{-# LANGUAGE DataKinds #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE TypeFamilies #-}

{- |
Provides a clock that ticks at every multiple of a fixed number of milliseconds.
-}
module FRP.Rhine.Clock.Realtime.Millisecond where

-- base
import Control.Concurrent (threadDelay)
import Data.Maybe (fromMaybe)
import Data.Time.Clock
import GHC.TypeLits

-- vector-sized
import Data.Vector.Sized (Vector, fromList)

-- rhine
import FRP.Rhine.Clock
import FRP.Rhine.Clock.FixedStep
import FRP.Rhine.Clock.Proxy
import FRP.Rhine.ResamplingBuffer
import FRP.Rhine.ResamplingBuffer.Collect
import FRP.Rhine.ResamplingBuffer.Util
import FRP.Rhine.Schedule

{- |
A clock ticking every 'n' milliseconds,
in real time.
Since 'n' is in the type signature,
it is ensured that when composing two signals on a 'Millisecond' clock,
they will be driven at the same rate.

The tag of this clock is 'Bool',
where 'True' represents successful realtime,
and 'False' a lag.
-}
newtype Millisecond (n :: Nat) = Millisecond (RescaledClockS IO (FixedStep n) UTCTime Bool)

-- TODO Consider changing the tag to Maybe Double

instance Clock IO (Millisecond n) where
  type Time (Millisecond n) = UTCTime
  type Tag (Millisecond n) = Bool
  initClock :: Millisecond n
-> RunningClockInit IO (Time (Millisecond n)) (Tag (Millisecond n))
initClock (Millisecond RescaledClockS IO (FixedStep n) UTCTime Bool
cl) = forall (m :: Type -> Type) cl.
Clock m cl =>
cl -> RunningClockInit m (Time cl) (Tag cl)
initClock RescaledClockS IO (FixedStep n) UTCTime Bool
cl

instance GetClockProxy (Millisecond n)

{- | This implementation measures the time after each tick,
   and waits for the remaining time until the next tick.
   If the next tick should already have occurred,
   the tag is set to 'False', representing a failed real time attempt.

   Note that this clock internally uses 'threadDelay' which can block
   for quite a lot longer than the requested time, which can cause
   the clock to miss one or more ticks when using low values of 'n'.
   When using 'threadDelay', the difference between the real wait time
   and the requested wait time will be larger when using
   the '-threaded' ghc option (around 800 microseconds) than when not using
   this option (around 100 microseconds). For low values of @n@ it is recommended
   that '-threaded' not be used in order to miss less ticks. The clock will adjust
   the wait time, up to no wait time at all, to catch up when a tick is missed.
-}
waitClock :: KnownNat n => Millisecond n
waitClock :: forall (n :: Nat). KnownNat n => Millisecond n
waitClock = forall (n :: Nat).
RescaledClockS IO (FixedStep n) UTCTime Bool -> Millisecond n
Millisecond forall a b. (a -> b) -> a -> b
$ forall (m :: Type -> Type) cl time tag.
cl -> RescalingSInit m cl time tag -> RescaledClockS m cl time tag
RescaledClockS forall (n :: Nat). KnownNat n => FixedStep n
FixedStep forall a b. (a -> b) -> a -> b
$ \Time (FixedStep n)
_ -> do
  UTCTime
initTime <- IO UTCTime
getCurrentTime
  let
    runningClock :: MSF IO (Integer, ()) (UTCTime, Bool)
runningClock = forall (m :: Type -> Type) a b. Monad m => (a -> m b) -> MSF m a b
arrM forall a b. (a -> b) -> a -> b
$ \(Integer
n, ()) -> do
      UTCTime
beforeSleep <- IO UTCTime
getCurrentTime
      let
        diff :: Double
        diff :: Double
diff = forall a b. (Real a, Fractional b) => a -> b
realToFrac forall a b. (a -> b) -> a -> b
$ UTCTime
beforeSleep UTCTime -> UTCTime -> NominalDiffTime
`diffUTCTime` UTCTime
initTime
        remaining :: Int
remaining = forall a. Num a => Integer -> a
fromInteger forall a b. (a -> b) -> a -> b
$ Integer
n forall a. Num a => a -> a -> a
* Integer
1000 forall a. Num a => a -> a -> a
- forall a b. (RealFrac a, Integral b) => a -> b
round (Double
diff forall a. Num a => a -> a -> a
* Double
1000000)
      Int -> IO ()
threadDelay Int
remaining
      UTCTime
now <- IO UTCTime
getCurrentTime -- TODO Test whether this is a performance penalty
      forall (m :: Type -> Type) a. Monad m => a -> m a
return (UTCTime
now, Int
remaining forall a. Ord a => a -> a -> Bool
> Int
0)
  forall (m :: Type -> Type) a. Monad m => a -> m a
return (MSF IO (Integer, ()) (UTCTime, Bool)
runningClock, UTCTime
initTime)

