{-# LANGUAGE AllowAmbiguousTypes #-}
{-# LANGUAGE UnboxedTuples       #-}
{-# OPTIONS_HADDOCK not-home #-}
-- |
-- Copyright: (c) 2021 Xy Ren
-- License: BSD3
-- Maintainer: xy.r@outlook.com
-- Stability: unstable
-- Portability: non-portable (GHC only)
--
-- This module contains functions for interpreting effects. Most of the times you won't need to import this directly;
-- the module "Cleff" reexports most of the functionalities.
--
-- __This is an /internal/ module and its API may change even between minor versions.__ Therefore you should be
-- extra careful if you're to depend on this module.
module Cleff.Internal.Interpret
  ( -- * Trivial handling
    adjust
  , raise
  , raiseN
  , inject
  , subsume
  , subsumeN
  , raiseUnder
  , raiseNUnder
  , raiseUnderN
  , raiseNUnderN
    -- * Handler types
  , Handling
  , esSend
  , Handler
  , Translator
    -- * Interpreting effects
  , interpret
  , reinterpret
  , reinterpret2
  , reinterpret3
  , reinterpretN
  , interpose
  , impose
  , imposeN
    -- * Translating effects
  , transform
  , translate
    -- * Combinators for interpreting higher effects
  , toEff
  , toEffWith
  , withFromEff
  ) where

import           Cleff.Internal.Monad
import           Cleff.Internal.Rec   (Rec)
import qualified Cleff.Internal.Rec   as Rec
import           Unsafe.Coerce        (unsafeCoerce)

-- * Trivial handling

-- | Adjust the effect stack by a contravariant transformation function over the stack. This function reveals the
-- profunctorial nature of 'Eff'; in particular, 'Eff' is a profunctor @['Effect'] -> 'Data.Kind.Type'@, @lmap@ is
-- 'adjust', and @rmap@ is 'fmap'.
adjust :: ∀ es es'. (∀ f. Rec f es' -> Rec f es) -> Eff es ~> Eff es'
adjust :: (forall (f :: Effect -> Type). Rec f es' -> Rec f es)
-> Eff es ~> Eff es'
adjust forall (f :: Effect -> Type). Rec f es' -> Rec f es
f Eff es a
m = (Env es' -> IO a) -> Eff es' a
forall (es :: [Effect]) a. (Env es -> IO a) -> Eff es a
Eff (Eff es a -> Env es -> IO a
forall (es :: [Effect]) a. Eff es a -> Env es -> IO a
unEff Eff es a
m (Env es -> IO a) -> (Env es' -> Env es) -> Env es' -> IO a
forall b c a. (b -> c) -> (a -> b) -> a -> c
. (Rec HandlerPtr es' -> Rec HandlerPtr es) -> Env es' -> Env es
forall (es' :: [Effect]) (es :: [Effect]).
(Rec HandlerPtr es -> Rec HandlerPtr es') -> Env es -> Env es'
adjustEnv Rec HandlerPtr es' -> Rec HandlerPtr es
forall (f :: Effect -> Type). Rec f es' -> Rec f es
f)

-- | Lift a computation into a bigger effect stack with one more effect. For a more general version see 'raiseN'.
raise :: ∀ e es. Eff es ~> Eff (e ': es)
raise :: Eff es a -> Eff (e : es) a
raise = forall (es :: [Effect]).
KnownList '[e] =>
Eff es ~> Eff ('[e] ++ es)
forall (es' :: [Effect]) (es :: [Effect]).
KnownList es' =>
Eff es ~> Eff (es' ++ es)
raiseN @'[e]

-- | Lift a computation into a bigger effect stack with arbitrarily more effects. This function requires
-- @TypeApplications@.
raiseN :: ∀ es' es. KnownList es' => Eff es ~> Eff (es' ++ es)
raiseN :: Eff es ~> Eff (es' ++ es)
raiseN = (forall (f :: Effect -> Type). Rec f (es' ++ es) -> Rec f es)
-> Eff es ~> Eff (es' ++ es)
forall (es :: [Effect]) (es' :: [Effect]).
(forall (f :: Effect -> Type). Rec f es' -> Rec f es)
-> Eff es ~> Eff es'
adjust (forall (es' :: [Effect]) (f :: Effect -> Type).
KnownList es' =>
Rec f (es' ++ es') -> Rec f es'
forall k (es :: [k]) (es' :: [k]) (f :: k -> Type).
KnownList es =>
Rec f (es ++ es') -> Rec f es'
Rec.drop @es')

