-- |
-- Module      : Streamly.Internal.Data.Stream.IsStream.Exception
-- Copyright   : (c) 2019 Composewell Technologies
-- License     : BSD-3-Clause
-- Maintainer  : streamly@composewell.com
-- Stability   : experimental
-- Portability : GHC

module Streamly.Internal.Data.Stream.IsStream.Exception
    (
      before
    , after_
    , after
    , bracket_
    , bracket
    , onException
    , finally_
    , finally
    , ghandle
    , handle
    )
where

import Control.Exception (Exception)
import Control.Monad.Catch (MonadCatch)
import Control.Monad.IO.Class (MonadIO(..))
import Control.Monad.Trans.Control (MonadBaseControl)
import Streamly.Internal.Data.Stream.StreamD (toStreamD)
import Streamly.Internal.Data.Stream.StreamK (IsStream)
import Streamly.Internal.Data.SVar (MonadAsync)

import qualified Streamly.Internal.Data.Stream.StreamD as D

------------------------------------------------------------------------------
-- Exceptions
------------------------------------------------------------------------------

-- | Run the action @m b@ before the stream yields its first element.
--
-- > before action xs = 'nilM' action <> xs
--
-- @since 0.7.0
{-# INLINE before #-}
before :: (IsStream t, Monad m) => m b -> t m a -> t m a
before action xs = D.fromStreamD $ D.before action $ D.toStreamD xs

-- | Like 'after', with following differences:
--
-- * action @m b@ won't run if the stream is garbage collected
--   after partial evaluation.
-- * Monad @m@ does not require any other constraints.
-- * has slightly better performance than 'after'.
--
-- Same as the following, but with stream fusion:
--
-- > after_ action xs = xs <> 'nilM' action
--
-- /Pre-release/
--
{-# INLINE after_ #-}
after_ :: (IsStream t, Monad m) => m b -> t m a -> t m a
after_ action xs = D.fromStreamD $ D.after_ action $ D.toStreamD xs

-- | Run the action @m b@ whenever the stream @t m a@ stops normally, or if it
-- is garbage collected after a partial lazy evaluation.
--
-- The semantics of the action @m b@ are similar to the semantics of cleanup
-- action in 'bracket'.
--
-- /See also 'after_'/
--
-- @since 0.7.0
--
{-# INLINE after #-}
after :: (IsStream t, MonadIO m, MonadBaseControl IO m)
    => m b -> t m a -> t m a
after action xs = D.fromStreamD $ D.after action $ D.toStreamD xs

-- | Run the action @m b@ if the stream aborts due to an exception. The
-- exception is not caught, simply rethrown.
--
-- /Inhibits stream fusion/
--
-- @since 0.7.0
{-# INLINE onException #-}
onException :: (IsStream t, MonadCatch m) => m b -> t m a -> t m a
onException action xs = D.fromStreamD $ D.onException action $ D.toStreamD xs

-- | Like 'finally' with following differences:
--
-- * action @m b@ won't run if the stream is garbage collected
--   after partial evaluation.
-- * does not require a 'MonadAsync' constraint.
-- * has slightly better performance than 'finally'.
--
-- /Inhibits stream fusion/
--
-- /Pre-release/
--
{-# INLINE finally_ #-}
finally_ :: (IsStream t, MonadCatch m) => m b -> t m a -> t m a
finally_ action xs = D.fromStreamD $ D.finally_ action $ D.toStreamD xs

-- | Run the action @m b@ whenever the stream @t m a@ stops normally, aborts
-- due to an exception or if it is garbage collected after a partial lazy
-- evaluation.
--
-- The semantics of running the action @m b@ are similar to the cleanup action
-- semantics described in 'bracket'.
--
-- @
-- finally release = bracket (return ()) (const release)
-- @
--
-- /See also 'finally_'/
--
-- /Inhibits stream fusion/
--
-- @since 0.7.0
--
{-# INLINE finally #-}
finally :: (IsStream t, MonadAsync m, MonadCatch m) => m b -> t m a -> t m a
finally action xs = D.fromStreamD $ D.finally action $ D.toStreamD xs

-- | Like 'bracket' but with following differences:
--
-- * alloc action @m b@ runs with async exceptions enabled
-- * cleanup action @b -> m c@ won't run if the stream is garbage collected
--   after partial evaluation.
-- * does not require a 'MonadAsync' constraint.
-- * has slightly better performance than 'bracket'.
--
-- /Inhibits stream fusion/
--
-- /Pre-release/
--
{-# INLINE bracket_ #-}
bracket_ :: (IsStream t, MonadCatch m)
    => m b -> (b -> m c) -> (b -> t m a) -> t m a
bracket_ bef aft bet = D.fromStreamD $
    D.bracket_ bef aft (toStreamD . bet)

-- | Run the alloc action @m b@ with async exceptions disabled but keeping
-- blocking operations interruptible (see 'Control.Exception.mask').  Use the
-- output @b@ as input to @b -> t m a@ to generate an output stream.
--
-- @b@ is usually a resource under the state of monad @m@, e.g. a file
-- handle, that requires a cleanup after use. The cleanup action @b -> m c@,
-- runs whenever the stream ends normally, due to a sync or async exception or
-- if it gets garbage collected after a partial lazy evaluation.
--
-- 'bracket' only guarantees that the cleanup action runs, and it runs with
-- async exceptions enabled. The action must ensure that it can successfully
-- cleanup the resource in the face of sync or async exceptions.
--
-- When the stream ends normally or on a sync exception, cleanup action runs
-- immediately in the current thread context, whereas in other cases it runs in
-- the GC context, therefore, cleanup may be delayed until the GC gets to run.
--
-- /See also: 'bracket_'/
--
-- /Inhibits stream fusion/
--
-- @since 0.7.0
--
{-# INLINE bracket #-}
bracket :: (IsStream t, MonadAsync m, MonadCatch m)
    => m b -> (b -> m c) -> (b -> t m a) -> t m a
bracket bef aft bet = D.fromStreamD $
    D.bracket bef aft (toStreamD . bet)

-- | Like 'handle' but the exception handler is also provided with the stream
-- that generated the exception as input. The exception handler can thus
-- re-evaluate the stream to retry the action that failed. The exception
-- handler can again call 'ghandle' on it to retry the action multiple times.
--
-- This is highly experimental. In a stream of actions we can map the stream
-- with a retry combinator to retry each action on failure.
--
-- /Inhibits stream fusion/
--
-- /Pre-release/
--
{-# INLINE ghandle #-}
ghandle :: (IsStream t, MonadCatch m, Exception e)
    => (e -> t m a -> t m a) -> t m a -> t m a
ghandle handler =
      D.fromStreamD
    . D.ghandle (\e xs -> D.toStreamD $ handler e (D.fromStreamD xs))
    . D.toStreamD

-- | When evaluating a stream if an exception occurs, stream evaluation aborts
-- and the specified exception handler is run with the exception as argument.
--
-- /Inhibits stream fusion/
--
-- @since 0.7.0
{-# INLINE handle #-}
handle :: (IsStream t, MonadCatch m, Exception e)
    => (e -> t m a) -> t m a -> t m a
handle handler xs =
    D.fromStreamD $ D.handle (D.toStreamD . handler) $ D.toStreamD xs