lang/langfilter/langfilter.hs

import Text.Pandoc.Definition
import Text.Pandoc.JSON
import Text.Pandoc.Builder
import Text.Pandoc.Walk
import Data.Char (isUpper, isDigit)
import Data.Maybe
import Data.Text (Text)
import qualified Data.Text as Text

main :: IO ()
main = toJSONFilter (filter :: Pandoc -> Pandoc) where
  filter =
    walk (concatMap makeFigures) .
    walk spans .
    walk (concatMap glosses)

spans :: Inline -> Inline
spans = \case
  Code attrs txt
    | Just ('\\', txt') <- Text.uncons txt      -> Code attrs txt'
    | Just _            <- enclosed '/' '/' txt -> ipaB txt
    | Just _            <- enclosed '[' ']' txt -> ipaN txt
    | Just txt'         <- enclosed '{' '}' txt -> lang txt'
    | Just txt'         <- enclosed '!' '!' txt -> abbr txt'
  i -> i

ipaB, ipaN, lang, abbr :: Text -> Inline
ipaB = Span (cls ["ipa", "ipa-broad"])  . text'
ipaN = Span (cls ["ipa", "ipa-narrow"]) . text'
lang = Span (cls ["lang"])              . lang'
abbr = Span (cls ["abbr"])              . text' . endash

text' :: Text -> [Inline]
text' = toList . text

lang' :: Text -> [Inline]
lang' txt = case Text.uncons txt of
  Nothing          -> []
  Just ('{', txt') -> RawInline "html" "<u>"  : lang' txt'
  Just ('}', txt') -> RawInline "html" "</u>" : lang' txt'
  _                -> Str a : lang' b
    where (a, b) = Text.span (\c -> c /= '{' && c /= '}') txt

cls :: [Text] -> Attr
cls cs = ("", cs, [])

glosses :: Block -> [Block]
glosses = \case
  Div (_, cs, _) blocks | "glosses" `elem` cs ->
    [RawBlock (Format "html") "<figure class=glosses>"] ++
    mapMaybe glossTable blocks ++
    [RawBlock (Format "html") "</figure>"]
  b -> [b]

pattern Gloss l g w t = BulletList [[Plain l], [Plain g], [Plain w], [Plain t]]
pattern PGloss l p g w t =
  BulletList [[Plain l], [Plain p], [Plain g], [Plain w], [Plain t]]

glossTable :: Block -> Maybe Block
glossTable = \case
  Gloss  l   s g t -> Just $ make l Nothing  s g t
  PGloss l p s g t -> Just $ make l (Just p) s g t
  HorizontalRule   -> Nothing
  b                -> error $ "found " ++ show b ++ " in gloss section"
 where
  make l p s g t =
    let n = length $ splitInlines s
        colspecs = replicate n (AlignDefault, ColWidthDefault)
        l' = cell1 n l; p' = cell1 n <$> p
        ss = cells s; gs = cells g; t' = cell1 n t
    in
    Table ("", ["gloss"], []) (Caption Nothing []) colspecs
      (TableHead mempty [])
      [TableBody mempty (RowHeadColumns 0) [] $ concat
        [[row ["gloss-lang", "lang"] [l']],
         maybe [] (pure . row ["gloss-pron", "ipa"] . pure) p',
         [row ["gloss-split", "lang"] ss],
         [row ["gloss-gloss"] gs],
         [row ["gloss-trans"] [t']]]]
      (TableFoot mempty [])
  cell is = Cell mempty AlignDefault (RowSpan 1) (ColSpan 1) [Plain is]
  cell1 n is = Cell mempty AlignDefault (RowSpan 1) (ColSpan n) [Plain is]
  cells = map (cell . concatMap abbrs) . splitInlines
  row c = Row ("", c, [])

endash :: Text -> Text
endash = Text.map \case '-' -> '–'; '_' -> ' '; c -> c

abbrs :: Inline -> [Inline]
abbrs (Str txt) = go $ endash txt where
  go "" = []
  go txt
    | (l, r) <- Text.span isAbbr txt,
      not $ Text.null l
    = abbr' l : go r
    | (l, r) <- Text.break isAbbr txt
    = Str l : go r
  abbr' txt = if Text.length txt == 1 then Str txt else abbr txt
  isAbbr c = isUpper c || isDigit c || c `elem` (",.;\\[]" :: String)
abbrs i = [i]

splitInlines :: [Inline] -> [Inlines]
splitInlines is = filter (not . null) $ go is where
  go [] = []
  go is =
    let (is1, is') = break (== Space) is in
    fromList is1 : splitInlines (dropWhile (== Space) is')


makeFigures :: Block -> [Block]
makeFigures (Div ("", ["figure"], []) blks) =
  [html "<figure>"] ++ blks ++ [html "</figure>"]
  where html = RawBlock (Format "html")
makeFigures b = [b]


enclosed :: Char -> Char -> Text -> Maybe Text
enclosed o c txt
  | Text.length txt >= 2,
    Text.head txt == o,
    Text.last txt == c
  = Just $ Text.init $ Text.tail txt
enclosed _ _ _ = Nothing