summaryrefslogtreecommitdiff
path: root/src/Text/Pandoc/Writers/ConTeXt.hs
blob: f0f4cd00ee7f977aab9a1340b65b53f17ca6157e (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
{-# LANGUAGE OverloadedStrings   #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-
Copyright (C) 2007-2017 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.ConTeXt
   Copyright   : Copyright (C) 2007-2017 John MacFarlane
   License     : GNU GPL, version 2 or above

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

Conversion of 'Pandoc' format into ConTeXt.
-}
module Text.Pandoc.Writers.ConTeXt ( writeConTeXt ) where
import Control.Monad.State.Strict
import Data.Char (ord, isDigit)
import Data.List (intercalate, intersperse)
import Data.Maybe (mapMaybe)
import Data.Text (Text)
import Network.URI (unEscapeString)
import Text.Pandoc.BCP47
import Text.Pandoc.Class (PandocMonad, report, toLang)
import Text.Pandoc.Definition
import Text.Pandoc.ImageSize
import Text.Pandoc.Logging
import Text.Pandoc.Options
import Text.Pandoc.Pretty
import Text.Pandoc.Shared
import Text.Pandoc.Templates (renderTemplate')
import Text.Pandoc.Walk (query)
import Text.Pandoc.Writers.Shared
import Text.Printf (printf)

data WriterState =
  WriterState { stNextRef          :: Int  -- number of next URL reference
              , stOrderedListLevel :: Int  -- level of ordered list
              , stOptions          :: WriterOptions -- writer options
              }

orderedListStyles :: [Char]
orderedListStyles = cycle "narg"

-- | Convert Pandoc to ConTeXt.
writeConTeXt :: PandocMonad m => WriterOptions -> Pandoc -> m Text
writeConTeXt options document =
  let defaultWriterState = WriterState { stNextRef = 1
                                       , stOrderedListLevel = 0
                                       , stOptions = options
                                       }
  in evalStateT (pandocToConTeXt options document) defaultWriterState

type WM = StateT WriterState

pandocToConTeXt :: PandocMonad m => WriterOptions -> Pandoc -> WM m Text
pandocToConTeXt options (Pandoc meta blocks) = do
  let colwidth = if writerWrapText options == WrapAuto
                    then Just $ writerColumns options
                    else Nothing
  let render' :: Doc -> Text
      render' = render colwidth
  metadata <- metaToJSON options
              (fmap render' . blockListToConTeXt)
              (fmap render' . inlineListToConTeXt)
              meta
  body <- mapM (elementToConTeXt options) $ hierarchicalize blocks
  let main = (render' . vcat) body
  let layoutFromMargins = intercalate [','] $ mapMaybe (\(x,y) ->
                                ((x ++ "=") ++) <$> getField y metadata)
                              [("leftmargin","margin-left")
                              ,("rightmargin","margin-right")
                              ,("top","margin-top")
                              ,("bottom","margin-bottom")
                              ]
  mblang <- fromBCP47 (getLang options meta)
  let context =   defField "toc" (writerTableOfContents options)
                $ defField "placelist" (intercalate ("," :: String) $
                     take (writerTOCDepth options +
                           case writerTopLevelDivision options of
                             TopLevelPart    -> 0
                             TopLevelChapter -> 0
                             _               -> 1)
                       ["chapter","section","subsection","subsubsection",
                        "subsubsubsection","subsubsubsubsection"])
                $ defField "body" main
                $ defField "layout" layoutFromMargins
                $ defField "number-sections" (writerNumberSections options)
                $ maybe id (defField "context-lang") mblang
                $ (case getField "papersize" metadata of
                        Just (('a':d:ds) :: String)
                          | all isDigit (d:ds) -> resetField "papersize"
                                                     (('A':d:ds) :: String)
                        _                     -> id) metadata
  let context' = defField "context-dir" (toContextDir
                                         $ getField "dir" context) context
  case writerTemplate options of
       Nothing  -> return main
       Just tpl -> renderTemplate' tpl context'

toContextDir :: Maybe String -> String
toContextDir (Just "rtl") = "r2l"
toContextDir (Just "ltr") = "l2r"
toContextDir _            = ""

