{-# LANGUAGE GeneralizedNewtypeDeriving
 , TypeFamilies
 , FlexibleInstances
 , MultiParamTypeClasses
 , UndecidableInstances
 , DeriveDataTypeable
 , ExistentialQuantification
 , StandaloneDeriving
 #-}

module AWS.Class
    ( AWS
    , runAWS
    , runAWSwithManager
    , AWSException(..)
    , AWSContext(..)
    , getLastRequestId
      -- * re-export
    , monadThrow
    ) where

import Control.Monad.State (StateT(..), MonadState)
import qualified Control.Monad.State as S
import Control.Monad.Reader (ReaderT(..), MonadReader)
import qualified Control.Monad.Reader as R
import Control.Applicative
import Control.Monad
import Control.Monad.Base (MonadBase)
import Control.Monad.IO.Class (MonadIO, liftIO)
import Control.Monad.Trans.Class (MonadTrans, lift)
import Control.Monad.Trans.Control
    ( MonadBaseControl(..)
    , MonadTransControl(..)
    , ComposeSt
    , defaultLiftBaseWith
    , defaultRestoreM
    )
import Control.Exception (Exception)
import Data.Typeable (Typeable)
import Data.Conduit (MonadThrow, monadThrow)
import Text.XML.Stream.Parse (XmlException)

import qualified Network.HTTP.Conduit as HTTP
import Data.Text (Text)
import Data.ByteString (ByteString)
import Data.ByteString.Char8 ()

import AWS.Credential

data AWSException
    = ClientError
        { clientErrorAction :: ByteString
        , clientErrorStatus :: Int
        , clientErrorCode :: Text
        , clientErrorMessage :: Maybe Text
        , clientErrorRequestId :: Text
        } -- ^ This error is caused by client requests.
    | ServerError
        { serverErrorAction :: ByteString
        , serverErrorStatus :: Int
        , serverErrorCode :: Text
        , serverErrorMessage :: Maybe Text
        , serverErrorRequestId :: Text
        } -- ^ This error is caused by server error in AWS.
    | ResponseParseError Text
    | FromTextError Text
        -- ^ parse error: cannot convert Text to oher data type.
    | XmlParserError XmlException
    | forall e . Exception e => ConnectionException e
    | forall e . Exception e => OtherInternalException e -- ^ bug
    | NextToken Text -- ^ This response has next token.
  deriving (Typeable)
deriving instance Show AWSException

instance Exception AWSException

data AWSContext = AWSContext
    { manager :: HTTP.Manager
    , endpoint :: ByteString
    , lastRequestId :: Maybe Text
    }

newtype AWS context m a = AWST
    { runAWST :: StateT context (ReaderT Credential m) a
    } deriving
    ( Monad
    , Applicative
    , Functor
    , MonadIO
    , MonadState context
    , MonadReader Credential
    , MonadBase base
    )

instance MonadTrans (AWS c)
  where
    lift = AWST . lift . lift

instance MonadTransControl (AWS c)
  where
    newtype StT (AWS c) a = StAWS { unStAWS :: (a, c) }
    liftWith f = AWST . StateT $ \s -> ReaderT $ \r ->
        liftM (\x -> (x, s))
            (f $ \a -> liftM StAWS
                (R.runReaderT (S.runStateT (runAWST a) s) r))
    restoreT
        = AWST . StateT . const . ReaderT . const . liftM unStAWS

instance MonadBaseControl base m => MonadBaseControl base (AWS c m)
  where
    newtype StM (AWS c m) a
        = StMAWS { unStMAWS :: ComposeSt (AWS c) m a }
    liftBaseWith = defaultLiftBaseWith StMAWS
    restoreM = defaultRestoreM unStMAWS

runAWS :: MonadIO m
    => (HTTP.Manager -> c)
    -> Credential
    -> AWS c m a
    -> m a
runAWS ctx cred app = do
    mgr <- liftIO $ HTTP.newManager HTTP.def
    runAWSwithManager mgr ctx cred app

runAWSwithManager :: Monad m
    => HTTP.Manager
    -> (HTTP.Manager -> c)
    -> Credential
    -> AWS c m a
    -> m a
runAWSwithManager mgr ctx cred app =
    R.runReaderT
        (S.evalStateT (runAWST app) $ ctx mgr)
        cred

getLastRequestId :: (Monad m, Functor m) => AWS AWSContext m (Maybe Text)
getLastRequestId = lastRequestId <$> S.get