aboutsummaryrefslogtreecommitdiff
path: root/src/Text/Pandoc/Writers/HTML.hs
blob: 64eccd35edffec2e751a2c08204b6d2a055ca23e (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
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
{-# LANGUAGE OverloadedStrings, CPP, ViewPatterns, 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.HTML
   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 HTML.
-}
module Text.Pandoc.Writers.HTML (
  writeHtml4,
  writeHtml4String,
  writeHtml5,
  writeHtml5String,
  writeHtmlStringForEPUB,
  writeS5,
  writeSlidy,
  writeSlideous,
  writeDZSlides,
  writeRevealJs
  ) where
import Text.Pandoc.Definition
import Text.Pandoc.Walk
import Data.Monoid ((<>))
import Text.Pandoc.Shared
import Text.Pandoc.Writers.Shared
import Text.Pandoc.Options
import Text.Pandoc.ImageSize
import Text.Pandoc.Templates
import Text.Pandoc.Writers.Math
import Text.Pandoc.Slides
import Text.Pandoc.Highlighting ( highlight, styleToCss,
                                  formatHtmlInline, formatHtmlBlock )
import Text.Pandoc.XML (fromEntities, escapeStringForXML)
import Network.URI ( parseURIReference, URI(..), unEscapeString )
import Network.HTTP ( urlEncode )
import Numeric ( showHex )
import Data.Char ( ord, toLower )
import Data.List ( isPrefixOf, intersperse )
import Data.String ( fromString )
import Data.Maybe ( catMaybes, fromMaybe, isJust )
import Control.Monad.State
import Text.Blaze.Html hiding(contents)
#if MIN_VERSION_blaze_markup(0,6,3)
#else
import Text.Blaze.Internal(preEscapedString)
#endif
#if MIN_VERSION_blaze_html(0,5,1)
import qualified Text.Blaze.XHtml5 as H5
#else
import qualified Text.Blaze.Html5 as H5
#endif
import qualified Text.Blaze.XHtml1.Transitional as H
import qualified Text.Blaze.XHtml1.Transitional.Attributes as A
import Text.Blaze.Html.Renderer.String (renderHtml)
import Text.TeXMath
import Text.XML.Light.Output
import Text.XML.Light (unode, elChildren, unqual)
import qualified Text.XML.Light as XML
import System.FilePath (takeExtension)
import Data.Aeson (Value)
import Control.Monad.Except (throwError)
import Text.Pandoc.Error
import Text.Pandoc.Class (PandocMonad)

data WriterState = WriterState
    { stNotes            :: [Html]  -- ^ List of notes
    , stMath             :: Bool    -- ^ Math is used in document
    , stQuotes           :: Bool    -- ^ <q> tag is used
    , stHighlighting     :: Bool    -- ^ Syntax highlighting is used
    , stSecNum           :: [Int]   -- ^ Number of current section
    , stElement          :: Bool    -- ^ Processing an Element
    , stHtml5            :: Bool    -- ^ Use HTML5
    , stEPUBVersion      :: Maybe EPUBVersion -- ^ EPUB version if for epub
    , stSlideVariant     :: HTMLSlideVariant
    }

defaultWriterState :: WriterState
defaultWriterState = WriterState {stNotes= [], stMath = False, stQuotes = False,
                                  stHighlighting = False, stSecNum = [],
                                  stElement = False, stHtml5 = False,
                                  stEPUBVersion = Nothing,
                                  stSlideVariant = NoSlides}

-- Helpers to render HTML with the appropriate function.

strToHtml :: String -> Html
strToHtml ('\'':xs) = preEscapedString "\'" `mappend` strToHtml xs
strToHtml xs@(_:_)  = case break (=='\'') xs of
                           (_ ,[]) -> toHtml xs
                           (ys,zs) -> toHtml ys `mappend` strToHtml zs
strToHtml [] = ""

-- | Hard linebreak.
nl :: WriterOptions -> Html
nl opts = if writerWrapText opts == WrapNone
             then mempty
             else preEscapedString "\n"

-- | Convert Pandoc document to Html 5 string.
writeHtml5String :: PandocMonad m => WriterOptions -> Pandoc -> m String
writeHtml5String = writeHtmlString'
                      defaultWriterState{ stHtml5 = True }

-- | Convert Pandoc document to Html 5 structure.
writeHtml5 :: PandocMonad m => WriterOptions -> Pandoc -> m Html
writeHtml5 = writeHtml' defaultWriterState{ stHtml5 = True }

-- | Convert Pandoc document to Html 4 string.
writeHtml4String :: PandocMonad m => WriterOptions -> Pandoc -> m String
writeHtml4String = writeHtmlString'
                      defaultWriterState{ stHtml5 = False }

-- | Convert Pandoc document to Html 4 structure.
writeHtml4 :: PandocMonad m => WriterOptions -> Pandoc -> m Html
writeHtml4 = writeHtml' defaultWriterState{ stHtml5 = False }

-- | Convert Pandoc document to Html appropriate for an epub version.
writeHtmlStringForEPUB :: PandocMonad m
                       => EPUBVersion -> WriterOptions -> Pandoc -> m String
writeHtmlStringForEPUB version = writeHtmlString'
                      defaultWriterState{ stHtml5 = version == EPUB3,
                                          stEPUBVersion = Just version }

-- | Convert Pandoc document to Reveal JS HTML slide show.
writeRevealJs :: PandocMonad m
              => WriterOptions -> Pandoc -> m String
writeRevealJs = writeHtmlSlideShow' RevealJsSlides

-- | Convert Pandoc document to S5 HTML slide show.
writeS5 :: PandocMonad m
        => WriterOptions -> Pandoc -> m String
writeS5 = writeHtmlSlideShow' S5Slides

