- escape if para starts with ordered list marker
    variant <- asks envVariant
    let escapeMarker = T.concatMap $ \x -> if T.any (== x) ".()"
                                           then T.pack ['\\', x]
                                           else T.singleton x
    let startsWithSpace (Space:_)     = True
        startsWithSpace (SoftBreak:_) = True
        startsWithSpace _             = False
    let inlines' =
          if variant == PlainText
             then inlines
             else case inlines of
                    (Str t:ys)
                      | null ys || startsWithSpace ys
                      , beginsWithOrderedListMarker t
                      -> RawInline (Format "markdown") (escapeMarker t):ys
                    (Str t:_)
                      | t == "+" || t == "-" ||
                        (t == "%" && isEnabled Ext_pandoc_title_block opts &&
                                     isEnabled Ext_all_symbols_escapable opts)
                      -> RawInline (Format "markdown") "\\" : inlines
                    _ -> inlines
    contents <- inlineListToMarkdown opts inlines'
    return $ contents <> cr
  blockToMarkdown' opts (Para inlines) =
    (<> blankline) `fmap` blockToMarkdown opts (Plain inlines)
  blockToMarkdown' opts (LineBlock lns) = do
    variant <- asks envVariant
    case variant of
      PlainText -> do
        let emptyToBlank l = if isEmpty l then blankline else l
        mdLines <- mapM (liftM emptyToBlank . inlineListToMarkdown opts) lns
        return $ vcat mdLines <> blankline
      _ ->
        if isEnabled Ext_line_blocks opts
        then do
          mdLines <- mapM (inlineListToMarkdown opts) lns
          return $ vcat (map (hang 2 (literal "| ")) mdLines) <> blankline
        else blockToMarkdown opts $ linesToPara lns
  blockToMarkdown' opts b@(RawBlock f str) = do
    variant <- asks envVariant
    let Format fmt = f
    let rawAttribBlock = return $
           (literal "```{=" <> literal fmt <> "}") $$
           literal str $$
           (literal "```" <> literal "\n")
    let renderEmpty = mempty <$ report (BlockNotRendered b)
    case variant of
      PlainText
        | f == "plain" -> return $ nest 0 (literal str) <> literal "\n"
      Commonmark
        | f `elem` ["gfm", "commonmark", "commonmark_x", "markdown"]
           -> return $ nest 0 (literal str) $$ blankline
        | f `elem` ["html", "html5", "html4"]
           -> return $ literal (removeBlankLinesInHTML str) $$ blankline
      Markdown
        | f `elem` ["markdown", "markdown_github", "markdown_phpextra",
                    "markdown_mmd", "markdown_strict"]
          -- the 'nest 0' ensures that leading and trailing newlines
          -- don't get collapsed. See #10477 for context;
           -> return $ nest 0 (literal str) <> literal "\n"
      Markua -> renderEmpty
      _ | f `elem` ["html", "html5", "html4"]
        , isEnabled Ext_markdown_attribute opts
           -> return $ literal (addMarkdownAttribute str) <> literal "\n"
        | f `elem` ["html", "html5", "html4"]
        , isEnabled Ext_raw_html opts
           -> return $ literal str <> literal "\n"
        | f `elem` ["latex", "tex"]
        , isEnabled Ext_raw_tex opts
           -> return $ literal str <> literal "\n"
        | isEnabled Ext_raw_attribute opts -> rawAttribBlock
      _ -> renderEmpty
  blockToMarkdown' opts HorizontalRule = do
    variant <- asks envVariant
    let indicator = case variant of
                          Markua -> "* * *"
                          _ -> T.replicate (writerColumns opts) "-"
    return $ blankline <> literal indicator <> blankline
  blockToMarkdown' opts (Header level attr inlines) = do
    -- first, if we're putting references at the end of a section, we
    -- put them here.
    blkLevel <- asks envBlockLevel
    refs <- if writerReferenceLocation opts == EndOfSection && blkLevel == 1
            then notesAndRefs opts
            else return empty
    variant <- asks envVariant
    -- we calculate the id that would be used by auto_identifiers
    -- or gfm_auto_identifiers
    -- so we know whether to print an explicit identifier
    ids <- gets stIds
    let autoId = uniqueIdent (writerExtensions opts) inlines ids
    modify $ \st -> st{ stIds = Set.insert autoId ids }
    let attr' = case attr of
                     ("",[],[]) -> empty
                     (id',[],[]) | (isEnabled Ext_auto_identifiers opts
                                    || isEnabled Ext_gfm_auto_identifiers opts)
                                   && id' == autoId -> empty
                     (id',_,_)   | isEnabled Ext_mmd_header_identifiers opts ->
                                      space <> brackets (literal id')
                     _ | variant == Markua -> attrsToMarkua opts attr
                       | isEnabled Ext_header_attributes opts ||
                         isEnabled Ext_attributes opts ->
                                      space <> attrsToMarkdown opts attr
                       | otherwise -> empty
    contents <- inlineListToMarkdown opts $
                   -- ensure no newlines; see #3736
                   walk lineBreakToSpace $
                     if level == 1 && variant == PlainText &&
                        isEnabled Ext_gutenberg opts
                        then capitalize inlines
                        else inlines
  