-- | Like 'raise', but adds the new effect under the top effect. This is useful for transforming an interpreter
-- @e' ':>' es => 'Eff' (e ': es) '~>` 'Eff' es@ into a reinterpreter @'Eff' (e ': es) '~>' 'Eff' (e' ': es)@:
--
-- @
-- myInterpreter :: Bar ':>' es => 'Eff' (Foo ': es) '~>' 'Eff' es
-- myInterpreter = ...
--
-- myReinterpreter :: 'Eff' (Foo ': es) '~>' 'Eff' (Bar ': es)
-- myReinterpreter = myInterpreter '.' 'raiseUnder'
-- @
--
-- In other words,
--
-- @
-- 'reinterpret' h == 'interpret' h . 'raiseUnder'
-- @
--
-- However, note that this function is suited for transforming an existing interpreter into a reinterpreter; if you
-- want to define a reinterpreter from scratch, you should still prefer 'reinterpret', which is both easier to use and
-- more efficient.
--
-- @since 0.2.0.0
raiseUnder :: ∀ e' e es. Eff (e ': es) ~> Eff (e ': e' ': es)
raiseUnder :: Eff (e : es) a -> Eff (e : e' : es) a
raiseUnder = forall (es' :: [Effect]) (e :: Effect) (es :: [Effect]).
KnownList es' =>
Eff (e : es) ~> Eff (e : (es' ++ es))
forall (e :: Effect) (es :: [Effect]).
KnownList '[e'] =>
Eff (e : es) ~> Eff (e : ('[e'] ++ es))
raiseNUnder @'[e']

-- | Like 'raiseUnder', but allows introducing multiple effects. This function requires @TypeApplications@.
--
-- @since 0.2.0.0
raiseNUnder :: ∀ es' e es. KnownList es' => Eff (e ': es) ~> Eff (e ': es' ++ es)
raiseNUnder :: Eff (e : es) ~> Eff (e : (es' ++ es))
raiseNUnder = forall (es :: [Effect]).
(KnownList '[e], KnownList es') =>
Eff ('[e] ++ es) ~> Eff ('[e] ++ (es' ++ es))
forall (es'' :: [Effect]) (es' :: [Effect]) (es :: [Effect]).
(KnownList es', KnownList es'') =>
Eff (es' ++ es) ~> Eff (es' ++ (es'' ++ es))
raiseNUnderN @es' @'[e]

-- | Like 'raiseUnder', but allows introducing the effect under multiple effects. This function requires
-- @TypeApplications@.
--
-- @since 0.2.0.0
raiseUnderN :: ∀ e es' es. KnownList es' => Eff (es' ++ es) ~> Eff (es' ++ e ': es)
raiseUnderN :: Eff (es' ++ es) ~> Eff (es' ++ (e : es))
raiseUnderN = (KnownList es', KnownList '[e]) =>
Eff (es' ++ es) ~> Eff (es' ++ ('[e] ++ es))
forall (es'' :: [Effect]) (es' :: [Effect]) (es :: [Effect]).
(KnownList es', KnownList es'') =>
Eff (es' ++ es) ~> Eff (es' ++ (es'' ++ es))
raiseNUnderN @'[e] @es' @es

-- | A generalization of both 'raiseUnderN' and 'raiseNUnder', allowing introducing multiple effects under multiple
-- effects. This function requires @TypeApplications@ and is subject to serious type ambiguity; you most likely will
-- need to supply all three type variables explicitly.
--
-- @since 0.2.0.0
raiseNUnderN :: ∀ es'' es' es. (KnownList es', KnownList es'') => Eff (es' ++ es) ~> Eff (es' ++ (es'' ++ es))
raiseNUnderN :: Eff (es' ++ es) ~> Eff (es' ++ (es'' ++ es))
raiseNUnderN = (forall (f :: Effect -> Type).
 Rec f (es' ++ (es'' ++ es)) -> Rec f (es' ++ es))
-> Eff (es' ++ es) ~> Eff (es' ++ (es'' ++ es))
forall (es :: [Effect]) (es' :: [Effect]).
(forall (f :: Effect -> Type). Rec f es' -> Rec f es)
-> Eff es ~> Eff es'
adjust \Rec f (es' ++ (es'' ++ es))
re -> Rec f es' -> Rec f es -> Rec f (es' ++ es)
forall a (f :: a -> Type) (es :: [a]) (es' :: [a]).
Rec f es -> Rec f es' -> Rec f (es ++ es')
Rec.concat
  (Rec f (es' ++ (es'' ++ es)) -> Rec f es'
forall k (es :: [k]) (es' :: [k]) (f :: k -> Type).
KnownList es =>
Rec f (es ++ es') -> Rec f es
Rec.take @es' @(es'' ++ es) Rec f (es' ++ (es'' ++ es))
re) (Rec f (es'' ++ es) -> Rec f es
forall k (es :: [k]) (es' :: [k]) (f :: k -> Type).
KnownList es =>
Rec f (es ++ es') -> Rec f es'
Rec.drop @es'' @es (Rec f (es' ++ (es'' ++ es)) -> Rec f (es'' ++ es)
forall k (es :: [k]) (es' :: [k]) (f :: k -> Type).
KnownList es =>
Rec f (es ++ es') -> Rec f es'
Rec.drop @es' @(es'' ++ es) Rec f (es' ++ (es'' ++ es))
re))

