-- | Module providing a happstack backend for the digestive-functors library
--
{-# LANGUAGE FlexibleInstances, MultiParamTypeClasses #-}
{-# OPTIONS_GHC -fno-warn-orphans #-}
module Text.Digestive.Forms.Happstack
( HappstackForm
, happstackEnvironment
, eitherHappstackForm
) where
import Control.Monad (MonadPlus, liftM)
import Control.Applicative (Alternative, optional)
import Data.ByteString.Lazy.UTF8 as LB (toString)
import Data.Either
import Data.Text.Lazy as Text (toStrict)
import Data.Text.Lazy.Encoding as Text (decodeUtf8)
import Happstack.Server ( Input (..), HasRqData (..), lookInputs
, Method (..), ServerMonad (..), rqMethod
)
import Text.Digestive.Forms (FormInput (..))
import Text.Digestive.Types (Form (..), Environment (..), viewForm, eitherForm)
instance FormInput [Input] (String, FilePath) where
getInputStrings inps =
map LB.toString $ rights $ map inputValue inps
getInputTexts inps =
map (Text.toStrict . Text.decodeUtf8) $ rights $ map inputValue inps
getInputFile inps =
case inps of
(inp:_) ->
case inputValue inp of
(Left fp) ->
do fn <- inputFilename inp
return (fn, fp)
_ -> Nothing
_ -> Nothing
-- | Simplification of the `Form` type, instantiated to Happstack
--
type HappstackForm m = Form m [Input]
-- | Environment that will fetch input from the parameters parsed by Happstack
--
happstackEnvironment :: (HasRqData m, MonadPlus m, Alternative m)
=> Environment m [Input]
happstackEnvironment = Environment $ fmap toMaybe . lookInputs . show
where
toMaybe :: [a] -> Maybe [a]
toMaybe [] = Nothing
toMaybe l = Just l
-- | Run a happstack form
--
-- * When we are responding to a GET request, you will simply receive the form
-- as a view
--
-- * When we are responding to another request method, the form data will be
-- used. When errors occur, you will receive the form as a view, otherwise,
-- you will get the actual result
--
eitherHappstackForm :: (HasRqData m, MonadPlus m, Alternative m, ServerMonad m)
=> HappstackForm m e v a -- ^ Form
-> String -- ^ Form name
-> m (Either v a) -- ^ Result
eitherHappstackForm form name = askRq >>= \rq ->
case rqMethod rq of GET -> liftM Left $ viewForm form name
_ -> eitherForm form name happstackEnvironment