{-# LANGUAGE FlexibleContexts, TypeFamilies, GeneralizedNewtypeDeriving,
             MultiParamTypeClasses #-}
module Test.WebDriver.Monad
       ( WD(..), runWD, runSession, withSession, finallyClose, closeOnException

import Test.WebDriver.Classes
import Test.WebDriver.Commands 
import Test.WebDriver.Capabilities
import Test.WebDriver.Internal

import Control.Monad.Base (MonadBase, liftBase)
import Control.Monad (liftM)
import Control.Monad.Trans (lift)
import Control.Monad.Trans.Control (MonadBaseControl(..), StM)
import Control.Monad.State.Strict (StateT, MonadState, evalStateT, get, put)
import Control.Monad.IO.Class (MonadIO)
import Control.Exception.Lifted
import Control.Monad.CatchIO (MonadCatchIO)
import Control.Applicative

{- |A monadic interface to the WebDriver server. This monad is a simple, strict 
layer over 'IO', threading session information between sequential commands
newtype WD a = WD (StateT WDSession IO a)
  deriving (Functor, Applicative, Monad, MonadIO, MonadCatchIO)

instance MonadBase IO WD where
  liftBase = WD . liftBase

instance MonadBaseControl IO WD where
  data StM WD a = StWD {unStWD :: StM (StateT WDSession IO) a}
  liftBaseWith f = WD $  
    liftBaseWith $ \runInBase ->
    f (\(WD sT) -> liftM StWD . runInBase $ sT)

  restoreM = WD . restoreM . unStWD

instance SessionState WD where
  getSession = WD get
  putSession = WD . put

instance WebDriver WD where
  doCommand method path args = do
    r <- mkRequest [] method path args
    handleHTTPErr r
    handleHTTPResp r

-- |Executes a 'WD' computation within the 'IO' monad, using the given 
-- 'WDSession'.
runWD :: WDSession -> WD a -> IO a
runWD sess (WD wd) = evalStateT wd sess

-- |Like 'runWD', but automatically creates a session beforehand and closes it
-- afterwards. This is a very common use case.
runSession :: WDSession -> Capabilities -> WD a -> IO a
runSession s caps wd = runWD s $ createSession caps >> wd  <* closeSession

-- |Locally sets a 'WDSession' for use within the given 'WD' action.
-- The state of the outer action is unaffected by this function.
-- This function is useful if you need to work with multiple sessions at once.
withSession :: WDSession -> WD a -> WD a
withSession s' (WD wd) = WD . lift $ evalStateT wd s'

-- |A finalizer ensuring that the session is always closed at the end of 
-- the given 'WD' action, regardless of any exceptions.
finallyClose:: WebDriver wd => wd a -> wd a 
finallyClose wd = closeOnException wd <* closeSession

-- |A variant of 'finallyClose' that only closes the session when an 
-- asynchronous exception is thrown, but otherwise leaves the session open
-- if the action was successful.
closeOnException :: WebDriver wd => wd a -> wd a
closeOnException wd = wd `onException` closeSession