-- | Convert Pandoc document to Slidy HTML slide show.
writeSlidy :: PandocMonad m
           => WriterOptions -> Pandoc -> m String
writeSlidy = writeHtmlSlideShow' SlidySlides

-- | Convert Pandoc document to Slideous HTML slide show.
writeSlideous :: PandocMonad m
              => WriterOptions -> Pandoc -> m String
writeSlideous = writeHtmlSlideShow' SlideousSlides

-- | Convert Pandoc document to DZSlides HTML slide show.
writeDZSlides :: PandocMonad m
              => WriterOptions -> Pandoc -> m String
writeDZSlides = writeHtmlSlideShow' DZSlides

writeHtmlSlideShow' :: PandocMonad m
                    => HTMLSlideVariant -> WriterOptions -> Pandoc -> m String
writeHtmlSlideShow' variant = writeHtmlString'
    defaultWriterState{ stSlideVariant = variant
                      , stHtml5 = case variant of
                                       RevealJsSlides -> True
                                       S5Slides       -> False
                                       SlidySlides    -> False
                                       DZSlides       -> True
                                       SlideousSlides -> False
                                       NoSlides       -> False
                      }

writeHtmlString' :: PandocMonad m
                 => WriterState -> WriterOptions -> Pandoc -> m String
writeHtmlString' st opts d = do
  (body, context) <- evalStateT (pandocToHtml opts d) st
  return $ case writerTemplate opts of
             Nothing  -> renderHtml body
             Just tpl -> renderTemplate' tpl $
                           defField "body" (renderHtml body) context

writeHtml' :: PandocMonad m => WriterState -> WriterOptions -> Pandoc -> m Html
writeHtml' st opts d = do
  (body, context) <- evalStateT (pandocToHtml opts d) st
  return $ case writerTemplate opts of
             Nothing  -> body
             Just tpl -> renderTemplate' tpl $
                           defField "body" (renderHtml body) context

-- result is (title, authors, date, toc, body, new variables)
pandocToHtml :: PandocMonad m
             => WriterOptions
             -> Pandoc
             -> StateT WriterState m (Html, Value)
pandocToHtml opts (Pandoc meta blocks) = do
  metadata <- metaToJSON opts
              (fmap renderHtml . blockListToHtml opts)
              (fmap renderHtml . inlineListToHtml opts)
              meta
  let stringifyHTML = escapeStringForXML . stringify
  let authsMeta = map stringifyHTML $ docAuthors meta
  let dateMeta  = stringifyHTML $ docDate meta
  let slideLevel = fromMaybe (getSlideLevel blocks) $ writerSlideLevel opts
  slideVariant <- gets stSlideVariant
  let sects = hierarchicalize $
              if slideVariant == NoSlides
                 then blocks
                 else prepSlides slideLevel blocks
  toc <- if writerTableOfContents opts && slideVariant /= S5Slides
            then tableOfContents opts sects
            else return Nothing
  blocks' <- liftM (mconcat . intersperse (nl opts)) $
                 mapM (elementToHtml slideLevel opts) sects
  st <- get
  notes <- footnoteSection opts (reverse (stNotes st))
  let thebody = blocks' >> notes
  let  math = case writerHTMLMathMethod opts of
                      LaTeXMathML (Just url) ->
                         H.script ! A.src (toValue url)
                                  ! A.type_ "text/javascript"
                                  $ mempty
                      MathJax url ->
                         H.script ! A.src (toValue url)
                                  ! A.type_ "text/javascript"
                                  $ case slideVariant of
                                         SlideousSlides ->
                                            preEscapedString
                                            "MathJax.Hub.Queue([\"Typeset\",MathJax.Hub]);"
                                         _ -> mempty
                      JsMath (Just url) ->
                         H.script ! A.src (toValue url)
                                  ! A.type_ "text/javascript"
                                  $ mempty
                      KaTeX js css ->
                         (H.script ! A.src (toValue js) $ mempty) <>
                         (H.link ! A.rel "stylesheet" ! A.href (toValue css)) <>
                         (H.script ! A.type_ "text/javascript" $ toHtml renderKaTeX)
                      _ -> case lookup "mathml-script" (writerVariables opts) of
                                 Just s | not (stHtml5 st) ->
                                   H.script ! A.type_ "text/javascript"
                                      $ preEscapedString
                                       ("/*<![CDATA[*/\n" ++ s ++ "/*]]>*/\n")
                                        | otherwise -> mempty
                                 Nothing -> mempty
  let context =   (if stHighlighting st
                      then case writerHighlightStyle opts of
                                Just sty -> defField "highlighting-css"
                                              (styleToCss sty)
                                Nothing  -> id
                      else id) $
                  (if stMath st
                      then defField "math" (renderHtml math)
                      else id) $
                  defField "quotes" (stQuotes st) $
                  maybe id (defField "toc" . renderHtml) toc $
                  defField "author-meta" authsMeta $
                  maybe id (defField "date-meta") (normalizeDate dateMeta) $
                  defField "pagetitle" (stringifyHTML $ docTitle meta) $
                  defField "idprefix" (writerIdentifierPrefix opts) $
                  -- these should maybe be set in pandoc.hs
                  defField "slidy-url"
                    ("http://www.w3.org/Talks/Tools/Slidy2" :: String) $
                  defField "slideous-url" ("slideous" :: String) $
                  defField "revealjs-url" ("reveal.js" :: String) $
                  defField "s5-url" ("s5/default" :: String) $
                  defField "html5" (stHtml5 st) $
                  metadata
  return (thebody, context)

