aboutsummaryrefslogtreecommitdiff
path: root/src/Text/Pandoc/Writers/Markdown.hs
blob: 2ad9eabd986c78a0cb76749d1d563c3c23ca5add (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
{-# LANGUAGE MultiWayIf          #-}
{-# LANGUAGE OverloadedStrings   #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE TupleSections       #-}
{-# LANGUAGE ViewPatterns        #-}
{- |
   Module      : Text.Pandoc.Writers.Markdown
   Copyright   : Copyright (C) 2006-2021 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,
  writePlain) where
import Control.Monad.Reader
import Control.Monad.State.Strict
import Data.Default
import Data.List (intersperse, sortOn, transpose)
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 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)
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_pipe_tables $
                   enableExtension Ext_intraword_underscores $
                     writerExtensions 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 if isNothing $ foldM needsDoubleQuotes True x
           then "\"" <> fmap escapeInDoubleQuotes x <> "\""
           else x
    where
      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
  toc <- if writerTableOfContents opts
         then blockToMarkdown opts ( 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 spacer = case writerTabStop opts - markerSize of
                     n | n > 0  -> literal $ T.replicate n " "
                     _ -> literal " "
  return $ if isEnabled Ext_footnotes opts
              then hang (writerTabStop opts) (marker <> spacer) contents
              else marker <> spacer <> contents

attrsToMarkdown :: Attr -> Doc Text
attrsToMarkdown attribs = braces $ hsep [attribId, attribClasses, attribKeys]
        where attribId = case attribs of
                                ("",_,_) -> empty
                                (i,_,_)  -> "#" <> escAttr i
              attribClasses = case attribs of
                                (_,[],_) -> empty
                                (_,cs,_) -> hsep $
                                            map (escAttr . ("."<>))
                                            cs
              attribKeys = case attribs of
                                (_,_,[]) -> empty
                                (_,_,ks) -> hsep $
                                            map (\(k,v) -> escAttr k
                                              <> "=\"" <>
                                              escAttr v <> "\"") ks
              escAttr          = mconcat . map escAttrChar . T.unpack
              escAttrChar '"'  = literal "\\\""
              escAttrChar '\\' = literal "\\\\"
              escAttrChar c    = literal $ T.singleton c

-- | (Code) blocks with a single class can just use it standalone,
-- no need to bother with curly braces.
classOrAttrsToMarkdown :: Attr -> Doc Text
classOrAttrsToMarkdown ("",[cls],_) = literal cls
classOrAttrsToMarkdown attrs = attrsToMarkdown attrs

linkAttributes :: WriterOptions -> Attr -> Doc Text
linkAttributes opts attr =
  if isEnabled Ext_link_attributes opts && attr /= nullAttr
     then attrsToMarkdown attr
     else empty

