{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE FlexibleInstances #-}
module Text.Haiji.Types
       ( Template(..)
       , render
       , Environment
       , autoEscape
       , Escape
       , escapeBy
       , rawEscape
       , htmlEscape
       , ToLT
       , toLT
       ) where

import Control.Monad.Trans.Reader
import Data.Default
import qualified Data.Text as T
import qualified Data.Text.Lazy as LT

data Escape = Escape { unEscape :: LT.Text -> LT.Text }

escapeBy :: LT.Text -> Escape -> LT.Text
escapeBy = flip unEscape

rawEscape :: Escape
rawEscape = Escape id

htmlEscape :: Escape
htmlEscape = Escape (LT.concatMap replace) where
  replace '&'  = "&"
  replace '"'  = """
  replace '\'' = "'"
  replace '<'  = "&lt;"
  replace '>'  = "&gt;"
  replace h    = LT.singleton h

-- | A template environment
data Environment =
  Environment
  { autoEscape :: Bool -- ^ XML/HTML autoescaping
  } deriving (Eq, Show)

instance Default Environment where
  def = Environment { autoEscape = True
                    }

-- | Haiji template
newtype Template dict = Template { unTmpl :: Reader dict LT.Text }

-- | Render Haiji template with given dictionary
render :: Template dict -> dict -> LT.Text
render = runReader . unTmpl

class ToLT a where toLT :: a -> LT.Text
instance ToLT T.Text  where toLT = LT.fromStrict
instance ToLT Integer where toLT = LT.pack . show
instance ToLT Bool    where toLT = LT.pack . show