-- | Like Text.XHtml's identifier, but adds the writerIdentifierPrefix
prefixedId :: WriterOptions -> String -> Attribute
prefixedId opts s =
  case s of
    ""       -> mempty
    _        -> A.id $ toValue $ writerIdentifierPrefix opts ++ s

toList :: PandocMonad m
       => (Html -> Html)
       -> WriterOptions
       -> [Html]
       -> StateT WriterState m Html
toList listop opts items = do
    slideVariant <- gets stSlideVariant
    return $
      if (writerIncremental opts)
         then if (slideVariant /= RevealJsSlides)
                 then (listop $ mconcat items) ! A.class_ "incremental"
                 else listop $ mconcat $ map (! A.class_ "fragment") items
         else listop $ mconcat items

unordList :: PandocMonad m
          => WriterOptions -> [Html] -> StateT WriterState m Html
unordList opts = toList H.ul opts . toListItems opts

ordList :: PandocMonad m
        => WriterOptions -> [Html] -> StateT WriterState m Html
ordList opts = toList H.ol opts . toListItems opts

defList :: PandocMonad m
        => WriterOptions -> [Html] -> StateT WriterState m Html
defList opts items = toList H.dl opts (items ++ [nl opts])

-- | Construct table of contents from list of elements.
tableOfContents :: PandocMonad m => WriterOptions -> [Element] -> StateT WriterState m (Maybe Html)
tableOfContents _ [] = return Nothing
tableOfContents opts sects = do
  contents  <- mapM (elementToListItem opts) sects
  let tocList = catMaybes contents
  if null tocList
     then return Nothing
     else Just <$> unordList opts tocList

-- | Convert section number to string
showSecNum :: [Int] -> String
showSecNum = concat . intersperse "." . map show

-- | Converts an Element to a list item for a table of contents,
-- retrieving the appropriate identifier from state.
elementToListItem :: PandocMonad m => WriterOptions -> Element -> StateT WriterState m (Maybe Html)
-- Don't include the empty headers created in slide shows
-- shows when an hrule is used to separate slides without a new title:
elementToListItem _ (Sec _ _ _ [Str "\0"] _) = return Nothing
elementToListItem opts (Sec lev num (id',classes,_) headerText subsecs)
  | lev <= writerTOCDepth opts = do
  let num' = zipWith (+) num (writerNumberOffset opts ++ repeat 0)
  let sectnum = if writerNumberSections opts && not (null num) &&
                   "unnumbered" `notElem` classes
                   then (H.span ! A.class_ "toc-section-number"
                        $ toHtml $ showSecNum num') >> preEscapedString " "
                   else mempty
  txt <- liftM (sectnum >>) $ inlineListToHtml opts $ walk deNote headerText
  subHeads <- mapM (elementToListItem opts) subsecs >>= return . catMaybes
  subList <- if null subHeads
                then return mempty
                else unordList opts subHeads
  -- in reveal.js, we need #/apples, not #apples:
  slideVariant <- gets stSlideVariant
  let revealSlash = ['/' | slideVariant== RevealJsSlides]
  return $ Just
         $ if null id'
              then (H.a $ toHtml txt) >> subList
              else (H.a ! A.href (toValue $ "#" ++ revealSlash ++
                    writerIdentifierPrefix opts ++ id')
                       $ toHtml txt) >> subList
elementToListItem _ _ = return Nothing

-- | Convert an Element to Html.
elementToHtml :: PandocMonad m => Int -> WriterOptions -> Element -> StateT WriterState m Html
elementToHtml _slideLevel opts (Blk block) = blockToHtml opts block
elementToHtml slideLevel opts (Sec level num (id',classes,keyvals) title' elements) = do
  slideVariant <- gets stSlideVariant
  let slide = slideVariant /= NoSlides && level <= slideLevel
  let num' = zipWith (+) num (writerNumberOffset opts ++ repeat 0)
  modify $ \st -> st{stSecNum = num'}  -- update section number
  html5 <- gets stHtml5
  let titleSlide = slide && level < slideLevel
  header' <- if title' == [Str "\0"]  -- marker for hrule
                then return mempty
                else do
                  modify (\st -> st{ stElement = True})
                  res <- blockToHtml opts
                           (Header level (id',classes,keyvals) title')
                  modify (\st -> st{ stElement = False})
                  return res

  let isSec (Sec _ _ _ _ _) = True
      isSec (Blk _)         = False
  let isPause (Blk x) = x == Para [Str ".",Space,Str ".",Space,Str "."]
      isPause _       = False
  let fragmentClass = case slideVariant of
                           RevealJsSlides  -> "fragment"
                           _               -> "incremental"
  let inDiv xs = Blk (RawBlock (Format "html") ("<div class=\""
                       ++ fragmentClass ++ "\">")) :
                   (xs ++ [Blk (RawBlock (Format "html") "</div>")])
  innerContents <- mapM (elementToHtml slideLevel opts)
                   $ if titleSlide
                        -- title slides have no content of their own
                        then filter isSec elements
                        else case splitBy isPause elements of
                                  []     -> []
                                  (x:xs) -> x ++ concatMap inDiv xs
  let inNl x = mconcat $ nl opts : intersperse (nl opts) x ++ [nl opts]
  let classes' = ["titleslide" | titleSlide] ++ ["slide" | slide] ++
                  ["section" | (slide || writerSectionDivs opts) &&
                               not html5 ] ++
                  ["level" ++ show level | slide || writerSectionDivs opts ]
                  ++ classes
  let secttag  = if html5
                    then H5.section
                    else H.div
  let attr = (id',classes',keyvals)
  return $ if titleSlide
              then (if slideVariant == RevealJsSlides
                       then H5.section
                       else id) $ mconcat $
                       (addAttrs opts attr $ secttag $ header') : innerContents
              else if writerSectionDivs opts || slide
                   then addAttrs opts attr
                        $ secttag $ inNl $ header' : innerContents
                   else mconcat $ intersperse (nl opts)
                        $ addAttrs opts attr header' : innerContents