-- | escape things as needed for ConTeXt
escapeCharForConTeXt :: WriterOptions -> Char -> String
escapeCharForConTeXt opts ch =
 let ligatures = isEnabled Ext_smart opts in
 case ch of
    '{'      -> "\\{"
    '}'      -> "\\}"
    '\\'     -> "\\letterbackslash{}"
    '$'      -> "\\$"
    '|'      -> "\\letterbar{}"
    '%'      -> "\\letterpercent{}"
    '~'      -> "\\lettertilde{}"
    '#'      -> "\\#"
    '['      -> "{[}"
    ']'      -> "{]}"
    '\160'   -> "~"
    '\x2014' | ligatures -> "---"
    '\x2013' | ligatures -> "--"
    '\x2019' | ligatures -> "'"
    '\x2026' -> "\\ldots{}"
    x        -> [x]

-- | Escape string for ConTeXt
stringToConTeXt :: WriterOptions -> String -> String
stringToConTeXt opts = concatMap (escapeCharForConTeXt opts)

-- | Sanitize labels
toLabel :: String -> String
toLabel z = concatMap go z
 where go x
         | x `elem` ("\\#[]\",{}%()|=" :: String) = "ux" ++ printf "%x" (ord x)
         | otherwise = [x]

-- | Convert Elements to ConTeXt
elementToConTeXt :: PandocMonad m => WriterOptions -> Element -> WM m Doc
elementToConTeXt _ (Blk block) = blockToConTeXt block
elementToConTeXt opts (Sec level _ attr title' elements) = do
  header' <- sectionHeader attr level title'
  innerContents <- mapM (elementToConTeXt opts) elements
  return $ vcat (header' : innerContents)

-- | Convert Pandoc block element to ConTeXt.
blockToConTeXt :: PandocMonad m => Block -> WM m Doc
blockToConTeXt Null = return empty
blockToConTeXt (Plain lst) = inlineListToConTeXt lst
-- title beginning with fig: indicates that the image is a figure
blockToConTeXt (Para [Image attr txt (src,'f':'i':'g':':':_)]) = do
  capt <- inlineListToConTeXt txt
  img  <- inlineToConTeXt (Image attr txt (src, ""))
  let (ident, _, _) = attr
      label = if null ident
                 then empty
                 else "[]" <> brackets (text $ toLabel ident)
  return $ blankline $$ "\\placefigure" <> label <> braces capt <> img <> blankline
blockToConTeXt (Para lst) = do
  contents <- inlineListToConTeXt lst
  return $ contents <> blankline
blockToConTeXt (LineBlock lns) = do
  doclines <- nowrap . vcat <$> mapM inlineListToConTeXt lns
  return $ "\\startlines" $$ doclines $$ "\\stoplines" <> blankline
blockToConTeXt (BlockQuote lst) = do
  contents <- blockListToConTeXt lst
  return $ "\\startblockquote" $$ nest 0 contents $$ "\\stopblockquote" <> blankline
blockToConTeXt (CodeBlock _ str) =
  return $ flush ("\\starttyping" <> cr <> text str <> cr <> "\\stoptyping") $$ blankline
  -- blankline because \stoptyping can't have anything after it, inc. '}'
blockToConTeXt (RawBlock "context" str) = return $ text str <> blankline
blockToConTeXt b@(RawBlock _ _ ) = do
  report $ BlockNotRendered b
  return empty
blockToConTeXt (Div (ident,_,kvs) bs) = do
  let align dir txt = "\\startalignment[" <> dir <> "]" $$ txt $$ "\\stopalignment"
  mblang <- fromBCP47 (lookup "lang" kvs)
  let wrapRef txt = if null ident
                       then txt
                       else ("\\reference" <> brackets (text $ toLabel ident) <>
                              braces empty <> "%") $$ txt
      wrapDir = case lookup "dir" kvs of
                  Just "rtl" -> align "righttoleft"
                  Just "ltr" -> align "lefttoright"
                  _          -> id
      wrapLang txt = case mblang of
                       Just lng -> "\\start\\language["
                                     <> text lng <> "]" $$ txt $$ "\\stop"
                       Nothing  -> txt
      wrapBlank txt = blankline <> txt <> blankline
  (wrapBlank . wrapLang . wrapDir . wrapRef) <$> blockListToConTeXt bs
blockToConTeXt (BulletList lst) = do
  contents <- mapM listItemToConTeXt lst
  return $ ("\\startitemize" <> if isTightList lst
                                   then brackets "packed"
                                   else empty) $$
    vcat contents $$ text "\\stopitemize" <> blankline
blockToConTeXt (OrderedList (start, style', delim) lst) = do
    st <- get
    let level = stOrderedListLevel st
    put st {stOrderedListLevel = level + 1}
    contents <- mapM listItemToConTeXt lst
    put st {stOrderedListLevel = level}
    let start' = if start == 1 then "" else "start=" ++ show start
    let delim' = case delim of
                        DefaultDelim -> ""
                        Period       -> "stopper=."
                        OneParen     -> "stopper=)"
                        TwoParens    -> "left=(,stopper=)"
    let width = maximum $ map length $ take (length contents)
                          (orderedListMarkers (start, style', delim))
    let width' = (toEnum width + 1) / 2
    let width'' = if width' > (1.5 :: Double)
                     then "width=" ++ show width' ++ "em"
                     else ""
    let specs2Items = filter (not . null) [start', delim', width'']
    let specs2 = if null specs2Items
                    then ""
                    else "[" ++ intercalate "," specs2Items ++ "]"
    let style'' = '[': (case style' of
                          DefaultStyle -> orderedListStyles !! level
                          Decimal      -> 'n'
                          Example      -> 'n'
                          LowerRoman   -> 'r'
                          UpperRoman   -> 'R'
                          LowerAlpha   -> 'a'
                          UpperAlpha   -> 'A') :
                       if isTightList lst then ",packed]" else "]"
    let specs = style'' ++ specs2
    return $ "\\startitemize" <> text specs $$ vcat contents $$
             "\\stopitemize" <> blankline
blockToConTeXt (DefinitionList lst) =
  liftM vcat $ mapM defListItemToConTeXt lst
blockToConTeXt HorizontalRule = return $ "\\thinrule" <> blankline
-- If this is ever executed, provide a default for the reference identifier.
blockToConTeXt (Header level attr lst) = sectionHeader attr level lst
blockToConTeXt (Table caption aligns widths heads rows) = do
    let colDescriptor colWidth alignment = (case alignment of
                                               AlignLeft    -> 'l'
                                               AlignRight   -> 'r'
                                               AlignCenter  -> 'c'
                                               AlignDefault -> 'l'):
           if colWidth == 0
              then "|"
              else ("p(" ++ printf "%.2f" colWidth ++ "\\textwidth)|")
    let colDescriptors = "|" ++ concat (
                                 zipWith colDescriptor widths aligns)
    headers <- if all null heads
                  then return empty
                  else liftM ($$ "\\HL") $ tableRowToConTeXt heads
    captionText <- inlineListToConTeXt caption
    rows' <- mapM tableRowToConTeXt rows
    return $ "\\placetable" <> (if null caption
                                   then brackets "none"
                                   else empty)
                            <> braces captionText $$
             "\\starttable" <> brackets (text colDescriptors) $$
             "\\HL" $$ headers $$
             vcat rows' $$ "\\HL" $$ "\\stoptable" <> blankline

