module Data.HList.String
    ( HString
    , hString
    )
    where

import Data.HList.Prelude
import Language.Haskell.TH
import Language.Haskell.TH.Quote
import Types.Data.Num.Decimal.Literals.TH
import Types.Data.Num.Ops


class (Show s, Eq s) => HString s

instance HString Nil

instance ( Show c
         , Show s
         , Eq c
         , Eq s
         , IntegerT c
         )
    => HString (Cons c s)

hString :: QuasiQuoter
hString = QuasiQuoter quoteStrExp quoteStrPat

quoteStrExp :: String -> ExpQ
quoteStrExp []     = varE (mkName "hNil")
quoteStrExp (c:cs) = appsE [ varE (mkName "hCons")
                           , decLiteralV (toInteger $ fromEnum c)
                           , quoteStrExp cs
                           ]

quoteStrPat :: String -> PatQ
quoteStrPat []     = varP (mkName "Nil")
quoteStrPat (c:cs) = conP (mkName "Cons")
                     [ sigP wildP (decLiteralT $ toInteger $ fromEnum c)
                     , quoteStrPat cs
                     ]