    let setext = writerSetextHeaders opts
    when (not setext && isEnabled Ext_literate_haskell opts) $
      report $ ATXHeadingInLHS level (render Nothing contents)
  
    let hdr = nowrap $ case level of
              1 | variant == PlainText ->
                  if isEnabled Ext_gutenberg opts
                     then blanklines 3 <> contents <> blanklines 2
                     else contents <> blankline
                | setext ->
                    contents <> attr' <> cr <> literal (T.replicate (offset contents) "=") <>
                    blankline
              2 | variant == PlainText ->
                  if isEnabled Ext_gutenberg opts
                     then blanklines 2 <> contents <> blankline
                     else contents <> blankline
                | setext ->
                    contents <> attr' <> cr <> literal (T.replicate (offset contents) "-") <>
                    blankline
              -- ghc interprets '#' characters in column 1 as linenum specifiers.
              _ | variant == PlainText || isEnabled Ext_literate_haskell opts ->
                  contents <> blankline
              _ | variant == Markua -> attr' <> cr <> literal (T.replicate level "#")
                                          <> space <> contents <> blankline
              _ -> literal (T.replicate level "#") <> space <> contents <> attr' <> blankline
  
    return $ refs <> hdr
  blockToMarkdown' opts (CodeBlock (_,classes,_) str)
    | "haskell" `elem` classes && "literate" `elem` classes &&
      isEnabled Ext_literate_haskell opts =
    return $ prefixed "> " (literal str) <> blankline
  blockToMarkdown' opts (CodeBlock attribs str) = do
    variant <- asks envVariant
    return $
     case attribs == nullAttr of
       False | variant == Commonmark ||
               isEnabled Ext_backtick_code_blocks opts ->
            backticks <> attrs <> cr <> literal str <> cr <> backticks <> blankline
             | isEnabled Ext_fenced_code_blocks opts ->
            tildes <> attrs <> cr <> literal str <> cr <> tildes <> blankline
       _ | variant == Markua -> blankline <> attrsToMarkua opts attribs <> cr <> backticks <> cr <>
                                  literal str <> cr <> backticks <> cr <> blankline
         | otherwise -> nest (writerTabStop opts) (literal str) <> blankline
     where
       endlineLen c = maybe 3 ((+1) . maximum) $ nonEmpty
                          [T.length ln
                           | ln <- map trim (T.lines str)
                           , T.pack [c,c,c] `T.isPrefixOf` ln
                           , T.all (== c) ln]
       endline c = literal $ T.replicate (endlineLen c) $ T.singleton c
       backticks = endline '`'
       tildes = endline '~'
       attrs  = if isEnabled Ext_fenced_code_attributes opts ||
                   isEnabled Ext_attributes opts
                   then nowrap $ " " <> classOrAttrsToMarkdown opts attribs
                   else
                     let (_,cls,_) = attribs
                      in case getLangFromClasses cls of
                                Just l -> " " <> literal l
                                Nothing -> empty
  blockToMarkdown' opts (BlockQuote blocks) = do
    variant <- asks envVariant
    -- if we're writing literate haskell, put a space before the bird tracks
    -- so they won't be interpreted as lhs...
    let leader
          | isEnabled Ext_literate_haskell opts = " > "
          | variant == PlainText = "  "
          | otherwise            = "> "
    contents <- blockListToMarkdown opts blocks
    return $ text leader <> prefixed leader contents <> blankline
  blockToMarkdown' opts t@(Table attr blkCapt specs thead tbody tfoot) = do
    let (caption, aligns, widths, headers, rows) = toLegacyTable blkCapt specs thead tbody tfoot