-- | Lift a computation with a fixed, known effect stack into some superset of the stack.
inject :: ∀ es' es. Subset es' es => Eff es' ~> Eff es
inject :: Eff es' ~> Eff es
inject = (forall (f :: Effect -> Type). Rec f es -> Rec f es')
-> Eff es' ~> Eff es
forall (es :: [Effect]) (es' :: [Effect]).
(forall (f :: Effect -> Type). Rec f es' -> Rec f es)
-> Eff es ~> Eff es'
adjust (forall (es' :: [Effect]) (f :: Effect -> Type).
Subset es' es' =>
Rec f es' -> Rec f es'
forall k (es :: [k]) (es' :: [k]) (f :: k -> Type).
Subset es es' =>
Rec f es' -> Rec f es
Rec.pick @es')

-- | Eliminate a duplicate effect from the top of the effect stack. For a more general version see 'subsumeN'.
subsume :: ∀ e es. e :> es => Eff (e ': es) ~> Eff es
subsume :: Eff (e : es) ~> Eff es
subsume = forall (es :: [Effect]).
Subset '[e] es =>
Eff ('[e] ++ es) ~> Eff es
forall (es' :: [Effect]) (es :: [Effect]).
Subset es' es =>
Eff (es' ++ es) ~> Eff es
subsumeN @'[e]

-- | Eliminate several duplicate effects from the top of the effect stack. This function requires @TypeApplications@.
subsumeN :: ∀ es' es. Subset es' es => Eff (es' ++ es) ~> Eff es
subsumeN :: Eff (es' ++ es) ~> Eff es
subsumeN = (forall (f :: Effect -> Type). Rec f es -> Rec f (es' ++ es))
-> Eff (es' ++ es) ~> Eff es
forall (es :: [Effect]) (es' :: [Effect]).
(forall (f :: Effect -> Type). Rec f es' -> Rec f es)
-> Eff es ~> Eff es'
adjust \Rec f es
re -> Rec f es' -> Rec f es -> Rec f (es' ++ es)
forall a (f :: a -> Type) (es :: [a]) (es' :: [a]).
Rec f es -> Rec f es' -> Rec f (es ++ es')
Rec.concat (Rec f es -> Rec f es'
forall k (es :: [k]) (es' :: [k]) (f :: k -> Type).
Subset es es' =>
Rec f es' -> Rec f es
Rec.pick @es' Rec f es
re) Rec f es
re

-- * Handler types

-- | The send-site environment.
data SendSite esSend e = SendSite
  {-# UNPACK #-} !(Env esSend) -- ^ The send-site 'Env'.
  {-# UNPACK #-} !(HandlerPtr e) -- ^ The pointer to the current effect handler.

-- | The typeclass that denotes a handler scope, handling effect @e@ sent from the effect stack @esSend@ in the
-- effect stack @es@.
--
-- You should not define instances for this typeclass whatsoever.
class Handling esSend e es | esSend -> e es where
  -- @esSend@ is existential so it uniquely determines the other two variables. As handling scopes can nest, the other
  -- two variables cannot determine anything.

  -- | Obtain the send-site environment.
  sendSite :: SendSite esSend e
  sendSite = [Char] -> SendSite esSend e
forall a. HasCallStack => [Char] -> a
error
    [Char]
"Cleff.Internal.Interpret.sendSite: Attempting to access the send site without a reflected value. This is perhaps \
    \because you are trying to define an instance for the 'Handling' typeclass, which you should not be doing \
    \whatsoever. If that or other shenanigans seem unlikely, please report this as a bug."

-- | Get the pointer to the current effect handler itself.
hdlPtr :: ∀ esSend e es. Handling esSend e es => HandlerPtr e
hdlPtr :: HandlerPtr e
hdlPtr = let SendSite Env esSend
_ HandlerPtr e
ptr = forall k (esSend :: [Effect]) (e :: Effect) (es :: k).
Handling esSend e es =>
SendSite esSend e
forall (e :: Effect) (es :: k).
Handling esSend e es =>
SendSite esSend e
sendSite @esSend in HandlerPtr e
ptr
{-# INLINE hdlPtr #-}