tableRowToConTeXt :: PandocMonad m => [[Block]] -> WM m Doc
tableRowToConTeXt cols = do
  cols' <- mapM blockListToConTeXt cols
  return $ vcat (map ("\\NC " <>) cols') $$ "\\NC\\AR"

listItemToConTeXt :: PandocMonad m => [Block] -> WM m Doc
listItemToConTeXt list = blockListToConTeXt list >>=
  return . ("\\item" $$) . nest 2

defListItemToConTeXt :: PandocMonad m => ([Inline], [[Block]]) -> WM m Doc
defListItemToConTeXt (term, defs) = do
  term' <- inlineListToConTeXt term
  def'  <- liftM vsep $ mapM blockListToConTeXt defs
  return $ "\\startdescription" <> braces term' $$ nest 2 def' $$
           "\\stopdescription" <> blankline

-- | Convert list of block elements to ConTeXt.
blockListToConTeXt :: PandocMonad m => [Block] -> WM m Doc
blockListToConTeXt lst = liftM vcat $ mapM blockToConTeXt lst

-- | Convert list of inline elements to ConTeXt.
inlineListToConTeXt :: PandocMonad m
                    => [Inline]  -- ^ Inlines to convert
                    -> WM m Doc
inlineListToConTeXt lst = liftM hcat $ mapM inlineToConTeXt $ addStruts lst
  -- We add a \strut after a line break that precedes a space,
  -- or the space gets swallowed
  where addStruts (LineBreak : s : xs) | isSpacey s =
           LineBreak : RawInline (Format "context") "\\strut " : s :
             addStruts xs
        addStruts (x:xs) = x : addStruts xs
        addStruts [] = []
        isSpacey Space            = True
        isSpacey (Str ('\160':_)) = True
        isSpacey _                = False

