{-# LANGUAGE Arrows #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE RecordWildCards #-}
{-# LANGUAGE TupleSections #-}
{-# LANGUAGE TypeFamilies #-}

{- |
In the Rhine philosophy, _event sources are clocks_.
Often, we want to extract certain subevents from event sources,
e.g. single out only left mouse button clicks from all input device events.
This module provides a general purpose selection clock
that ticks only on certain subevents.
-}
module FRP.Rhine.Clock.Select where

-- rhine
import FRP.Rhine.Clock
import FRP.Rhine.Clock.Proxy
import FRP.Rhine.Schedule

-- dunai
import Data.MonadicStreamFunction.Async (concatS)

-- base
import Data.Maybe (catMaybes, maybeToList)

{- | A clock that selects certain subevents of type 'a',
   from the tag of a main clock.

   If two 'SelectClock's would tick on the same type of subevents,
   but should not have the same type,
   one should @newtype@ the subevent.
-}
data SelectClock cl a = SelectClock
  { forall cl a. SelectClock cl a -> cl
mainClock :: cl
  -- ^ The main clock
  -- | Return 'Nothing' if no tick of the subclock is required,
  --   or 'Just a' if the subclock should tick, with tag 'a'.
  , forall cl a. SelectClock cl a -> Tag cl -> Maybe a
select :: Tag cl -> Maybe a
  }

instance (Semigroup a, Semigroup cl) => Semigroup (SelectClock cl a) where
  SelectClock cl a
cl1 <> :: SelectClock cl a -> SelectClock cl a -> SelectClock cl a
<> SelectClock cl a
cl2 =
    SelectClock
      { mainClock :: cl
mainClock = forall cl a. SelectClock cl a -> cl
mainClock SelectClock cl a
cl1 forall a. Semigroup a => a -> a -> a
<> forall cl a. SelectClock cl a -> cl
mainClock SelectClock cl a
cl2
      , select :: Tag cl -> Maybe a
select = \Tag cl
tag -> forall cl a. SelectClock cl a -> Tag cl -> Maybe a
select SelectClock cl a
cl1 Tag cl
tag forall a. Semigroup a => a -> a -> a
<> forall cl a. SelectClock cl a -> Tag cl -> Maybe a
select SelectClock cl a
cl2 Tag cl
tag
      }

instance (Monoid cl, Semigroup a) => Monoid (SelectClock cl a) where
  mempty :: SelectClock cl a
mempty =
    SelectClock
      { mainClock :: cl
mainClock = forall a. Monoid a => a
mempty
      , select :: Tag cl -> Maybe a
select = forall a b. a -> b -> a
const forall a. Monoid a => a
mempty
      }

instance (Monad m, Clock m cl) => Clock m (SelectClock cl a) where
  type Time (SelectClock cl a) = Time cl
  type Tag (SelectClock cl a) = a
  initClock :: SelectClock cl a
-> RunningClockInit
     m (Time (SelectClock cl a)) (Tag (SelectClock cl a))
initClock SelectClock {cl
Tag cl -> Maybe a
select :: Tag cl -> Maybe a
mainClock :: cl
select :: forall cl a. SelectClock cl a -> Tag cl -> Maybe a
mainClock :: forall cl a. SelectClock cl a -> cl
..} = do
    (MSF m () (Time cl, Tag cl)
runningClock, Time cl
initialTime) <- forall (m :: Type -> Type) cl.
Clock m cl =>
cl -> RunningClockInit m (Time cl) (Tag cl)
initClock cl
mainClock
    let
      runningSelectClock :: MSF m () (Time cl, a)
runningSelectClock = forall (m :: Type -> Type) b.
Monad m =>
MSF m () (Maybe b) -> MSF m () b
filterS forall a b. (a -> b) -> a -> b
$ proc ()
_ -> do
        (Time cl
time, Tag cl
tag) <- MSF m () (Time cl, Tag cl)
runningClock -< ()
        forall (a :: Type -> Type -> Type) b. Arrow a => a b b
returnA -< (Time cl
time,) forall (f :: Type -> Type) a b. Functor f => (a -> b) -> f a -> f b
<$> Tag cl -> Maybe a
select Tag cl
tag
    forall (m :: Type -> Type) a. Monad m => a -> m a
return (MSF m () (Time cl, a)
runningSelectClock, Time cl
initialTime)

instance GetClockProxy (SelectClock cl a)