    let isColRowSpans (Cell _ _ rs cs _) = rs > 1 || cs > 1
    let rowHasColRowSpans (Row _ cs) = any isColRowSpans cs
    let tbodyHasColRowSpans (TableBody _ _ rhs rs) =
          any rowHasColRowSpans rhs || any rowHasColRowSpans rs
    let theadHasColRowSpans (TableHead _ rs) = any rowHasColRowSpans rs
    let tfootHasColRowSpans (TableFoot _ rs) = any rowHasColRowSpans rs
    let hasColRowSpans = theadHasColRowSpans thead ||
                         any tbodyHasColRowSpans tbody ||
                         tfootHasColRowSpans tfoot
    let numcols = maximum (length aligns :| length widths :
                             map length (headers:rows))
    caption' <- inlineListToMarkdown opts caption
    let caption'' = if attr == nullAttr
                       then caption'
                       else caption' <+> attrsToMarkdown opts attr
    let caption'''
          | null caption = blankline
          | isEnabled Ext_table_captions opts
          = blankline $$ (": " <> caption'') $$ blankline
          | otherwise = blankline $$ caption'' $$ blankline
    let hasSimpleCells = onlySimpleTableCells $ headers : rows
    let isSimple = hasSimpleCells && all (==0) widths && not hasColRowSpans
    let isPlainBlock (Plain _) = True
        isPlainBlock _         = False
    let hasBlocks = not (all (all (all isPlainBlock)) $ headers:rows)
    let padRow r = case numcols - length r of
                         x | x > 0 -> r ++ replicate x empty
                           | otherwise -> r
    let aligns' = case numcols - length aligns of
                       x | x > 0 -> aligns ++ replicate x AlignDefault
                         | otherwise -> aligns
    let widths' = case numcols - length widths of
                       x | x > 0 -> widths ++ replicate x 0.0
                         | otherwise -> widths
    let mkTable f = do
         rawHeaders <- padRow <$> mapM (blockListToMarkdown opts) headers
         rawRows <- mapM (fmap padRow . mapM (blockListToMarkdown opts)) rows
         f (all null headers) aligns' widths' rawHeaders rawRows
    case True of
       _ | isSimple &&
           isEnabled Ext_simple_tables opts -> do
             tbl <- mkTable (pandocTable opts False)
             return $ nest 2 (tbl $$ caption''') $$ blankline
         | isSimple &&
           isEnabled Ext_pipe_tables opts -> do
             tbl <- mkTable (pipeTable opts)
             return $ (tbl $$ caption''') $$ blankline
         | not (hasBlocks || hasColRowSpans) &&
           isEnabled Ext_multiline_tables opts -> do
             tbl <- mkTable (pandocTable opts True)
             return $ nest 2 (tbl $$ caption''') $$ blankline
         | isEnabled Ext_grid_tables opts &&
            (hasColRowSpans || writerColumns opts >= 8 * numcols) -> do
             tbl <- gridTable opts blockListToMarkdown
                       specs thead tbody tfoot
             return $ (tbl $$ caption''') $$ blankline
         | hasSimpleCells,
           not hasColRowSpans,
           isEnabled Ext_pipe_tables opts -> do
             tbl <- mkTable (pipeTable opts)
             return $ (tbl $$ caption''') $$ blankline
         | isEnabled Ext_raw_html opts -> do -- HTML fallback
             tbl <- literal . removeBlankLinesInHTML <$>
                       writeHtml5String opts{ writerTemplate = Nothing }
                       (Pandoc nullMeta [t])
             return $ tbl $$ blankline  -- caption is in the HTML table
         | hasSimpleCells,
           hasColRowSpans,
           isEnabled Ext_pipe_tables opts -> do
             -- In this case an approximate pipe table will be rendered,
             -- without col/row spans. This is better than nothing, since
             -- we have no other way to render the table correctly (#11128).
             tbl <- mkTable (pipeTable opts)