-- | Convert inline element to ConTeXt
inlineToConTeXt :: PandocMonad m
                => Inline    -- ^ Inline to convert
                -> WM m Doc
inlineToConTeXt (Emph lst) = do
  contents <- inlineListToConTeXt lst
  return $ braces $ "\\em " <> contents
inlineToConTeXt (Strong lst) = do
  contents <- inlineListToConTeXt lst
  return $ braces $ "\\bf " <> contents
inlineToConTeXt (Strikeout lst) = do
  contents <- inlineListToConTeXt lst
  return $ "\\overstrikes" <> braces contents
inlineToConTeXt (Superscript lst) = do
  contents <- inlineListToConTeXt lst
  return $ "\\high" <> braces contents
inlineToConTeXt (Subscript lst) = do
  contents <- inlineListToConTeXt lst
  return $ "\\low" <> braces contents
inlineToConTeXt (SmallCaps lst) = do
  contents <- inlineListToConTeXt lst
  return $ braces $ "\\sc " <> contents
inlineToConTeXt (Code _ str) | not ('{' `elem` str || '}' `elem` str) =
  return $ "\\type" <> braces (text str)
inlineToConTeXt (Code _ str) = do
  opts <- gets stOptions
  return $ "\\mono" <> braces (text $ stringToConTeXt opts str)
inlineToConTeXt (Quoted SingleQuote lst) = do
  contents <- inlineListToConTeXt lst
  return $ "\\quote" <> braces contents
inlineToConTeXt (Quoted DoubleQuote lst) = do
  contents <- inlineListToConTeXt lst
  return $ "\\quotation" <> braces contents
inlineToConTeXt (Cite _ lst) = inlineListToConTeXt lst
inlineToConTeXt (Str str) = do
  opts <- gets stOptions
  return $ text $ stringToConTeXt opts str
inlineToConTeXt (Math InlineMath str) =
  return $ char '$' <> text str <> char '$'
inlineToConTeXt (Math DisplayMath str) =
  return $ text "\\startformula "  <> text str <> text " \\stopformula" <> space
inlineToConTeXt (RawInline "context" str) = return $ text str
inlineToConTeXt (RawInline "tex" str) = return $ text str
inlineToConTeXt il@(RawInline _ _) = do
  report $ InlineNotRendered il
  return empty
inlineToConTeXt LineBreak = return $ text "\\crlf" <> cr
inlineToConTeXt SoftBreak = do
  wrapText <- gets (writerWrapText . stOptions)
  return $ case wrapText of
               WrapAuto     -> space
               WrapNone     -> space
               WrapPreserve -> cr
inlineToConTeXt Space = return space
-- Handle HTML-like internal document references to sections
inlineToConTeXt (Link _ txt ('#' : ref, _)) = do
  opts <- gets stOptions
  contents <-  inlineListToConTeXt txt
  let ref' = toLabel $ stringToConTeXt opts ref
  return $ text "\\goto"
           <> braces contents
           <> brackets (text ref')

inlineToConTeXt (Link _ txt (src, _)) = do
  let isAutolink = txt == [Str (unEscapeString src)]
  st <- get
  let next = stNextRef st
  put $ st {stNextRef = next + 1}
  let ref = "url" ++ show next
  contents <-  inlineListToConTeXt txt
  return $ "\\useURL"
           <> brackets (text ref)
           <> brackets (text $ escapeStringUsing [('#',"\\#"),('%',"\\%")] src)
           <> (if isAutolink
                  then empty
                  else brackets empty <> brackets contents)
           <> "\\from"
           <> brackets (text ref)
inlineToConTeXt (Image attr@(_,cls,_) _ (src, _)) = do
  opts <- gets stOptions
  let showDim dir = let d = text (show dir) <> "="
                    in case dimension dir attr of
                         Just (Pixel a)   ->
                           [d <> text (showInInch opts (Pixel a)) <> "in"]
                         Just (Percent a) ->
                           [d <> text (showFl (a / 100)) <> "\\textwidth"]
                         Just dim         ->
                           [d <> text (show dim)]
                         Nothing          ->
                           []
      dimList = showDim Width ++ showDim Height
      dims = if null dimList
                then empty
                else brackets $ cat (intersperse "," dimList)
      clas = if null cls
                then empty
                else brackets $ text $ toLabel $ head cls
      src' = if isURI src
                then src
                else unEscapeString src
  return $ braces $ "\\externalfigure" <> brackets (text src') <> dims <> clas
inlineToConTeXt (Note contents) = do
  contents' <- blockListToConTeXt contents
  let codeBlock x@(CodeBlock _ _) = [x]
      codeBlock _                 = []
  let codeBlocks = query codeBlock contents
  return $ if null codeBlocks
              then text "\\footnote{" <> nest 2 contents' <> char '}'
              else text "\\startbuffer " <> nest 2 contents' <>
                   text "\\stopbuffer\\footnote{\\getbuffer}"
inlineToConTeXt (Span (_,_,kvs) ils) = do
  mblang <- fromBCP47 (lookup "lang" kvs)
  let wrapDir txt = case lookup "dir" kvs of
                      Just "rtl" -> braces $ "\\righttoleft " <> txt
                      Just "ltr" -> braces $ "\\lefttoright " <> txt
                      _          -> txt
      wrapLang txt = case mblang of
                       Just lng -> "\\start\\language[" <> text lng
                                      <> "]" <> txt <> "\\stop "
                       Nothing -> txt
  (wrapLang . wrapDir) <$> inlineListToConTeXt ils

