{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE TypeSynonymInstances #-}
module Servant.Common.Text
  ( FromText(..)
  , ToText(..)
  ) where

import Data.String.Conversions ( cs )
import Data.Int ( Int8, Int16, Int32, Int64 )
import Data.Text ( Text )
import Data.Text.Read ( rational, signed, decimal, Reader )
import Data.Word ( Word, Word8, Word16, Word32, Word64 )

-- | For getting values from url captures and query string parameters
class FromText a where
  fromText :: Text -> Maybe a

-- | For putting values in paths and query string parameters
class ToText a where
  toText :: a -> Text

instance FromText Text where
  fromText = Just

instance ToText Text where
  toText = id

instance FromText String where
  fromText = Just . cs

instance ToText String where
  toText = cs

-- |
-- > fromText "true"  = Just True
-- > fromText "false" = Just False
-- > fromText _       = Nothing
instance FromText Bool where
  fromText "true"  = Just True
  fromText "false" = Just False
  fromText _       = Nothing

-- |
-- > toText True  = "true"
-- > toText False = "false"
instance ToText Bool where
  toText True  = "true"
  toText False = "false"

instance FromText Int where
  fromText = runReader (signed decimal)

instance ToText Int where
  toText = cs . show

instance FromText Int8 where
  fromText = runReader (signed decimal)

instance ToText Int8 where
  toText = cs . show

instance FromText Int16 where
  fromText = runReader (signed decimal)

instance ToText Int16 where
  toText = cs . show

instance FromText Int32 where
  fromText = runReader (signed decimal)

instance ToText Int32 where
  toText = cs . show

instance FromText Int64 where
  fromText = runReader (signed decimal)

instance ToText Int64 where
  toText = cs . show

instance FromText Word where
  fromText = runReader decimal

instance ToText Word where
  toText = cs . show

instance FromText Word8 where
  fromText = runReader decimal

instance ToText Word8 where
  toText = cs . show

instance FromText Word16 where
  fromText = runReader decimal

instance ToText Word16 where
  toText = cs . show

instance FromText Word32 where
  fromText = runReader decimal

instance ToText Word32 where
  toText = cs . show

instance FromText Word64 where
  fromText = runReader decimal

instance ToText Word64 where
  toText = cs . show

instance FromText Integer where
  fromText = runReader decimal

instance ToText Integer where
  toText = cs . show

instance FromText Double where
  fromText = runReader rational

instance ToText Double where
  toText = cs . show

instance FromText Float where
  fromText = runReader rational

instance ToText Float where
  toText = cs . show

runReader :: Reader a -> Text -> Maybe a
runReader reader t = either (const Nothing) (Just . fst) $ reader t