TH.hs

module LambdaCube.STLC.TH
  ( lc
  ) where

import           Data.Data                  (Data)
import           Data.Generics              (extQ)
import           Data.Text                  (Text)
import qualified Data.Text                  as Text
import           LambdaCube.STLC.Ast
import           LambdaCube.STLC.Parser
import           Language.Haskell.TH.Lib    (ExpQ, varE)
import           Language.Haskell.TH.Quote  (QuasiQuoter (..))
import           Language.Haskell.TH.Syntax (Loc (loc_start), dataToExpQ, lift,
                                             location, mkName)
import qualified Text.Megaparsec            as P
import qualified Text.Megaparsec.Error      as PE

lc :: QuasiQuoter
lc =
  QuasiQuoter
    { quoteExp = expLc
    , quotePat = undefined
    , quoteType = undefined
    , quoteDec = undefined
    }

expLc :: String -> ExpQ
expLc str = do
  l <- location
  case P.parse pTopLC ("<quote at " <> show (loc_start l) <> ">") (Text.pack str) of
    Right e  -> dataToExpQ converter e
    Left err -> fail $ PE.errorBundlePretty err
  where
    converter :: Data b => b -> Maybe ExpQ
    converter =
      const Nothing
      `extQ` quotedMVar
      `extQ` quotedMTVar
      `extQ` (Just . lift :: Text -> Maybe ExpQ)

    quotedMVar (ExtLCMVar x) = Just . varE $ mkName x
    quotedMVar _             = Nothing

    quotedMTVar (ExtLCMTVar x) = Just . varE $ mkName x
    quotedMTVar _              = Nothing