-- | Get the send-site 'Env'.
esSend :: Handling esSend e es => Env esSend
esSend :: Env esSend
esSend = let SendSite Env esSend
env HandlerPtr e
_ = SendSite esSend e
forall k (esSend :: [Effect]) (e :: Effect) (es :: k).
Handling esSend e es =>
SendSite esSend e
sendSite in Env esSend
env
{-# INLINE esSend #-}

-- | Newtype wrapper for instantiating the 'Handling' typeclass locally, a la the reflection trick. We do not use
-- the @reflection@ library directly so as not to expose this piece of implementation detail to the user.
newtype InstHandling esSend e es a = InstHandling (Handling esSend e es => a)

-- | Instantiate an 'Handling' typeclass, i.e. pass an implicit send-site environment in. This function shouldn't
-- be directly used anyhow.
instHandling :: ∀ esSend e es a. (Handling esSend e es => a) -> SendSite esSend e -> a
instHandling :: (Handling esSend e es => a) -> SendSite esSend e -> a
instHandling Handling esSend e es => a
x = InstHandling esSend e es a -> SendSite esSend e -> a
forall a b. a -> b
unsafeCoerce ((Handling esSend e es => a) -> InstHandling esSend e es a
forall k (esSend :: [Effect]) (e :: Effect) (es :: k) a.
(Handling esSend e es => a) -> InstHandling esSend e es a
InstHandling Handling esSend e es => a
x :: InstHandling esSend e es a)
{-# INLINE instHandling #-}

-- | The type of an /effect handler/, which is a function that transforms an effect @e@ from an arbitrary effect stack
-- into computations in the effect stack @es@.
type Handler e es = ∀ esSend. Handling esSend e es => e (Eff esSend) ~> Eff es

-- | The type of a simple transformation function from effect @e@ to @e'@.
type Translator e e' = ∀ esSend. e (Eff esSend) ~> e' (Eff esSend)

-- * Interpreting effects

-- | Transform a 'Handler' into an 'InternalHandler' given a pointer that is going to point to the 'InternalHandler'
-- and the current 'Env'.
mkInternalHandler :: HandlerPtr e -> Env es -> Handler e es -> InternalHandler e
mkInternalHandler :: HandlerPtr e -> Env es -> Handler e es -> InternalHandler e
mkInternalHandler HandlerPtr e
ptr Env es
es Handler e es
handle = (forall (es :: [Effect]). e (Eff es) ~> Eff es)
-> InternalHandler e
forall (e :: Effect).
(forall (es :: [Effect]). e (Eff es) ~> Eff es)
-> InternalHandler e
InternalHandler \e (Eff es) a
e -> (Env es -> IO a) -> Eff es a
forall (es :: [Effect]) a. (Env es -> IO a) -> Eff es a
Eff \Env es
ess ->
  Eff es a -> Env es -> IO a
forall (es :: [Effect]) a. Eff es a -> Env es -> IO a
unEff ((Handling es e es => e (Eff es) a -> Eff es a)
-> SendSite es e -> e (Eff es) a -> Eff es a
forall k (esSend :: [Effect]) (e :: Effect) (es :: k) a.
(Handling esSend e es => a) -> SendSite esSend e -> a
instHandling Handling es e es => e (Eff es) a -> Eff es a
Handler e es
handle (Env es -> HandlerPtr e -> SendSite es e
forall (esSend :: [Effect]) (e :: Effect).
Env esSend -> HandlerPtr e -> SendSite esSend e
SendSite Env es
ess HandlerPtr e
ptr) e (Eff es) a
e) (Env es -> Env es -> Env es
forall (es :: [Effect]) (es' :: [Effect]).
Env es' -> Env es -> Env es
updateEnv Env es
ess Env es
es)

-- | Interpret an effect @e@ in terms of effects in the effect stack @es@ with an effect handler.
interpret :: ∀ e es. Handler e es -> Eff (e ': es) ~> Eff es
interpret :: Handler e es -> Eff (e : es) ~> Eff es
interpret = forall (es' :: [Effect]) (e :: Effect) (es :: [Effect]).
KnownList es' =>
Handler e (es' ++ es) -> Eff (e : es) ~> Eff (es' ++ es)
forall (e :: Effect) (es :: [Effect]).
KnownList '[] =>
Handler e ('[] ++ es) -> Eff (e : es) ~> Eff ('[] ++ es)
reinterpretN @'[]

-- | Like 'interpret', but adds a new effect @e'@ to the stack that can be used in the handler.
reinterpret :: ∀ e' e es. Handler e (e' ': es) -> Eff (e ': es) ~> Eff (e' ': es)
reinterpret :: Handler e (e' : es) -> Eff (e : es) ~> Eff (e' : es)
reinterpret = forall (es' :: [Effect]) (e :: Effect) (es :: [Effect]).
KnownList es' =>
Handler e (es' ++ es) -> Eff (e : es) ~> Eff (es' ++ es)
forall (e :: Effect) (es :: [Effect]).
KnownList '[e'] =>
Handler e ('[e'] ++ es) -> Eff (e : es) ~> Eff ('[e'] ++ es)
reinterpretN @'[e']