-- | Ordered list start parser for use in Para below.
olMarker :: Parser 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' _ Null = return empty
blockToMarkdown' opts (Div attrs ils) = do
  contents <- blockListToMarkdown opts ils
  variant <- asks envVariant
  return $
    case () of
         _ | isEnabled Ext_fenced_divs opts &&
             attrs /= nullAttr ->
                nowrap (literal ":::" <+> classOrAttrsToMarkdown attrs) $$
                chomp contents $$
                literal ":::" <> 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 x `elemText` ".()"
                                         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
-- title beginning with fig: indicates figure
blockToMarkdown' opts (Para [Image attr alt (src,tgt@(T.stripPrefix "fig:" -> Just tit))])
  | isEnabled Ext_raw_html opts &&
    not (isEnabled Ext_link_attributes opts) &&
    attr /= nullAttr = -- use raw HTML
    (<> blankline) . literal . T.strip <$>
      writeHtml5String opts{ writerTemplate = Nothing }
        (Pandoc nullMeta [Para [Image attr alt (src,tgt)]])
  | otherwise = blockToMarkdown opts (Para [Image attr alt (src,tit)])
blockToMarkdown' opts (Para inlines) =
  (<> blankline) `fmap` blockToMarkdown opts (Plain inlines)
blockToMarkdown' opts (LineBlock lns) =
  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 -> renderEmpty
    Commonmark
      | f `elem` ["gfm", "commonmark", "commonmark_x", "markdown"]
         -> return $ literal str <> literal "\n"
    Markdown
      | f `elem` ["markdown", "markdown_github", "markdown_phpextra",
                  "markdown_mmd", "markdown_strict"]
         -> return $ literal str <> literal "\n"
    _ | isEnabled Ext_raw_attribute opts -> rawAttribBlock
      | 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"
    _ -> renderEmpty
blockToMarkdown' opts HorizontalRule =
  return $ blankline <> literal (T.replicate (writerColumns opts) "-") <> 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
  -- 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
                                 && id' == autoId -> empty
                   (id',_,_)   | isEnabled Ext_mmd_header_identifiers opts ->
                                    space <> brackets (literal id')
                   _ | isEnabled Ext_header_attributes opts ->
                                    space <> attrsToMarkdown 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
            _ -> 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
     _ -> 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
                 then nowrap $ " " <> classOrAttrsToMarkdown attribs
                 else case attribs of
                            (_,cls:_,_) -> " " <> literal cls
                            _             -> 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 $ prefixed leader contents <> blankline
blockToMarkdown' opts t@(Table _ blkCapt specs thead tbody tfoot) = do
  let (caption, aligns, widths, headers, rows) = toLegacyTable blkCapt specs thead tbody tfoot
  let numcols = maximum (length aligns :| length widths :
                           map length (headers:rows))
  caption' <- inlineListToMarkdown opts caption
  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
  let isPlainBlock (Plain _) = True
      isPlainBlock _         = False
  let hasBlocks = not (all isPlainBlock $ concat . concat $ 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
  (nst,tbl) <-
     case True of
          _ | isSimple &&
              isEnabled Ext_simple_tables opts -> do
                rawHeaders <- padRow <$> mapM (blockListToMarkdown opts) headers
                rawRows <- mapM (fmap padRow . mapM (blockListToMarkdown opts))
                           rows
                (nest 2,) <$> pandocTable opts False (all null headers)
                                aligns' widths' rawHeaders rawRows
            | isSimple &&
              isEnabled Ext_pipe_tables opts -> do
                rawHeaders <- padRow <$> mapM (blockListToMarkdown opts) headers
                rawRows <- mapM (fmap padRow . mapM (blockListToMarkdown opts))
                           rows
                (id,) <$> pipeTable (all null headers) aligns' rawHeaders rawRows
            | not hasBlocks &&
              isEnabled Ext_multiline_tables opts -> do
                rawHeaders <- padRow <$> mapM (blockListToMarkdown opts) headers
                rawRows <- mapM (fmap padRow . mapM (blockListToMarkdown opts))
                           rows
                (nest 2,) <$> pandocTable opts True (all null headers)
                                aligns' widths' rawHeaders rawRows
            | isEnabled Ext_grid_tables opts &&
               writerColumns opts >= 8 * numcols -> (id,) <$>
                gridTable opts blockListToMarkdown
                  (all null headers) aligns' widths' headers rows
            | hasSimpleCells &&
              isEnabled Ext_pipe_tables opts -> do
                rawHeaders <- padRow <$> mapM (blockListToMarkdown opts) headers
                rawRows <- mapM (fmap padRow . mapM (blockListToMarkdown opts))
                           rows
                (id,) <$> pipeTable (all null headers) aligns' rawHeaders rawRows
            | isEnabled Ext_raw_html opts -> fmap (id,) $
                   literal <$>
                   writeHtml5String opts{ writerTemplate = Nothing } (Pandoc nullMeta [t])
            | otherwise -> return (id, literal "[TABLE]")
  return $ nst (tbl $$ caption'') $$ 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' = if isEnabled Ext_fancy_lists opts then delim else DefaultDelim
  let attribs = (start', sty', delim')
  let markers  = orderedListMarkers attribs
  let 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

