-----------------------------------------------------------------------------
-- |
-- Module      :  Control.Behaviour.GenStatem
-- Copyright   :  (c) 2020-2021 EMQ Technologies Co., Ltd.
-- License     :  BSD-style (see the LICENSE file)
--
-- Maintainer  :  Feng Lee, feng@emqx.io
--                Yang M, yangm@emqx.io
-- Stability   :  experimental
-- Portability :  portable
--
-- The GenStatem Behaviour.
--
-----------------------------------------------------------------------------
module Control.Behaviour.GenStatem
  ( class GenStatem
  , Init
  , OnEvent
  , HandleEvent
  , handleEvent
  , handleWith
    -- * start/stop
  , start
  , startWith
  , startLink
  , startLinkWith
  , startMonitor
  , startMonitorWith
  , stop
  , stopPid
  , stopRef
  , stopWith
    -- * client apis
  , call
  , callTo
  , callRef
  , callTimeout
  , cast
  , castTo
  , castRef
  , sendRequest
    -- * init result
  , initOk
  , initOkWith
  , initIgnore
  , initStop
    -- * transition
  , keep
  , keepWith
  , next
  , nextWith
  , repeat
  , repeatWith
  , shutdown
    -- * helper funcs
  , replyTo
  , unhandled
  , module Control.Behaviour.GenStatem.Types
  ) where

import Control.Monad (pure)
import Control.Process (Process, ExitReason(..))
import Data.Function (($), (<<<))
import Data.Map as M
import Data.Pid (Pid)
import Data.Ref (Reference)
import Data.Timeout (Timeout)
import Data.Unit (Unit)
import Foreign (ffiIO1, ffiIO2)
import Control.Behaviour.GenStatem.Types

-- | Init Action
type Init e s d = Process (InitResult e s d)

-- | Handle Event
type HandleEvent e s d
  = EventType -> e -> s -> d -> Process (Transition e s d)

-- | On Event
type OnEvent e s d
  = EventType -> e -> d -> Process (Transition e s d)

class GenStatem e s d | e -> s, s -> d, d -> e where
  handleEvent :: HandleEvent e s d

foreign import start
  :: forall e s d. GenStatem e s d => (Init e s d) -> Process Pid

foreign import startWith
  :: forall e s d. GenStatem e s d => Name -> (Init e s d) -> Process Pid

foreign import startLink
  :: forall e s d. GenStatem e s d => (Init e s d) -> Process Pid

foreign import startLinkWith
  :: forall e s d. GenStatem e s d => Name -> (Init e s d) -> Process Pid

foreign import startMonitor
  :: forall e s d. GenStatem e s d => (Init e s d) -> Process (Pid, Reference)

foreign import startMonitorWith
  :: forall e s d. GenStatem e s d => Name -> (Init e s d) -> Process (Pid, Reference)

-- Stop the Statem Process.
stop :: Name -> Process ()
stop = ffiIO1 :gen_statem :stop

stopPid :: Pid -> Process ()
stopPid = ffiIO1 :gen_statem :stop

-- Stop the Statem Process.
foreign import stopRef :: StatemRef -> Process ()

-- Stop the Statem Process with ExitReason.
foreign import stopWith
  :: StatemRef -> ExitReason -> Timeout -> Process ()

call :: forall req rep. Name -> req -> Process rep
call = ffiIO2 :gen_statem :call

-- | Synchronous call to the Server process directly.
callTo :: forall req rep. Pid -> req -> Process rep
callTo = ffiIO2 :gen_statem :call

foreign import callRef
  :: forall req rep. StatemRef -> req -> Process rep

foreign import callTimeout
  :: forall req rep. StatemRef -> req -> Timeout -> Process rep

cast :: forall msg. Name -> msg -> Process ()
cast = ffiIO2 :gen_statem :cast

-- | Sends an asynchronous request to the Server process directly.
castTo :: forall req. Pid -> req -> Process ()
castTo = ffiIO2 :gen_statem :cast

foreign import castRef
  :: forall msg. StatemRef -> msg -> Process ()

replyTo :: forall rep. From -> rep -> Process ()
replyTo = ffiIO2 :gen_statem :reply

foreign import sendRequest
  :: forall req. StatemRef -> req -> Process RequestId

-- TODO:
-- wait_response(RequestId :: request_id()) ->
-- {reply, Reply :: term()} | {error, {term(), server_ref()}}

-- | Handle with state functions.
handleWith :: forall e s d. [(s, OnEvent e s d)] -> HandleEvent e s d
handleWith stateFuns =
  let funsMap = M.fromList stateFuns
   in \t e s d -> let f = M.get s funsMap in f t e d

foreign import unhandled :: forall e s d. HandleEvent e s d

-----------------------------------------------------------------------------
-- | Init result
-----------------------------------------------------------------------------

initOk :: forall e s d. s -> d -> Process (InitResult e s d)
initOk s d = pure $ InitOk s d []

initOkWith :: forall e s d. s -> d -> [Action e] -> Process (InitResult e s d)
initOkWith s d = pure <<< InitOk s d

initIgnore :: forall e s d. Process (InitResult e s d)
initIgnore = pure InitIgnore

initStop :: forall e s d. ExitReason -> Process (InitResult e s d)
initStop = pure <<< InitStop

-----------------------------------------------------------------------------
-- | State Transition
-----------------------------------------------------------------------------

keep :: forall e s d. d -> Process (Transition e s d)
keep d = pure $ Keep d []

keepWith :: forall e s d. d -> [Action e] -> Process (Transition e s d)
keepWith d = pure <<< Keep d

next :: forall e s d. s -> d -> Process (Transition e s d)
next s d = pure $ Next s d []

nextWith :: forall e s d. s -> d -> [Action e] -> Process (Transition e s d)
nextWith s d = pure <<< Next s d

repeat :: forall e s d. d -> Process (Transition e s d)
repeat d = pure $ Repeat d []

repeatWith :: forall e s d. d -> [Action e] -> Process (Transition e s d)
repeatWith d = pure <<< Repeat d

shutdown :: forall e s d. Atom -> d -> Process (Transition e s d)
shutdown r = pure <<< Shutdown (ExitReason r)