             return $ (tbl $$ caption''') $$ blankline
         | otherwise
           -> do
             report (BlockNotRendered t)
             return $ (literal "[TABLE]" $$ caption''') $$ blankline
  blockToMarkdown' opts (BulletList items) = do
    contents <- inList $ mapM (bulletListItemToMarkdown opts) items
    return $ (if isTightList items then vcat else vsep)
                    contents <> blankline
  blockToMarkdown' opts (OrderedList (start,sty,delim) items) = do
    variant <- asks envVariant
    let start' = if variant == Commonmark || isEnabled Ext_startnum opts
                    then start
                    else 1
    let sty'   = if isEnabled Ext_fancy_lists opts then sty else DefaultStyle
    let delim' | isEnabled Ext_fancy_lists opts =
                 case variant of
                     -- Markua supports 'fancy' enumerators, but no TwoParens
                     Markua -> if delim == TwoParens then OneParen else delim
                     _ -> delim
               | variant == Commonmark && --commonmark only supports one paren
                     (delim == OneParen || delim == TwoParens) = OneParen
               | otherwise = DefaultDelim
    let attribs = (start', sty', delim')
    let markers  = orderedListMarkers attribs
    let markers' = case variant of
                          Markua -> markers
                          _ -> map (\m -> if T.length m < 3
                                     then m <> T.replicate (3 - T.length m) " "
                                     else m) markers
    contents <- inList $
                zipWithM (orderedListItemToMarkdown opts) markers' items
    return $ (if isTightList items then vcat else vsep) contents <> blankline
  blockToMarkdown' opts (DefinitionList items) = do
    contents <- inList $ mapM (definitionListItemToMarkdown opts) items
    return $ mconcat contents <> blankline
  blockToMarkdown' opts (Figure figattr capt body) = do
    let combinedAttr imgattr = case imgattr of
          ("", cls, kvs)
            | (figid, [], []) <- figattr
              -> Just (figid, cls, [(k,v) | (k,v) <- kvs
                                          , k /= "alt" ||
                                            v /= "" && v /= trim (stringify capt)])
          _ -> Nothing
    case body of
      [Plain [Image imgAttr alt (src, ttl)]]
        | isEnabled Ext_implicit_figures opts
        , Just imgAttr' <- combinedAttr imgAttr
        , isEnabled Ext_link_attributes opts || imgAttr' == nullAttr
          -> do
            -- use implicit figures if possible
            let tgt' = (src, fromMaybe ttl $ T.stripPrefix "fig:" ttl)
            let descr = case capt of
                          Caption _ bs -> blocksToInlines bs
            -- add alt attribute if image description different from caption,
            -- so this won't be lost:
            let imgAttr'' = case imgAttr' of
                              (i,c,kv)
                                | not (null alt)
                                , Nothing <- lookup "alt" kv
                                , stringify descr /= stringify alt ->
                                   (i, c, ("alt", stringify alt) : kv)
                              _ -> imgAttr'
            contents <- inlineListToMarkdown opts [Image imgAttr'' descr tgt']
            return $ contents <> blankline
      _ ->
        -- fallback to raw html if possible or div otherwise
        if isEnabled Ext_raw_html opts
        then figureToMarkdown opts figattr capt body
        else if (isEnabled Ext_fenced_divs opts || isEnabled Ext_native_divs opts) ||
                    not (isEnabled Ext_implicit_figures opts)
                then blockToMarkdown' opts $ figureDiv figattr capt body
                else blockListToMarkdown opts body
  
