module Util.TH where

import Prelude
import Language.Haskell.TH.Syntax as TH
import Language.Haskell.TH.Quote as TH
import qualified Domain
import qualified DomainCore.Model as Model


tryQuoteExp :: QuasiQuoter -> String -> Q Exp
tryQuoteExp q =
  recover (pure (ConE 'Nothing)) .
  fmap (AppE (ConE 'Just)) .
  quoteExp q

tryExpQ :: Q Exp -> Q Exp
tryExpQ =
  recover (pure (ConE 'Nothing)) .
  fmap (AppE (ConE 'Just))

mapQQExpQ :: (Q Exp -> Q Exp) -> QuasiQuoter -> QuasiQuoter
mapQQExpQ mapper (QuasiQuoter a b c d) =
  QuasiQuoter (mapper . a) b c d

maybeDecsQQ :: QuasiQuoter
maybeDecsQQ =
  mapQQExpQ (fmap mapper . tryExpQ) Domain.schema
  where
    mapper =
      AppE
        (AppE (VarE 'fmap) 
          (SigE (VarE 'unsafeCoerce) sig))
      where
        sig =
          AppT
            (AppT ArrowT (ConT ''Domain.Schema))
            (AppT ListT (ConT ''Model.TypeDec))