-- | Convert list of Note blocks to a footnote <div>.
-- Assumes notes are sorted.
footnoteSection :: PandocMonad m
                => WriterOptions -> [Html] -> StateT WriterState m Html
footnoteSection opts notes = do
  html5 <- gets stHtml5
  slideVariant <- gets stSlideVariant
  let hrtag = if html5 then H5.hr else H.hr
  let container x = if html5
                       then H5.section ! A.class_ "footnotes" $ x
                       else if slideVariant /= NoSlides
                            then H.div ! A.class_ "footnotes slide" $ x
                            else H.div ! A.class_ "footnotes" $ x
  return $
    if null notes
       then mempty
       else nl opts >> (container
            $ nl opts >> hrtag >> nl opts >>
              H.ol (mconcat notes >> nl opts) >> nl opts)

-- | Parse a mailto link; return Just (name, domain) or Nothing.
parseMailto :: String -> Maybe (String, String)
parseMailto s = do
  case break (==':') s of
       (xs,':':addr) | map toLower xs == "mailto" -> do
         let (name', rest) = span (/='@') addr
         let domain = drop 1 rest
         return (name', domain)
       _ -> fail "not a mailto: URL"

-- | Obfuscate a "mailto:" link.
obfuscateLink :: PandocMonad m => WriterOptions -> Attr -> Html -> String -> m Html
obfuscateLink opts attr txt s | writerEmailObfuscation opts == NoObfuscation =
  return $ addAttrs opts attr $ H.a ! A.href (toValue s) $ txt
obfuscateLink opts attr (renderHtml -> txt) s =
  let meth = writerEmailObfuscation opts
      s' = map toLower (take 7 s) ++ drop 7 s
  in  case parseMailto s' of
        (Just (name', domain)) ->
          let domain'  = substitute "." " dot " domain
              at'      = obfuscateChar '@'
              (linkText, altText) =
                 if txt == drop 7 s' -- autolink
                    then ("e", name' ++ " at " ++ domain')
                    else ("'" ++ obfuscateString txt ++ "'",
                          txt ++ " (" ++ name' ++ " at " ++ domain' ++ ")")
          in  case meth of
                ReferenceObfuscation ->
                     -- need to use preEscapedString or &'s are escaped to &amp; in URL
                     return $
                     preEscapedString $ "<a href=\"" ++ (obfuscateString s')
                     ++ "\" class=\"email\">" ++ (obfuscateString txt) ++ "</a>"
                JavascriptObfuscation ->
                     return $
                     (H.script ! A.type_ "text/javascript" $
                     preEscapedString ("\n<!--\nh='" ++
                     obfuscateString domain ++ "';a='" ++ at' ++ "';n='" ++
                     obfuscateString name' ++ "';e=n+a+h;\n" ++
                     "document.write('<a h'+'ref'+'=\"ma'+'ilto'+':'+e+'\" clas'+'s=\"em' + 'ail\">'+" ++
                     linkText  ++ "+'<\\/'+'a'+'>');\n// -->\n")) >>
                     H.noscript (preEscapedString $ obfuscateString altText)
                _ -> throwError $ PandocSomeError $ "Unknown obfuscation method: " ++ show meth
        _ -> return $ addAttrs opts attr $ H.a ! A.href (toValue s) $ toHtml txt  -- malformed email

-- | Obfuscate character as entity.
obfuscateChar :: Char -> String
obfuscateChar char =
  let num    = ord char
      numstr = if even num then show num else "x" ++ showHex num ""
  in  "&#" ++ numstr ++ ";"

-- | Obfuscate string using entities.
obfuscateString :: String -> String
obfuscateString = concatMap obfuscateChar . fromEntities

addAttrs :: WriterOptions -> Attr -> Html -> Html
addAttrs opts attr h = foldl (!) h (attrsToHtml opts attr)

toAttrs :: [(String, String)] -> [Attribute]
toAttrs kvs = map (\(x,y) -> customAttribute (fromString x) (toValue y)) kvs

attrsToHtml :: WriterOptions -> Attr -> [Attribute]
attrsToHtml opts (id',classes',keyvals) =
  [prefixedId opts id' | not (null id')] ++
  [A.class_ (toValue $ unwords classes') | not (null classes')] ++ toAttrs keyvals

imgAttrsToHtml :: WriterOptions -> Attr -> [Attribute]
imgAttrsToHtml opts attr =
    attrsToHtml opts (ident,cls,kvs') ++
    toAttrs (dimensionsToAttrList opts attr)
  where
    (ident,cls,kvs) = attr
    kvs' = filter isNotDim kvs
    isNotDim ("width", _)  = False
    isNotDim ("height", _) = False
    isNotDim _ = True

dimensionsToAttrList :: WriterOptions -> Attr -> [(String, String)]
dimensionsToAttrList opts attr = (go Width) ++ (go Height)
  where
    go dir = case (dimension dir attr) of
               (Just (Percent a)) -> [("style", show dir ++ ":" ++ show (Percent a))]
               (Just dim)         -> [(show dir, showInPixel opts dim)]
               _ -> []


imageExts :: [String]
imageExts = [ "art", "bmp", "cdr", "cdt", "cpt", "cr2", "crw", "djvu", "erf",
              "gif", "ico", "ief", "jng", "jpg", "jpeg", "nef", "orf", "pat", "pbm",
              "pcx", "pgm", "png", "pnm", "ppm", "psd", "ras", "rgb", "svg", "tiff",
              "wbmp", "xbm", "xpm", "xwd" ]

treatAsImage :: FilePath -> Bool
treatAsImage fp =
  let path = case uriPath `fmap` parseURIReference fp of
                  Nothing -> fp
                  Just up -> up
      ext  = map toLower $ drop 1 $ takeExtension path
  in  null ext || ext `elem` imageExts