-- | Craft the section header, inserting the section reference, if supplied.
sectionHeader :: PandocMonad m
              => Attr
              -> Int
              -> [Inline]
              -> WM m Doc
sectionHeader (ident,classes,_) hdrLevel lst = do
  contents <- inlineListToConTeXt lst
  st <- get
  let opts = stOptions st
  let level' = case writerTopLevelDivision opts of
                 TopLevelPart    -> hdrLevel - 2
                 TopLevelChapter -> hdrLevel - 1
                 TopLevelSection -> hdrLevel
                 TopLevelDefault -> hdrLevel
  let ident' = if null ident
                  then empty
                  else brackets (text (toLabel ident))
  let (section, chapter) = if "unnumbered" `elem` classes
                              then (text "subject", text "title")
                              else (text "section", text "chapter")
  return $ case level' of
             -1                   -> text "\\part" <> ident' <> braces contents
             0                    -> char '\\' <> chapter <> ident' <>
                                           braces contents
             n | n >= 1 && n <= 5 -> char '\\'
                                     <> text (concat (replicate (n - 1) "sub"))
                                     <> section
                                     <> ident'
                                     <> braces contents
                                     <> blankline
             _                    -> contents <> blankline

fromBCP47 :: PandocMonad m => Maybe String -> WM m (Maybe String)
fromBCP47 mbs = fromBCP47' <$> toLang mbs

-- Takes a list of the constituents of a BCP 47 language code
-- and irons out ConTeXt's exceptions
-- https://tools.ietf.org/html/bcp47#section-2.1
-- http://wiki.contextgarden.net/Language_Codes
fromBCP47' :: Maybe Lang -> Maybe String
fromBCP47' (Just (Lang "ar" _ "SY" _)     ) = Just "ar-sy"
fromBCP47' (Just (Lang "ar" _ "IQ" _)     ) = Just "ar-iq"
fromBCP47' (Just (Lang "ar" _ "JO" _)     ) = Just "ar-jo"
fromBCP47' (Just (Lang "ar" _ "LB" _)     ) = Just "ar-lb"
fromBCP47' (Just (Lang "ar" _ "DZ" _)     ) = Just "ar-dz"
fromBCP47' (Just (Lang "ar" _ "MA" _)     ) = Just "ar-ma"
fromBCP47' (Just (Lang "de" _ _ ["1901"]) ) = Just "deo"
fromBCP47' (Just (Lang "de" _ "DE" _)     ) = Just "de-de"
fromBCP47' (Just (Lang "de" _ "AT" _)     ) = Just "de-at"
fromBCP47' (Just (Lang "de" _ "CH" _)     ) = Just "de-ch"
fromBCP47' (Just (Lang "el" _ _ ["poly"]) ) = Just "agr"
fromBCP47' (Just (Lang "en" _ "US" _)     ) = Just "en-us"
fromBCP47' (Just (Lang "en" _ "GB" _)     ) = Just "en-gb"
fromBCP47' (Just (Lang "grc"_  _ _)       ) = Just "agr"
fromBCP47' (Just (Lang "el" _ _ _)        ) = Just "gr"
fromBCP47' (Just (Lang "eu" _ _ _)        ) = Just "ba"
fromBCP47' (Just (Lang "he" _ _ _)        ) = Just "il"
fromBCP47' (Just (Lang "jp" _ _ _)        ) = Just "ja"
fromBCP47' (Just (Lang "uk" _ _ _)        ) = Just "ua"
fromBCP47' (Just (Lang "vi" _ _ _)        ) = Just "vn"
fromBCP47' (Just (Lang "zh" _ _ _)        ) = Just "cn"
fromBCP47' (Just (Lang l _ _ _)           ) = Just l
fromBCP47' Nothing                          = Nothing