-- TODO It would be great if this could be directly implemented in terms of downsampleFixedStep
downsampleMillisecond ::
  (KnownNat n, Monad m) =>
  ResamplingBuffer m (Millisecond k) (Millisecond (n * k)) a (Vector n a)
downsampleMillisecond :: forall (n :: Nat) (m :: Type -> Type) (k :: Nat) a.
(KnownNat n, Monad m) =>
ResamplingBuffer
  m (Millisecond k) (Millisecond (n * k)) a (Vector n a)
downsampleMillisecond = forall (m :: Type -> Type) cl1 cl2 a.
Monad m =>
ResamplingBuffer m cl1 cl2 a [a]
collect forall (m :: Type -> Type) cl1 cl2 a b c.
Monad m =>
ResamplingBuffer m cl1 cl2 a b
-> ClSF m cl2 b c -> ResamplingBuffer m cl1 cl2 a c
>>-^ forall (a :: Type -> Type -> Type) b c.
Arrow a =>
(b -> c) -> a b c
arr (forall (n :: Nat) a. KnownNat n => [a] -> Maybe (Vector n a)
fromList 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}. Maybe a -> a
assumeSize)
  where
    assumeSize :: Maybe a -> a
assumeSize =
      forall a. a -> Maybe a -> a
fromMaybe forall a b. (a -> b) -> a -> b
$
        forall a. HasCallStack => [Char] -> a
error forall a b. (a -> b) -> a -> b
$
          [[Char]] -> [Char]
unwords
            [ [Char]
"You are using an incorrectly implemented schedule"
            , [Char]
"for two Millisecond clocks."
            , [Char]
"Use a correct schedule like downsampleMillisecond."
            ]

-- | Two 'Millisecond' clocks can always be scheduled deterministically.
scheduleMillisecond :: Schedule IO (Millisecond n1) (Millisecond n2)
scheduleMillisecond :: forall (n1 :: Nat) (n2 :: Nat).
Schedule IO (Millisecond n1) (Millisecond n2)
scheduleMillisecond = forall (m :: Type -> Type) cl1 cl2.
(Time cl1 ~ Time cl2) =>
(cl1
 -> cl2
 -> RunningClockInit m (Time cl1) (Either (Tag cl1) (Tag cl2)))
-> Schedule m cl1 cl2
Schedule forall {n1 :: Nat} {n2 :: Nat}.
Millisecond n1
-> Millisecond n2 -> RunningClockInit IO UTCTime (Either Bool Bool)
initSchedule'
  where
    initSchedule' :: Millisecond n1
-> Millisecond n2
-> RunningClockInit
     IO
     (Time (RescaledClockS IO (FixedStep n1) UTCTime Bool))
     (Either
        (Tag (RescaledClockS IO (FixedStep n1) UTCTime Bool))
        (Tag (RescaledClockS IO (FixedStep n2) UTCTime Bool)))
initSchedule' (Millisecond RescaledClockS IO (FixedStep n1) UTCTime Bool
cl1) (Millisecond RescaledClockS IO (FixedStep n2) UTCTime Bool
cl2) =
      forall (m :: Type -> Type) cl1 cl2.
Schedule m cl1 cl2
-> cl1
-> cl2
-> RunningClockInit m (Time cl1) (Either (Tag cl1) (Tag cl2))
initSchedule (forall (m :: Type -> Type) cl1 cl2 time tag1 tag2.
Monad m =>
Schedule m cl1 cl2
-> Schedule
     m (RescaledClockS m cl1 time tag1) (RescaledClockS m cl2 time tag2)
rescaledScheduleS forall (m :: Type -> Type) (n1 :: Nat) (n2 :: Nat).
Monad m =>
Schedule m (FixedStep n1) (FixedStep n2)
scheduleFixedStep) RescaledClockS IO (FixedStep n1) UTCTime Bool
cl1 RescaledClockS IO (FixedStep n2) UTCTime Bool
cl2