Pandoc filter to insert non-breaking spaces.

gistfile1.hs

module Main where

import Text.Pandoc.JSON
import Data.List (isPrefixOf)
import Data.Char (isAlphaNum)

main = toJSONFilter insertSpaces

insertSpaces :: Inline -> Inline
insertSpaces l@(Link [Str x] (url, tit))
  | x == url = Link [Str (insertSpaces' x)] (url, tit)
  | otherwise = l
insertSpaces el = el

insertSpaces' :: String -> String
insertSpaces' s = start ++ foldr go "" end
  where
    (start, end) = findSplit s
    go c xs
      | isAlphaNum c =  c : xs
      | otherwise    = nb : c : nb : xs
    nb = '\x8203'

findSplit :: String -> (String, String)
findSplit xss@(x:xs)
  | "://" `isPrefixOf` xss = ("://",drop 3 xss)
  | otherwise = let (f, b) = findSplit xs in (x:f, b)