-- | Convert Pandoc block element to HTML.
blockToHtml :: PandocMonad m => WriterOptions -> Block -> StateT WriterState m Html
blockToHtml _ Null = return mempty
blockToHtml opts (Plain lst) = inlineListToHtml opts lst
-- title beginning with fig: indicates that the image is a figure
blockToHtml opts (Para [Image attr txt (s,'f':'i':'g':':':tit)]) = do
  img <- inlineToHtml opts (Image attr txt (s,tit))
  html5 <- gets stHtml5
  let tocapt = if html5
                  then H5.figcaption
                  else H.p ! A.class_ "caption"
  capt <- if null txt
             then return mempty
             else tocapt `fmap` inlineListToHtml opts txt
  return $ if html5
              then H5.figure $ mconcat
                    [nl opts, img, capt, nl opts]
              else H.div ! A.class_ "figure" $ mconcat
                    [nl opts, img, nl opts, capt, nl opts]
blockToHtml opts (Para lst)
  | isEmptyRaw lst = return mempty
  | otherwise = do
      contents <- inlineListToHtml opts lst
      return $ H.p contents
  where
    isEmptyRaw [RawInline f _] = f /= (Format "html")
    isEmptyRaw _                 = False
blockToHtml opts (LineBlock lns) =
  if writerWrapText opts == WrapNone
  then blockToHtml opts $ linesToPara lns
  else do
    let lf = preEscapedString "\n"
    htmlLines <- mconcat . intersperse lf <$> mapM (inlineListToHtml opts) lns
    return $ H.div ! A.style "white-space: pre-line;" $ htmlLines
blockToHtml opts (Div attr@(ident, classes, kvs) bs) = do
  html5 <- gets stHtml5
  let speakerNotes = "notes" `elem` classes
  -- we don't want incremental output inside speaker notes, see #1394
  let opts' = if speakerNotes then opts{ writerIncremental = False } else opts
  contents <- blockListToHtml opts' bs
  let contents' = nl opts >> contents >> nl opts
  let (divtag, classes') = if html5 && "section" `elem` classes
                              then (H5.section, filter (/= "section") classes)
                              else (H.div, classes)
  slideVariant <- gets stSlideVariant
  return $
     if speakerNotes
        then case slideVariant of
                  RevealJsSlides -> addAttrs opts' attr $ H5.aside $ contents'
                  DZSlides       -> (addAttrs opts' attr $ H5.div $ contents')
                                      ! (H5.customAttribute "role" "note")
                  NoSlides       -> addAttrs opts' attr $ H.div $ contents'
                  _              -> mempty
        else addAttrs opts (ident, classes', kvs) $ divtag $ contents'
blockToHtml opts (RawBlock f str)
  | f == Format "html" = return $ preEscapedString str
  | (f == Format "latex" || f == Format "tex") &&
     allowsMathEnvironments (writerHTMLMathMethod opts) &&
     isMathEnvironment str = blockToHtml opts $ Plain [Math DisplayMath str]
  | otherwise          = return mempty
blockToHtml _ (HorizontalRule) = do
  html5 <- gets stHtml5
  return $ if html5 then H5.hr else H.hr
blockToHtml opts (CodeBlock (id',classes,keyvals) rawCode) = do
  let tolhs = isEnabled Ext_literate_haskell opts &&
                any (\c -> map toLower c == "haskell") classes &&
                any (\c -> map toLower c == "literate") classes
      classes' = if tolhs
                    then map (\c -> if map toLower c == "haskell"
                                       then "literatehaskell"
                                       else c) classes
                    else classes
      adjCode  = if tolhs
                    then unlines . map ("> " ++) . lines $ rawCode
                    else rawCode
      hlCode   = if isJust (writerHighlightStyle opts)
                    then highlight formatHtmlBlock
                            (id',classes',keyvals) adjCode
                    else Nothing
  case hlCode of
         Nothing -> return $ addAttrs opts (id',classes,keyvals)
                           $ H.pre $ H.code $ toHtml adjCode
         Just  h -> modify (\st -> st{ stHighlighting = True }) >>
                    return (addAttrs opts (id',[],keyvals) h)
blockToHtml opts (BlockQuote blocks) = do
  -- in S5, treat list in blockquote specially
  -- if default is incremental, make it nonincremental;
  -- otherwise incremental
  slideVariant <- gets stSlideVariant
  if slideVariant /= NoSlides
     then let inc = not (writerIncremental opts) in
          case blocks of
             [BulletList lst]  -> blockToHtml (opts {writerIncremental = inc})
                                  (BulletList lst)
             [OrderedList attribs lst] ->
                                  blockToHtml (opts {writerIncremental = inc})
                                  (OrderedList attribs lst)
             [DefinitionList lst] ->
                                  blockToHtml (opts {writerIncremental = inc})
                                  (DefinitionList lst)
             _                 -> do contents <- blockListToHtml opts blocks
                                     return $ H.blockquote
                                            $ nl opts >> contents >> nl opts
     else do
       contents <- blockListToHtml opts blocks
       return $ H.blockquote $ nl opts >> contents >> nl opts
blockToHtml opts (Header level attr@(_,classes,_) lst) = do
  contents <- inlineListToHtml opts lst
  secnum <- liftM stSecNum get
  let contents' = if writerNumberSections opts && not (null secnum)
                     && "unnumbered" `notElem` classes
                     then (H.span ! A.class_ "header-section-number" $ toHtml
                          $ showSecNum secnum) >> strToHtml " " >> contents
                     else contents
  inElement <- gets stElement
  return $ (if inElement then id else addAttrs opts attr)
         $ case level of
              1 -> H.h1 contents'
              2 -> H.h2 contents'
              3 -> H.h3 contents'
              4 -> H.h4 contents'
              5 -> H.h5 contents'
              6 -> H.h6 contents'
              _ -> H.p contents'
blockToHtml opts (BulletList lst) = do
  contents <- mapM (blockListToHtml opts) lst
  unordList opts contents
blockToHtml opts (OrderedList (startnum, numstyle, _) lst) = do
  contents <- mapM (blockListToHtml opts) lst
  html5 <- gets stHtml5
  let numstyle' = case numstyle of
                       Example -> "decimal"
                       _       -> camelCaseToHyphenated $ show numstyle
  let attribs = (if startnum /= 1
                   then [A.start $ toValue startnum]
                   else []) ++
                (if numstyle == Example
                    then [A.class_ "example"]
                    else []) ++
                (if numstyle /= DefaultStyle
                   then if html5
                           then [A.type_ $
                                 case numstyle of
                                      Decimal    -> "1"
                                      LowerAlpha -> "a"
                                      UpperAlpha -> "A"
                                      LowerRoman -> "i"
                                      UpperRoman -> "I"
                                      _          -> "1"]
                           else [A.style $ toValue $ "list-style-type: " ++
                                   numstyle']
                   else [])
  l <- ordList opts contents
  return $ foldl (!) l attribs
blockToHtml opts (DefinitionList lst) = do
  contents <- mapM (\(term, defs) ->
                  do term' <- if null term
                                 then return mempty
                                 else liftM H.dt $ inlineListToHtml opts term
                     defs' <- mapM ((liftM (\x -> H.dd $ (x >> nl opts))) .
                                    blockListToHtml opts) defs
                     return $ mconcat $ nl opts : term' : nl opts :
                                        intersperse (nl opts) defs') lst
  defList opts contents
blockToHtml opts (Table capt aligns widths headers rows') = do
  captionDoc <- if null capt
                   then return mempty
                   else do
                     cs <- inlineListToHtml opts capt
                     return $ H.caption cs >> nl opts
  html5 <- gets stHtml5
  let percent w = show (truncate (100*w) :: Integer) ++ "%"
  let coltags = if all (== 0.0) widths
                   then mempty
                   else do
                     H.colgroup $ do
                       nl opts
                       mapM_ (\w -> do
                            if html5
                               then H.col ! A.style (toValue $ "width: " ++
                                                      percent w)
                               else H.col ! A.width (toValue $ percent w)
                            nl opts) widths
                     nl opts
  head' <- if all null headers
              then return mempty
              else do
                contents <- tableRowToHtml opts aligns 0 headers
                return $ H.thead (nl opts >> contents) >> nl opts
  body' <- liftM (\x -> H.tbody (nl opts >> mconcat x)) $
               zipWithM (tableRowToHtml opts aligns) [1..] rows'
  let tbl = H.table $
              nl opts >> captionDoc >> coltags >> head' >> body' >> nl opts
  let totalWidth = sum widths
  -- When widths of columns are < 100%, we need to set width for the whole
  -- table, or some browsers give us skinny columns with lots of space between:
  return $ if totalWidth == 0 || totalWidth == 1
              then tbl
              else tbl ! A.style (toValue $ "width:" ++
                              show (round (totalWidth * 100) :: Int) ++ "%;")