-- | Like 'reinterpret', but adds two new effects.
reinterpret2 :: ∀ e' e'' e es. Handler e (e' ': e'' ': es) -> Eff (e ': es) ~> Eff (e' ': e'' ': es)
reinterpret2 :: Handler e (e' : e'' : es) -> Eff (e : es) ~> Eff (e' : e'' : es)
reinterpret2 = forall (es' :: [Effect]) (e :: Effect) (es :: [Effect]).
KnownList es' =>
Handler e (es' ++ es) -> Eff (e : es) ~> Eff (es' ++ es)
forall (e :: Effect) (es :: [Effect]).
KnownList '[e', e''] =>
Handler e ('[e', e''] ++ es)
-> Eff (e : es) ~> Eff ('[e', e''] ++ es)
reinterpretN @'[e', e'']

-- | Like 'reinterpret', but adds three new effects.
reinterpret3 :: ∀ e' e'' e''' e es. Handler e (e' ': e'' ': e''' ': es) -> Eff (e ': es) ~> Eff (e' ': e'' ': e''' ': es)
reinterpret3 :: Handler e (e' : e'' : e''' : es)
-> Eff (e : es) ~> Eff (e' : e'' : e''' : es)
reinterpret3 = forall (es' :: [Effect]) (e :: Effect) (es :: [Effect]).
KnownList es' =>
Handler e (es' ++ es) -> Eff (e : es) ~> Eff (es' ++ es)
forall (e :: Effect) (es :: [Effect]).
KnownList '[e', e'', e'''] =>
Handler e ('[e', e'', e'''] ++ es)
-> Eff (e : es) ~> Eff ('[e', e'', e'''] ++ es)
reinterpretN @'[e', e'', e''']

-- | Like 'reinterpret', but adds arbitrarily many new effects. This function requires @TypeApplications@.
reinterpretN :: ∀ es' e es. KnownList es' => Handler e (es' ++ es) -> Eff (e ': es) ~> Eff (es' ++ es)
reinterpretN :: Handler e (es' ++ es) -> Eff (e : es) ~> Eff (es' ++ es)
reinterpretN Handler e (es' ++ es)
handle Eff (e : es) a
m = (Env (es' ++ es) -> IO a) -> Eff (es' ++ es) a
forall (es :: [Effect]) a. (Env es -> IO a) -> Eff es a
Eff \Env (es' ++ es)
es ->
  let (# HandlerPtr e
ptr, Env (es' ++ es)
es' #) = Env (es' ++ es) -> (# HandlerPtr e, Env (es' ++ es) #)
forall (e :: Effect) (es :: [Effect]).
Env es -> (# HandlerPtr e, Env es #)
allocaEnv Env (es' ++ es)
es
  in Eff (e : es) a -> Env (e : es) -> IO a
forall (es :: [Effect]) a. Eff es a -> Env es -> IO a
unEff Eff (e : es) a
m (Env (e : es) -> IO a) -> Env (e : es) -> IO a
forall a b. (a -> b) -> a -> b
$ HandlerPtr e -> InternalHandler e -> Env es -> Env (e : es)
forall (e :: Effect) (es :: [Effect]).
HandlerPtr e -> InternalHandler e -> Env es -> Env (e : es)
appendEnv HandlerPtr e
ptr (HandlerPtr e
-> Env (es' ++ es) -> Handler e (es' ++ es) -> InternalHandler e
forall (e :: Effect) (es :: [Effect]).
HandlerPtr e -> Env es -> Handler e es -> InternalHandler e
mkInternalHandler HandlerPtr e
ptr Env (es' ++ es)
es' Handler e (es' ++ es)
handle) (Env es -> Env (e : es)) -> Env es -> Env (e : es)
forall a b. (a -> b) -> a -> b
$ (Rec HandlerPtr (es' ++ es) -> Rec HandlerPtr es)
-> Env (es' ++ es) -> Env es
forall (es' :: [Effect]) (es :: [Effect]).
(Rec HandlerPtr es -> Rec HandlerPtr es') -> Env es -> Env es'
adjustEnv (forall (es' :: [Effect]) (f :: Effect -> Type).
KnownList es' =>
Rec f (es' ++ es') -> Rec f es'
forall k (es :: [k]) (es' :: [k]) (f :: k -> Type).
KnownList es =>
Rec f (es ++ es') -> Rec f es'
Rec.drop @es') Env (es' ++ es)
es'
{-# INLINE reinterpretN #-}