  inList :: Monad m => MD m a -> MD m a
  inList p = local (\env -> env {envInList = True}) p
  
  addMarkdownAttribute :: Text -> Text
  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
  
  -- | Converts a figure to Markdown by wrapping it in a div named `figure`.
  figureToMarkdown :: PandocMonad m
                   => WriterOptions
                   -> Attr
                   -> Caption
                   -> [Block]
                   -> MD m (Doc Text)
  figureToMarkdown opts attr@(ident, classes, kvs) capt body
    | isEnabled Ext_raw_html opts =
        (<> blankline) . literal . T.strip <$>
        writeHtml5String
          opts{ writerTemplate = Nothing }
          (Pandoc nullMeta [Figure attr capt body])
    | otherwise = do
        let attr' = (ident, ["figure"] `union` classes, kvs)
        let Caption _mbshort caption = capt
        let captionBs = [Div ("",["caption"],[]) caption | not (null caption)]
        blockToMarkdown' opts (Div attr' (body <> captionBs))
  
  itemEndsWithTightList :: [Block] -> Bool
  itemEndsWithTightList bs =
    case bs of
          [Plain _, BulletList xs]    -> isTightList xs
          [Plain _, OrderedList _ xs] -> isTightList xs
          _                           -> False
  
  -- | Convert bullet list item (list of blocks) to markdown.
  bulletListItemToMarkdown :: PandocMonad m => WriterOptions -> [Block] -> MD m (Doc Text)
  bulletListItemToMarkdown opts bs = do
    variant <- asks envVariant
    let exts = writerExtensions opts
    contents <- blockListToMarkdown opts $ taskListItemToAscii exts bs
    let start = case variant of
                Markua -> "* "
                Commonmark -> "- "
                Markdown
                  | isEnabled Ext_four_space_rule opts
                    -> "- " <> T.replicate (writerTabStop opts - 2) " "
                PlainText
                  | isEnabled Ext_four_space_rule opts
                    -> "- " <> T.replicate (writerTabStop opts - 2) " "
                _ -> "- "
    -- remove trailing blank line if item ends with a tight list
    let contents' = if itemEndsWithTightList bs
                       then chomp contents <> cr
                       else contents
    return $ hang (T.length start) (literal start) contents'
  
  -- | Convert ordered list item (a list of blocks) to markdown.
  orderedListItemToMarkdown :: PandocMonad m
                            => WriterOptions -- ^ options
                            -> Text          -- ^ list item marker
                            -> [Block]       -- ^ list item (list of blocks)
                            -> MD m (Doc Text)
  orderedListItemToMarkdown opts marker bs = do
    let exts = writerExtensions opts
    contents <- blockListToMarkdown opts $ taskListItemToAscii exts bs
    variant <- asks envVariant
    let sps = case writerTabStop opts - T.length marker of
                     n | n > 0 -> literal $ T.replicate n " "
                     _ -> literal " "
    let ind = if isEnabled Ext_four_space_rule opts
                 then writerTabStop opts
                 else max (writerTabStop opts) (T.length marker + 1)
    let start = case variant of
                Markua -> literal marker <> " "
                _      -> literal marker <> sps
    -- remove trailing blank line if item ends with a tight list
    let contents' = if itemEndsWithTightList bs
                       then chomp contents <> cr
                       else contents
    return $ hang ind start contents'
  
  -- | Convert definition list item (label, list of blocks) to markdown.
  definitionListItemToMarkdown :: PandocMonad m
                               => WriterOptions
                               -> ([Inline],[[Block]])
                               -> MD m (Doc Text)
  definitionListItemToMarkdown opts (label, defs) = do
    labelText <- blockToMarkdown opts (Plain label)
    defs' <- mapM (mapM (blockToMarkdown opts)) defs
    if isEnabled Ext_definition_lists opts
       then do
         let tabStop = writerTabStop opts
         variant <- asks envVariant
         let leader  = case variant of
                          PlainText -> " "
                          _ -> ":"
         let leadingChars = case tabStop of
                              -- Always use two leading characters for Markua
                              n | n >= 2 && variant /= Markua -> n
                              _ -> 2
         let sps = literal $ T.replicate (leadingChars - 1) " "
         let isTight = case defs of
                          ((Plain _ : _): _) -> True
                          _                  -> False
         let contents = (if isTight then vcat else vsep) $ map
                         (\d -> hang leadingChars (leader <> sps) $ vcat d)
                         defs'
         return $ blankline <> nowrap labelText $$
                  (if isTight then empty else blankline) <> contents <> blankline
       else
         return $ nowrap (chomp labelText <> literal "  " <> cr) <>
                  vsep (map vsep defs') <> blankline
  