tableRowToHtml :: PandocMonad m
               => WriterOptions
               -> [Alignment]
               -> Int
               -> [[Block]]
               -> StateT WriterState m Html
tableRowToHtml opts aligns rownum cols' = do
  let mkcell = if rownum == 0 then H.th else H.td
  let rowclass = case rownum of
                      0                  -> "header"
                      x | x `rem` 2 == 1 -> "odd"
                      _                  -> "even"
  cols'' <- sequence $ zipWith
            (\alignment item -> tableItemToHtml opts mkcell alignment item)
            aligns cols'
  return $ (H.tr ! A.class_ rowclass $ nl opts >> mconcat cols'')
          >> nl opts

alignmentToString :: Alignment -> [Char]
alignmentToString alignment = case alignment of
                                 AlignLeft    -> "left"
                                 AlignRight   -> "right"
                                 AlignCenter  -> "center"
                                 AlignDefault -> ""

tableItemToHtml :: PandocMonad m
                => WriterOptions
                -> (Html -> Html)
                -> Alignment
                -> [Block]
                -> StateT WriterState m Html
tableItemToHtml opts tag' align' item = do
  contents <- blockListToHtml opts item
  html5 <- gets stHtml5
  let alignStr = alignmentToString align'
  let attribs = if html5
                   then A.style (toValue $ "text-align: " ++ alignStr ++ ";")
                   else A.align (toValue alignStr)
  let tag'' = if null alignStr
                 then tag'
                 else tag' ! attribs
  return $ (tag'' $ contents) >> nl opts

toListItems :: WriterOptions -> [Html] -> [Html]
toListItems opts items = map (toListItem opts) items ++ [nl opts]

toListItem :: WriterOptions -> Html -> Html
toListItem opts item = nl opts >> H.li item

blockListToHtml :: PandocMonad m => WriterOptions -> [Block] -> StateT WriterState m Html
blockListToHtml opts lst =
  fmap (mconcat . intersperse (nl opts)) $ mapM (blockToHtml opts) lst

-- | Convert list of Pandoc inline elements to HTML.
inlineListToHtml :: PandocMonad m => WriterOptions -> [Inline] -> StateT WriterState m Html
inlineListToHtml opts lst =
  mapM (inlineToHtml opts) lst >>= return . mconcat

-- | Annotates a MathML expression with the tex source
annotateMML :: XML.Element -> String -> XML.Element
annotateMML e tex = math (unode "semantics" [cs, unode "annotation" (annotAttrs, tex)])
  where
    cs = case elChildren e of
          [] -> unode "mrow" ()
          [x] -> x
          xs -> unode "mrow" xs
    math childs = XML.Element q as [XML.Elem childs] l
      where
        (XML.Element q as _ l) = e
    annotAttrs = [XML.Attr (unqual "encoding") "application/x-tex"]