-- | Respond to an effect, but does not eliminate it from the stack. This means you can re-send the operations in the
-- effect handler; it is often useful when you need to "intercept" operations so you can add extra behaviors like
-- logging.
interpose :: ∀ e es. e :> es => Handler e es -> Eff es ~> Eff es
interpose :: Handler e es -> Eff es ~> Eff es
interpose = forall (es' :: [Effect]) (e :: Effect) (es :: [Effect]).
(KnownList es', e :> es) =>
Handler e (es' ++ es) -> Eff es ~> Eff (es' ++ es)
forall (e :: Effect) (es :: [Effect]).
(KnownList '[], e :> es) =>
Handler e ('[] ++ es) -> Eff es ~> Eff ('[] ++ es)
imposeN @'[]

-- | Like 'interpose', but allows to introduce one new effect to use in the handler.
impose :: ∀ e' e es. e :> es => Handler e (e' ': es) -> Eff es ~> Eff (e' ': es)
impose :: Handler e (e' : es) -> Eff es ~> Eff (e' : es)
impose = forall (es' :: [Effect]) (e :: Effect) (es :: [Effect]).
(KnownList es', e :> es) =>
Handler e (es' ++ es) -> Eff es ~> Eff (es' ++ es)
forall (e :: Effect) (es :: [Effect]).
(KnownList '[e'], e :> es) =>
Handler e ('[e'] ++ es) -> Eff es ~> Eff ('[e'] ++ es)
imposeN @'[e']

-- | Like 'impose', but allows introducing arbitrarily many effects. This requires @TypeApplications@.
imposeN :: ∀ es' e es. (KnownList es', e :> es) => Handler e (es' ++ es) -> Eff es ~> Eff (es' ++ es)
imposeN :: Handler e (es' ++ es) -> Eff es ~> Eff (es' ++ es)
imposeN Handler e (es' ++ es)
handle Eff es a
m = (Env (es' ++ es) -> IO a) -> Eff (es' ++ es) a
forall (es :: [Effect]) a. (Env es -> IO a) -> Eff es a
Eff \Env (es' ++ es)
es ->
  let (# HandlerPtr e
ptr, Env (es' ++ es)
es' #) = Env (es' ++ es) -> (# HandlerPtr e, Env (es' ++ es) #)
forall (e :: Effect) (es :: [Effect]).
Env es -> (# HandlerPtr e, Env es #)
allocaEnv Env (es' ++ es)
es
  in Eff es a -> Env es -> IO a
forall (es :: [Effect]) a. Eff es a -> Env es -> IO a
unEff Eff es a
m (Env es -> IO a) -> Env es -> IO a
forall a b. (a -> b) -> a -> b
$ HandlerPtr e -> InternalHandler e -> Env es -> Env es
forall (e :: Effect) (es :: [Effect]).
Elem e es =>
HandlerPtr e -> InternalHandler e -> Env es -> Env es
replaceEnv HandlerPtr e
ptr (HandlerPtr e
-> Env (es' ++ es) -> Handler e (es' ++ es) -> InternalHandler e
forall (e :: Effect) (es :: [Effect]).
HandlerPtr e -> Env es -> Handler e es -> InternalHandler e
mkInternalHandler HandlerPtr e
ptr Env (es' ++ es)
es' Handler e (es' ++ es)
handle) (Env es -> Env es) -> Env es -> Env es
forall a b. (a -> b) -> a -> b
$ (Rec HandlerPtr (es' ++ es) -> Rec HandlerPtr es)
-> Env (es' ++ es) -> Env es
forall (es' :: [Effect]) (es :: [Effect]).
(Rec HandlerPtr es -> Rec HandlerPtr es') -> Env es -> Env es'
adjustEnv (forall (es' :: [Effect]) (f :: Effect -> Type).
KnownList es' =>
Rec f (es' ++ es') -> Rec f es'
forall k (es :: [k]) (es' :: [k]) (f :: k -> Type).
KnownList es =>
Rec f (es ++ es') -> Rec f es'
Rec.drop @es') Env (es' ++ es)
es'
{-# INLINE imposeN #-}