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

pipeTable :: PandocMonad m
          => Bool -> [Alignment] -> [Doc Text] -> [[Doc Text]]
          -> MD m (Doc Text)
pipeTable headless aligns rawHeaders rawRows = do
  let sp = literal " "
  let blockFor AlignLeft   x y = lblock (x + 2) (sp <> y) <> lblock 0 empty
      blockFor AlignCenter x y = cblock (x + 2) (sp <> y <> sp) <> lblock 0 empty
      blockFor AlignRight  x y = rblock (x + 2) (y <> sp) <> lblock 0 empty
      blockFor _           x y = lblock (x + 2) (sp <> y) <> lblock 0 empty
  let widths = map (max 3 . maybe 3 maximum . nonEmpty . map offset) $
                     transpose (rawHeaders : rawRows)
  let torow cs = nowrap $ literal "|" <>
                    hcat (intersperse (literal "|") $
                          zipWith3 blockFor aligns widths (map chomp cs))
                    <> literal "|"
  let toborder a w = literal $ case a of
                          AlignLeft    -> ":" <> T.replicate (w + 1) "-"
                          AlignCenter  -> ":" <> T.replicate w "-" <> ":"
                          AlignRight   -> T.replicate (w + 1) "-" <> ":"
                          AlignDefault -> T.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 $ literal "|" <> hcat (intersperse (literal "|") $
                        zipWith toborder aligns widths) <> literal "|"
  let body   = vcat $ map torow rawRows
  return $ header $$ border $$ body

pandocTable :: PandocMonad m
            => WriterOptions -> Bool -> Bool -> [Alignment] -> [Double]
            -> [Doc Text] -> [[Doc Text]] -> MD m (Doc Text)
pandocTable opts multiline 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
  -- Number of characters per column necessary to output every cell
  -- without requiring a line break.
  -- The @+2@ is needed for specifying the alignment.
  let numChars    = (+ 2) . maybe 0 maximum . nonEmpty . map offset
  -- Number of characters per column necessary to output every cell
  -- without requiring a line break *inside a word*.
  -- The @+2@ is needed for specifying the alignment.
  let minNumChars = (+ 2) . maybe 0 maximum . nonEmpty . map minOffset
  let columns = transpose (rawHeaders : rawRows)
  -- minimal column width without wrapping a single word
  let relWidth w col =
         max (floor $ fromIntegral (writerColumns opts - 1) * w)
             (if writerWrapText opts == WrapAuto
                 then minNumChars col
                 else numChars col)
  let widthsInChars
        | isSimple  = map numChars columns
        | otherwise = zipWith relWidth widths columns
  let makeRow = hcat . intersperse (lblock 1 (literal " ")) .
                   zipWith3 alignHeader aligns widthsInChars
  let rows' = map makeRow rawRows
  let head' = makeRow rawHeaders
  let underline = mconcat $ intersperse (literal " ") $
                  map (\width -> literal (T.replicate width "-")) widthsInChars
  let border
        | multiline = literal (T.replicate (sum widthsInChars +
                        length widthsInChars - 1) "-")
        | headless  = underline
        | otherwise = empty
  let head'' = if headless
                  then empty
                  else border <> cr <> head'
  let body = if multiline
                then vsep rows' $$
                     if length rows' < 2
                        then blankline -- #4578
                        else empty
                else vcat rows'
  let bottom = if headless
                  then underline
                  else border
  return $ head'' $$ underline $$ body $$ bottom

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
  let exts = writerExtensions opts
  contents <- blockListToMarkdown opts $ taskListItemToAscii exts bs
  let sps = T.replicate (writerTabStop opts - 2) " "
  let start = literal $ "- " <> 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 (writerTabStop opts) 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
  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 = 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  = if variant == PlainText then "   " else ":  "
       let sps = case writerTabStop opts - 3 of
                      n | n > 0   -> literal $ T.replicate n " "
                      _ -> literal " "
       let isTight = case defs of
                        ((Plain _ : _): _) -> True
                        _                  -> False
       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 = (if isTight then vcat else vsep) $ map
                            (\d -> hang tabStop (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) | 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        = Null
        | 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