-- |
-- Module      :  Text.URI.QQ
-- Copyright   :  © 2017 Mark Karpov
-- License     :  BSD 3 clause
--
-- Maintainer  :  Mark Karpov <markkarpov92@gmail.com>
-- Stability   :  experimental
-- Portability :  portable
--
-- Quasi-quoters for compile-time construction of URIs and refined text
-- values.

{-# LANGUAGE CPP             #-}
{-# LANGUAGE RankNTypes      #-}
{-# LANGUAGE TemplateHaskell #-}

module Text.URI.QQ
  ( uri
  , scheme
  , host
  , username
  , password
  , pathPiece
  , queryKey
  , queryValue
  , fragment )
where

import Control.Exception (SomeException, Exception (..))
import Data.Data (Data)
import Data.Text (Text)
import Data.Typeable (cast)
import Language.Haskell.TH
import Language.Haskell.TH.Quote (QuasiQuoter (..))
import Language.Haskell.TH.Syntax (lift)
import Text.URI.Parser.Text
import Text.URI.Types
import qualified Data.Text as T

#if MIN_VERSION_template_haskell(2,11,0)
import Language.Haskell.TH.Syntax (dataToExpQ)
#else
dataToExpQ :: Data a => (forall b. Data b => b -> Maybe (Q Exp)) -> a -> Q Exp
dataToExpQ _ _ = fail "The feature requires at least GHC 8 to work"
#endif

-- | Construct a 'URI' value at compile time.

uri :: QuasiQuoter
uri = liftToQQ mkURI

-- | Construct a @'RText' 'Scheme'@ value at compile time.

scheme :: QuasiQuoter
scheme = liftToQQ mkScheme

-- | Construct a @'RText' 'Host'@ value at compile time.

host :: QuasiQuoter
host = liftToQQ mkHost

-- | Construct a @'RText' 'Username'@ value at compile time.

username :: QuasiQuoter
username = liftToQQ mkUsername

-- | Construct a @'RText' 'Password'@ value at compile time.

password :: QuasiQuoter
password = liftToQQ mkPassword

-- | Construct a @'RText' 'PathPiece'@ value at compile time.

pathPiece :: QuasiQuoter
pathPiece = liftToQQ mkPathPiece

-- | Construct a @'RText' 'QueryKey'@ value at compile time.

queryKey :: QuasiQuoter
queryKey = liftToQQ mkQueryKey

-- | Construct a @'RText 'QueryValue'@ value at compile time.

queryValue :: QuasiQuoter
queryValue = liftToQQ mkQueryValue

-- | Construct a @'RText' 'Fragment'@ value at compile time.

fragment :: QuasiQuoter
fragment = liftToQQ mkFragment

----------------------------------------------------------------------------
-- Helpers

-- | Lift a smart constructor for refined text into a 'QuasiQuoter'.

liftToQQ :: Data a => (Text -> Either SomeException a) -> QuasiQuoter
liftToQQ f = QuasiQuoter
  { quoteExp  = \str ->
      case f (T.pack str) of
        Left err -> fail (displayException err)
        Right x  -> dataToExpQ (fmap liftText . cast) x
  , quotePat  = error "This usage is not supported"
  , quoteType = error "This usage is not supported"
  , quoteDec  = error "This usage is not supported" }

-- | Lift strict 'T.Text' to @'Q' 'Exp'@.

liftText :: T.Text -> Q Exp
liftText txt = AppE (VarE 'T.pack) <$> lift (T.unpack txt)