-- * Translating effects

-- | Interpret an effect in terms of another effect in the stack via a simple 'Translator'.
--
-- @
-- 'transform' trans = 'interpret' ('sendVia' 'toEff' '.' trans)
-- @
transform :: ∀ e e' es. e' :> es => Translator e e' -> Eff (e ': es) ~> Eff es
transform :: Translator e e' -> Eff (e : es) ~> Eff es
transform Translator e e'
trans = Handler e es -> Eff (e : es) ~> Eff es
forall (e :: Effect) (es :: [Effect]).
Handler e es -> Eff (e : es) ~> Eff es
interpret ((Eff esSend ~> Eff es) -> e' (Eff esSend) ~> Eff es
forall (e :: Effect) (es' :: [Effect]) (es :: [Effect]).
(e :> es') =>
(Eff es ~> Eff es') -> e (Eff es) ~> Eff es'
sendVia forall (esSend :: [Effect]) (e :: Effect) (es :: [Effect]).
Handling esSend e es =>
Eff esSend ~> Eff es
Eff esSend ~> Eff es
toEff (e' (Eff esSend) a -> Eff es a)
-> (e (Eff esSend) a -> e' (Eff esSend) a)
-> e (Eff esSend) a
-> Eff es a
forall b c a. (b -> c) -> (a -> b) -> a -> c
. e (Eff esSend) a -> e' (Eff esSend) a
Translator e e'
trans)

-- | Like 'transform', but instead of using an effect in stack, add a new one to the top of it.
--
-- @
-- 'translate' trans = 'reinterpret' ('sendVia' 'toEff' '.' trans)
-- @
translate :: ∀ e e' es. Translator e e' -> Eff (e ': es) ~> Eff (e' ': es)
translate :: Translator e e' -> Eff (e : es) ~> Eff (e' : es)
translate Translator e e'
trans = Handler e (e' : es) -> Eff (e : es) ~> Eff (e' : es)
forall (e' :: Effect) (e :: Effect) (es :: [Effect]).
Handler e (e' : es) -> Eff (e : es) ~> Eff (e' : es)
reinterpret ((Eff esSend ~> Eff (e' : es)) -> e' (Eff esSend) ~> Eff (e' : es)
forall (e :: Effect) (es' :: [Effect]) (es :: [Effect]).
(e :> es') =>
(Eff es ~> Eff es') -> e (Eff es) ~> Eff es'
sendVia forall (esSend :: [Effect]) (e :: Effect) (es :: [Effect]).
Handling esSend e es =>
Eff esSend ~> Eff es
Eff esSend ~> Eff (e' : es)
toEff (e' (Eff esSend) a -> Eff (e' : es) a)
-> (e (Eff esSend) a -> e' (Eff esSend) a)
-> e (Eff esSend) a
-> Eff (e' : es) a
forall b c a. (b -> c) -> (a -> b) -> a -> c
. e (Eff esSend) a -> e' (Eff esSend) a
Translator e e'
trans)

-- * Combinators for interpreting higher effects

-- | Run a computation in the current effect stack; this is useful for interpreting higher-order effects. For example,
-- if you want to interpret a bracketing effects in terms of 'IO':
--
-- @
-- data Resource m a where
--   Bracket :: m a -> (a -> m ()) -> (a -> m b) -> Resource m b
-- @
--
-- You will not be able to simply write this for the effect:
--
-- @
-- runBracket :: IOE ':>' es => 'Eff' (Resource ': es) a -> 'Eff' es a
-- runBracket = 'interpret' \\case
--   Bracket alloc dealloc use -> UnliftIO.'UnliftIO.bracket' alloc dealloc use
-- @
--
-- This is because effects are sended from all kinds of stacks that has @Resource@ in it, so effect handlers received
-- the effect as @Resource esSend a@, where @esSend@ is an arbitrary stack with @Resource@, instead of
-- @Resource es a@. This means @alloc@, @dealloc@ and @use@ are of type @'Eff' esSend a@, while 'UnliftIO.bracket' can
-- only take and return @'Eff' es a@. So we need to use 'toEff', which converts an @'Eff' esSend a@ into
-- an @'Eff' es a@:
--
-- @
-- runBracket :: IOE ':>' es => 'Eff' (Resource ': es) a -> 'Eff' es a
-- runBracket = 'interpret' \\case
--   Bracket alloc dealloc use -> UnliftIO.'UnliftIO.bracket'
--     ('toEff' alloc)
--     ('toEff' . dealloc)
--     ('toEff' . use)
-- @
toEff :: Handling esSend e es => Eff esSend ~> Eff es
toEff :: Eff esSend ~> Eff es
toEff Eff esSend a
m = (Env es -> IO a) -> Eff es a
forall (es :: [Effect]) a. (Env es -> IO a) -> Eff es a
Eff \Env es
es -> Eff esSend a -> Env esSend -> IO a
forall (es :: [Effect]) a. Eff es a -> Env es -> IO a
unEff Eff esSend a
m (Env es -> Env esSend -> Env esSend
forall (es :: [Effect]) (es' :: [Effect]).
Env es' -> Env es -> Env es
updateEnv Env es
es Env esSend
forall k (esSend :: [Effect]) (e :: Effect) (es :: k).
Handling esSend e es =>
Env esSend
esSend)

