Text QuasiQuoter

quoter.hs

module Quoter where

import Data.Char (isSpace)
import Language.Haskell.TH
import Language.Haskell.TH.Quote


data ParserState = 
      Start
    | Break
    | Line
    deriving (Show, Eq)

parse :: String -> String
parse s = parse_ Start s 
    where  
        parse_ _ [] = []

        parse_ Start ('\n':cs) = parse_ Break cs
        parse_ Start cs = parse_ Break cs

        parse_ Break (c:cs) | isSpace c = parse_ Break cs
                            | otherwise = c : parse_ Line cs

        parse_ Line ('\n':[]) = []
        parse_ Line ('\n':cs) = '\n' : parse_ Break cs
        parse_ Line (c:cs) = c : parse_ Line cs

quoteExpr :: String -> Q Exp
quoteExpr s = pure $ LitE $ StringL $ parse s

text :: QuasiQuoter
text = QuasiQuoter quoteExpr notSupported notSupported notSupported
    where
        notSupported _ = fail "Text quoter in this context is not supported"