-- | Convert Pandoc inline element to HTML.
inlineToHtml :: PandocMonad m
             => WriterOptions -> Inline -> StateT WriterState m Html
inlineToHtml opts inline = do
  html5 <- gets stHtml5
  case inline of
    (Str str)        -> return $ strToHtml str
    (Space)          -> return $ strToHtml " "
    (SoftBreak)      -> return $ case writerWrapText opts of
                                       WrapNone     -> preEscapedString " "
                                       WrapAuto     -> preEscapedString " "
                                       WrapPreserve -> preEscapedString "\n"
    (LineBreak)      -> return $ (if html5 then H5.br else H.br)
                                 <> strToHtml "\n"
    (Span (id',classes,kvs) ils)
                     -> inlineListToHtml opts ils >>=
                           return . addAttrs opts attr' . H.span
                        where attr' = (id',classes',kvs')
                              classes' = filter (`notElem` ["csl-no-emph",
                                              "csl-no-strong",
                                              "csl-no-smallcaps"]) classes
                              kvs' = if null styles
                                        then kvs
                                        else (("style", concat styles) : kvs)
                              styles = ["font-style:normal;"
                                         | "csl-no-emph" `elem` classes]
                                    ++ ["font-weight:normal;"
                                         | "csl-no-strong" `elem` classes]
                                    ++ ["font-variant:normal;"
                                         | "csl-no-smallcaps" `elem` classes]
    (Emph lst)       -> inlineListToHtml opts lst >>= return . H.em
    (Strong lst)     -> inlineListToHtml opts lst >>= return . H.strong
    (Code attr str)  -> case hlCode of
                             Nothing -> return
                                        $ addAttrs opts attr
                                        $ H.code $ strToHtml str
                             Just  h -> do
                               modify $ \st -> st{ stHighlighting = True }
                               return $ addAttrs opts (id',[],keyvals) h
                        where (id',_,keyvals) = attr
                              hlCode = if isJust (writerHighlightStyle opts)
                                          then highlight formatHtmlInline
                                                   attr str
                                          else Nothing
    (Strikeout lst)  -> inlineListToHtml opts lst >>=
                        return . H.del
    (SmallCaps lst)   -> inlineListToHtml opts lst >>=
                         return . (H.span ! A.style "font-variant: small-caps;")
    (Superscript lst) -> inlineListToHtml opts lst >>= return . H.sup
    (Subscript lst)   -> inlineListToHtml opts lst >>= return . H.sub
    (Quoted quoteType lst) ->
                        let (leftQuote, rightQuote) = case quoteType of
                              SingleQuote -> (strToHtml "‘",
                                              strToHtml "’")
                              DoubleQuote -> (strToHtml "“",
                                              strToHtml "”")
                        in  if writerHtmlQTags opts
                               then do
                                 modify $ \st -> st{ stQuotes = True }
                                 H.q `fmap` inlineListToHtml opts lst
                               else (\x -> leftQuote >> x >> rightQuote)
                                    `fmap` inlineListToHtml opts lst
    (Math t str) -> do
      modify (\st -> st {stMath = True})
      let mathClass = toValue $ ("math " :: String) ++
                      if t == InlineMath then "inline" else "display"
      case writerHTMLMathMethod opts of
           LaTeXMathML _ ->
              -- putting LaTeXMathML in container with class "LaTeX" prevents
              -- non-math elements on the page from being treated as math by
              -- the javascript
              return $ H.span ! A.class_ "LaTeX" $
                     case t of
                       InlineMath  -> toHtml ("$" ++ str ++ "$")
                       DisplayMath -> toHtml ("$$" ++ str ++ "$$")
           JsMath _ -> do
              let m = preEscapedString str
              return $ case t of
                       InlineMath -> H.span ! A.class_ mathClass $ m
                       DisplayMath -> H.div ! A.class_ mathClass $ m
           WebTeX url -> do
              let imtag = if html5 then H5.img else H.img
              let m = imtag ! A.style "vertical-align:middle"
                            ! A.src (toValue $ url ++ urlEncode str)
                            ! A.alt (toValue str)
                            ! A.title (toValue str)
              let brtag = if html5 then H5.br else H.br
              return $ case t of
                        InlineMath  -> m
                        DisplayMath -> brtag >> m >> brtag
           GladTeX ->
              return $ case t of
                         InlineMath -> preEscapedString $ "<EQ ENV=\"math\">" ++ str ++ "</EQ>"
                         DisplayMath -> preEscapedString $ "<EQ ENV=\"displaymath\">" ++ str ++ "</EQ>"
           MathML -> do
              let conf = useShortEmptyTags (const False)
                           defaultConfigPP
              res <- lift $ convertMath writeMathML t str
              case res of
                    Right r  -> return $ preEscapedString $
                        ppcElement conf (annotateMML r str)
                    Left il  -> (H.span ! A.class_ mathClass) <$>
                                   inlineToHtml opts il
           MathJax _ -> return $ H.span ! A.class_ mathClass $ toHtml $
              case t of
                InlineMath  -> "\\(" ++ str ++ "\\)"
                DisplayMath -> "\\[" ++ str ++ "\\]"
           KaTeX _ _ -> return $ H.span ! A.class_ mathClass $
              toHtml (case t of
                        InlineMath -> str
                        DisplayMath -> "\\displaystyle " ++ str)
           PlainMath -> do
              x <- lift (texMathToInlines t str) >>= inlineListToHtml opts
              let m = H.span ! A.class_ mathClass $ x
              let brtag = if html5 then H5.br else H.br
              return  $ case t of
                         InlineMath  -> m
                         DisplayMath -> brtag >> m >> brtag
    (RawInline f str)
      | f == Format "html" -> return $ preEscapedString str
      | otherwise          -> return mempty
    (Link attr txt (s,_)) | "mailto:" `isPrefixOf` s -> do
                        linkText <- inlineListToHtml opts txt
                        lift $ obfuscateLink opts attr linkText s
    (Link attr txt (s,tit)) -> do
                        linkText <- inlineListToHtml opts txt
                        slideVariant <- gets stSlideVariant
                        let s' = case s of
                                   '#':xs -> let prefix = if slideVariant == RevealJsSlides
                                                             then "/"
                                                             else writerIdentifierPrefix opts
                                             in  '#' : prefix ++ xs
                                   _ -> s
                        let link = H.a ! A.href (toValue s') $ linkText
                        let link' = if txt == [Str (unEscapeString s)]
                                       then link ! A.class_ "uri"
                                       else link
                        let link'' = addAttrs opts attr link'
                        return $ if null tit
                                    then link''
                                    else link'' ! A.title (toValue tit)
    (Image attr txt (s,tit)) | treatAsImage s -> do
                        let alternate' = stringify txt
                        let attributes = [A.src $ toValue s] ++
                                         [A.title $ toValue tit | not (null tit)] ++
                                         [A.alt $ toValue alternate' | not (null txt)] ++
                                         imgAttrsToHtml opts attr
                        let tag = if html5 then H5.img else H.img
                        return $ foldl (!) tag attributes
                        -- note:  null title included, as in Markdown.pl
    (Image attr _ (s,tit)) -> do
                        let attributes = [A.src $ toValue s] ++
                                         [A.title $ toValue tit | not (null tit)] ++
                                         imgAttrsToHtml opts attr
                        return $ foldl (!) H5.embed attributes
                        -- note:  null title included, as in Markdown.pl
    (Note contents) -> do
                        notes <- gets stNotes
                        let number = (length notes) + 1
                        let ref = show number
                        htmlContents <- blockListToNote opts ref contents
                        epubVersion <- gets stEPUBVersion
                        -- push contents onto front of notes
                        modify $ \st -> st {stNotes = (htmlContents:notes)}
                        slideVariant <- gets stSlideVariant
                        let revealSlash = ['/' | slideVariant == RevealJsSlides]
                        let link = H.a ! A.href (toValue $ "#" ++
                                         revealSlash ++
                                         writerIdentifierPrefix opts ++ "fn" ++ ref)
                                       ! A.class_ "footnoteRef"
                                       ! prefixedId opts ("fnref" ++ ref)
                                       $ (if isJust epubVersion
                                             then id
                                             else H.sup)
                                       $ toHtml ref
                        return $ case epubVersion of
                                      Just EPUB3 -> link ! customAttribute "epub:type" "noteref"
                                      _          -> link
    (Cite cits il)-> do contents <- inlineListToHtml opts il
                        let citationIds = unwords $ map citationId cits
                        let result = H.span ! A.class_ "citation" $ contents
                        return $ if html5
                                    then result ! customAttribute "data-cites" (toValue citationIds)
                                    else result