{- | A universal schedule for two subclocks of the same main clock.
   The main clock must be a 'Semigroup' (e.g. a singleton).
-}
schedSelectClocks ::
  (Monad m, Semigroup cl, Clock m cl) =>
  Schedule m (SelectClock cl a) (SelectClock cl b)
schedSelectClocks :: forall (m :: Type -> Type) cl a b.
(Monad m, Semigroup cl, Clock m cl) =>
Schedule m (SelectClock cl a) (SelectClock cl b)
schedSelectClocks = Schedule {forall {m :: Type -> Type} {cl} {a} {b}.
(Monad m, Clock m cl, Semigroup cl) =>
SelectClock cl a
-> SelectClock cl b -> m (MStream m (Time cl, Either a b), Time cl)
initSchedule :: SelectClock cl a
-> SelectClock cl b
-> RunningClockInit
     m
     (Time (SelectClock cl a))
     (Either (Tag (SelectClock cl a)) (Tag (SelectClock cl b)))
initSchedule :: forall {m :: Type -> Type} {cl} {a} {b}.
(Monad m, Clock m cl, Semigroup cl) =>
SelectClock cl a
-> SelectClock cl b -> m (MStream m (Time cl, Either a b), Time cl)
..}
  where
    initSchedule :: SelectClock cl a
-> SelectClock cl b -> m (MStream m (Time cl, Either a b), Time cl)
initSchedule SelectClock cl a
subClock1 SelectClock cl b
subClock2 = do
      (MSF m () (Time cl, Tag cl)
runningClock, Time cl
initialTime) <-
        forall (m :: Type -> Type) cl.
Clock m cl =>
cl -> RunningClockInit m (Time cl) (Tag cl)
initClock forall a b. (a -> b) -> a -> b
$
          forall cl a. SelectClock cl a -> cl
mainClock SelectClock cl a
subClock1 forall a. Semigroup a => a -> a -> a
<> forall cl a. SelectClock cl a -> cl
mainClock SelectClock cl b
subClock2
      let
        runningSelectClocks :: MStream m (Time cl, Either a b)
runningSelectClocks = forall (m :: Type -> Type) b.
Monad m =>
MStream m [b] -> MStream m b
concatS forall a b. (a -> b) -> a -> b
$ proc ()
_ -> do
          (Time cl
time, Tag cl
tag) <- MSF m () (Time cl, Tag cl)
runningClock -< ()
          forall (a :: Type -> Type -> Type) b. Arrow a => a b b
returnA
            -<
              forall a. [Maybe a] -> [a]
catMaybes
                [ (Time cl
time,) forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall a b. a -> Either a b
Left forall (f :: Type -> Type) a b. Functor f => (a -> b) -> f a -> f b
<$> forall cl a. SelectClock cl a -> Tag cl -> Maybe a
select SelectClock cl a
subClock1 Tag cl
tag
                , (Time cl
time,) forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall a b. b -> Either a b
Right forall (f :: Type -> Type) a b. Functor f => (a -> b) -> f a -> f b
<$> forall cl a. SelectClock cl a -> Tag cl -> Maybe a
select SelectClock cl b
subClock2 Tag cl
tag
                ]
      forall (m :: Type -> Type) a. Monad m => a -> m a
return (MStream m (Time cl, Either a b)
runningSelectClocks, Time cl
initialTime)

-- | A universal schedule for a subclock and its main clock.
schedSelectClockAndMain ::
  (Monad m, Semigroup cl, Clock m cl) =>
  Schedule m cl (SelectClock cl a)
schedSelectClockAndMain :: forall (m :: Type -> Type) cl a.
(Monad m, Semigroup cl, Clock m cl) =>
Schedule m cl (SelectClock cl a)
schedSelectClockAndMain = Schedule {forall {m :: Type -> Type} {cl} {b}.
(Monad m, Clock m cl, Semigroup cl) =>
cl
-> SelectClock cl b
-> m (MStream m (Time cl, Either (Tag cl) b), Time cl)
initSchedule :: forall {m :: Type -> Type} {cl} {b}.
(Monad m, Clock m cl, Semigroup cl) =>
cl
-> SelectClock cl b
-> m (MStream m (Time cl, Either (Tag cl) b), Time cl)
initSchedule :: cl
-> SelectClock cl a
-> RunningClockInit
     m (Time cl) (Either (Tag cl) (Tag (SelectClock cl a)))
..}
  where
    initSchedule :: cl
-> SelectClock cl b
-> m (MStream m (Time cl, Either (Tag cl) b), Time cl)
initSchedule cl
mainClock' SelectClock {cl
Tag cl -> Maybe b
select :: Tag cl -> Maybe b
mainClock :: cl
select :: forall cl a. SelectClock cl a -> Tag cl -> Maybe a
mainClock :: forall cl a. SelectClock cl a -> cl
..} = do
      (MSF m () (Time cl, Tag cl)
runningClock, Time cl
initialTime) <-
        forall (m :: Type -> Type) cl.
Clock m cl =>
cl -> RunningClockInit m (Time cl) (Tag cl)
initClock forall a b. (a -> b) -> a -> b
$
          cl
mainClock' forall a. Semigroup a => a -> a -> a
<> cl
mainClock
      let
        runningSelectClock :: MStream m (Time cl, Either (Tag cl) b)
runningSelectClock = forall (m :: Type -> Type) b.
Monad m =>
MStream m [b] -> MStream m b
concatS forall a b. (a -> b) -> a -> b
$ proc ()
_ -> do
          (Time cl
time, Tag cl
tag) <- MSF m () (Time cl, Tag cl)
runningClock -< ()
          forall (a :: Type -> Type -> Type) b. Arrow a => a b b
returnA
            -<
              forall a. [Maybe a] -> [a]
catMaybes
                [ forall a. a -> Maybe a
Just (Time cl
time, forall a b. a -> Either a b
Left Tag cl
tag)
                , (Time cl
time,) forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall a b. b -> Either a b
Right forall (f :: Type -> Type) a b. Functor f => (a -> b) -> f a -> f b
<$> Tag cl -> Maybe b
select Tag cl
tag
                ]
      forall (m :: Type -> Type) a. Monad m => a -> m a
return (MStream m (Time cl, Either (Tag cl) b)
runningSelectClock, Time cl
initialTime)

{- | Helper function that runs an 'MSF' with 'Maybe' output
   until it returns a value.
-}
filterS :: Monad m => MSF m () (Maybe b) -> MSF m () b
filterS :: forall (m :: Type -> Type) b.
Monad m =>
MSF m () (Maybe b) -> MSF m () b
filterS = forall (m :: Type -> Type) b.
Monad m =>
MStream m [b] -> MStream m b
concatS forall b c a. (b -> c) -> (a -> b) -> a -> c
. (forall {k} (cat :: k -> k -> Type) (a :: k) (b :: k) (c :: k).
Category cat =>
cat a b -> cat b c -> cat a c
>>> forall (a :: Type -> Type -> Type) b c.
Arrow a =>
(b -> c) -> a b c
arr forall a. Maybe a -> [a]
maybeToList)