{-# LANGUAGE FlexibleInstances, TemplateHaskell #-}

module Network.Salvia.Core.Handler (
    Handler
  , ResourceHandler
  , UriHandler
  ) where

import Control.Applicative (Applicative, pure, (<*>))
import Control.Monad.State (StateT, ap)
import Network.Protocol.Uri (URI)
import Network.Salvia.Core.Context
import System.IO

{- |
A HTTP request handler lives in `IO` and carries a server context in the
`State` monad. This module also provides an `Applicative` instance for `StateT`
`Context` `IO`.
-}

type Handler a = StateT Context IO a

{- | A resource handler is something that works on some filesystem resource. -}

type ResourceHandler a = FilePath -> Handler a

{- | A URI handler is something that works on an request URI. -}

type UriHandler a = URI -> Handler a

-- Make handlers applicative.
instance Applicative (StateT Context IO) where
  pure  = return
  (<*>) = ap