-- | Run a computation in the current effect stack, just like 'toEff', but takes a 'Handler' of the current effect
-- being interpreted, so that inside the computation being ran, the effect is interpreted differently. This is useful
-- for interpreting effects with local contexts, like 'Cleff.Reader.Local':
--
-- @
-- runReader :: r -> 'Eff' ('Cleff.Reader.Reader' r ': es) '~>' 'Eff' es
-- runReader x = 'interpret' (handle x)
--   where
--     handle :: r -> 'Handler' ('Cleff.Reader.Reader' r) es
--     handle r = \\case
--       'Cleff.Reader.Ask'       -> 'pure' r
--       'Cleff.Reader.Local' f m -> 'toEffWith' (handle $ f r) m
-- @
toEffWith :: ∀ esSend e es. Handling esSend e es => Handler e es -> Eff esSend ~> Eff es
toEffWith :: Handler e es -> Eff esSend ~> Eff es
toEffWith Handler e es
handle Eff esSend a
m = (Env es -> IO a) -> Eff es a
forall (es :: [Effect]) a. (Env es -> IO a) -> Eff es a
Eff \Env es
es -> Eff esSend a -> Env esSend -> IO a
forall (es :: [Effect]) a. Eff es a -> Env es -> IO a
unEff Eff esSend a
m (Env esSend -> IO a) -> Env esSend -> IO a
forall a b. (a -> b) -> a -> b
$
  -- The 'Handling' constraint of 'handle' will NOT be prematurely initialized here because that will make 'handle'
  -- monomorphic. Therefore this usage is safe.
  HandlerPtr e -> InternalHandler e -> Env esSend -> Env esSend
forall (e :: Effect) (es :: [Effect]).
HandlerPtr e -> InternalHandler e -> Env es -> Env es
writeEnv (forall k (esSend :: [Effect]) (e :: Effect) (es :: k).
Handling esSend e es =>
HandlerPtr e
forall (e :: Effect) (es :: [Effect]).
Handling esSend e es =>
HandlerPtr e
hdlPtr @esSend) (HandlerPtr e -> Env es -> Handler e es -> InternalHandler e
forall (e :: Effect) (es :: [Effect]).
HandlerPtr e -> Env es -> Handler e es -> InternalHandler e
mkInternalHandler (forall k (esSend :: [Effect]) (e :: Effect) (es :: k).
Handling esSend e es =>
HandlerPtr e
forall (e :: Effect) (es :: [Effect]).
Handling esSend e es =>
HandlerPtr e
hdlPtr @esSend) Env es
es Handler e es
handle) (Env esSend -> Env esSend) -> Env esSend -> Env esSend
forall a b. (a -> b) -> a -> b
$ Env es -> Env esSend -> Env esSend
forall (es :: [Effect]) (es' :: [Effect]).
Env es' -> Env es -> Env es
updateEnv Env es
es Env esSend
forall k (esSend :: [Effect]) (e :: Effect) (es :: k).
Handling esSend e es =>
Env esSend
esSend

-- | Temporarily gain the ability to lift some @'Eff' es@ actions into @'Eff' esSend@. This is only useful for dealing
-- with effect operations with the monad type in the negative position, which means it's unlikely that you need to use
-- this function in implementing your effects.
withFromEff :: Handling esSend e es => ((Eff es ~> Eff esSend) -> Eff esSend a) -> Eff es a
withFromEff :: ((Eff es ~> Eff esSend) -> Eff esSend a) -> Eff es a
withFromEff (Eff es ~> Eff esSend) -> Eff esSend a
f = (Env es -> IO a) -> Eff es a
forall (es :: [Effect]) a. (Env es -> IO a) -> Eff es a
Eff \Env es
es -> Eff esSend a -> Env esSend -> IO a
forall (es :: [Effect]) a. Eff es a -> Env es -> IO a
unEff ((Eff es ~> Eff esSend) -> Eff esSend a
f \Eff es a
m -> (Env esSend -> IO a) -> Eff esSend a
forall (es :: [Effect]) a. (Env es -> IO a) -> Eff es a
Eff \Env esSend
ess -> Eff es a -> Env es -> IO a
forall (es :: [Effect]) a. Eff es a -> Env es -> IO a
unEff Eff es a
m (Env esSend -> Env es -> Env es
forall (es :: [Effect]) (es' :: [Effect]).
Env es' -> Env es -> Env es
updateEnv Env esSend
ess Env es
es)) (Env es -> Env esSend -> Env esSend
forall (es :: [Effect]) (es' :: [Effect]).
Env es' -> Env es -> Env es
updateEnv Env es
es Env esSend
forall k (esSend :: [Effect]) (e :: Effect) (es :: k).
Handling esSend e es =>
Env esSend
esSend)