blockListToNote :: PandocMonad m => WriterOptions -> String -> [Block] -> StateT WriterState m Html
blockListToNote opts ref blocks =
  -- If last block is Para or Plain, include the backlink at the end of
  -- that block. Otherwise, insert a new Plain block with the backlink.
  let backlink = [Link nullAttr [Str "↩"] ("#" ++ writerIdentifierPrefix opts ++ "fnref" ++ ref,[])]
      blocks'  = if null blocks
                    then []
                    else let lastBlock   = last blocks
                             otherBlocks = init blocks
                         in  case lastBlock of
                                  (Para lst)  -> otherBlocks ++
                                                 [Para (lst ++ backlink)]
                                  (Plain lst) -> otherBlocks ++
                                                 [Plain (lst ++ backlink)]
                                  _           -> otherBlocks ++ [lastBlock,
                                                 Plain backlink]
  in  do contents <- blockListToHtml opts blocks'
         let noteItem = H.li ! (prefixedId opts ("fn" ++ ref)) $ contents
         epubVersion <- gets stEPUBVersion
         let noteItem' = case epubVersion of
                              Just EPUB3 -> noteItem ! customAttribute "epub:type" "footnote"
                              _          -> noteItem
         return $ nl opts >> noteItem'

-- Javascript snippet to render all KaTeX elements
renderKaTeX :: String
renderKaTeX = unlines [
    "window.onload = function(){var mathElements = document.getElementsByClassName(\"math\");"
  , "for (var i=0; i < mathElements.length; i++)"
  , "{"
  , " var texText = mathElements[i].firstChild"
  , " katex.render(texText.data, mathElements[i])"
  , "}}"
  ]

isMathEnvironment :: String -> Bool
isMathEnvironment s = "\\begin{" `isPrefixOf` s &&
                         envName `elem` mathmlenvs
  where envName = takeWhile (/= '}') (drop 7 s)
        mathmlenvs = [ "align"
                     , "align*"
                     , "alignat"
                     , "alignat*"
                     , "aligned"
                     , "alignedat"
                     , "array"
                     , "Bmatrix"
                     , "bmatrix"
                     , "cases"
                     , "CD"
                     , "eqnarray"
                     , "eqnarray*"
                     , "equation"
                     , "equation*"
                     , "gather"
                     , "gather*"
                     , "gathered"
                     , "matrix"
                     , "multline"
                     , "multline*"
                     , "pmatrix"
                     , "smallmatrix"
                     , "split"
                     , "subarray"
                     , "Vmatrix"
                     , "vmatrix" ]

allowsMathEnvironments :: HTMLMathMethod -> Bool
allowsMathEnvironments (MathJax _) = True
allowsMathEnvironments (MathML)    = True
allowsMathEnvironments (WebTeX _)  = True
allowsMathEnvironments _           = False