  -- | Convert list of Pandoc block elements to markdown.
  blockListToMarkdown :: PandocMonad m
                      => WriterOptions -- ^ Options
                      -> [Block]       -- ^ List of block elements
                      -> MD m (Doc Text)
  blockListToMarkdown opts blocks = do
    inlist <- asks envInList
    variant <- asks envVariant
    -- a) insert comment between list and indented code block, or the
    -- code block will be treated as a list continuation paragraph
    -- b) change Plain to Para unless it's followed by a RawBlock
    -- or has a list as its parent (#3487)
    let fixBlocks (b : CodeBlock attr x : rest)
         | (not (variant == Commonmark ||
                 isEnabled Ext_backtick_code_blocks opts ||
                   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 (Plain ils : bs@(RawBlock{}:_)) =
             Plain ils : fixBlocks bs
        fixBlocks (Plain ils : bs@(Div{}:_))
            | isEnabled Ext_fenced_divs opts =
             Para ils : fixBlocks bs
        fixBlocks (Plain ils : bs) | inlist =
             Plain ils : fixBlocks bs
        fixBlocks (Plain ils : bs) =
             Para ils : fixBlocks bs
        fixBlocks (r@(RawBlock f raw) : b : bs)
          | not (T.null raw)
          , T.last raw /= '\n' =
          case b of
               Plain{}    -> r : fixBlocks (b:bs)
               RawBlock{} -> r : fixBlocks (b:bs)
               _          -> RawBlock f (raw <> "\n") : fixBlocks (b:bs) -- #4629
        fixBlocks (x : xs)             = x : fixBlocks xs
        fixBlocks []                   = []
        isListBlock (BulletList _)     = True
        isListBlock (OrderedList _ _)  = True
        isListBlock (DefinitionList _) = True
        isListBlock _                  = False
        commentSep
          | variant == PlainText        = Plain []
          | variant == Markua           = Plain []
          | isEnabled Ext_raw_html opts = RawBlock "html" "<!-- -->\n"
          | otherwise                   = RawBlock "markdown" "&nbsp;\n"
    mconcat <$> mapM (blockToMarkdown opts) (fixBlocks blocks)
  
  lineBreakToSpace :: Inline -> Inline
  lineBreakToSpace LineBreak = Space
  lineBreakToSpace SoftBreak = Space
  lineBreakToSpace x         = x
  
  removeBlankLinesInHTML :: Text -> Text
  removeBlankLinesInHTML = T.pack . go False . T.unpack
    where go _ [] = []
          go True ('\n':cs) = "&#10;" <> go False cs
          go False ('\n':cs) = '\n' : go True cs
          go !afternewline (!c:cs)
            | isSpace c = c : go afternewline cs
            | otherwise = c : go False cs
  
  computeDivNestingLevel :: [Block] -> Int
  computeDivNestingLevel = foldr go 0
   where
     go (Div _ bls') n = max (n + 1) (foldr go (n + 1) bls')
     go _ n = n
  
  -- Identify the class in a list of classes that corresponds to
  -- the language syntax.  language-X turns to X.
  getLangFromClasses :: [Text] -> Maybe Text
  getLangFromClasses cs =
    case find ("language-" `T.isPrefixOf`) cs of
      Just x -> Just (T.drop 9 x)
      Nothing ->
        case filter (/= "sourceCode") cs of
          (x:_) -> Just x
          [] -> Nothing
  