lang/langfilter/lib/LangFilter.hs

module LangFilter where

import Lang
import Ebnf
import Spans
import Glosses

import Text.Pandoc.Definition
import Text.Pandoc.Walk
import Data.Maybe
import qualified Data.Map as Map
import Data.Text (Text)
import qualified Data.Text as Text
import Control.Applicative
import Control.Monad


langFilter :: Text -> Pandoc -> IO Pandoc
langFilter col p@(Pandoc (Meta m) _) = do
  lang <- toLang $ Map.lookup "conlang" m
  let ?lang = lang
  let ?defColor = col
  let f = map (walk spans . fixFigureClass . makeEbnf .
               makeQuotes . letterList) .
          concatMap (makeBlocks <=< glosses)
  pure $ walk f p

pluck :: Eq a => a -> [a] -> Maybe [a]
pluck _ []                 = Nothing
pluck x (y:ys) | x == y    = Just ys
               | otherwise = (x :) <$> pluck x ys

pluck1 :: Eq a => [a] -> [a] -> Maybe (a, [a])
pluck1 []     _  = Nothing
pluck1 (x:xs) ys = (x,) <$> pluck x ys <|> pluck1 xs ys


fixFigureClass :: Block -> Block
fixFigureClass (Figure (i1, c1, a1) cap [Plain [Image (i2, c2, a2) alt path]]) =
  Figure (iF, c1 ++ c2, a1 ++ a2) cap [Plain [Image (iI, [], []) alt path]]
  where iF = if Text.null i1 then i2 else i1
        iI = if Text.null i1 then "" else i2
fixFigureClass b = b

makeBlocks :: Block -> [Block]
makeBlocks (Div ("", clss, []) blks)
  | Just (cls, rest) <- pluck1 ["figure", "aside"] clss =
      let html  = RawBlock $ Format "html"
          open  = if null rest then
                    html $ "<" <> cls <> ">"
                  else
                    html $ "<" <> cls <> " class='" <> Text.unwords rest <> "'>"
          close = html $ "</" <> cls <> ">"
      in
      [open] ++ blks ++ [close]
makeBlocks b = [b]

makeQuotes :: Block -> Block
makeQuotes para@(Para b) = fromMaybe para $ do
    inner <- split b
    return (BlockQuote [Para inner])
  where
    isDelim str = Text.length str == 3 && Text.all isQuote str
    isQuote c = c == '"' || c == '“' || c == '”'

    split (Str begin:SoftBreak:rest) = guard (isDelim begin) *> checkEnd rest
    split _                          = empty

    checkEnd [SoftBreak, Str end] = [] <$ guard (isDelim end)
    checkEnd (start:rest)         = (start :) <$> checkEnd rest
    checkEnd _                    = empty
makeQuotes other = other

letterList :: Block -> Block
letterList (Div a@(_, cs, _) blks)
  | "letter-list" `elem` cs = Div a (walk go blks)
 where
  go (Para xs) = Plain xs
  go b         = b
letterList b = b